BIND 10 Guide

Administrator Reference for BIND 10

This is the reference guide for BIND 10 version 1.2.0rc1.

Abstract

BIND 10 is a framework that features Domain Name System (DNS) suite and Dynamic Host Configuration Protocol (DHCP) servers with development managed by Internet Systems Consortium (ISC). It includes DNS libraries, modular components for controlling authoritative and recursive DNS servers, and experimental DHCPv4 and DHCPv6 servers (codenamed Kea).

This is the reference guide for BIND 10 version 1.2.0rc1. The most up-to-date version of this document (in PDF, HTML, and plain text formats), along with other documents for BIND 10, can be found at http://bind10.isc.org/docs.


Table of Contents

Preface
1. Acknowledgements
1. Introduction
1.1. Supported Platforms
1.2. Required Software at Run-time
1.3. Starting and Stopping the Server
1.4. Managing BIND 10
2. Quick start
2.1. Quick start guide for authoritative DNS service
3. Installation
3.1. Packages
3.2. Install Hierarchy
3.3. Building Requirements
3.4. Installation from source
3.4.1. Download Tar File
3.4.2. Retrieve from Git
3.4.3. Configure before the build
3.4.4. Build
3.4.5. Install
4. Starting BIND 10 with bind10
4.1. Starting BIND 10
5. Command channel
6. Configuration manager
7. Remote control daemon
7.1. Configuration specification for b10-cmdctl
8. Control and configure user interface
8.1. bindctl command-line options
8.2. General syntax of bindctl commands
8.3. Bindctl help
8.4. Command arguments
8.5. Module commands
8.6. Configuration commands
8.6.1. List of configuration commands
8.6.2. Configuration data types
8.7. The execute command
8.7.1. Execute directives
8.7.2. Notes on execute scripts
9. Common configuration elements
9.1. TSIG keys
9.1.1. Key anatomy and syntax
9.1.2. Key ring
9.2. ACLs
9.2.1. Matching properties
9.2.2. More complicated matches
9.2.3. Examples
9.2.4. Interaction with bindctl
10. bind10 Control and Configuration
10.1. Stopping bind10
10.2. Configuration to start processes
11. Authoritative Server
11.1. Server Configurations
11.2. Data Source Backends
11.2.1. Data source types
11.2.2. Examples
11.2.3. Adding a static data source
11.3. Loading Master Zones Files
12. Incoming Zone Transfers
12.1. Configuration for Incoming Zone Transfers
12.2. TSIG
12.3. Control the use of IXFR
12.4. Secondary Manager
12.5. Trigger an Incoming Zone Transfer Manually
12.6. Incoming Transfers with In-memory Datasource
13. Outbound Zone Transfers
14. Dynamic DNS Update
14.1. Enabling Dynamic Update
14.2. Access Control
14.3. Miscellaneous Operational Issues
15. Recursive Name Server
15.1. Access Control
15.2. Forwarding
16. DHCP
16.1. DHCP Database Installation and Configuration
16.1.1. Building with MySQL support
16.1.2. Create MySQL Database and Kea User
16.1.3. Building with PostgreSQL support
16.1.4. Create PostgreSQL Database and Kea User
17. The DHCPv4 Server
17.1. Starting and Stopping the DHCPv4 Server
17.2. Configuring the DHCPv4 Server
17.2.1. Default storage for leases
17.2.2. Database Configuration
17.2.3. Interface selection
17.2.4. IPv4 Subnet Identifier
17.2.5. Configuration of IPv4 Address Pools
17.2.6. Standard DHCPv4 options
17.2.7. Custom DHCPv4 options
17.2.8. DHCPv4 vendor specific options
17.2.9. Nested DHCPv4 options (custom option spaces)
17.2.10. Client Classification in DHCPv4
17.2.11. Limiting access to IPv4 subnet to certain classes
17.2.12. Configuring DHCPv4 for DDNS
17.3. Server Identifier in DHCPv4
17.4. Next server (siaddr)
17.5. Echoing client-id (RFC6842)
17.6. How DHCPv4 server selects subnet for a client
17.7. Using specific relay agent for a subnet
17.8. Segregating IPv4 clients in a cable network
17.9. Supported Standards
17.10. DHCPv4 Server Limitations
18. The DHCPv6 Server
18.1. Starting and Stopping the DHCPv6 Server
18.2. DHCPv6 Server Configuration
18.2.1. Default storage for leases
18.2.2. Database Configuration
18.2.3. Interface selection
18.2.4. IPv6 Subnet Identifier
18.2.5. Unicast traffic support
18.2.6. Subnet and Address Pool
18.2.7. Subnet and Prefix Delegation Pools
18.2.8. Standard DHCPv6 options
18.2.9. Custom DHCPv6 options
18.2.10. DHCPv6 vendor specific options
18.2.11. Nested DHCPv6 options (custom option spaces)
18.2.12. IPv6 Subnet Selection
18.2.13. DHCPv6 Relays
18.2.14. Client Classification in DHCPv6
18.2.15. Limiting access to IPv6 subnet to certain classes
18.2.16. Configuring DHCPv6 for DDNS
18.3. Server Identifier in DHCPv6
18.4. Using specific relay agent for a subnet
18.5. Segregating IPv6 clients in a cable network
18.6. Supported Standards
18.7. DHCPv6 Server Limitations
19. The DHCP-DDNS Server
19.1. Starting and Stopping the DHCP-DDNS Server
19.2. Configuring the DHCP-DDNS Server
19.2.1. General Server Parameters
19.2.2. TSIG Key List
19.2.3. Forward DDNS
19.2.4. Reverse DDNS
19.2.5. Example DHCP-DDNS Server Configuration
19.3. DHCP-DDNS Server Limitations
20. libdhcp++ library
20.1. Interface detection and Socket handling
21. Statistics
22. Logging
22.1. Logging configuration
22.1.1. Loggers
22.1.2. Output Options
22.1.3. Example session
22.2. Logging Message Format

List of Tables

10.1. Special startup components
17.1. List of standard DHCPv4 options
17.2. List of standard DHCPv4 options (continued)
17.3. List of standard DHCP option types
17.4. Default FQDN Flag Behavior
18.1. List of standard DHCPv6 options
18.2. Default FQDN Flag Behavior
19.1. Our example network
19.2. Forward DDNS Domains Needed
19.3. Reverse DDNS Domains Needed

Preface

Table of Contents

1. Acknowledgements

1. Acknowledgements

BIND 10 is a sponsored development project, and would not be possible without the generous support of the sponsors.

JPRS and CIRA are Patron Level sponsors.

AFNIC, CNNIC, CZ.NIC, DENIC eG, Google, RIPE NCC, Registro.br, .nz Registry Services, and Technical Center of Internet are current sponsors.

Afilias, IIS.SE, Nominet, and SIDN were founding sponsors of the project.

Support for BIND 10 development of the DHCPv4 and DHCPv6 components is provided by Comcast.

Chapter 1. Introduction

BIND is the popular implementation of a DNS server, developer interfaces, and DNS tools. BIND 10 is a rewrite of BIND 9 and ISC DHCP. BIND 10 is written in C++ and Python and provides a modular environment for serving, maintaining, and developing DNS and DHCP. BIND 10 provides a EDNS0- and DNSSEC-capable authoritative DNS server and a caching recursive name server which also provides forwarding. It also provides experimental DHCPv4 and DHCPv6 servers.

This guide covers BIND 10 version 1.2.0rc1.

1.1. Supported Platforms

BIND 10 builds have been tested on (in no particular order) Debian GNU/Linux 6 and unstable, Ubuntu 9.10, NetBSD 5, Solaris 10 and 11, FreeBSD 7 and 8, CentOS Linux 5.3, MacOS 10.6 and 10.7, and OpenBSD 5.1. It has been tested on Sparc, i386, and amd64 hardware platforms. It is planned for BIND 10 to build, install and run on Windows and standard Unix-type platforms.

1.2. Required Software at Run-time

Running BIND 10 uses various extra software which may not be provided in some operating systems' default installations nor standard packages collections. You may need to install this required software separately. (For the build requirements, also see Section 3.3, “Building Requirements”.)

BIND 10 requires at least Python 3.1 (http://www.python.org/). It also works with Python 3.2.

BIND 10 uses the Botan crypto library for C++ (http://botan.randombit.net/). It requires at least Botan version 1.8.

BIND 10 uses the log4cplus C++ logging library (http://log4cplus.sourceforge.net/). It requires at least log4cplus version 1.0.3.

The authoritative DNS server uses SQLite3 (http://www.sqlite.org/). It needs at least SQLite version 3.3.9.

The b10-ddns, b10-xfrin, b10-xfrout, and b10-zonemgr components require the libpython3 library and the Python _sqlite3.so module (which is included with Python). Python modules need to be built for the corresponding Python 3.

1.3. Starting and Stopping the Server

BIND 10 is modular. Part of this modularity is accomplished using multiple cooperating processes which, together, provide the server functionality. This is a change from the previous generation of BIND software, which used a single process.

At first, running many different processes may seem confusing. However, these processes are started by running a single command, bind10. This command starts a master process, b10-init, which will start other required processes and other processes when configured. The processes that may be started have names starting with "b10-", including:

  • b10-auth — Authoritative DNS server. This process serves DNS requests.
  • b10-cfgmgr — Configuration manager. This process maintains all of the configuration for BIND 10.
  • b10-cmdctl — Command and control service. This process allows external control of the BIND 10 system.
  • b10-ddns — Dynamic DNS update service. This process is used to handle incoming DNS update requests to allow granted clients to update zones for which BIND 10 is serving as a primary server.
  • b10-msgq — Message bus daemon. This process coordinates communication between all of the other BIND 10 processes.
  • b10-resolver — Recursive name server. This process handles incoming DNS queries and provides answers from its cache or by recursively doing remote lookups. (This is an experimental proof of concept.)
  • b10-sockcreator — Socket creator daemon. This process creates sockets used by network-listening BIND 10 processes.
  • b10-stats — Statistics collection daemon. This process collects and reports statistics data.
  • b10-stats-httpd — HTTP server for statistics reporting. This process reports statistics data in XML format over HTTP.
  • b10-xfrin — Incoming zone transfer service. This process is used to transfer a new copy of a zone into BIND 10, when acting as a secondary server.
  • b10-xfrout — Outgoing zone transfer service. This process is used to handle transfer requests to send a local zone to a remote secondary server.
  • b10-zonemgr — Secondary zone manager. This process keeps track of timers and other necessary information for BIND 10 to act as a slave server.

These do not need to be manually started independently.

1.4. Managing BIND 10

Once BIND 10 is running, a few commands are used to interact directly with the system:

  • bindctl — Interactive administration interface. This is a low-level command-line tool which allows a developer or an experienced administrator to control BIND 10.
  • b10-loadzone — Zone file loader. This tool will load standard masterfile-format zone files into BIND 10.
  • b10-cmdctl-usermgr — User access control. This tool allows an administrator to authorize additional users to manage BIND 10.

The tools and modules are covered in full detail in this guide. In addition, manual pages are also provided in the default installation.

BIND 10 also provides libraries and programmer interfaces for C++ and Python for the message bus, configuration backend, and, of course, DNS. These include detailed developer documentation and code examples.

Chapter 2. Quick start

This quickly covers the standard steps for installing and deploying BIND 10. For further details, full customizations, and troubleshooting, see the respective chapters in the BIND 10 guide.

2.1. Quick start guide for authoritative DNS service

  1. Install required run-time and build dependencies.
  2. Download the BIND 10 source tar file from ftp://ftp.isc.org/isc/bind10/.
  3. Extract the tar file:

    $ gzcat bind10-VERSION.tar.gz | tar -xvf -

  4. Go into the source and run configure:

    $ cd bind10-VERSION
    $ ./configure

  5. Build it:

    $ make

  6. Install it as root (by default to prefix /usr/local/):

    $ make install

  7. Change directory to the install prefix (by default /usr/local/):

    $ cd /usr/local/

  8. Create a user for yourself:

    $ sbin/b10-cmdctl-usermgr add root

    and enter a newly chosen password when prompted.

  9. Start the server (as root):

    $ sbin/bind10

  10. DNS and DHCP components are not started in the default configuration. In another console, enable the authoritative DNS service (by using the bindctl utility to configure the b10-auth component to run):

    $ bin/bindctl

    (Login with the username and password you used above to create a user.)

    > config add Init/components b10-auth
    > config set Init/components/b10-auth/special auth
    > config set Init/components/b10-auth/kind needed
    > config commit
    > quit
                

  11. Test it; for example:

    $ dig @127.0.0.1 -c CH -t TXT version.bind

  12. Load desired zone file(s), for example:

    $ bin/b10-loadzone -c '{"database_file": "/usr/local/var/bind10/zone.sqlite3"}' your.zone.example.org your.zone.file

    (If you use the sqlite3 data source with the default DB file, you can omit the -c option).
  13. Test the new zone.

Chapter 3. Installation

3.1. Packages

Some operating systems or software package vendors may provide ready-to-use, pre-built software packages for the BIND 10 suite. Installing a pre-built package means you do not need to install build-only prerequisites and do not need to make the software.

FreeBSD ports, NetBSD pkgsrc, and Debian testing package collections provide all the prerequisite packages.

3.2. Install Hierarchy

The following is the standard, common layout of the complete BIND 10 installation:

  • bin/ — general tools and diagnostic clients.
  • etc/bind10/ — configuration files.
  • lib/ — libraries and python modules.
  • libexec/bind10/ — executables that a user wouldn't normally run directly and are not run independently. These are the BIND 10 modules which are daemons started by the b10-init master process.
  • sbin/ — commands used by the system administrator.
  • share/bind10/ — configuration specifications.
  • share/doc/bind10/ — this guide and other supplementary documentation.
  • share/man/ — manual pages (online documentation).
  • var/bind10/ — data source and configuration databases.

3.3. Building Requirements

In addition to the run-time requirements (listed in Section 1.2, “Required Software at Run-time”), building BIND 10 from source code requires various development include headers and program development tools.

Note

Some operating systems have split their distribution packages into a run-time and a development package. You will need to install the development package versions, which include header files and libraries, to build BIND 10 from source code.

Building from source code requires the Boost build-time headers (http://www.boost.org/). At least Boost version 1.35 is required.

To build BIND 10, also install the Botan (at least version 1.8) and the log4cplus (at least version 1.0.3) development include headers.

Building BIND 10 also requires a C++ compiler and standard development headers, make, and pkg-config. BIND 10 builds have been tested with GCC g++ 3.4.3, 4.1.2, 4.1.3, 4.2.1, 4.3.2, and 4.4.1; Clang++ 2.8; and Sun C++ 5.10.

Visit the user-contributed wiki at http://bind10.isc.org/wiki/SystemSpecificNotes for system-specific installation tips.

3.4. Installation from source

BIND 10 is open source software written in C++ and Python. It is freely available in source code form from ISC as a downloadable tar file or via BIND 10's Git code revision control service. (It may also be available in pre-compiled ready-to-use packages from operating system vendors.)

3.4.1. Download Tar File

Downloading a release tar file is the recommended method to obtain the source code.

The BIND 10 releases are available as tar file downloads from ftp://ftp.isc.org/isc/bind10/. Periodic development snapshots may also be available.

3.4.2. Retrieve from Git

Downloading this "bleeding edge" code is recommended only for developers or advanced users. Using development code in a production environment is not recommended.

Note

When using source code retrieved via Git, additional software will be required: automake (v1.11 or newer), libtoolize, and autoconf (2.59 or newer). These may need to be installed.

The latest development code (and temporary experiments and un-reviewed code) is available via the BIND 10 code revision control system. This is powered by Git and all the BIND 10 development is public. The leading development is done in the master branch.

The code can be checked out from git://git.bind10.isc.org/bind10; for example:

$ git clone git://git.bind10.isc.org/bind10

When checking out the code from the code version control system, it doesn't include the generated configure script, Makefile.in files, nor their related build files. They can be created by running autoreconf with the --install switch. This will run autoconf, aclocal, libtoolize, autoheader, automake, and related commands.

3.4.3. Configure before the build

BIND 10 uses the GNU Build System to discover build environment details. To generate the makefiles using the defaults, simply run:

$ ./configure

Run ./configure with the --help switch to view the different options. Some commonly-used options are:

--prefix
Define the installation location (the default is /usr/local/).
--with-boost-include
Define the path to find the Boost headers.
--with-pythonpath
Define the path to Python 3.1 if it is not in the standard execution path.
--with-gtest
Enable building the C++ Unit Tests using the Google Tests framework. Optionally this can define the path to the gtest header files and library.
--without-werror
Disable the default use of the -Werror compiler flag so that compiler warnings aren't build failures.

Note

For additional instructions concerning the building and installation of BIND 10 DHCP, see Section 16.1, “DHCP Database Installation and Configuration”.

For example, the following configures it to find the Boost headers, find the Python interpreter, and sets the installation location:

$ ./configure \
      --with-boost-include=/usr/pkg/include \
      --with-pythonpath=/usr/pkg/bin/python3.1 \
      --prefix=/opt/bind10

If the configure fails, it may be due to missing or old dependencies.

3.4.4. Build

After the configure step is complete, to build the executables from the C++ code and prepare the Python scripts, run:

$ make

3.4.5. Install

To install the BIND 10 executables, support files, and documentation, run:

$ make install

Please don't use any form of parallel or job server options (such as GNU make's -j option) when performing this step. Doing so may cause errors.

Note

The install step may require superuser privileges.

If required, run ldconfig as root with /usr/local/lib (or with ${prefix}/lib if configured with --prefix) in /etc/ld.so.conf (or the relevant linker cache configuration file for your OS):

$ ldconfig

Note

If you do not run ldconfig where it is required, you may see errors like the following:

	      program: error while loading shared libraries: libb10-something.so.1:
	      cannot open shared object file: No such file or directory
	    

Chapter 4. Starting BIND 10 with bind10

Table of Contents

4.1. Starting BIND 10

BIND 10 is started with the bind10 command. It runs the b10-init daemon which starts up the required processes, and will also restart some processes that exit unexpectedly. bind10 is the only command needed to start the BIND 10 system.

After starting the b10-msgq communications channel, b10-init connects to it, runs the configuration manager, and reads its own configuration. Then it starts the other modules.

The b10-sockcreator, b10-msgq and b10-cfgmgr services make up the core. The b10-msgq daemon provides the communication channel between every part of the system. The b10-cfgmgr daemon is always needed by every module, if only to send information about themselves somewhere, but more importantly to ask about their own settings, and about other modules. The b10-sockcreator daemon helps allocate Internet addresses and ports as needed for BIND 10 network services.

In its default configuration, the b10-init master process will also start up b10-cmdctl for administration tools to communicate with the system, and b10-stats for statistics collection. The DNS and DHCP servers are not started by default. The configuration of components to start is covered in Section 10.2, “Configuration to start processes”.

4.1. Starting BIND 10

To start the BIND 10 service, simply run bind10 as root. It will run in the foreground and your shell prompt will not be available. It will output various log messages as it starts up and is used. Run it with the --verbose switch to get additional debugging or diagnostic output.

Note

If the setproctitle Python module is detected at start up, the process names for the Python-based daemons will be renamed to better identify them instead of just python. This is not needed on some operating systems.

Chapter 5. Command channel

The BIND 10 components use the b10-msgq message routing daemon to communicate with other BIND 10 components. The b10-msgq implements what is called the Command Channel. Processes intercommunicate by sending messages on the command channel. Example messages include shutdown, get configurations, and set configurations. This Command Channel is not used for DNS message passing. It is used only to control and monitor the BIND 10 system.

Administrators do not communicate directly with the b10-msgq daemon. By default, BIND 10 uses a UNIX domain socket file named /usr/local/var/bind10/msg_socket for this interprocess communication.

Chapter 6. Configuration manager

The configuration manager, b10-cfgmgr, handles all BIND 10 system configuration. It provides persistent storage for configuration, and notifies running modules of configuration changes.

The b10-auth and b10-xfrin daemons and other components receive their configurations from the configuration manager over the b10-msgq command channel.

The administrator doesn't connect to it directly, but uses a user interface to communicate with the configuration manager via b10-cmdctl's REST-ful interface. b10-cmdctl is covered in Chapter 7, Remote control daemon.

Note

The current release only provides bindctl as a user interface to b10-cmdctl. Upcoming releases will provide another interactive command-line interface and a web-based interface.

The b10-cfgmgr daemon can send all specifications and all current settings to the bindctl client (via b10-cmdctl). b10-cfgmgr relays configurations received from b10-cmdctl to the appropriate modules.

The stored configuration file is at /usr/local/var/bind10/b10-config.db. (The directory is what was defined at build configure time for --localstatedir. The default is /usr/local/var/.) The format is loosely based on JSON and is directly parseable python, but this may change in a future version. This configuration data file is not manually edited by the administrator.

The configuration manager does not have any command line arguments. Normally it is not started manually, but is automatically started using the b10-init master process (as covered in Chapter 4, Starting BIND 10 with bind10).

Chapter 7. Remote control daemon

b10-cmdctl is the gateway between administrators and the BIND 10 system. It is a HTTPS server that uses standard HTTP Digest Authentication for username and password validation. It provides a REST-ful interface for accessing and controlling BIND 10.

When b10-cmdctl starts, it firsts asks b10-cfgmgr about what modules are running and what their configuration is (over the b10-msgq channel). Then it will start listening on HTTPS for clients — the user interface — such as bindctl.

b10-cmdctl directly sends commands (received from the user interface) to the specified component. Configuration changes are actually commands to b10-cfgmgr so are sent there.

The HTTPS server requires a private key, such as a RSA PRIVATE KEY. The default location is at /usr/local/etc/bind10/cmdctl-keyfile.pem. (A sample key is at /usr/local/share/bind10/cmdctl-keyfile.pem.) It also uses a certificate located at /usr/local/etc/bind10/cmdctl-certfile.pem. (A sample certificate is at /usr/local/share/bind10/cmdctl-certfile.pem.) This may be a self-signed certificate or purchased from a certification authority.

Note

The HTTPS server doesn't support a certificate request from a client (at this time). The b10-cmdctl daemon does not provide a public service. If any client wants to control BIND 10, then a certificate needs to be first received from the BIND 10 administrator. The BIND 10 installation provides a sample PEM bundle that matches the sample key and certificate.

The b10-cmdctl daemon also requires the user account file located at /usr/local/etc/bind10/cmdctl-accounts.csv. This comma-delimited file lists the accounts with a user name, hashed password, and salt.

The administrator may create a user account with the b10-cmdctl-usermgr tool.

By default the HTTPS server listens on the localhost port 8080. The port can be set by using the --port command line option. The address to listen on can be set using the --address command line argument. Each HTTPS connection is stateless and times out in 1200 seconds by default. This can be redefined by using the --idle-timeout command line argument.

7.1. Configuration specification for b10-cmdctl

The configuration items for b10-cmdctl are: accounts_file which defines the path to the user accounts database (the default is /usr/local/etc/bind10/cmdctl-accounts.csv); cert_file which defines the path to the PEM certificate file (the default is /usr/local/etc/bind10/cmdctl-certfile.pem); and key_file which defines the path to the PEM private key file (the default is /usr/local/etc/bind10/cmdctl-keyfile.pem).

Chapter 8. Control and configure user interface

Note

For the current release, bindctl is the only user interface. It is expected that upcoming releases will provide another interactive command-line interface and a web-based interface for controlling and configuring BIND 10.

Note

bindctl has an internal command history, as well as tab-completion for most of the commands and arguments. However, these are only enabled if the python readline module is available on the system. If not, neither of these features will be supported.

The bindctl tool provides an interactive prompt for configuring, controlling, and querying the BIND 10 components. It communicates directly with a REST-ful interface over HTTPS provided by b10-cmdctl. It doesn't communicate to any other components directly.

8.1. bindctl command-line options

-a <address>, --address=<address>
IP address that BIND 10's b10-cmdctl module is listening on. By default, this is 127.0.0.1.
-c <certificate file>, --certificate-chain=<certificate file>
PEM-formatted server certificate file. When this option is given, bindctl will verify the server certificate using the given file as the root of the certificate chain. If not specified, bindctl does not validate the certificate.
--csv-file-dir=<csv file>
bindctl stores the username and password for logging in in a file called default_user.csv; this option specifies the directory where this file is stored and read from. When not specified, ~/.bind10/ is used.

Note

Currently, this file contains an unencrypted password.
-h, --help
Shows a short overview of the command-line options of bindctl, and exits.
--version
Shows the version of bindctl, and exits.
-p <port number>, --port=<port number>
Port number that BIND 10's b10-cmdctl module is listening on. By default, this is port 8080.

8.2. General syntax of bindctl commands

The bindctl tool is an interactive command-line tool, with dynamic commands depending on the BIND 10 modules that are running. There are a number of fixed commands that have no module and that are always available. The general syntax of a command is
<module> <command> [argument(s)]
For example, the Init module has a 'shutdown' command to shut down BIND 10, with an optional argument 'help':
> Init shutdown help
Command  shutdown 	(Shut down BIND 10)
		help (Get help for command)
This command has no parameters
        
There are no mandatory arguments, only the optional 'help'.

8.3. Bindctl help

help is both a command and an option that is available to all other commands. When run as a command directly, it shows the available modules.
> help
usage: <module name> <command name> [param1 = value1 [, param2 = value2]]
Type Tab character to get the hint of module/command/parameters.
Type "help(? h)" for help on bindctl.
Type "<module_name> help" for help on the specific module.
Type "<module_name> <command_name> help" for help on the specific command.

Available module names:
(list of modules)
        
When 'help' is used as a command to a module, it shows the supported commands for the module; for example:
> Init help
Module  Init 	Master process
Available commands:
    help        Get help for module.
    shutdown    Shut down BIND 10
    ping        Ping the Init process
    show_processes
            List the running BIND 10 processes
        
And when added to a module command, it shows the description and parameters of that specific command; for example:
> Auth loadzone help
Command  loadzone 	((Re)load a specified zone)
		help (Get help for command)
Parameters:
    class (string, optional)
    origin (string, mandatory)
    

8.4. Command arguments

Commands can have arguments, which can be either optional or mandatory. They can be specified by name (e.g. <command> <argument name>=<argument value>), or positionally, (e.g. <command> <argument value 1> <argument value 2>).

<command> help shows the arguments a command supports and which of those are mandatory, and in which order the arguments are expected if positional arguments are used.

For example, the loadzone command of the Auth module, as shown in the last example of the previous section, has two arguments, one of which is optional. The positional arguments in this case are class first and origin second; for example:

> Auth loadzone IN example.com.
But since the class is optional (defaulting to IN), leaving it out works as well:
> Auth loadzone example.com.

The arguments can also be provided with their names, in which case the order does not matter:

> Auth loadzone origin="example.com." class="IN"

8.5. Module commands

Each module has its own set of commands (if any), which will only be available if the module is running. For instance, the Auth module has a loadzone command. The commands a module provides are documented in this guide in the section of that module or in the module's corresponding manual page.

8.6. Configuration commands

Configuration commands are used to view and change the configuration of BIND 10 and its modules. Module configuration is only shown if that module is running, but similar to commands, there are a number of top-level configuration items that are always available (for instance tsig_keys and data_sources). Configuration changes (set, unset, add and remove) are done locally first, and have no immediate effect. The changes can be viewed with config diff, and either reverted (config revert), or committed (config commit). In the latter case, all local changes are submitted to the configuration manager, which verifies them, and if they are accepted, applied and saved in persistent storage. When identifying items in configuration commands, the format is
Module/example/item
Sub-elements of names, lists and sets (see Section 8.6.2, “Configuration data types”) are separated with the '/' character, and list indices are identified with [<index>]; for example:
Module/example/list[2]/foo

8.6.1. List of configuration commands

The following configuration commands are available:
show [all] [item name]
Shows the current configuration of the given item. If 'all' is given, it will recurse through the entire set, and show every nested value.
show_json [item name]
Shows the full configuration of the given item in JSON format.
add <item name> [value]
Add an entry to configuration list or a named set (see Section 8.6.2, “Configuration data types”). When adding to a list, the command has one optional argument, a value to add to the list. The value must be in correct JSON and complete. When adding to a named set, it has one mandatory parameter (the name to add), and an optional parameter value, similar to when adding to a list. In either case, when no value is given, an entry will be constructed with default values.
remove
Remove an item from a configuration list or a named set. When removing an item for a list, either the index needs to be specified, or the complete value of the element to remove must be specified (in JSON format).
set <item name> <value>
Directly set the value of the given item to the given value.
unset <item name>
Remove any user-specified value for the given item.
diff
Show all current local changes that have not been committed yet.
revert
Revert all local changes without committing them.
commit
Send all local changes to the configuration manager, which will validate them, and apply them if validation succeeds.
go
Go to a specific configuration part, similar to the 'cd' command in a shell.

Note

There are a number of problems with the current implementation of go within bindctl, and we recommend not using it for general cases.

8.6.2. Configuration data types

Configuration data can be of different types, which can be modified in ways that depend on the types. There are a few syntax restrictions on these types, but only basic ones. Modules may impose additional restrictions on the values of elements.
integer
A basic integer; can be set directly with config set, to any integer value. The value must not be quoted, or else, it will be parsed as a string.
real
A basic floating point number; can be set directly with config set, to any floating point value. The value must not be quoted, or else, it will be parsed as a string.
boolean
A basic boolean value; can be set directly with config set, to either true or false. The value must not be quoted, or else, it will be parsed as a string. Integer values are not allowed.
string
A basic string value; can be set directly with config set to any string. Double quotation marks are optional.
null
This is a special type representing 'no value at all'; usable in compound structures that have optional elements that are not set.
maps

Maps are (pre-defined) compound collections of other elements of any other type. They are not usually modified directly, but their elements are. Every top-level element for a module is a map containing the configuration values for that map, which can themselves be maps again. For instance, the Auth module configuration is a map containing the elements 'listen_on' (list) and 'tcp_recv_timeout' (integer). When changing one of its values, they can be modified directly with config set Auth/tcp_recv_timeout 3000.

Some map entries are optional. If they are, and currently have a value, the value can be unset by using either config unset <item name> or config set <item name> null.

Maps can be modified as a whole, but using the full JSON representation of the entire map to set. Since this involves a lot of text, this is usually not recommended.

Another example is the Logging virtual module, which is, like any module, a map, but it only contains one element: a list of loggers. Normally, an administrator would only modify that list (or its elements) directly, but it is possible to set the entire map in one command; for example: config set Logging { "loggers": [] }

list

A list is a compound list of other elements of the same type. Elements can be added with config add <list name> [value], and removed with config remove <list name> [value] or config remove <list name><index>. The index is of the form square bracket, number, square bracket (e.g. [0]), and it immediately follows the list name (there is no separator or space between them). List indices start with 0 for the first element.

For addition, if the value is omitted, an entry with default values will be added. For removal, either the index or the full value (in JSON format) needs to be specified.

Lists can also be used with config set, but like maps, only by specifying the entire list value in JSON format.

For example, this command shows the port number used for the second element of the list listen_on in the Auth module: config show Auth/listen_on[1]/port

named set

Named sets are similar to lists, in that they are sets of elements of the same type, but they are not indexed by numbers, but by strings.

Values can be added with config add <item name> <string> [value] where 'string' is the name of the element. If 'value' is ommitted, default values will be used. Elements can be removed with config remove <item name> <string>

Elements in a named set can be addressed similarly to maps.

For example, the Init/components elements is a named set; adding, showing, and then removing an element can be done with the following three commands (note the '/'-character versus the space before 'example_module'):

config add Init/components example_module

config show Init/components/example_module

config remove Init/components example_module

any
The 'any' type is a special type that can have any form. Apart from that, it must consist of elements as described in this chapter, there is no restriction on which element types are used. This type is used in places where different data formats could be used. Element modification commands depend on the actual type of the value. For instance, if the value of an 'any' element is a list, config add and config remove work as for other lists.

8.7. The execute command

The execute command executes a set of commands, either from a file or from a pre-defined set. Currently, the only predefined set is init_authoritative_server, which adds b10-auth, b10-xfrin, and b10-xfrout to the set of components to be started by BIND 10. This pre-defined set does not commit the changes, so these modules do not show up for commands or configuration until the user enters config commit after execute init_authoritative_server. For example:
> execute init_authoritative_server
> execute file /tmp/example_commands
The optional argument show displays the exact set of commands that would be executed; for example:
> execute init_authoritative_server show
!echo adding Authoritative server component
config add /Init/components b10-auth
config set /Init/components/b10-auth/kind needed
config set /Init/components/b10-auth/special auth
!echo adding Xfrin component
config add /Init/components b10-xfrin
config set /Init/components/b10-xfrin/address Xfrin
config set /Init/components/b10-xfrin/kind dispensable
!echo adding Xfrout component
config add /Init/components b10-xfrout
config set /Init/components/b10-xfrout/address Xfrout
config set /Init/components/b10-xfrout/kind dispensable
!echo adding Zone Manager component
config add /Init/components b10-zonemgr
config set /Init/components/b10-zonemgr/address Zonemgr
config set /Init/components/b10-zonemgr/kind dispensable
!echo Components added. Please enter "config commit" to
!echo finalize initial setup and run the components.
        
The optional show argument may also be used when executing a script from a file; for example:
> execute file /tmp/example_commands show

8.7.1. Execute directives

Within sets of commands to be run with the execute command, a number of directives are supported:
!echo <string>
Prints the given string to bindctl's output.
!verbose on
Enables verbose mode; all following commands that are to be executed are also printed.
!verbose off
Disables verbose mode; following commands that are to be executed are no longer printed.

8.7.2. Notes on execute scripts

Within scripts, you can add or remove modules with the normal configuration commands for Init/components. However, as module configuration and commands do not show up until the module is running, it is currently not possible to add a module and set its configuration in one script. This will be addressed in the future, but for now the only option is to add and configure modules in separate commands and execute scripts.

Chapter 9. Common configuration elements

Some things are configured in the same or similar manner across many modules. So we show them here in one place.

9.1. TSIG keys

TSIG is a way to sign requests and responses in DNS. It is defined in RFC 2845 and uses symmetric cryptography to sign the DNS messages. If you want to make any use of TSIG (to authenticate transfers or DDNS, for example), you need to set up shared secrets between the endpoints.

BIND 10 uses a global key ring for the secrets. It doesn't currently mean they would be stored differently, they are just in one place of the configuration.

9.1.1. Key anatomy and syntax

Each key has three attributes. One is a name by which it is referred both in DNS packets and the rest of the configuration. Another is the algorithm used to compute the signature. And the last part is a base64 encoded secret, which might be any blob of data.

The parts are written into a string, concatenated together by colons. So if you wanted to have a key called "example.key", used as a HMAC-MD5 key with secret "secret", you'd write it as:

"example.key.:c2VjcmV0:hmac-md5"

The HMAC-MD5 algorithm is the default, so you can omit it. You could write the same key as:

"example.key.:c2VjcmV0"

You can also use these algorithms (which may not be omitted from the key definition if used):

  • hmac-sha1
  • hmac-sha224
  • hmac-sha256
  • hmac-sha384
  • hmac-sha512

The name of the key must be a valid DNS name.

9.1.2. Key ring

The key ring lives in the configuration in "tsig_keys/keys". Most of the system uses the keys from there — ACLs, authoritative server to sign responses to signed queries, and b10-xfrin and b10-xfrout to sign transfers.

The key ring is just a list of strings, each describing one key. So, to add a new key, you can do this:

> config add tsig_keys/keys "example.key.:c2VjcmV0"
> config show tsig_keys/keys
tsig_keys/keys[0]   "example.key.:c2VjcmV0" string  (modified)
> config commit

You can keep as many keys as you want in the key ring, but each must have a different name.

9.2. ACLs

An ACL, or Access Control List, is a way to describe if a request is allowed or disallowed. The principle is, there's a list of rules. Each rule is a name-value mapping (a dictionary, in the JSON terminology). Each rule must contain exactly one mapping called "action", which describes what should happen if the rule applies. There may be more mappings, called matches, which describe the conditions under which the rule applies.

When there's a query, the first rule is examined. If it matches, the action in it is taken. If not, next rule is examined. If there are no more rules to examine, a default action is taken.

There are three possible "action" values. The "ACCEPT" value means the query is handled. If it is "REJECT", the query is not answered, but a polite error message is sent back (if that makes sense in the context). The "DROP" action acts like a black hole. The query is not answered and no error message is sent.

If there are multiple matching conditions inside the rule, all of them must be satisfied for the rule to apply. This can be used, for example, to require the query to be signed by a TSIG key and originate from given address.

This is encoded in form of JSON. Semi-formal description could look something like this. It is described in more details below.

ACL := [ RULE, RULE, ... ]
RULE := { "action": "ACCEPT"|"REJECT"|"DROP", MATCH, MATCH, ... }
RULE_RAW := { MATCH, MATCH, ... }
MATCH := FROM_MATCH|KEY_MATCH|NOT_MATCH|OR_MATCH|AND_MATCH|...
FROM_MATCH := "from": [RANGE, RANGE, RANGE, ...] | RANGE
RANGE := "<ip range>"
KEY_MATCH := "key": [KEY, KEY, KEY, ...] | KEY
KEY := "<key name>"
NOT_MATCH := "NOT": RULE_RAW
OR_MATCH := "ANY": [ RULE_RAW, RULE_RAW, ... ]
AND_MATCH := "ALL": [ RULE_RAW, RULE_RAW, ... ]

9.2.1. Matching properties

The first thing you can check against is the source address of request. The name is from and the value is a string containing either a single IPv4 or IPv6 address, or a range in the usual slash notation (eg. "192.0.2.0/24").

The other is TSIG key by which the message was signed. The ACL contains only the name (under the name "key"), the key itself must be stored in the global key ring (see Section 9.1.2, “Key ring”). This property is applicable only to the DNS context.

More properties to match are planned — the destination address, ports, matches against the packet content.

9.2.2. More complicated matches

From time to time, you need to express something more complex than just a single address or key.

You can specify a list of values instead of single value. Then the property needs to match at least one of the values listed — so you can say "from": ["192.0.2.0/24", "2001:db8::/32"] to match any address in the ranges set aside for documentation. The keys or any future properties will work in a similar way.

If that is not enough, you can compose the matching conditions to logical expressions. They are called "ANY", "ALL" and "NOT". The "ANY" and "ALL" ones contain lists of subexpressions — each subexpression is a similar dictionary, just not containing the "action" element. The "NOT" contains single subexpression. Their function should be obvious — "NOT" matches if and only if the subexpression does not match. The "ALL" matches exactly when each of the subexpressions matches and "ANY" when at least one matches.

9.2.3. Examples

All the examples here is just the JSON representing the ACL, nicely formatted and split across lines. They are out of any surrounding context. This is similar to what you'd get from config show_json called on the entry containing the ACL.

In the first example, the ACL accepts queries from two known hosts. Each host has an IP addresses (both IPv4 and IPv6) and a TSIG key. Other queries are politely rejected. The last entry in the list has no conditions — making it match any query.

[
  {
    "from": ["192.0.2.1", "2001:db8::1"],
    "key": "first.key",
    "action": "ACCEPT"
  },
  {
    "from": ["192.0.2.2", "2001:db8::2"],
    "key": "second.key",
    "action": "ACCEPT"
  },
  {
    "action": "REJECT"
  }
]

Now we show two ways to accept only the queries from private ranges. This is the same as rejecting anything that is outside.

[
  {
    "from": [
      "10.0.0.0/8",
      "172.16.0.0/12",
      "192.168.0.0/16",
      "fc00::/7"
    ],
    "action": "ACCEPT"
  },
  {
    "action": "REJECT"
  }
]

[
  {
    "NOT": {
       "ANY": [
         {"from": "10.0.0.0/8"},
         {"from": "172.16.0.0/12"},
         {"from": "192.168.0.0/16"},
         {"from": "fc00::/7"}
       ]
    },
    "action": "REJECT"
  },
  {
    "action": "ACCEPT"
  }
]

9.2.4. Interaction with bindctl

Currently, bindctl has hard time coping with the variable nature of the ACL syntax. This technical limitation makes it impossible to edit parts of the entries. You need to set the whole entry at once, providing the whole JSON value.

This limitation is planned to be solved soon at least partially.

You'd do something like this to create the second example. Note that the whole JSON must be on a single line.

> config add somewhere/acl
> config set somewhere/acl[0] { "from": [ "10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16", "fc00::/7" ], "action": "ACCEPT" }
> config add somewhere/acl
> config set somewhere/acl[1] { "action": "REJECT" }
> config commit

Chapter 10. bind10 Control and Configuration

This chapter explains how to control and configure the b10-init parent. The startup of this resident process that runs the BIND 10 daemons is covered in Chapter 4, Starting BIND 10 with bind10.

10.1. Stopping bind10

The BIND 10 suite may be shut down by stopping the parent b10-init process. This may be done by running the Init shutdown command at the bindctl prompt.

10.2. Configuration to start processes

The processes to be used can be configured for b10-init to start, with the exception of the required b10-sockcreator, b10-msgq and b10-cfgmgr components. The configuration is in the Init/components section. Each element represents one component, which is an abstraction of a process.

To add a process to the set, let's say the resolver (which is not started by default), you would do this:

> config add Init/components b10-resolver
> config set Init/components/b10-resolver/special resolver
> config set Init/components/b10-resolver/kind needed
> config set Init/components/b10-resolver/priority 10
> config commit

Now, what it means. We add an entry called b10-resolver. It is both a name used to reference this component in the configuration and the name of the process to start. Then we set some parameters on how to start it.

The special setting is for components that need some kind of special care during startup or shutdown. Unless specified, the component is started in a usual way. This is the list of components that need to be started in a special way, with the value of special used for them:

Table 10.1. Special startup components

ComponentSpecialDescription
b10-authauthAuthoritative DNS server
b10-resolverresolverDNS resolver
b10-cmdctlcmdctlCommand control (remote control interface)


The kind specifies how a failure of the component should be handled. If it is set to dispensable (the default unless you set something else), it will get started again if it fails. If it is set to needed and it fails at startup, the whole b10-init shuts down and exits with an error exit code. But if it fails some time later, it is just started again. If you set it to core, you indicate that the system is not usable without the component and if such component fails, the system shuts down no matter when the failure happened. This is the behavior of the core components (the ones you can't turn off), but you can declare any other components as core as well if you wish (but you can turn these off, they just can't fail).

The priority defines order in which the components should start. The ones with higher numbers are started sooner than the ones with lower ones. If you don't set it, 0 (zero) is used as the priority. Usually, leaving it at the default is enough.

There are other parameters we didn't use in our example. One of them is address. It is the address used by the component on the b10-msgq message bus. The special components already know their address, but the usual ones don't. The address is by convention the thing after b10-, with the first letter capitalized (eg. b10-stats would have Stats as its address).

The last one is process. It is the name of the process to be started. It defaults to the name of the component if not set, but you can use this to override it. (The special components also already know their executable name.)

Note

The configuration is quite powerful, but that includes a lot of space for mistakes. You could turn off the b10-cmdctl, but then you couldn't change it back the usual way, as it would require it to be running (you would have to find and edit the configuration directly). Also, some modules might have dependencies: b10-stats-httpd needs b10-stats, b10-xfrout needs b10-auth to be running, etc.

In short, you should think twice before disabling something here.

It is possible to start some components multiple times (currently b10-auth and b10-resolver). You might want to do that to gain more performance (each one uses only single core). Just put multiple entries under different names, like this, with the same config:

> config add Init/components b10-resolver-2
> config set Init/components/b10-resolver-2/special resolver
> config set Init/components/b10-resolver-2/kind needed
> config commit

However, this is work in progress and the support is not yet complete. For example, each resolver will have its own cache, each authoritative server will keep its own copy of in-memory data and there could be problems with locking the sqlite database, if used. The configuration might be changed to something more convenient in future. Other components don't expect such a situation, so it would probably not do what you want. Such support is yet to be implemented.

The running processes started by b10-init may be listed by running Init show_processes using bindctl.

Chapter 11. Authoritative Server

The b10-auth is the authoritative DNS server. It supports EDNS0, DNSSEC, IPv6, and SQLite3 and in-memory zone data backends. Normally it is started by the b10-init master process.

11.1. Server Configurations

b10-auth is configured via the b10-cfgmgr configuration manager. The module name is Auth. The configuration data items are:

database_file
This is an optional string to define the path to find the SQLite3 database file. Note: This may be a temporary setting because the DNS server can use various data source backends.
datasources
datasources configures data sources. The list items include: type to define the required data source type (such as memory); class to optionally select the class (it defaults to IN); and zones to define the file path name, the filetype (sqlite3 to load from a SQLite3 database file or text to load from a master text file), and the origin (default domain). By default, this is empty.

Note

Currently this is only used for the memory data source. Only the IN class is supported at this time. By default, the memory data source is disabled. Also, currently the zone file must be canonical such as generated by named-compilezone -D, or must be an SQLite3 database.

listen_on
listen_on is a list of addresses and ports for b10-auth to listen on. The list items are the address string and port number. By default, b10-auth listens on port 53 on the IPv6 (::) and IPv4 (0.0.0.0) wildcard addresses.

Note

The default configuration is currently not appropriate for a multi-homed host. In case you have multiple public IP addresses, it is possible the query UDP packet comes through one interface and the answer goes out through another. The answer will probably be dropped by the client, as it has a different source address than the one it sent the query to. The client would fallback on TCP after several attempts, which works well in this situation, but is clearly not ideal.

There are plans to solve the problem such that the server handles it by itself. But until it is actually implemented, it is recommended to alter the configuration — remove the wildcard addresses and list all addresses explicitly. Then the server will answer on the same interface the request came on, preserving the correct address.

tcp_recv_timeout
tcp_recv_timeout is the timeout used on incoming TCP connections, in milliseconds. If the query is not sent within this time, the connection is closed. Setting this to 0 will disable TCP timeouts completely.

The configuration commands are:

loadzone
loadzone tells b10-auth to load or reload a zone file. The arguments include: class which optionally defines the class (it defaults to IN); origin is the domain name of the zone; and datasrc optionally defines the type of datasource (it defaults to memory).

Note

Currently this only supports the IN class and the memory data source.

getstats
getstats requests b10-auth to send its statistics data to b10-stats(8) as a response of the command.
shutdown
Stop the authoritative DNS server. This has an optional pid argument to select the process ID to stop. (Note that the BIND 10 init process may restart this service if configured.)

11.2. Data Source Backends

Bind 10 has the concept of data sources. A data source is a place where authoritative zone data reside and where they can be served from. This can be a master file, a database or something completely different.

Once a query arrives, b10-auth goes through a configured list of data sources and finds the one containing a best matching zone. From the equally good ones, the first one is taken. This data source is then used to answer the query.

Note

In the current release, b10-auth can serve data from a SQLite3 data source backend and from master files. Upcoming versions will be able to use multiple different data sources, such as MySQL and Berkeley DB.

The configuration is located in data_sources/classes. Each item there represents one RR class and a list used to answer queries for that class. The default contains two classes. The CH class contains a built-in data source — one that serves things like AUTHORS.BIND.. The IN class contains single SQLite3 data source with database file located at /usr/local/var/bind10/zone.sqlite3.

Each data source has several options. The first one is type, which specifies the type of data source to use. Valid types include the ones listed below, but BIND 10 uses dynamically loaded modules for them, so there may be more in your case. This option is mandatory.

Another option is params. This option is type specific; it holds different data depending on the type above. Also, depending on the type, it could be possible to omit it.

There are two options related to the so-called cache. If you enable cache, zone data from the data source are loaded into memory. Then, when answering a query, b10-auth looks into the memory only instead of the data source, which speeds answering up. The first option is cache-enable, a boolean value turning the cache on and off (off is the default). The second one, cache-zones, is a list of zone origins to load into in-memory.

11.2.1. Data source types

As mentioned, the type used by default is sqlite3. It has single configuration option inside paramsdatabase_file, which contains the path to the SQLite3 file containing the data.

Another type is called MasterFiles. This one is slightly special. The data are stored in RFC1034 master files. Because answering directly from them would be impractical, this type mandates the cache to be enabled. Also, the list of zones (cache-zones) should be omitted. The params is a dictionary mapping from zone origins to the files they reside in.

11.2.2. Examples

As this is one of the more complex configurations of BIND 10, we show some examples. They all assume they start with default configuration.

First, let's disable the built-in data source (VERSION.BIND and friends). As it is the only data source in the CH class, we can remove the whole class.

> config remove data_sources/classes CH
> config commit

Another one, let's say our default data source contains zones example.org. and example.net.. We want them to be served from memory to make the answering faster.

> config set data_sources/classes/IN[0]/cache-enable true
> config add data_sources/classes/IN[0]/cache-zones example.org.
> config add data_sources/classes/IN[0]/cache-zones example.net.
> config commit

Now every time the zone in the data source is changed by the operator, the authoritative server needs to be told to reload it, by

> Auth loadzone example.org

You don't need to do this when the zone is modified by b10-xfrin; it does so automatically.

Now, the last example is when there are master files we want to serve in addition to whatever is inside the SQLite3 database.

> config add data_sources/classes/IN
> config set data_sources/classes/IN[1]/type MasterFiles
> config set data_sources/classes/IN[1]/cache-enable true
> config set data_sources/classes/IN[1]/params { "example.org": "/path/to/example.org", "example.com": "/path/to/example.com" }
> config commit

Unfortunately, due to current technical limitations, the params must be set as one JSON blob. To reload a zone, use the same Auth loadzone command as above.

Initially, a map value has to be set, but this value may be an empty map. After that, key/value pairs can be added with config add and keys can be removed with config remove. The initial value may be an empty map, but it has to be set before zones are added or removed.

> config set data_sources/classes/IN[1]/params {}
> config add data_sources/classes/IN[1]/params another.example.org /path/to/another.example.org
> config add data_sources/classes/IN[1]/params another.example.com /path/to/another.example.com
> config remove data_sources/classes/IN[1]/params another.example.org
> config commit

Note

There's also Auth/database_file configuration variable, pointing to a SQLite3 database file. This is no longer used by b10-auth, but it is left in place for now, since other modules use it. Once b10-zonemgr, b10-xfrout and b10-ddns are ported to the new configuration, this will disappear. But for now, make sure that if you use any of these modules, the new and old configuration correspond. The defaults are consistent, so unless you tweaked either the new or the old configuration, you're good.

11.2.3. Adding a static data source

BIND 10 includes a zone file named static.zone in the CH (Chaos) class for providing information about the server via the AUTHORS.BIND and VERSION.BIND TXT records. By default, this BIND zone is configured and its records are served.

If you have removed this zone from the configuration (e.g., by using the commands in the previous section to disable the "built-in data source"), here is how you can add it back to serve the zones in the static.zone file.

First, add the CH class if it doesn't exist:

> config add data_sources/classes CH
> config commit

Then, add a data source of type MasterFiles in the CH class to serve the zones in static.zone:

> config add data_sources/classes/CH
> config set data_sources/classes/CH[0]/type MasterFiles
> config set data_sources/classes/CH[0]/cache-enable true
> config set data_sources/classes/CH[0]/params {"BIND": "/usr/local/bind10/share/bind10/static.zone"}
> config commit

Then, lookup the static data from static.zone to test it (assuming your authoritative server is running on localhost):

> dig @localhost -c CH -t TXT version.bind
> dig @localhost -c CH -t TXT authors.bind

11.3. Loading Master Zones Files

RFC 1035 style DNS master zone files may imported into a BIND 10 SQLite3 data source by using the b10-loadzone utility.

b10-loadzone supports the following special directives (control entries):

$INCLUDE
Loads an additional zone file. This may be recursive.
$ORIGIN
Defines the relative domain name.
$TTL
Defines the time-to-live value used for following records that don't include a TTL.

Note

In the current release, only the SQLite3 back end is used by b10-loadzone. Multiple zones are stored in a single SQLite3 zone database.

If you reload a zone already existing in the database, all records from that prior zone disappear and a whole new set appears.

Chapter 12. Incoming Zone Transfers

Incoming zones are transferred using the b10-xfrin process which is started by b10-init. When received, the zone is stored in the corresponding BIND 10 data source, and its records can be served by b10-auth. In combination with b10-zonemgr (for automated SOA checks), this allows the BIND 10 server to provide secondary service.

The b10-xfrin process supports both AXFR and IXFR.

12.1. Configuration for Incoming Zone Transfers

In order to enable incoming zone transfers for a secondary zone, you will first need to make the zone "exist" in some data source. One easy way to do this is to create an empty zone using the b10-loadzone utility. For example, this makes an empty zone (or empties any existing content of the zone) "example.com" in the default data source for b10-loadzone (which is SQLite3-based data source):

$ b10-loadzone -e example.com

Next, you need to specify a list of secondary zones to enable incoming zone transfers for these zones in most practical cases (you can still trigger a zone transfer manually, without a prior configuration (see below)).

For example, to enable zone transfers for a zone named "example.com" (whose master address is assumed to be 2001:db8::53 here), run the following at the bindctl prompt:

> config add Xfrin/zones
> config set Xfrin/zones[0]/name "example.com"
> config set Xfrin/zones[0]/master_addr "2001:db8::53"
> config commit

(We assume there has been no zone configuration before).

Note

There is a plan to revise overall zone management configuration (which are primary and secondary zones, which data source they are stored, etc) so it can be configured more consistently and in a unified way among various BIND 10 modules. When it's done, part or all of the initial configuration setup described in this section may be deprecated.

12.2. TSIG

If you want to use TSIG for incoming transfers, a system wide TSIG key ring must be configured (see Section 9.1.2, “Key ring”). To specify a key to use, set tsig_key value to the name of the key to use from the key ring. > config set Xfrin/zones[0]/tsig_key "example.key"

12.3. Control the use of IXFR

By default, b10-xfrin uses IXFR for transferring zones specified in the Xfrin/zones list of the configuration, unless it doesn't know the current SOA serial of the zone (including the case where the zone has never transferred or locally loaded), in which case it automatically uses AXFR. If the attempt of IXFR fails, b10-xfrin automatically retries the transfer using AXFR. In general, this works for any master server implementations including those that don't support IXFR and in any local state of the zone. So there should normally be no need to configure on whether to use IXFR.

In some cases, however, it may be desirable to specify how and whether to use IXFR and AXFR. The request_ixfr configuration item under Xfrin/zones can be used to control such policies. It can take the following values.

yes
This is the default behavior as described above.
no
Only use AXFR. Note that this value normally shouldn't be needed thanks to the automatic fallback from IXFR to IXFR. A possible case where this value needs to be used is that the master server has a bug and crashes if it receives an IXFR request.
only
Only use IXFR except when the current SOA serial is not known. This value has a severe drawback, that is, if the master server does not support IXFR zone transfers never succeed (except for the very first one, which will use AXFR), and the zone will eventually expire. Therefore it should not be used in general. Still, in some special cases the use of this value may make sense. For example, if the operator is sure that the master server supports IXFR and the zone is very large, they may want to avoid falling back to AXFR as it can be more expensive.

Note

There used to be a boolean configuration item named use_ixfr. It was deprecated for the finer control described above. The request_ixfr item should be used instead.

12.4. Secondary Manager

The b10-zonemgr process is started by b10-init. It keeps track of SOA refresh, retry, and expire timers and other details for BIND 10 to perform as a slave. When the b10-auth authoritative DNS server receives a NOTIFY message, b10-zonemgr may tell b10-xfrin to do a refresh to start an inbound zone transfer. The secondary manager resets its counters when a new zone is transferred in.

Note

Access control (such as allowing notifies) is not yet provided. The primary/secondary service is not yet complete.

The following example shows using bindctl to configure the server to be a secondary for the example zone:

> config add Zonemgr/secondary_zones
> config set Zonemgr/secondary_zones[0]/name "example.com"
> config commit

If the zone does not exist in the data source already (i.e. no SOA record for it), b10-zonemgr will automatically tell b10-xfrin to transfer the zone in.

12.5. Trigger an Incoming Zone Transfer Manually

To manually trigger a zone transfer to retrieve a remote zone, you may use the bindctl utility. For example, at the bindctl prompt run:

> Xfrin retransfer zone_name="foo.example.org" master=192.0.2.99

The retransfer command always uses AXFR. To use IXFR for a zone that has already been transferred once, use the refresh command. It honors the Xfrin/zones/request_ixfr configuration item (see Section 12.3, “Control the use of IXFR”.), and if it's configured to use IXFR, it will be used.

Both the retransfer and refresh commands can be used for an initial transfer before setting up secondary configurations. In this case AXFR will be used for the obvious reason.

12.6. Incoming Transfers with In-memory Datasource

In the case of an incoming zone transfer, the received zone is first stored in the corresponding BIND 10 datasource. In case the secondary zone is served by an in-memory datasource with an SQLite3 backend, b10-auth is automatically sent a loadzone command to reload the corresponding zone into memory from the backend.

The administrator doesn't have to do anything for b10-auth to serve the new version of the zone, except for the configuration such as the one described in Section 11.2, “Data Source Backends”.

Chapter 13. Outbound Zone Transfers

The b10-xfrout process is started by b10-init. When the b10-auth authoritative DNS server receives an AXFR or IXFR request, b10-auth internally forwards the request to b10-xfrout, which handles the rest of this request processing. This is used to provide primary DNS service to share zones to secondary name servers. The b10-xfrout is also used to send NOTIFY messages to secondary servers.

A global or per zone transfer_acl configuration can be used to control accessibility of the outbound zone transfer service. By default, b10-xfrout allows any clients to perform zone transfers for any zones.

> config show Xfrout/transfer_acl
Xfrout/transfer_acl[0]	{"action": "ACCEPT"}	any	(default)

If you want to require TSIG in access control, a system wide TSIG key ring must be configured (see Section 9.1.2, “Key ring”). In this example, we allow client matching both the IP address and key.

> config set tsig_keys/keys ["key.example:<base64-key>"]
> config set Xfrout/zone_config[0]/transfer_acl [{"action": "ACCEPT", "from": "192.0.2.1", "key": "key.example"}]
> config commit

Both b10-xfrout and b10-auth will use the system wide key ring to check TSIGs in the incoming messages and to sign responses.

For further details on ACL configuration, see Section 9.2, “ACLs”.

Note

The way to specify zone specific configuration (ACLs, etc) is likely to be changed.

Chapter 14. Dynamic DNS Update

BIND 10 supports the server side of the Dynamic DNS Update (DDNS) protocol as defined in RFC 2136. This service is provided by the b10-ddns component, which is started by the b10-init process if configured so.

When the b10-auth authoritative DNS server receives an UPDATE request, it internally forwards the request to b10-ddns, which handles the rest of this request processing. When the processing is completed, b10-ddns will send a response to the client as specified in RFC 2136 (NOERROR for successful update, REFUSED if rejected due to ACL check, etc). If the zone has been changed as a result, it will internally notify b10-xfrout so that other secondary servers will be notified via the DNS NOTIFY protocol. In addition, if b10-auth serves the updated zone (as described in Section 11.2, “Data Source Backends”), b10-ddns will also notify b10-auth so that b10-auth will re-cache the updated zone content if necessary.

The b10-ddns component supports requests over both UDP and TCP, and both IPv6 and IPv4; for TCP requests, however, it terminates the TCP connection immediately after each single request has been processed. Clients cannot reuse the same TCP connection for multiple requests. (This is a current implementation limitation of b10-ddns. While RFC 2136 doesn't specify anything about such reuse of TCP connection, there is no reason for disallowing it as RFC 1035 generally allows multiple requests sent over a single TCP connection. BIND 9 supports such reuse.)

As of this writing b10-ddns does not support update forwarding for secondary zones. If it receives an update request for a secondary zone, it will immediately return a not implemented response.

Note

For feature completeness, update forwarding should be eventually supported. But currently it's considered a lower priority task and there is no specific plan of implementing this feature.

14.1. Enabling Dynamic Update

First off, it must be made sure that a few components on which b10-ddns depends are configured to run, which are b10-auth and b10-zonemgr. In addition, b10-xfrout should also be configured to run; otherwise the notification after an update (see above) will fail with a timeout, suspending the DDNS service while b10-ddns waits for the response (see the description of the DDNS_UPDATE_NOTIFY_FAIL log message for further details). If BIND 10 is already configured to provide authoritative DNS service they should normally be configured to run already.

Second, for the obvious reason dynamic update requires that the underlying data source storing the zone data be writable. In the current implementation this means the zone must be stored in an SQLite3-based data source. Also, in this current version, the b10-ddns component configures itself with the data source referring to the database_file configuration parameter of b10-auth. So this information must be configured correctly before starting b10-ddns.

Note

The way to configure data sources is now being revised. Configuration on the data source for DDNS will be very likely to be changed in a backward incompatible manner in a near future version.

In general, if something goes wrong regarding the dependency described above, b10-ddns will log the related event at the warning or error level. It's advisable to check the log message when you first enable DDNS or if it doesn't work as you expect to see if there's any warning or error log message.

Next, to enable the DDNS service, b10-ddns needs to be explicitly configured to run. It can be done by using the bindctl utility. For example:

> config add Init/components b10-ddns
> config set Init/components/b10-ddns/address DDNS
> config set Init/components/b10-ddns/kind dispensable
> config commit

Note

In theory kind could be omitted because "dispensable" is its default. But there's some peculiar behavior (which should be a bug and should be fixed eventually; see Trac ticket #2064) with bindctl and you'll still need to specify that explicitly. Likewise, address may look unnecessary because b10-ddns would start and work without specifying it. But for it to shutdown gracefully this parameter should also be specified.

14.2. Access Control

By default, b10-ddns rejects any update requests from any clients by returning a REFUSED response. To allow updates to take effect, an access control rule (called update ACL) with a policy allowing updates must explicitly be configured. Update ACL must be configured per zone basis in the zones configuration parameter of b10-ddns. This is a list of per-zone configurations regarding DDNS. Each list element consists of the following parameters:

origin
The zone's origin name
class
The RR class of the zone (normally IN, and in that case can be omitted in configuration)
update_acl
List of access control rules (ACL) for the zone

The syntax of the ACL is the same as ACLs for other components. Specific examples are given below.

In general, an update ACL rule that allows an update request should be configured with a TSIG key. This is an example update ACL that allows updates to the zone named example.org (of default RR class IN) from clients that send requests signed with a TSIG whose key name is "key.example.org" (and refuses all others):

> config add DDNS/zones
> config set DDNS/zones[0]/origin example.org
> config add DDNS/zones[0]/update_acl {"action": "ACCEPT", "key": "key.example.org"}
> config commit

The TSIG key must be configured system wide (see Section 9.1, “TSIG keys”).

The full description of ACLs can be found in Section 9.2, “ACLs”.

Note

The b10-ddns component accepts an ACL rule that just allows updates from a specific IP address (i.e., without requiring TSIG), but this is highly discouraged (remember that requests can be made over UDP and spoofing the source address of a UDP packet is often pretty easy). Unless you know what you are doing and that you can accept its consequence, any update ACL rule that allows updates should have a TSIG key in its constraints.

Currently update ACL can only control updates per zone basis; it's not possible to specify access control with higher granularity such as for particular domain names or specific types of RRs.

Note

Contrary to what RFC 2136 (literally) specifies, b10-ddns checks the update ACL before checking the prerequisites of the update request. This is a deliberate implementation decision. This counter intuitive specification has been repeatedly discussed among implementers and in the IETF, and it is now widely agreed that it does not make sense to strictly follow that part of RFC. One known specific bad result of following the RFC is that it could leak information about which name or record exists or does not exist in the zone as a result of prerequisite checks even if a zone is somehow configured to reject normal queries from arbitrary clients. There have been other troubles that could have been avoided if the ACL could be checked before the prerequisite check.

14.3. Miscellaneous Operational Issues

Unlike BIND 9, BIND 10 currently does not support automatic re-signing of DNSSEC-signed zone when it's updated via DDNS. It could be possible to re-sign the updated zone afterwards or make sure the update request also updates related DNSSEC records, but that will be pretty error-prone operation. In general, it's not advisable to allow DDNS for a signed zone at this moment.

Also unlike BIND 9, it's currently not possible to freeze a zone temporarily in order to suspend DDNS while you manually update the zone. If you need to make manual updates to a dynamic zone, you'll need to temporarily reject any updates to the zone via the update ACLs.

Dynamic updates are only applicable to primary zones. In order to avoid updating secondary zones via DDNS requests, b10-ddns refers to the secondary_zones configuration of b10-zonemgr. Zones listed in secondary_zones will never be updated via DDNS regardless of the update ACL configuration; b10-ddns will return a NOTAUTH (server not authoritative for the zone) response. If you have a "conceptual" secondary zone whose content is a copy of some external source but is not updated via the standard zone transfers and therefore not listed in secondary_zones, be careful not to allow DDNS for the zone; it would be quite likely to lead to inconsistent state between different servers. Normally this should not be a problem because the default update ACL rejects any update requests, but you may want to take an extra care about the configuration if you have such type of secondary zones.

The difference of two versions of a zone, before and after a DDNS transaction, is automatically recorded in the underlying data source, and can be retrieved in the form of outbound IXFR. This is done automatically; it does not require specific configuration to make this possible.

Chapter 15. Recursive Name Server

Note

The b10-resolver is an experimental proof of concept.

The b10-resolver daemon provides an iterative caching and forwarding DNS server. The process is started by b10-init.

The main b10-init process can be configured to select to run either the authoritative or resolver or both. By default, it doesn't start either one. You may change this using bindctl, for example:

> config add Init/components b10-resolver
> config set Init/components/b10-resolver/special resolver
> config set Init/components/b10-resolver/kind needed
> config set Init/components/b10-resolver/priority 10
> config commit

The master b10-init process will stop and start the desired services.

By default, the resolver listens on port 53 for 127.0.0.1 and ::1. The following example shows how it can be configured to listen on an additional address (and port):

> config add Resolver/listen_on
> config set Resolver/listen_on[2]/address "192.168.1.1"
> config set Resolver/listen_on[2]/port 53
> config commit

(Replace the 2 as needed; run config show Resolver/listen_on if needed.)

15.1. Access Control

By default, the b10-resolver daemon only accepts DNS queries from the localhost (127.0.0.1 and ::1). The Resolver/query_acl configuration may be used to reject, drop, or allow specific IPs or networks. See Section 9.2, “ACLs”.

The following session is an example of extending the ACL to also allow queries from 192.0.2.0/24:

> config show Resolver/query_acl
Resolver/query_acl[0]   {"action": "ACCEPT", "from": "127.0.0.1"}   any (default)
Resolver/query_acl[1]   {"action": "ACCEPT", "from": "::1"} any (default)
> config add Resolver/query_acl
> config set Resolver/query_acl[2] {"action": "ACCEPT", "from": "192.0.2.0/24"}
> config add Resolver/query_acl
> config show Resolver/query_acl
Resolver/query_acl[0]   {"action": "ACCEPT", "from": "127.0.0.1"}   any (modified)
Resolver/query_acl[1]   {"action": "ACCEPT", "from": "::1"} any (modified)
Resolver/query_acl[2]   {"action": "ACCEPT", "from": "192.0.2.0/24"}  any (modified)
Resolver/query_acl[3]   {"action": "REJECT"}    any (modified)
> config commit

Note that we didn't set the value of the last final rule (query_acl[3]) -- in the case of resolver, rejecting all queries is the default value of a new rule. In fact, this rule can even be omitted completely, as the default, when a query falls off the list, is rejection.

15.2. Forwarding

To enable forwarding, the upstream address and port must be configured to forward queries to, such as:

> config set Resolver/forward_addresses [{ "address": "192.168.1.1", "port": 53 }]
> config commit

(Replace 192.168.1.1 to point to your full resolver.)

Normal iterative name service can be re-enabled by clearing the forwarding address(es); for example:

> config set Resolver/forward_addresses []
> config commit

Chapter 16. DHCP

The Dynamic Host Configuration Protocol for IPv4 (DHCP or DHCPv4) and Dynamic Host Configuration Protocol for IPv6 (DHCPv6) are protocols that allow one node (server) to provision configuration parameters to many hosts and devices (clients). To ease deployment in larger networks, additional nodes (relays) may be deployed that facilitate communication between servers and clients. Even though principles of both DHCPv4 and DHCPv6 are somewhat similar, these are two radically different protocols. BIND 10 offers two server implementations, one for DHCPv4 and one for DHCPv6. The DHCP part of the BIND 10 project is codenamed Kea. The DHCPv4 component is colloquially referred to as Kea4 and its DHCPv6 counterpart is called Kea6.

In addition to providing lease management services, both Kea4 and Kea6 can provide dynamic DNS (DDNS) updates driven by the lease changes they make. These updates are carried out with the assistance of the DHCP-DDNS server, colloquially referred to as D2. When configured to do so, Kea servers will notify D2 of lease changes. D2 will match them to the appropriate DNS servers and instruct those severs to add or delete the requisite DNS entries.

This chapter covers those parts of BIND 10 that are common to both servers. DHCPv4-specific details are covered in Chapter 17, The DHCPv4 Server, while those details specific to DHCPv6 are described in Chapter 18, The DHCPv6 Server. The DHCP-DDNS server details are covered in Chapter 19, The DHCP-DDNS Server

Note

In this release of BIND 10, the DHCPv4 and DHCPv6 servers must be considered experimental.

16.1. DHCP Database Installation and Configuration

BIND 10 DHCP stores its leases in a lease database. The software has been written in a way that makes it possible to choose which database product should be used to store the lease information. At present, Kea supports 3 database backends: MySQL, PostgreSQL and memfile. To limit external dependencies, both MySQL and PostgreSQL support are disabled by default and only memfile (which is implemented in pure C++) is available. Support for a given database backend must be explicitly included when BIND 10 is built. This section covers the building of BIND 10 with MySQL and/or PostgreSQL and the creation of the lease database.

16.1.1. Building with MySQL support

Install MySQL according to the instructions for your system. The client development libraries must be installed.

Build and install BIND 10 as described in Chapter 3, Installation, with the following modification: to enable the MySQL database code, at the "configure" step (see Section 3.4.3, “Configure before the build”), specify the location of the MySQL configuration program "mysql_config" with the "--with-dhcp-mysql" switch, i.e.

./configure [other-options] --with-dhcp-mysql

...if MySQL was installed in the default location, or:

./configure [other-options] --with-dhcp-mysql=path-to-mysql_config

...if not.

16.1.2. Create MySQL Database and Kea User

The next task is to create both the lease database and the user under which the servers will access it. A number of steps are required:

1. Log into MySQL as "root":

$ mysql -u root -p
Enter password:
   :
mysql>

2. Create the database:

mysql> CREATE DATABASE database-name;

... database-name is the name you have chosen for the database.

3. Create the database tables:

mysql> CONNECT database-name;
mysql> SOURCE path-to-bind10/share/bind10/dhcpdb_create.mysql

4. Create the user under which BIND 10 will access the database (and give it a password), then grant it access to the database tables:

mysql> CREATE USER 'user-name'@'localhost' IDENTIFIED BY 'password';
mysql> GRANT ALL ON database-name.* TO 'user-name'@'localhost';

5. Exit MySQL:

mysql> quit
Bye
$

16.1.3. Building with PostgreSQL support

Install PostgreSQL according to the instructions for your system. The client development libraries must be installed. Client development libraries are often packaged as "libpq".

Build and install BIND 10 as described in Chapter 3, Installation, with the following modification: to enable the PostgreSQL database code, at the "configure" step (see Section 3.4.3, “Configure before the build”), specify the location of the PostgreSQL configuration program "pg_config" with the "--with-dhcp-pgsql" switch, i.e.

./configure [other-options] --with-dhcp-pgsql

...if Postgresql was installed in the default location, or:

./configure [other-options] --with-dhcp-pgsql=path-to-pg_config

...if not.

16.1.4. Create PostgreSQL Database and Kea User

The next task is to create both the lease database and the user under which the servers will access it. A number of steps are required:

1. Log into PostgreSQL as "root":

$ sudo -u postgres psql postgres
Enter password:
   :
postgres=#

2. Create the database:

postgres=# CREATE DATABASE database-name;
CREATE DATABASE
postgres=#

... database-name is the name you have chosen for the database.

3. Create the user under which Kea will access the database (and give it a password), then grant it access to the database:

postgres=# CREATE USER user-name WITH PASSWORD 'password';
CREATE ROLE
postgres=#
postgres=# GRANT ALL PRIVILEGES ON DATABASE database-name TO user-name;
GRANT
postgres=#

4. Exit PostgreSQL:

postgres=# \q
Bye
$

5. Create the database tables using the new user's credentials. After entering the following command, you will be prompted for the new user's password. When the command completes you will be returned to the shell prompt. You should see output similiar to following:

$ psql -d database-name -U user-name -f path-to-bind10/share/bind10/dhcpdb_create.pgsql
Password for user user-name:
CREATE TABLE
CREATE INDEX
CREATE INDEX
CREATE TABLE
CREATE INDEX
CREATE TABLE
START TRANSACTION
INSERT 0 1
INSERT 0 1
INSERT 0 1
COMMIT
CREATE TABLE
START TRANSACTION
INSERT 0 1
COMMIT
$

If instead you encounter an error such as shown below:

psql: FATAL:  no pg_hba.conf entry for host "[local]", user "user-name", database "database-name", SSL off

This indicates that the Postgresql configuration needs to be modified. Kea uses password authentication when connecting to the database and must have the appropriate entries added to Posgresql's pg_hba.conf file. This file is normally located in the primary data directory for your Postgresql server. The precise path may vary but the default location for Postgres 9.3 on Centos 6.5 is: /var/lib/pgsql/9.3/data/pg_hba.conf. Assuming Kea is running on the same host as Postgresql, adding lines similiar to following should be sufficient to provide password-authenticated access to Kea's database:

local   database-name    user-name                                 password
host    database-name    user-name          127.0.0.1/32           password
host    database-name    user-name          ::1/128                password

Please consult your PostgreSQL user manual before making these changes as they may expose your other databases that you run on the same system.

Chapter 17. The DHCPv4 Server

17.1. Starting and Stopping the DHCPv4 Server

b10-dhcp4 is the BIND 10 DHCPv4 server and, like other parts of BIND 10, is configured through the bindctl program.

After starting BIND 10 and entering bindctl, the first step in configuring the server is to add it to the list of running BIND 10 services.

> config add Init/components b10-dhcp4
> config set Init/components/b10-dhcp4/kind dispensable
> config commit

To remove b10-dhcp4 from the set of running services, the b10-dhcp4 is removed from list of Init components:

> config remove Init/components b10-dhcp4
> config commit

Note that the server was only removed from the list, so BIND10 will not restart it, but the server itself is still running. Hence it is usually desired to stop it:

> Dhcp4 shutdown

On start-up, the server will detect available network interfaces and will attempt to open UDP sockets on all interfaces that are up, running, are not loopback, and have IPv4 address assigned. The server will then listen to incoming traffic. Currently supported client messages are DISCOVER and REQUEST. The server will respond to them with OFFER and ACK, respectively. Since the DHCPv4 server opens privileged ports, it requires root access. Make sure you run this daemon as root.

17.2. Configuring the DHCPv4 Server

Once the server is started, it can be configured. To view the current configuration, use the following command in bindctl:

> config show Dhcp4

When starting the DHCPv4 daemon for the first time, the default configuration will be available. It will look similar to this:

> config show Dhcp4
Dhcp4/hooks-libraries	[]	list	(default)
Dhcp4/interfaces/	list
Dhcp4/renew-timer	1800	integer
Dhcp4/rebind-timer	2000	integer	(default)
Dhcp4/valid-lifetime	4000	integer	(default)
Dhcp4/next-server	""	string	(default)
Dhcp4/echo-client-id	true	boolean	(default)
Dhcp4/option-def	[]	list	(default)
Dhcp4/option-data	[]	list	(default)
Dhcp4/lease-database/type	""	string	(default)
Dhcp4/lease-database/name	""	string	(default)
Dhcp4/lease-database/user	""	string	(default)
Dhcp4/lease-database/host	""	string	(default)
Dhcp4/lease-database/password	""	string	(default)
Dhcp4/subnet4/	list
Dhcp4/dhcp-ddns/enable-updates	true	boolean
Dhcp4/dhcp-ddns/server-ip	"127.0.0.1"	string
Dhcp4/dhcp-ddns/server-port	53001	integer
Dhcp4/dhcp-ddns/ncr-protocol	"UDP"	string
Dhcp4/dhcp-ddns/ncr-format	"JSON"	string
Dhcp4/dhcp-ddns/override-no-update	false	boolean
Dhcp4/dhcp-ddns/override-client-update	false	boolean
Dhcp4/dhcp-ddns/replace-client-name	false	boolean
Dhcp4/dhcp-ddns/generated-prefix	"myhost"	string
Dhcp4/dhcp-ddns/qualifying-suffix	"example.com"	string

To change one of the parameters, simply follow the usual bindctl procedure. For example, to make the leases longer, change their valid-lifetime parameter:

> config set Dhcp4/valid-lifetime 7200
> config commit

Please note that most Dhcp4 parameters are of global scope and apply to all defined subnets, unless they are overridden on a per-subnet basis.

17.2.1. Default storage for leases

The server is able to store lease data in different repositories. Larger deployments may elect to store leases in a database. Section 17.2.2, “Database Configuration” describes one way to do it. By default, the server will use a CSV file rather than a database to store lease information. One of the advantages of using a file is that it eliminates dependency on third party database software.

The configuration of the file backend (Memfile) is controlled through the Dhcp4/lease-database parameters. When default parameters are used, the Memfile backend will write leases to a disk in the [bind10-install-dir]/var/bind10/kea-leases4.csv.

It is possible to alter the default location of the lease file. The following configuration:

> config set Dhcp4/lease-database/type "memfile"
> config set Dhcp4/lease-database/persist true
> config set Dhcp4/lease-database/name "/tmp/kea-leases4.csv"
> config commit

will change the default location of the lease file to /tmp/kea-leases4.csv.

The "persist" parameter controls whether the leases are written to disk. It is strongly recommended that this parameter is set to "true" at all times during the normal operation of the server

17.2.2. Database Configuration

All leases issued by the server are stored in the lease database. Currently there are 3 database backends available: MySQL, PostgreSQL and memfile. [1], and so the server must be configured to access the correct database with the appropriate credentials.

Note

Database access information must be configured for the DHCPv4 server, even if it has already been configured for the DHCPv6 server. The servers store their information independently, so each server can use a separate database or both servers can use the same database.

Database configuration is controlled through the Dhcp4/lease-database parameters. The type of the database must be set to "mysql", "postgresql" or "memfile":

> config set Dhcp4/lease-database/type "mysql"

Next, the name of the database is to hold the leases must be set: this is the name used when the lease database was created (see Section 16.1.2, “Create MySQL Database and Kea User” or Section 16.1.4, “Create PostgreSQL Database and Kea User”).

> config set Dhcp4/lease-database/name "database-name"

If the database is located on a different system to the DHCPv4 server, the database host name must also be specified (although note that this configuration may have a severe impact on server performance):

> config set Dhcp4/lease-database/host "remote-host-name"

The usual state of affairs will be to have the database on the same machine as the DHCPv4 server. In this case, set the value to the empty string (this is the default):

> config set Dhcp4/lease-database/host ""

Finally, the credentials of the account under which the server will access the database should be set:

> config set Dhcp4/lease-database/user "user-name"
> config set Dhcp4/lease-database/password "password"

If there is no password to the account, set the password to the empty string "". (This is also the default.)

Note

The password is echoed when entered and is stored in clear text in the BIND 10 configuration database. Improved password security will be added in a future version of BIND 10 DHCP

17.2.3. Interface selection

When DHCPv4 server starts up, by default it will listen to the DHCP traffic and respond to it on all interfaces detected during startup. However, in many cases it is desired to configure the server to listen and respond on selected interfaces only. The sample commands in this section show how to make interface selection using bindctl.

The default configuration can be presented with the following command:

> config show Dhcp4/interfaces
Dhcp4/interfaces[0] "*" string

An asterisk sign plays a role of the wildcard and means "listen on all interfaces".

In order to override the default configuration, the existing entry can be replaced with the actual interface name:

> config set Dhcp4/interfaces[0] eth1
> config commit

Other interface names can be added on one-by-one basis:

> config add Dhcp4/interfaces eth2
> config commit

Configuration will now contain two interfaces which can be presented as follows:

> config show Dhcp4/interfaces
Dhcp4/interfaces[0]	"eth1"	string
Dhcp4/interfaces[1]	"eth2"	string

When configuration gets committed, the server will start to listen on eth1 and eth2 interfaces only.

It is possible to use wildcard interface name (asterisk) concurrently with explicit interface names:

> config add Dhcp4/interfaces *
> config commit

This will result in the following configuration:

> config show Dhcp4/interfaces
Dhcp4/interfaces[0]	"eth1"	string
Dhcp4/interfaces[1]	"eth2"	string
Dhcp4/interfaces[2]	"*"	string

The presence of the wildcard name implies that server will listen on all interfaces. In order to fall back to the previous configuration when server listens on eth1 and eth2:

> config remove Dhcp4/interfaces[2]
> config commit

17.2.4. IPv4 Subnet Identifier

Subnet identifier is a unique number associated with a particular subnet. In principle, it is used to associate clients' leases with respective subnets. When subnet identifier is not specified for a subnet being configured, it will be automatically assigned by the configuration mechanism. The identifiers are assigned from 1 and are monotonically increased for each subsequent subnet: 1, 2, 3 ....

If there are multiple subnets configured with auto-generated identifiers and one of them is removed, the subnet identifiers may be renumbered. For example: if there are 4 subnets and 3rd is removed the last subnet will be assigned identifier that the 3rd subnet had before removal. As a result, the leases stored in the lease database for subnet 3 are now associated with the subnet 4, which may have unexpected consequences. In the future it is planned to implement the mechanism to preserve auto-generated subnet ids upon removal of one of the subnets. Currently, the only remedy for this issue is to manually specify the unique subnet identifier for each subnet.

The following configuration:

> config add Dhcp4/subnet4
> config set Dhcp4/subnet4[0]/subnet "192.0.2.0/24"
> config set Dhcp4/subnet4[0]/id 1024
> config commit
        

will assign the arbitrary subnet identifier to the newly configured subnet. This identifier will not change for this subnet until "id" parameter is removed or set to 0. The value of 0 forces auto-generation of subnet identifier.

17.2.5. Configuration of IPv4 Address Pools

The essential role of DHCPv4 server is address assignment. The server has to be configured with at least one subnet and one pool of dynamic addresses to be managed. For example, assume that the server is connected to a network segment that uses the 192.0.2.0/24 prefix. The Administrator of that network has decided that addresses from range 192.0.2.10 to 192.0.2.20 are going to be managed by the Dhcp4 server. Such a configuration can be achieved in the following way:

> config add Dhcp4/subnet4
> config set Dhcp4/subnet4[0]/subnet "192.0.2.0/24"
> config set Dhcp4/subnet4[0]/pool [ "192.0.2.10 - 192.0.2.20" ]
> config commit

Note that subnet is defined as a simple string, but the pool parameter is actually a list of pools: for this reason, the pool definition is enclosed in square brackets, even though only one range of addresses is specified.

It is possible to define more than one pool in a subnet: continuing the previous example, further assume that 192.0.2.64/26 should be also be managed by the server. It could be written as 192.0.2.64 to 192.0.2.127. Alternatively, it can be expressed more simply as 192.0.2.64/26. Both formats are supported by Dhcp4 and can be mixed in the pool list. For example, one could define the following pools:

> config set Dhcp4/subnet4[0]/pool [ "192.0.2.10-192.0.2.20", "192.0.2.64/26" ]
> config commit

The number of pools is not limited, but for performance reasons it is recommended to use as few as possible. Space and tabulations in pool definitions are ignored, so spaces before and after hyphen are optional. They can be used to improve readability.

The server may be configured to serve more than one subnet. To add a second subnet, use a command similar to the following:

> config add Dhcp4/subnet4
> config set Dhcp4/subnet4[1]/subnet "192.0.3.0/24"
> config set Dhcp4/subnet4[1]/pool [ "192.0.3.0/24" ]
> config commit

Arrays are counted from 0. subnet[0] refers to the subnet defined in the previous example. The config add Dhcp4/subnet4 command adds another (second) subnet. It can be referred to as Dhcp4/subnet4[1]. In this example, we allow server to dynamically assign all addresses available in the whole subnet.

When configuring a DHCPv4 server using prefix/length notation, please pay attention to the boundary values. When specifying that the server should use a given pool, it will be able to allocate also first (typically network address) and the last (typically broadcast address) address from that pool. In the aforementioned example of pool 192.0.3.0/24, both 192.0.3.0 and 192.0.3.255 addresses may be assigned as well. This may be invalid in some network configurations. If you want to avoid this, please use the "min-max" notation.

17.2.6. Standard DHCPv4 options

One of the major features of DHCPv4 server is to provide configuration options to clients. Although there are several options that require special behavior, most options are sent by the server only if the client explicitly requested them. The following example shows how to configure DNS servers, which is one of the most frequently used options. Options specified in this way are considered global and apply to all configured subnets.

> config add Dhcp4/option-data
> config set Dhcp4/option-data[0]/name "domain-name-servers"
> config set Dhcp4/option-data[0]/code 6
> config set Dhcp4/option-data[0]/space "dhcp4"
> config set Dhcp4/option-data[0]/csv-format true
> config set Dhcp4/option-data[0]/data "192.0.3.1, 192.0.3.2"
> config commit

The first line creates new entry in option-data table. It contains information on all global options that the server is supposed to configure in all subnets. The second line specifies option name. For a complete list of currently supported names, see Table 17.1, “List of standard DHCPv4 options” below. The third line specifies option code, which must match one of the values from that list. Line 4 specifies option space, which must always be set to "dhcp4" as these are standard DHCPv4 options. For other option spaces, including custom option spaces, see Section 17.2.9, “Nested DHCPv4 options (custom option spaces)”. The fifth line specifies the format in which the data will be entered: use of CSV (comma separated values) is recommended. The sixth line gives the actual value to be sent to clients. Data is specified as a normal text, with values separated by commas if more than one value is allowed.

Options can also be configured as hexadecimal values. If csv-format is set to false, option data must be specified as a hex string. The following commands configure the domain-name-servers option for all subnets with the following addresses: 192.0.3.1 and 192.0.3.2. Note that csv-format is set to false.

> config add Dhcp4/option-data
> config set Dhcp4/option-data[0]/name "domain-name-servers"
> config set Dhcp4/option-data[0]/code 6
> config set Dhcp4/option-data[0]/space "dhcp4"
> config set Dhcp4/option-data[0]/csv-format false
> config set Dhcp4/option-data[0]/data "C0 00 03 01 C0 00 03 02"
> config commit
        

It is possible to override options on a per-subnet basis. If clients connected to most of your subnets are expected to get the same values of a given option, you should use global options: you can then override specific values for a small number of subnets. On the other hand, if you use different values in each subnet, it does not make sense to specify global option values (Dhcp4/option-data), rather you should set only subnet-specific values (Dhcp4/subnet[X]/option-data[Y]).

The following commands override the global DNS servers option for a particular subnet, setting a single DNS server with address 192.0.2.3.

> config add Dhcp4/subnet4[0]/option-data
> config set Dhcp4/subnet4[0]/option-data[0]/name "domain-name-servers"
> config set Dhcp4/subnet4[0]/option-data[0]/code 6
> config set Dhcp4/subnet4[0]/option-data[0]/space "dhcp4"
> config set Dhcp4/subnet4[0]/option-data[0]/csv-format true
> config set Dhcp4/subnet4[0]/option-data[0]/data "192.0.2.3"
> config commit

Note

In a future version of Kea, it will not be necessary to specify the option code, space and csv-format fields as they will be set automatically.

The currently supported standard DHCPv4 options are listed in Table 17.1, “List of standard DHCPv4 options” and Table 17.2, “List of standard DHCPv4 options (continued)”. The "Name" and "Code" are the values that should be used as a name in the option-data structures. "Type" designates the format of the data: the meanings of the various types is given in Table 17.3, “List of standard DHCP option types”.

Some options are designated as arrays, which means that more than one value is allowed in such an option. For example the option time-servers allows the specification of more than one IPv4 address, so allowing clients to obtain the the addresses of multiple NTP servers.

The Section 17.2.7, “Custom DHCPv4 options” describes the configuration syntax to create custom option definitions (formats). It is generally not allowed to create custom definitions for standard options, even if the definition being created matches the actual option format defined in the RFCs. There is an exception from this rule for standard options for which Kea does not provide a definition yet. In order to use such options, a server administrator must create a definition as described in Section 17.2.7, “Custom DHCPv4 options” in the 'dhcp4' option space. This definition should match the option format described in the relevant RFC but configuration mechanism would allow any option format as it has no means to validate it at the moment.

Table 17.1. List of standard DHCPv4 options

NameCodeTypeArray?
subnet-mask1ipv4-addressfalse
time-offset2int32false
routers3ipv4-addresstrue
time-servers4ipv4-addresstrue
name-servers5ipv4-addressfalse
domain-name-servers6ipv4-addresstrue
log-servers7ipv4-addresstrue
cookie-servers8ipv4-addresstrue
lpr-servers9ipv4-addresstrue
impress-servers10ipv4-addresstrue
resource-location-servers11ipv4-addresstrue
host-name12stringfalse
boot-size13uint16false
merit-dump14stringfalse
domain-name15fqdnfalse
swap-server16ipv4-addressfalse
root-path17stringfalse
extensions-path18stringfalse
ip-forwarding19booleanfalse
non-local-source-routing20booleanfalse
policy-filter21ipv4-addresstrue
max-dgram-reassembly22uint16false
default-ip-ttl23uint8false
path-mtu-aging-timeout24uint32false
path-mtu-plateau-table25uint16true
interface-mtu26uint16false
all-subnets-local27booleanfalse
broadcast-address28ipv4-addressfalse
perform-mask-discovery29booleanfalse
mask-supplier30booleanfalse
router-discovery31booleanfalse
router-solicitation-address32ipv4-addressfalse
static-routes33ipv4-addresstrue
trailer-encapsulation34booleanfalse
arp-cache-timeout35uint32false
ieee802-3-encapsulation36booleanfalse
default-tcp-ttl37uint8false
tcp-keepalive-internal38uint32false
tcp-keepalive-garbage39booleanfalse


Table 17.2. List of standard DHCPv4 options (continued)

NameCodeTypeArray?
nis-domain40stringfalse
nis-servers41ipv4-addresstrue
ntp-servers42ipv4-addresstrue
vendor-encapsulated-options43emptyfalse
netbios-name-servers44ipv4-addresstrue
netbios-dd-server45ipv4-addresstrue
netbios-node-type46uint8false
netbios-scope47stringfalse
font-servers48ipv4-addresstrue
x-display-manager49ipv4-addresstrue
dhcp-requested-address50ipv4-addressfalse
dhcp-option-overload52uint8false
dhcp-message56stringfalse
dhcp-max-message-size57uint16false
vendor-class-identifier60binaryfalse
nwip-domain-name62stringfalse
nwip-suboptions63binaryfalse
tftp-server-name66stringfalse
boot-file-name67stringfalse
user-class77binaryfalse
fqdn81recordfalse
dhcp-agent-options82emptyfalse
authenticate90binaryfalse
client-last-transaction-time91uint32false
associated-ip92ipv4-addresstrue
subnet-selection118ipv4-addressfalse
domain-search119binaryfalse
vivco-suboptions124binaryfalse
vivso-suboptions125binaryfalse


Table 17.3. List of standard DHCP option types

NameMeaning
binaryAn arbitrary string of bytes, specified as a set of hexadecimal digits.
booleanBoolean value with allowed values true or false
emptyNo value, data is carried in suboptions
fqdnFully qualified domain name (e.g. www.example.com)
ipv4-addressIPv4 address in the usual dotted-decimal notation (e.g. 192.0.2.1)
ipv6-addressIPv6 address in the usual colon notation (e.g. 2001:db8::1)
recordStructured data that may comprise any types (except "record" and "empty")
stringAny text
uint88 bit unsigned integer with allowed values 0 to 255
uint1616 bit unsinged integer with allowed values 0 to 65535
uint3232 bit unsigned integer with allowed values 0 to 4294967295


17.2.7. Custom DHCPv4 options

It is also possible to define options other than the standard ones. Assume that we want to define a new DHCPv4 option called "foo" which will have code 222 and will convey a single unsigned 32 bit integer value. We can define such an option by using the following commands:

> config add Dhcp4/option-def
> config set Dhcp4/option-def[0]/name "foo"
> config set Dhcp4/option-def[0]/code 222
> config set Dhcp4/option-def[0]/type "uint32"
> config set Dhcp4/option-def[0]/array false
> config set Dhcp4/option-def[0]/record-types ""
> config set Dhcp4/option-def[0]/space "dhcp4"
> config set Dhcp4/option-def[0]/encapsulate ""
> config commit

The "false" value of the "array" parameter determines that the option does NOT comprise an array of "uint32" values but rather a single value. Two other parameters have been left blank: "record-types" and "encapsulate". The former specifies the comma separated list of option data fields if the option comprises a record of data fields. The "record-fields" value should be non-empty if the "type" is set to "record". Otherwise it must be left blank. The latter parameter specifies the name of the option space being encapsulated by the particular option. If the particular option does not encapsulate any option space it should be left blank. Note that the above set of comments define the format of the new option and do not set its values.

Note

In the current release the default values are not propagated to the parser when the new configuration is being set. Therefore, all parameters must be specified at all times, even if their values are left blank.

Once the new option format is defined, its value is set in the same way as for a standard option. For example the following commands set a global value that applies to all subnets.

> config add Dhcp4/option-data
> config set Dhcp4/option-data[0]/name "foo"
> config set Dhcp4/option-data[0]/code 222
> config set Dhcp4/option-data[0]/space "dhcp4"
> config set Dhcp4/option-data[0]/csv-format true
> config set Dhcp4/option-data[0]/data "12345"
> config commit

New options can take more complex forms than simple use of primitives (uint8, string, ipv4-address etc): it is possible to define an option comprising a number of existing primitives.

Assume we want to define a new option that will consist of an IPv4 address, followed by unsigned 16 bit integer, followed by a boolean value, followed by a text string. Such an option could be defined in the following way:

> config add Dhcp4/option-def
> config set Dhcp4/option-def[0]/name "bar"
> config set Dhcp4/option-def[0]/code 223
> config set Dhcp4/option-def[0]/space "dhcp4"
> config set Dhcp4/option-def[0]/type "record"
> config set Dhcp4/option-def[0]/array false
> config set Dhcp4/option-def[0]/record-types "ipv4-address, uint16, boolean, string"
> config set Dhcp4/option-def[0]/encapsulate ""

The "type" is set to "record" to indicate that the option contains multiple values of different types. These types are given as a comma-separated list in the "record-types" field and should be those listed in Table 17.3, “List of standard DHCP option types”.

The values of the option are set as follows:

> config add Dhcp4/option-data
> config set Dhcp4/option-data[0]/name "bar"
> config set Dhcp4/option-data[0]/space "dhcp4"
> config set Dhcp4/option-data[0]/code 223
> config set Dhcp4/option-data[0]/csv-format true
> config set Dhcp4/option-data[0]/data "192.0.2.100, 123, true, Hello World"
> config commit

"csv-format" is set "true" to indicate that the "data" field comprises a command-separated list of values. The values in the "data" must correspond to the types set in the "record-types" field of the option definition.

Note

It is recommended that boolean values are specified using "true" and "false" strings. This helps to prevent errors when typing multiple comma separated values, as it make it easier to identify the type of the value being typed, and compare it with the order of data fields. Nevetheless, it is possible to use integer values: "1" and "0", instead of "true" and "false" accordingly. If other integer value is specified, the configuration is rejected.

17.2.8. DHCPv4 vendor specific options

Currently there are three option spaces defined: dhcp4 (to be used in DHCPv4 daemon) and dhcp6 (for the DHCPv6 daemon); there is also vendor-encapsulated-options-space, which is empty by default, but options can be defined in it. Those options are called vendor-specific information options. The following examples show how to define an option "foo" with code 1 that consists of an IPv4 address, an unsigned 16 bit integer and a string. The "foo" option is conveyed in a vendor specific information option.

The first step is to define the format of the option:

> config add Dhcp4/option-def
> config set Dhcp4/option-def[0]/name "foo"
> config set Dhcp4/option-def[0]/code 1
> config set Dhcp4/option-def[0]/space "vendor-encapsulated-options-space"
> config set Dhcp4/option-def[0]/type "record"
> config set Dhcp4/option-def[0]/array false
> config set Dhcp4/option-def[0]/record-types "ipv4-address, uint16, string"
> config set Dhcp4/option-def[0]/encapsulates ""
> config commit

(Note that the option space is set to "vendor-encapsulated-options-space".) Once the option format is defined, the next step is to define actual values for that option:

> config add Dhcp4/option-data
> config set Dhcp4/option-data[0]/name "foo"
> config set Dhcp4/option-data[0]/space "vendor-encapsulated-options-space"
> config set Dhcp4/option-data[0]/code 1
> config set Dhcp4/option-data[0]/csv-format true
> config set Dhcp4/option-data[0]/data "192.0.2.3, 123, Hello World"
> config commit

We also set up a dummy value for vendor-opts, the option that conveys our sub-option "foo". This is required else the option will not be included in messages sent to the client.

> config add Dhcp4/option-data
> config set Dhcp4/option-data[1]/name "vendor-encapsulated-options"
> config set Dhcp4/option-data[1]/space "dhcp4"
> config set Dhcp4/option-data[1]/code 43
> config set Dhcp4/option-data[1]/csv-format false
> config set Dhcp4/option-data[1]/data ""
> config commit

Note

With this version of BIND 10, the "vendor-encapsulated-options" option must be specified in the configuration although it has no configurable parameters. If it is not specified, the server will assume that it is not configured and will not send it to a client. In the future there will be no need to include this option in the configuration.

17.2.9. Nested DHCPv4 options (custom option spaces)

It is sometimes useful to define completely new option space. This is the case when user creates new option in the standard option space ("dhcp4 or "dhcp6") and wants this option to convey sub-options. Thanks to being in the separate space, sub-option codes will have a separate numbering scheme and may overlap with codes of standard options.

Note that creation of a new option space when defining sub-options for a standard option is not required, because it is created by default if the standard option is meant to convey any sub-options (see Section 17.2.8, “DHCPv4 vendor specific options”).

Assume that we want to have a DHCPv4 option called "container" with code 222 that conveys two sub-options with codes 1 and 2. First we need to define the new sub-options:

> config add Dhcp4/option-def
> config set Dhcp4/option-def[0]/name "subopt1"
> config set Dhcp4/option-def[0]/code 1
> config set Dhcp4/option-def[0]/space "isc"
> config set Dhcp4/option-def[0]/type "ipv4-address"
> config set Dhcp4/option-def[0]/record-types ""
> config set Dhcp4/option-def[0]/array false
> config set Dhcp4/option-def[0]/encapsulate ""
> config commit

> config add Dhcp4/option-def
> config set Dhcp4/option-def[1]/name "subopt2"
> config set Dhcp4/option-def[1]/code 2
> config set Dhcp4/option-def[1]/space "isc"
> config set Dhcp4/option-def[1]/type "string"
> config set Dhcp4/option-def[1]/record-types ""
> config set Dhcp4/option-def[1]/array false
> config set Dhcp4/option-def[1]/encapsulate ""
> config commit

Note that we have defined the options to belong to a new option space (in this case, "isc").

The next step is to define a regular DHCPv4 option with our desired code and specify that it should include options from the new option space:

> add Dhcp4/option-def
> set Dhcp4/option-def[2]/name "container"
> set Dhcp4/option-def[2]/code 222
> set Dhcp4/option-def[2]/space "dhcp4"
> set Dhcp4/option-def[2]/type "empty"
> set Dhcp4/option-def[2]/array false
> set Dhcp4/option-def[2]/record-types ""
> set Dhcp4/option-def[2]/encapsulate "isc"
> commit

The name of the option space in which the sub-options are defined is set in the "encapsulate" field. The "type" field is set to "empty" to indicate that this option does not carry any data other than sub-options.

Finally, we can set values for the new options:

> config add Dhcp4/option-data
> config set Dhcp4/option-data[0]/name "subopt1"
> config set Dhcp4/option-data[0]/space "isc"
> config set Dhcp4/option-data[0]/code 1
> config set Dhcp4/option-data[0]/csv-format true
> config set Dhcp4/option-data[0]/data "192.0.2.3"
> config commit

> config add Dhcp4/option-data
> config set Dhcp4/option-data[1]/name "subopt2"
> config set Dhcp4/option-data[1]/space "isc"
> config set Dhcp4/option-data[1]/code 2
> config set Dhcp4/option-data[1]/csv-format true
> config set Dhcp4/option-data[1]/data "Hello world"
> config commit

> config add Dhcp4/option-data
> config set Dhcp4/option-data[2]/name "container"
> config set Dhcp4/option-data[2]/space "dhcp4"
> config set Dhcp4/option-data[2]/code 222
> config set Dhcp4/option-data[2]/csv-format true
> config set Dhcp4/option-data[2]/data ""
> config commit

Even though the "container" option does not carry any data except sub-options, the "data" field must be explicitly set to an empty value. This is required because in the current version of BIND 10 DHCP, the default configuration values are not propagated to the configuration parsers: if the "data" is not set the parser will assume that this parameter is not specified and an error will be reported.

Note that it is possible to create an option which carries some data in addition to the sub-options defined in the encapsulated option space. For example, if the "container" option from the previous example was required to carry an uint16 value as well as the sub-options, the "type" value would have to be set to "uint16" in the option definition. (Such an option would then have the following data structure: DHCP header, uint16 value, sub-options.) The value specified with the "data" parameter - which should be a valid integer enclosed in quotes, e.g. "123" - would then be assigned to the uint16 field in the "container" option.

17.2.10. Client Classification in DHCPv4

Note

DHCPv4 server has been extended to support limited client classification. Although the current capability is modest, it is expected to be expanded in the future. It is envisaged that the majority of client classification extensions will be using hooks extensions.

In certain cases it is useful to differentiate between different types of clients and treat them differently. The process of doing classification is conducted in two steps. The first step is to assess incoming packet and assign it to zero or more classes. This classification is currently simple, but is expected to grow in capability soon. Currently the server checks whether incoming packet has vendor class identifier option (60). If it has, content of that option is prepended with "VENDOR_CLASS_" then is interpreted as a class. For example, modern cable modems will send this option with value "docsis3.0" and as a result the packet will belong to class "VENDOR_CLASS_docsis3.0".

It is envisaged that the client classification will be used for changing behavior of almost any part of the DHCP message processing, including assigning leases from different pools, assigning different option (or different values of the same options) etc. For now, there are only two mechanisms that are taking advantage of client classification: specific processing for cable modems and subnet selection.

For clients that belong to the VENDOR_CLASS_docsis3.0 class, the siaddr field is set to the value of next-server (if specified in a subnet). If there is boot-file-name option specified, its value is also set in the file field in the DHCPv4 packet. For eRouter1.0 class, the siaddr is always set to 0.0.0.0. That capability is expected to be moved to external hook library that will be dedicated to cable modems.

Kea can be instructed to limit access to given subnets based on class information. This is particularly useful for cases where two types of devices share the same link and are expected to be served from two different subnets. The primary use case for such a scenario is cable networks. There are two classes of devices: cable modem itself, which should be handled a lease from subnet A and all other devices behind modems that should get a lease from subnet B. That segregation is essential to prevent overly curious users from playing with their cable modems. For details on how to set up class restrictions on subnets, see Section 17.2.11, “Limiting access to IPv4 subnet to certain classes”.

17.2.11. Limiting access to IPv4 subnet to certain classes

In certain cases it beneficial to restrict access to certain subnets only to clients that belong to a given subnet. For details on client classes, see Section 17.2.10, “Client Classification in DHCPv4”. This is an extension of a previous example from Section 17.2.5, “Configuration of IPv4 Address Pools”. Let's assume that the server is connected to a network segment that uses the 192.0.2.0/24 prefix. The Administrator of that network has decided that addresses from range 192.0.2.10 to 192.0.2.20 are going to be managed by the Dhcp4 server. Only clients belonging to client class VENDOR_CLASS_docsis3.0 are allowed to use this subnet. Such a configuration can be achieved in the following way:

> config add Dhcp4/subnet4
> config set Dhcp4/subnet4[0]/subnet "192.0.2.0/24"
> config set Dhcp4/subnet4[0]/pool [ "192.0.2.10 - 192.0.2.20" ]
> config set Dhcp4/subnet4[0]/client-class "VENDOR_CLASS_docsis3.0"
> config commit

Care should be taken with client classification as it is easy to prevent clients that do not meet class criteria to be denied any service altogether.

17.2.12. Configuring DHCPv4 for DDNS

As mentioned earlier, DHCPv4 can be configured to generate requests to the DHCP-DDNS server to update DNS entries. These requests are known as NameChangeRequests or NCRs. Each NCR contains the following information:

  1. Whether it is a request to add (update) or remove DNS entries

  2. Whether the change requests forward DNS updates (A records), reverse DNS updates (PTR records), or both.

  3. The FQDN, lease address, and DHCID

The paramaters for controlling the generation of NCRs for submission to D2 are contained in the "dhcp-ddns" section of the DHCPv4 server configuration. The default values for this section appears as follows:

> config show Dhcp4/dhcp-ddns
Dhcp4/dhcp-ddns/enable-updates	true	boolean
Dhcp4/dhcp-ddns/server-ip	"127.0.0.1"	string
Dhcp4/dhcp-ddns/server-port	53001	integer
Dhcp4/dhcp-ddns/ncr-protocol	"UDP"	string
Dhcp4/dhcp-ddns/ncr-format	"JSON"	string
Dhcp4/dhcp-ddns/override-no-update	false	boolean
Dhcp4/dhcp-ddns/override-client-update	false	boolean
Dhcp4/dhcp-ddns/replace-client-name	false	boolean
Dhcp4/dhcp-ddns/generated-prefix	"myhost"	string
Dhcp4/dhcp-ddns/qualifying-suffix	"example.com"	string

The "enable-updates" parameter determines whether or not DHCPv4 will generate NCRs. By default, this value is false hence DDNS updates are disabled. To enable DDNS updates set this value to true:

> config set Dhcp4/dhcp-ddns/enable-updates true
> config commit

17.2.12.1. DHCP-DDNS Server Connectivty

In order for NCRs to reach the D2 server, DHCPv4 must be able to communicate with it and so the relevant parameters must be set appropriately. The parameters, "server-ip" and "server-port", specify the address of the D2 server. By default, D2 is assumed to running on the same machine as DHCPv4, and the default values for these two parameters should be sufficient. However, if D2 has been configured to listen on a different address or port, these values must altered accordingly. For example, if D2 has been configured to listen on 198.162.1.10 port 900, the following commands would be required:

> config set Dhcp4/dhcp-ddns/server-ip "198.162.1.10"
> config set Dhcp4/dhcp-ddns/server-port 900
> config commit

D2 can be configured to listen over IPv4 or IPv6, therefore server-ip may be either an IPv4 or IPv6 address.

The socket protocol that DHCPv4 should use to communicate with D2 is specified with the "ncr-protocol" parameter. Currently only UDP is supported.

The internal format for DDNS update requests sent by DHCPv4 is specified with the "ncr-format" parameter. Currently only JSON is supported.

17.2.12.2. When does the DHCPv4 server generate DDNS requests?

DHCPv4 follows the behavior prescribed for DHCP servers in RFC 4702. It is important to keep in mind that DHCPv4 provides the initial decision making of when and what to update and forwards that information to D2 in the form of NCRs. Carrying out the actual DNS updates and dealing with such things as conflict resolution are the purvue of D2 (Chapter 19, The DHCP-DDNS Server).

This section describes when DHCPv4 will generate NCRs and the configuration parameters that can be used to influence this decision. It assumes that the "enable-updates" paramater is true.

In general, DHCPv4 will generate DDNS udpate requests when:

  1. A new lease is granted in response to a DHCP REQUEST

  2. An existing lease is renewed but the FQDN associated with it has changed.

  3. An existing lease is released in response to a DHCP RELEASE

In the second case, lease renewal, two DDNS requests will be issued: one request to remove entries for the previous FQDN and a second request to add entries for the new FQDN. In the last case, a lease release, a single DDNS request to remove its entries will be made. The decision making involved when granting a new lease (the first case) is more involved and is discussed next.

When a new lease is granted, the DHCPv4 server will generate a DDNS update request if the DHCP REQUEST contains either the FQDN option (code 81) or the Host Name option (code 12). If both are present, the server will use the FQDN option. By default the DHCPv4 server will respect the FQDN N and S flags specified by the client as shown in the following table:

Table 17.4. Default FQDN Flag Behavior

Client Flags:N-SClient IntentServer ResponseServer Flags:N-S-O
0-0 Client wants to do forward updates, server should do reverse updates Server generates reverse-only request1-0-0
0-1Server should do both forward and reverse updatesServer generates request to update both directions0-1-0
1-0Client wants no updates doneServer does not generate a request1-0-0

The first row in the table above represents "client delegation". Here the DHCP client states that it intends to do the forward DNS updates and the server should do the reverese updates. By default, DHCPv4 will honor the client's wishes and generate a DDNS request to D2 to update only reverse DNS data. The parameter, "override-client-update", can be used to instruct the server to override client delegation requests. When this parameter is true, DHCPv4 will disregard requests for client delegation and generate a DDNS request to update both forward and reverse DNS data. In this case, the N-S-O flags in the server's response to the client will be 0-1-1 respectively.

(Note that the flag combination N=1, S=1 is prohibited according to RFC 4702. If such a combination is received from the client, the packet will be dropped by the DHCPv4 server.)

To override client delegation, issue the following commands:

> config set Dhcp4/dhcp-ddns/override-client-update true
> config commit

The third row in the table above describes the case in which the client requests that no DNS updates be done. The parameter, "override-no-update", can be used to instruct the server to disregard the client's wishes. When this parameter is true, DHCPv4 will generate DDNS udpate request to D2 even if the client requests no updates be done. The N-S-O flags in the server's response to the client will be 0-1-1.

To override client delegation, issue the following commands:

> config set Dhcp4/dhcp-ddns/override-no-update true
> config commit

DHCPv4 will always generate DDNS update requests if the client request only contains the Host Name option. In addition it will include an FQDN option in the response to the client with the FQDN N-S-O flags set to 0-1-0 respectively. The domain name portion of the FQDN option will be the name submitted to D2 in the DDNS update request.

17.2.12.3. DHCPv4 name generation for DDNS update requests

Each NameChangeRequest must of course include the fully qualified domain name whose DNS entries are to be affected. DHCPv4 can be configured to supply a portion or all of that name based upon what it receives from the client in the DHCP REQUEST.

The rules for determining the FQDN option are as follows:

  1. If configured to do, so ignore the REQUEST contents and generate a FQDN using a configurable prefix and suffix.

  2. If the REQUEST contains the client FQDN option, the candidate name is taken from there, otherwise it is taken from the Host Name option. The candiate name may then be modified:

    1. If the candidate name is a fully qualified domain name, use it.

    2. If the candidate name is a partial (i.e. unqualified) name then add a configurable suffix to the name and use the result as the FQDN.

    3. If the candidate name is a empty, generate a FQDN using a configurable prefix and suffix.

To instruct DHCPv4 to always generate the FQDN for a client, set the parameter "replace-client-name" to true as follows:

> config set Dhcp4/dhcp-ddns/replace-client-name true
> config commit

The prefix used in the generation of a FQDN is specified by the "generated-prefix" parameter. The default value is "myhost". To alter its value simply set it to the desired string:

> config set Dhcp4/dhcp-ddns/generated-prefix "another.host"
> config commit

The suffix used when generating a FQDN or when qualifying a partial name is specified by the "qualifying-suffix" parameter. The default value is "example.com". To alter its value simply set it to the desired string:

> config set Dhcp4/dhcp-ddns/generated-prefix "our.net"
> config commit

When generating a name, DHCPv4 will construct name of the format:

[generated-prefix]-[address-text].[qualifying-suffix].

where address-text is simply the lease IP address converted to a hyphenated string. For example, if lease address is 172.16.1.10 and assuming default values for generated-prefix and qualifying-suffix, the generated FQDN would be:

myhost-172-16-1-10.example.com.

17.3. Server Identifier in DHCPv4

The DHCPv4 protocol uses a "server identifier" for clients to be able to discriminate between several servers present on the same link: this value is an IPv4 address of the server. The server chooses the IPv4 address of the interface on which the message from the client (or relay) has been received. A single server instance will use multiple server identifiers if it is receiving queries on multiple interfaces.

Currently there is no mechanism to override the default server identifiers by an administrator. In the future, the configuration mechanism will be used to specify the custom server identifier.

17.4. Next server (siaddr)

In some cases, clients want to obtain configuration from the TFTP server. Although there is a dedicated option for it, some devices may use siaddr field in the DHCPv4 packet for that purpose. That specific field can be configured using next-server directive. It is possible to define it in global scope or for a given subnet only. If both are defined, subnet value takes precedence. The value in subnet can be set to 0.0.0.0, which means that next-server should not be sent. It may also be set to empty string, which means the same as if it was not defined at all - use global value.

> config add Dhcp4/next-server
> config set Dhcp4/next-server "192.0.2.123"
> config commit

> config add Dhcp4/subnet[0]/next-server
> config set Dhcp4/subnet[0]/next-server "192.0.2.234"
> config commit

17.5. Echoing client-id (RFC6842)

Original DHCPv4 spec (RFC2131) states that the DHCPv4 server must not send back client-id options when responding to clients. However, in some cases that confused clients that did not have MAC address or client-id. See RFC6842 for details. That behavior has changed with the publication of RFC6842 which updated RFC2131. That update now states that the server must send client-id if client sent it. That is the default behaviour that Kea offers. However, in some cases older devices that do not support RFC6842 may refuse to accept responses that include client-id option. To enable backward compatibility, an optional configuration parameter has been introduced. To configure it, use the following commands:

> config add Dhcp4/echo-client-id
> config set Dhcp4/echo-client-id False
> config commit

17.6. How DHCPv4 server selects subnet for a client

The DHCPv4 server differentiates between the directly connected clients, clients trying to renew leases and clients sending their messages through relays. For the directly connected clients the server will check the configuration of the interface on which the message has been received, and if the server configuration doesn't match any configured subnet the message is discarded.

Assuming that the server's interface is configured with the 192.0.2.3 IPv4 address, the server will only process messages received through this interface from the directly connected client, if there is a subnet configured, to which this IPv4 address belongs, e.g. 192.0.2.0/24. The server will use this subnet to assign IPv4 address for the client.

The rule above does not apply when the client unicasts its message, i.e. is trying to renew its lease. Such message is accepted through any interface. The renewing client sets ciaddr to the currently used IPv4 address. The server uses this address to select the subnet for the client (in particular, to extend the lease using this address).

If the message is relayed it is accepted through any interface. The giaddr set by the relay agent is used to select the subnet for the client.

It is also possible to specify a relay IPv4 address for a given subnet. It can be used to match incoming packets into a subnet in uncommon configurations, e.g. shared subnets. See Section 17.7, “Using specific relay agent for a subnet” for details.

Note

The subnet selection mechanism described in this section is based on the assumption that client classification is not used. The classification mechanism alters the way in which subnet is selected for the client, depending on the clasess that the client belongs to.

17.7. Using specific relay agent for a subnet

The relay has to have an interface connected to the link on which the clients are being configured. Typically the relay has an IPv4 address configured on that interface that belongs to the subnet that the server will assign addresses from. In such typical case, the server is able to use IPv4 address inserted by the relay (in GIADDR field of the DHCPv4 packet) to select appropriate subnet.

However, that is not always the case. In certain uncommon, but valid deployments, the relay address may not match the subnet. This usually means that there is more than one subnet allocated for a given link. Two most common examples where this is the case are long lasting network renumbering (where both old and new address space is still being used) and a cable network. In a cable network both cable modems and the devices behind them are physically connected to the same link, yet they use distinct addressing. In such case, the DHCPv4 server needs additional information (IPv4 address of the relay) to properly select an appropriate subnet.

The following example assumes that there is a subnet 192.0.2.0/24 that is accessible via relay that uses 10.0.0.1 as its IPv4 address. The server will be able to select this subnet for any incoming packets that came from a relay that has an address in 192.0.2.0/24 subnet. It will also select that subnet for a relay with address 10.0.0.1.

> config add Dhcp4/subnet4
> config set Dhcp4/subnet4[0]/subnet "192.0.2.0/24"
> config set Dhcp4/subnet4[0]/pool [ "192.0.2.10 - 192.0.2.20" ]
> config set Dhcp4/subnet4[0]/relay/ip-address "10.0.0.1"
> config commit

17.8. Segregating IPv4 clients in a cable network

In certain cases, it is useful to mix relay address information, introduced in Section 17.7, “Using specific relay agent for a subnet” with client classification, explained in Section 17.2.11, “Limiting access to IPv4 subnet to certain classes”. One specific example is cable network, where typically modems get addresses from a different subnet than all devices connected behind them.

Let's assume that there is one CMTS (Cable Modem Termination System) with one CM MAC (a physical link that modems are connected to). We want the modems to get addresses from the 10.1.1.0/24 subnet, while everything connected behind modems should get addresses from another subnet (192.0.2.0/24). The CMTS that acts as a relay an uses address 10.1.1.1. The following configuration can serve that configuration:

> config add Dhcp4/subnet4
> config set Dhcp4/subnet4[0]/subnet "10.1.1.0/24"
> config set Dhcp4/subnet4[0]/pool [ "10.1.1.2 - 10.1.1.20" ]
> config set Dhcp4/subnet4[0]/client-class "docsis3.0"
> config set Dhcp4/subnet4[0]/relay/ip-address "10.1.1.1"
> config add Dhcp4/subnet4
> config set Dhcp4/subnet4[1]/subnet "192.0.2.0/24"
> config set Dhcp4/subnet4[1]/pool [ "192.0.2.10 - 192.0.2.20" ]
> config set Dhcp4/subnet4[1]/relay/ip-address "10.1.1.1"
> config commit

17.9. Supported Standards

The following standards and draft standards are currently supported:

  • RFC 2131: Supported messages are DISCOVER, OFFER, REQUEST, RELEASE, ACK, and NAK.
  • RFC 2132: Supported options are: PAD (0), END(255), Message Type(53), DHCP Server Identifier (54), Domain Name (15), DNS Servers (6), IP Address Lease Time (51), Subnet mask (1), and Routers (3).
  • RFC 3046: Relay Agent Information option is supported.
  • RFC 3925: Vendor-Identifying Vendor Class and Vendor-Identifying Vendor-Specific Information option are supported.
  • RFC 6842: Server by default sends back client-id option. That capability may be disabled. See Section 17.5, “Echoing client-id (RFC6842)” for details.

17.10. DHCPv4 Server Limitations

These are the current limitations of the DHCPv4 server software. Most of them are reflections of the current stage of development and should be treated as not implemented yet, rather than actual limitations.

  • Removal of a subnet during server reconfiguration may cause renumbering of auto-generated subnet identifiers, as described in section Section 17.2.4, “IPv4 Subnet Identifier”.
  • BOOTP (RFC 951) is not supported.
  • Raw sockets operation is working on Linux only. See Section 20.1, “Interface detection and Socket handling” for details.
  • The DHCPv4 server does not verify that assigned address is unused. According to RFC 2131, the allocating server should verify that address is not used by sending ICMP echo request.
  • Address duplication report (DECLINE) is not supported yet.
  • The server doesn't act upon expired leases. In particular, when a lease expires, the server doesn't request the removal of the DNS records associated with it.


[1] The server comes with an in-memory database ("memfile") configured as the default database. This is used for internal testing and is not supported. In addition, it does not store lease information on disk: lease information will be lost if the server is restarted.

Chapter 18. The DHCPv6 Server

18.1. Starting and Stopping the DHCPv6 Server

b10-dhcp6 is the BIND 10 DHCPv6 server and, like other parts of BIND 10, is configured through the bindctl program.

After starting BIND 10 and starting bindctl, the first step in configuring the server is to add b10-dhcp6 to the list of running BIND 10 services.

> config add Init/components b10-dhcp6
> config set Init/components/b10-dhcp6/kind dispensable
> config commit

To remove b10-dhcp6 from the set of running services, the b10-dhcp6 is removed from list of Init components:

> config remove Init/components b10-dhcp6
> config commit

Note that the server was only removed from the list, so BIND10 will not restart it, but the server itself is still running. Hence it is usually desired to stop it:

> Dhcp6 shutdown

During start-up the server will detect available network interfaces and will attempt to open UDP sockets on all interfaces that are up, running, are not loopback, are multicast-capable, and have IPv6 address assigned. It will then listen to incoming traffic.

18.2. DHCPv6 Server Configuration

Once the server has been started, it can be configured. To view the current configuration, use the following command in bindctl:

> config show Dhcp6

When starting the Dhcp6 daemon for the first time, the default configuration will be available. It will look similar to this:

> config show Dhcp6
Dhcp6/hooks-libraries   []  list    (default)
Dhcp6/interfaces/   list    (default)
Dhcp6/renew-timer   1000    integer (default)
Dhcp6/rebind-timer  2000    integer (default)
Dhcp6/preferred-lifetime    3000    integer (default)
Dhcp6/valid-lifetime    4000    integer (default)
Dhcp6/option-def    []  list    (default)
Dhcp6/option-data   []  list    (default)
Dhcp6/lease-database/type   ""  string  (default)
Dhcp6/lease-database/name   ""  string  (default)
Dhcp6/lease-database/user   ""  string  (default)
Dhcp6/lease-database/host   ""  string  (default)
Dhcp6/lease-database/password   ""  string  (default)
Dhcp6/subnet6/  list
Dhcp6/dhcp-ddns/enable-updates  true    boolean
Dhcp6/dhcp-ddns/server-ip   "127.0.0.1" string
Dhcp6/dhcp-ddns/server-port 53001   integer
Dhcp6/dhcp-ddns/ncr-protocol    "UDP"   string
Dhcp6/dhcp-ddns/ncr-format  "JSON"  string
Dhcp6/dhcp-ddns/always-include-fqdn false   boolean
Dhcp6/dhcp-ddns/override-no-update  false   boolean
Dhcp6/dhcp-ddns/override-client-update  false   boolean
Dhcp6/dhcp-ddns/replace-client-name false   boolean
Dhcp6/dhcp-ddns/generated-prefix    "myhost"    string
Dhcp6/dhcp-ddns/qualifying-suffix   "example.com"   string

To change one of the parameters, simply follow the usual bindctl procedure. For example, to make the leases longer, change their valid-lifetime parameter:

> config set Dhcp6/valid-lifetime 7200
> config commit

Most Dhcp6 parameters are of global scope and apply to all defined subnets, unless they are overridden on a per-subnet basis.

Note

With this version of BIND 10, there are a number of known limitations and problems in the DHCPv6 server. See Section 18.7, “DHCPv6 Server Limitations”.

18.2.1. Default storage for leases

The server is able to store lease data in different repositories. Larger deployments may elect to store leases in a database. Section 18.2.2, “Database Configuration” describes one way to do it. By default, the server will use a CSV file rather than a database to store lease information. One of the advantages of using a file is that it eliminates dependency on third party database software.

The configuration of the file backend (Memfile) is controlled through the Dhcp6/lease-database parameters. When default parameters are left, the Memfile backend will write leases to a disk in the [bind10-install-dir]/var/bind10/kea-leases6.csv.

It is possible to alter the default location of the lease file. The following configuration:

> config set Dhcp4/lease-database/type "memfile"
> config set Dhcp4/lease-database/persist true
> config set Dhcp4/lease-database/leasefile "/tmp/kea-leases6.csv"
> config commit

will change the default location of the lease file to /tmp/kea-leases6.csv.

The "persist" parameter controls whether the leases are written to disk. It is strongly recommended that this parameter is set to "true" at all times during the normal operation of the server.

18.2.2. Database Configuration

All leases issued by the server are stored in the lease database. Currently there are 3 database backends available: MySQL, PostgreSQL and memfile. [2], and so the server must be configured to access the correct database with the appropriate credentials.

Note

Database access information must be configured for the DHCPv6 server, even if it has already been configured for the DHCPv4 server. The servers store their information independently, so each server can use a separate database or both servers can use the same database.

Database configuration is controlled through the Dhcp6/lease-database parameters. The type of the database must be set to "mysql", "postgresql" or "memfile":

> config set Dhcp6/lease-database/type "mysql"

Next, the name of the database is to hold the leases must be set: this is the name used when the lease database was created (see Section 16.1.2, “Create MySQL Database and Kea User” or Section 16.1.4, “Create PostgreSQL Database and Kea User”).

> config set Dhcp6/lease-database/name "database-name"

If the database is located on a different system to the DHCPv6 server, the database host name must also be specified (although note that this configuration may have a severe impact on server performance):

> config set Dhcp6/lease-database/host "remote-host-name"

The usual state of affairs will be to have the database on the same machine as the DHCPv6 server. In this case, set the value to the empty string (this is the default):

> config set Dhcp6/lease-database/host ""

Finally, the credentials of the account under which the server will access the database should be set:

> config set Dhcp6/lease-database/user "user-name"
> config set Dhcp6/lease-database/password "password"

If there is no password to the account, set the password to the empty string "". (This is also the default.)

Note

The password is echoed when entered and is stored in clear text in the BIND 10 configuration database. Improved password security will be added in a future version of BIND 10 DHCP

18.2.3. Interface selection

When DHCPv6 server starts up, by default it will listen to the DHCP traffic and respond to it on all interfaces detected during startup. However, in many cases it is desired to configure the server to listen and respond on selected interfaces only. The sample commands in this section show how to make interface selection using bindctl.

The default configuration can be presented with the following command:

> config show Dhcp6/interfaces
Dhcp6/interfaces[0] "*" string

An asterisk sign plays a role of the wildcard and means "listen on all interfaces".

In order to override the default configuration, the existing entry can be replaced with the actual interface name:

> config set Dhcp6/interfaces[0] eth1
> config commit

Other interface names can be added on one-by-one basis:

> config add Dhcp6/interfaces eth2
> config commit

Configuration will now contain two interfaces which can be presented as follows:

> config show Dhcp6/interfaces
Dhcp6/interfaces[0]	"eth1"	string
Dhcp6/interfaces[1]	"eth2"	string

When configuration gets committed, the server will start to listen on eth1 and eth2 interfaces only.

It is possible to use wildcard interface name (asterisk) concurrently with explicit interface names:

> config add Dhcp6/interfaces *
> config commit

This will result in the following configuration:

> config show Dhcp6/interfaces
Dhcp6/interfaces[0]	"eth1"	string
Dhcp6/interfaces[1]	"eth2"	string
Dhcp6/interfaces[2]	"*"	string

The presence of the wildcard name implies that server will listen on all interfaces. In order to fall back to the previous configuration when server listens on eth1 and eth2:

> config remove Dhcp6/interfaces[2]
> config commit

18.2.4. IPv6 Subnet Identifier

Subnet identifier is a unique number associated with a particular subnet. In principle, it is used to associate clients' leases with respective subnets. When subnet identifier is not specified for a subnet being configured, it will be automatically assigned by the configuration mechanism. The identifiers are assigned from 1 and are monotonically increased for each subsequent subnet: 1, 2, 3 ....

If there are multiple subnets configured with auto-generated identifiers and one of them is removed, the subnet identifiers may be renumbered. For example: if there are 4 subnets and 3rd is removed the last subnet will be assigned identifier that the 3rd subnet had before removal. As a result, the leases stored in the lease database for subnet 3 are now associated with the subnet 4, which may have unexpected consequences. In the future it is planned to implement the mechanism to preserve auto-generated subnet ids upon removal of one of the subnets. Currently, the only remedy for this issue is to manually specify the unique subnet identifier for each subnet.

The following configuration:

> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64"
> config set Dhcp6/subnet6[0]/id 1024
> config commit
        

will assign the arbitrary subnet identifier to the newly configured subnet. This identifier will not change for this subnet until "id" parameter is removed or set to 0. The value of 0 forces auto-generation of subnet identifier.

18.2.5. Unicast traffic support

When DHCPv6 server starts up, by default it listens to the DHCP traffic sent to multicast address ff02::1:2 on each interface that it is configured to listen on (see Section 18.2.3, “Interface selection”). In some cases it is useful to configure a server to handle incoming traffic sent to the global unicast addresses as well. The most common reason for that is to have relays send their traffic to the server directly. To configure server to listen on specific unicast address, a notation to specify interfaces has been extended. Interface name can be optionally followed by a slash, followed by global unicast address that server should listen on. That will be done in addition to normal link-local binding + listening on ff02::1:2 address. The sample commands listed below show how to listen on 2001:db8::1 (a global address) configured on the eth1 interface.

> config set Dhcp6/interfaces[0] eth1/2001:db8::1
> config commit

When configuration gets committed, the server will start to listen on eth1 on link-local address, mutlicast group (ff02::1:2) and 2001:db8::1.

It is possible to mix interface names, wildcards and interface name/addresses on the Dhcp6/interface list. It is not possible to specify more than one unicast address on a given interface.

Care should be taken to specify proper unicast addresses. The server will attempt to bind to those addresses specified, without any additional checks. That approach is selected on purpose, so in the software can be used to communicate over uncommon addresses if the administrator desires so.

18.2.6. Subnet and Address Pool

The essential role of a DHCPv6 server is address assignment. For this, the server has to be configured with at least one subnet and one pool of dynamic addresses to be managed. For example, assume that the server is connected to a network segment that uses the 2001:db8:1::/64 prefix. The Administrator of that network has decided that addresses from range 2001:db8:1::1 to 2001:db8:1::ffff are going to be managed by the Dhcp6 server. Such a configuration can be achieved in the following way:

> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64"
> config set Dhcp6/subnet6[0]/pool [ "2001:db8:1::0 - 2001:db8:1::ffff" ]
> config commit

Note that subnet is defined as a simple string, but the pool parameter is actually a list of pools: for this reason, the pool definition is enclosed in square brackets, even though only one range of addresses is specified.

It is possible to define more than one pool in a subnet: continuing the previous example, further assume that 2001:db8:1:0:5::/80 should be also be managed by the server. It could be written as 2001:db8:1:0:5:: to 2001:db8:1::5:ffff:ffff:ffff, but typing so many 'f's is cumbersome. It can be expressed more simply as 2001:db8:1:0:5::/80. Both formats are supported by Dhcp6 and can be mixed in the pool list. For example, one could define the following pools:

> config set Dhcp6/subnet6[0]/pool [ "2001:db8:1::1 - 2001:db8:1::ffff", "2001:db8:1:0:5::/80" ]
> config commit

The number of pools is not limited, but for performance reasons it is recommended to use as few as possible.

The server may be configured to serve more than one subnet. To add a second subnet, use a command similar to the following:

> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[1]/subnet "2001:db8:beef::/48"
> config set Dhcp6/subnet6[1]/pool [ "2001:db8:beef::/48" ]
> config commit

Arrays are counted from 0. subnet[0] refers to the subnet defined in the previous example. The config add Dhcp6/subnet6 command adds another (second) subnet. It can be referred to as Dhcp6/subnet6[1]. In this example, we allow server to dynamically assign all addresses available in the whole subnet. Although very wasteful, it is certainly a valid configuration to dedicate the whole /48 subnet for that purpose.

When configuring a DHCPv6 server using prefix/length notation, please pay attention to the boundary values. When specifying that the server should use a given pool, it will be able to allocate also first (typically network address) address from that pool. For example for pool 2001:db8::/64 the 2001:db8:: address may be assigned as well. If you want to avoid this, please use the "min-max" notation.

18.2.7. Subnet and Prefix Delegation Pools

Subnets may also be configured to delegate address prefixes.... A subnet may have one or more prefix delegation pools. Each pool has a prefixed address, which is specified as a prefix and a prefix length, as well as a delegated prefix length. A sample configuration is shown below:

> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64"
> config show Dhcp6/subnet6[0]
> config add Dhcp6/subnet6[0]/pd-pools
> config set Dhcp6/subnet6[0]/pd-pools[0]/prefix "2001:db8:1::"
> config set Dhcp6/subnet6[0]/pd-pools[0]/prefix-len 64
> config set Dhcp6/subnet6[0]/pd-pools[0]/delegated-len 96
> config commit

18.2.8. Standard DHCPv6 options

One of the major features of DHCPv6 server is to provide configuration options to clients. Although there are several options that require special behavior, most options are sent by the server only if the client explicitly requested them. The following example shows how to configure DNS servers, which is one of the most frequently used options. Numbers in the first column are added for easier reference and will not appear on screen. Options specified in this way are considered global and apply to all configured subnets.

1. > config add Dhcp6/option-data
2. > config set Dhcp6/option-data[0]/name "dns-servers"
3. > config set Dhcp6/option-data[0]/code 23
4. > config set Dhcp6/option-data[0]/space "dhcp6"
5. > config set Dhcp6/option-data[0]/csv-format true
6. > config set Dhcp6/option-data[0]/data "2001:db8::cafe, 2001:db8::babe"
7. > config commit

The first line creates new entry in option-data table. It contains information on all global options that the server is supposed to configure in all subnets. The second line specifies option name. For a complete list of currently supported names, see Table 18.1, “List of standard DHCPv6 options”. The third line specifies option code, which must match one of the values from that list. Line 4 specifies option space, which must always be set to "dhcp6" as these are standard DHCPv6 options. For other name spaces, including custom option spaces, see Section 18.2.11, “Nested DHCPv6 options (custom option spaces)”. The fifth line specifies the format in which the data will be entered: use of CSV (comma separated values) is recommended. The sixth line gives the actual value to be sent to clients. Data is specified as a normal text, with values separated by commas if more than one value is allowed.

Options can also be configured as hexadecimal values. If csv-format is set to false, the option data must be specified as a string of hexadecimal numbers. The following commands configure the DNS-SERVERS option for all subnets with the following addresses: 2001:db8:1::cafe and 2001:db8:1::babe.

> config add Dhcp6/option-data
> config set Dhcp6/option-data[0]/name "dns-servers"
> config set Dhcp6/option-data[0]/code 23
> config set Dhcp6/option-data[0]/space "dhcp6"
> config set Dhcp6/option-data[0]/csv-format false
> config set Dhcp6/option-data[0]/data "2001 0DB8 0001 0000 0000 0000
        0000 CAFE 2001 0DB8 0001 0000 0000 0000 0000 BABE"
> config commit
        

(The value for the setting of the "data" element is split across two lines in this document for clarity: when entering the command, the whole string should be entered on the same line.)

It is possible to override options on a per-subnet basis. If clients connected to most of your subnets are expected to get the same values of a given option, you should use global options: you can then override specific values for a small number of subnets. On the other hand, if you use different values in each subnet, it does not make sense to specify global option values (Dhcp6/option-data), rather you should set only subnet-specific values (Dhcp6/subnet[X]/option-data[Y]).

The following commands override the global DNS servers option for a particular subnet, setting a single DNS server with address 2001:db8:1::3.

> config add Dhcp6/subnet6[0]/option-data
> config set Dhcp6/subnet6[0]/option-data[0]/name "dns-servers"
> config set Dhcp6/subnet6[0]/option-data[0]/code 23
> config set Dhcp6/subnet6[0]/option-data[0]/space "dhcp6"
> config set Dhcp6/subnet6[0]/option-data[0]/csv-format true
> config set Dhcp6/subnet6[0]/option-data[0]/data "2001:db8:1::3"
> config commit

Note

In future versions of BIND 10 DHCP, it will not be necessary to specify option code, space and csv-format fields, as those fields will be set automatically.

The currently supported standard DHCPv6 options are listed in Table 18.1, “List of standard DHCPv6 options”. The "Name" and "Code" are the values that should be used as a name in the option-data structures. "Type" designates the format of the data: the meanings of the various types is given in Table 17.3, “List of standard DHCP option types”.

Some options are designated as arrays, which means that more than one value is allowed in such an option. For example the option dns-servers allows the specification of more than one IPv6 address, so allowing clients to obtain the the addresses of multiple DNS servers.

The Section 18.2.9, “Custom DHCPv6 options” describes the configuration syntax to create custom option definitions (formats). It is generally not allowed to create custom definitions for standard options, even if the definition being created matches the actual option format defined in the RFCs. There is an exception from this rule for standard options for which Kea does not provide a definition yet. In order to use such options, a server administrator must create a definition as described in Section 18.2.9, “Custom DHCPv6 options” in the 'dhcp6' option space. This definition should match the option format described in the relevant RFC but configuration mechanism would allow any option format as it has no means to validate it at the moment.

Table 18.1. List of standard DHCPv6 options

NameCodeTypeArray?
preference7uint8false
sip-server-dns21fqdntrue
sip-server-addr22ipv6-addresstrue
dns-servers23ipv6-addresstrue
domain-search24fqdntrue
nis-servers27ipv6-addresstrue
nisp-servers28ipv6-addresstrue
nis-domain-name29fqdntrue
nisp-domain-name30fqdntrue
sntp-servers31ipv6-addresstrue
information-refresh-time32uint32false
bcmcs-server-dns33fqdntrue
bcmcs-server-addr34ipv6-addresstrue
geoconf-civic36recordfalse
remote-id37recordfalse
subscriber-id38binaryfalse
client-fqdn39recordfalse
pana-agent40ipv6-addresstrue
new-posix-timezone41stringfalse
new-tzdb-timezone42stringfalse
ero43uint16true
lq-query44recordfalse
client-data45emptyfalse
clt-time46uint32false
lq-relay-data47recordfalse
lq-client-link48ipv6-addresstrue


18.2.9. Custom DHCPv6 options

It is also possible to define options other than the standard ones. Assume that we want to define a new DHCPv6 option called "foo" which will have code 100 and will convey a single unsigned 32 bit integer value. We can define such an option by using the following commands:

> config add Dhcp6/option-def
> config set Dhcp6/option-def[0]/name "foo"
> config set Dhcp6/option-def[0]/code 100
> config set Dhcp6/option-def[0]/type "uint32"
> config set Dhcp6/option-def[0]/array false
> config set Dhcp6/option-def[0]/record-types ""
> config set Dhcp6/option-def[0]/space "dhcp6"
> config set Dhcp6/option-def[0]/encapsulate ""
> config commit

The "false" value of the "array" parameter determines that the option does NOT comprise an array of "uint32" values but rather a single value. Two other parameters have been left blank: "record-types" and "encapsulate". The former specifies the comma separated list of option data fields if the option comprises a record of data fields. The "record-fields" value should be non-empty if the "type" is set to "record". Otherwise it must be left blank. The latter parameter specifies the name of the option space being encapsulated by the particular option. If the particular option does not encapsulate any option space it should be left blank. Note that the above set of comments define the format of the new option and do not set its values.

Once the new option format is defined, its value is set in the same way as for a standard option. For example the following commands set a global value that applies to all subnets.

> config add Dhcp6/option-data
> config set Dhcp6/option-data[0]/name "foo"
> config set Dhcp6/option-data[0]/code 100
> config set Dhcp6/option-data[0]/space "dhcp6"
> config set Dhcp6/option-data[0]/csv-format true
> config set Dhcp6/option-data[0]/data "12345"
> config commit

New options can take more complex forms than simple use of primitives (uint8, string, ipv6-address etc): it is possible to define an option comprising a number of existing primitives.

Assume we want to define a new option that will consist of an IPv6 address, followed by an unsigned 16 bit integer, followed by a boolean value, followed by a text string. Such an option could be defined in the following way:

> config add Dhcp6/option-def
> config set Dhcp6/option-def[0]/name "bar"
> config set Dhcp6/option-def[0]/code 101
> config set Dhcp6/option-def[0]/space "dhcp6"
> config set Dhcp6/option-def[0]/type "record"
> config set Dhcp6/option-def[0]/array false
> config set Dhcp6/option-def[0]/record-types "ipv6-address, uint16, boolean, string"
> config set Dhcp6/option-def[0]/encapsulate ""

The "type" is set to "record" to indicate that the option contains multiple values of different types. These types are given as a comma-separated list in the "record-types" field and should be those listed in Table 17.3, “List of standard DHCP option types”.

The values of the option are set as follows:

> config add Dhcp6/option-data
> config set Dhcp6/option-data[0]/name "bar"
> config set Dhcp6/option-data[0]/space "dhcp6"
> config set Dhcp6/option-data[0]/code 101
> config set Dhcp6/option-data[0]/csv-format true
> config set Dhcp6/option-data[0]/data "2001:db8:1::10, 123, false, Hello World"
> config commit

"csv-format" is set "true" to indicate that the "data" field comprises a command-separated list of values. The values in the "data" must correspond to the types set in the "record-types" field of the option definition.

Note

It is recommended that boolean values are specified using "true" and "false" strings. This helps to prevent errors when typing multiple comma separated values, as it make it easier to identify the type of the value being typed, and compare it with the order of data fields. Nevetheless, it is possible to use integer values: "1" and "0", instead of "true" and "false" accordingly. If other integer value is specified, the configuration is rejected.

18.2.10. DHCPv6 vendor specific options

Currently there are three option spaces defined: dhcp4 (to be used in DHCPv4 daemon) and dhcp6 (for the DHCPv6 daemon); there is also vendor-opts-space, which is empty by default, but options can be defined in it. Those options are called vendor-specific information options. The following examples show how to define an option "foo" with code 1 that consists of an IPv6 address, an unsigned 16 bit integer and a string. The "foo" option is conveyed in a vendor specific information option. This option comprises a single uint32 value that is set to "12345". The sub-option "foo" follows the data field holding this value.

> config add Dhcp6/option-def
> config set Dhcp6/option-def[0]/name "foo"
> config set Dhcp6/option-def[0]/code 1
> config set Dhcp6/option-def[0]/space "vendor-opts-space"
> config set Dhcp6/option-def[0]/type "record"
> config set Dhcp6/option-def[0]/array false
> config set Dhcp6/option-def[0]/record-types "ipv6-address, uint16, string"
> config set Dhcp6/option-def[0]/encapsulates ""
> config commit

(Note that the option space is set to "vendor-opts-space".) Once the option format is defined, the next step is to define actual values for that option:

> config add Dhcp6/option-data
> config set Dhcp6/option-data[0]/name "foo"
> config set Dhcp6/option-data[0]/space "vendor-opts-space"
> config set Dhcp6/option-data[0]/code 1
> config set Dhcp6/option-data[0]/csv-format true
> config set Dhcp6/option-data[0]/data "2001:db8:1::10, 123, Hello World"
> config commit

We should also define values for the vendor-opts, that will convey our option foo.

> config add Dhcp6/option-data
> config set Dhcp6/option-data[1]/name "vendor-opts"
> config set Dhcp6/option-data[1]/space "dhcp6"
> config set Dhcp6/option-data[1]/code 17
> config set Dhcp6/option-data[1]/csv-format true
> config set Dhcp6/option-data[1]/data "12345"
> config commit

18.2.11. Nested DHCPv6 options (custom option spaces)

It is sometimes useful to define completely new option spaces. This is useful if the user wants his new option to convey sub-options that use separate numbering scheme, for example sub-options with codes 1 and 2. Those option codes conflict with standard DHCPv6 options, so a separate option space must be defined.

Note that it is not required to create new option space when defining sub-options for a standard option because it is by default created if the standard option is meant to convey any sub-options (see Section 18.2.10, “DHCPv6 vendor specific options”).

Assume that we want to have a DHCPv6 option called "container" with code 102 that conveys two sub-options with codes 1 and 2. First we need to define the new sub-options:

> config add Dhcp6/option-def
> config set Dhcp6/option-def[0]/name "subopt1"
> config set Dhcp6/option-def[0]/code 1
> config set Dhcp6/option-def[0]/space "isc"
> config set Dhcp6/option-def[0]/type "ipv6-address"
> config set Dhcp6/option-def[0]/record-types ""
> config set Dhcp6/option-def[0]/array false
> config set Dhcp6/option-def[0]/encapsulate ""
> config commit
> 
> config add Dhcp6/option-def
> config set Dhcp6/option-def[1]/name "subopt2"
> config set Dhcp6/option-def[1]/code 2
> config set Dhcp6/option-def[1]/space "isc"
> config set Dhcp6/option-def[1]/type "string"
> config set Dhcp6/option-def[1]/record-types ""
> config set Dhcp6/option-def[1]/array false
> config set Dhcp6/option-def[1]/encapsulate ""
> config commit

Note that we have defined the options to belong to a new option space (in this case, "isc").

The next step is to define a regular DHCPv6 option and specify that it should include options from the isc option space:

> config add Dhcp6/option-def
> config set Dhcp6/option-def[2]/name "container"
> config set Dhcp6/option-def[2]/code 102
> config set Dhcp6/option-def[2]/space "dhcp6"
> config set Dhcp6/option-def[2]/type "empty"
> config set Dhcp6/option-def[2]/array false
> config set Dhcp6/option-def[2]/record-types ""
> config set Dhcp6/option-def[2]/encapsulate "isc"
> config commit

The name of the option space in which the sub-options are defined is set in the "encapsulate" field. The "type" field is set to "empty" which imposes that this option does not carry any data other than sub-options.

Finally, we can set values for the new options:

> config add Dhcp6/option-data
> config set Dhcp6/option-data[0]/name "subopt1"
> config set Dhcp6/option-data[0]/space "isc"
> config set Dhcp6/option-data[0]/code 1
> config set Dhcp6/option-data[0]/csv-format true
> config set Dhcp6/option-data[0]/data "2001:db8::abcd"
> config commit
> 
> config add Dhcp6/option-data
> config set Dhcp6/option-data[1]/name "subopt2"
> config set Dhcp6/option-data[1]/space "isc"
> config set Dhcp6/option-data[1]/code 2
> config set Dhcp6/option-data[1]/csv-format true
> config set Dhcp6/option-data[1]/data "Hello world"
> config commit
> 
> config add Dhcp6/option-data
> config set Dhcp6/option-data[2]/name "container"
> config set Dhcp6/option-data[2]/space "dhcp6"
> config set Dhcp6/option-data[2]/code 102
> config set Dhcp6/option-data[2]/csv-format true
> config set Dhcp6/option-data[2]/data ""
> config commit

Even though the "container" option does not carry any data except sub-options, the "data" field must be explicitly set to an empty value. This is required because in the current version of BIND 10 DHCP, the default configuration values are not propagated to the configuration parsers: if the "data" is not set the parser will assume that this parameter is not specified and an error will be reported.

Note that it is possible to create an option which carries some data in addition to the sub-options defined in the encapsulated option space. For example, if the "container" option from the previous example was required to carry an uint16 value as well as the sub-options, the "type" value would have to be set to "uint16" in the option definition. (Such an option would then have the following data structure: DHCP header, uint16 value, sub-options.) The value specified with the "data" parameter - which should be a valid integer enclosed in quotes, e.g. "123" - would then be assigned to the uint16 field in the "container" option.

18.2.12. IPv6 Subnet Selection

The DHCPv6 server may receive requests from local (connected to the same subnet as the server) and remote (connecting via relays) clients. As server may have many subnet configurations defined, it must select appropriate subnet for a given request.

The server can not assume which of configured subnets are local. It is possible in IPv4, where there is reasonable expectation that the server will have a (global) IPv4 address configured on the interface, and can use that information to detect whether a subnet is local or not. That assumption is not true in IPv6, as the DHCPv6 must be able to operate with having link-local addresses only. Therefore an optional "interface" parameter is available within a subnet definition to designate that a given subnet is local, i.e. reachable directly over specified interface. For example the server that is intended to serve a local subnet over eth0 may be configured as follows:

> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[1]/subnet "2001:db8:beef::/48"
> config set Dhcp6/subnet6[1]/pool [ "2001:db8:beef::/48" ]
> config set Dhcp6/subnet6[1]/interface "eth0"
> config commit

18.2.13. DHCPv6 Relays

A DHCPv6 server with multiple subnets defined must select the appropriate subnet when it receives a request from client. For clients connected via relays, two mechanisms are used:

The first uses the linkaddr field in the RELAY_FORW message. The name of this field is somewhat misleading in that it does not contain a link-layer address: instead, it holds an address (typically a global address) that is used to identify a link. The DHCPv6 server checks if the address belongs to a defined subnet and, if it does, that subnet is selected for the client's request.

The second mechanism is based on interface-id options. While forwarding a client's message, relays may insert an interface-id option into the message that identifies the interface on the relay that received the message. (Some relays allow configuration of that parameter, but it is sometimes hardcoded and may range from the very simple (e.g. "vlan100") to the very cryptic: one example seen on real hardware was "ISAM144|299|ipv6|nt:vp:1:110"). The server can use this information to select the appropriate subnet. The information is also returned to the relay which then knows the interface to use to transmit the response to the client. In order for this to work successfully, the relay interface IDs must be unique within the network and the server configuration must match those values.

When configuring the DHCPv6 server, it should be noted that two similarly-named parameters can be configured for a subnet:

  • "interface" defines which local network interface can be used to access a given subnet.
  • "interface-id" specifies the content of the interface-id option used by relays to identify the interface on the relay to which the response packet is sent.

The two are mutually exclusive: a subnet cannot be both reachable locally (direct traffic) and via relays (remote traffic). Specifying both is a configuration error and the DHCPv6 server will refuse such a configuration.

To specify interface-id with value "vlan123", the following commands can be used:

> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[0]/subnet "2001:db8:beef::/48"
> config set Dhcp6/subnet6[0]/pool [ "2001:db8:beef::/48" ]
> config set Dhcp6/subnet6[0]/interface-id "vland123"
> config commit

18.2.14. Client Classification in DHCPv6

Note

DHCPv6 server has been extended to support limited client classification. Although the current capability is modest, it is expected to be expanded in the future. It is envisaged that the majority of client classification extensions will be using hooks extensions.

In certain cases it is useful to differentiate between different types of clients and treat them differently. The process of doing classification is conducted in two steps. The first step is to assess incoming packet and assign it to zero or more classes. This classification is currently simple, but is expected to grow in capability soon. Currently the server checks whether incoming packet has vendor class option (16). If it has, content of that option is prepended with "VENDOR_CLASS_" interpreted as a class. For example, modern cable modems will send this option with value "docsis3.0" and as a result the packet will belong to class "VENDOR_CLASS_docsis3.0".

It is envisaged that the client classification will be used for changing behavior of almost any part of the DHCP engine processing, including assigning leases from different pools, assigning different option (or different values of the same options) etc. For now, there is only one mechanism that is taking advantage of client classification: subnet selection.

Kea can be instructed to limit access to given subnets based on class information. This is particularly useful for cases where two types of devices share the same link and are expected to be served from two different subnets. The primary use case for such a scenario are cable networks. There are two classes of devices: cable modem itself, which should be handled a lease from subnet A and all other devices behind modems that should get a lease from subnet B. That segregation is essential to prevent overly curious users from playing with their cable modems. For details on how to set up class restrictions on subnets, see Section 18.2.15, “Limiting access to IPv6 subnet to certain classes”.

18.2.15. Limiting access to IPv6 subnet to certain classes

In certain cases it beneficial to restrict access to certains subnets only to clients that belong to a given subnet. For details on client classes, see Section 18.2.14, “Client Classification in DHCPv6”. This is an extension of a previous example from Section 18.2.6, “Subnet and Address Pool”. Let's assume that the server is connected to a network segment that uses the 2001:db8:1::/64 prefix. The Administrator of that network has decided that addresses from range 2001:db8:1::1 to 2001:db8:1::ffff are going to be managed by the Dhcp6 server. Only clients belonging to the eRouter1.0 client class are allowed to use that pool. Such a configuration can be achieved in the following way:

> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64"
> config set Dhcp6/subnet6[0]/pool [ "2001:db8:1::0 - 2001:db8:1::ffff" ]
> config set Dhcp6/subnet6[0]/client-class "eRouter1.0"
> config commit

Care should be taken with client classification as it is easy to prevent clients that do not meet class criteria to be denied any service altogether.

18.2.16. Configuring DHCPv6 for DDNS

As mentioned earlier, DHCPv6 can be configured to generate requests to the DHCP-DDNS server (referred to here as the "D2" server) to update DNS entries. These requests are known as NameChangeRequests or NCRs. Each NCR contains the following information:

  1. Whether it is a request to add (update) or remove DNS entries

  2. Whether the change requests forward DNS updates (AAAA records), reverse DNS updates (PTR records), or both.

  3. The FQDN, lease address, and DHCID

The parameters controlling the generation of NCRs for submission to D2 are contained in the "dhcp-ddns" section of the DHCPv6 server configuration. The default values for this section appears as follows:

> config show Dhcp6/dhcp-ddns
Dhcp6/dhcp-ddns/enable-updates	true	boolean
Dhcp6/dhcp-ddns/server-ip	"127.0.0.1"	string
Dhcp6/dhcp-ddns/server-port	53001	integer
Dhcp6/dhcp-ddns/ncr-protocol	"UDP"	string
Dhcp6/dhcp-ddns/ncr-format	"JSON"	string
Dhcp6/dhcp-ddns/override-no-update	false	boolean
Dhcp6/dhcp-ddns/override-client-update	false	boolean
Dhcp6/dhcp-ddns/replace-client-name	false	boolean
Dhcp6/dhcp-ddns/generated-prefix	"myhost"	string
Dhcp6/dhcp-ddns/qualifying-suffix	"example.com"	string

The "enable-updates" parameter determines whether or not DHCPv6 will generate NCRs. By default, this value is false hence DDNS updates are disabled. To enable DDNS updates set this value to true as follows:

> config set Dhcp6/dhcp-ddns/enable-updates true
> config commit

18.2.16.1. DHCP-DDNS Server Connectivty

In order for NCRs to reach D2, DHCPv6 must be able to communicate with it. The following parameters are used to establish connectivty between DHCPv6 and D2.

The parameters, "server-ip" and "server-port", specify the address of the D2 server. By default, D2 is assumed to running on the same machine as DHCPv6, and the default values for these two parameters should be sufficient. However, if D2 has been configured to listen on a different address or port, these values must altered accordingly. For example, if D2 has been configured to listen on 198.162.1.10 port 900, the following commands would be required:

> config set Dhcp6/dhcp-ddns/server-ip "198.162.1.10"
> config set Dhcp6/dhcp-ddns/server-port 900
> config commit
D2 can be configured to listen over IPv4 or IPv6, therefore server-ip may be either an IPv4 or IPv6 address.

The socket protocol that DHCPv6 should use to communicate with D2 is specified with the "ncr-protocol" parameter. Currently only UDP is supported.

The internal format for DDNS update requests sent by DHCPv6 is specified with the "ncr-format" parameter. Currently only JSON is supported.

18.2.16.2. When does DHCPv6 generates DDNS request

DHCPv6 follows the behavior prescribed for DHCP servers in RFC 4704. It is important to keep in mind that DHCPv6 provides the initial decision making of when and what to update and forwards that information to D2 in the form of NCRs. Carrying out the actual DNS updates and dealing with such things as conflict resolution are the purvue of D2 (Chapter 19, The DHCP-DDNS Server).

This section describes when DHCPv6 will generate NCRs and the configuration parameters that can be used to influence this decision. It assumes that the "enable-updates" paramater is true.

Note

Currently the interface between DHCPv6 and D2 only supports requests which update DNS entries for a single IP address. If a lease grants more than one address, DHCPv6 will create the DDNS update request for only the first of these addresses. Support for multiple address mappings may be provided in a future release.

In general, DHCPv6 will generate DDNS udpate requests when:

  1. A new lease is granted in response to a DHCP REQUEST

  2. An existing lease is renewed but the FQDN associated with it has changed.

  3. An existing lease is released in response to a DHCP RELEASE

In the second case, lease renewal, two DDNS requests will be issued: one request to remove entries for the previous FQDN and a second request to add entries for the new FQDN. In the last case, a lease release, a single DDNS request to remove its entries will be made. The decision making involved when granting a new lease is more involved and is discussed next.

DHCPv6 will generate a DDNS update request only if the DHCP REQUEST contains the FQDN option (code 39). By default the DHCPv6 server will respect the FQDN N and S flags specified by the client as shown in the following table:

Table 18.2. Default FQDN Flag Behavior

Client Flags:N-SClient IntentServer ResponseServer Flags:N-S-O
0-0 Client wants to do forward updates, server should do reverse updates Server generates reverse-only request1-0-0
0-1Server should do both forward and reverse updatesServer generates request to update both directions0-1-0
1-0Client wants no updates doneServer does not generate a request1-0-0

The first row in the table above represents "client delegation". Here the DHCP client states that it intends to do the forward DNS updates and the server should do the reverese updates. By default, DHCPv6 will honor the client's wishes and generate a DDNS request to D2 to update only reverse DNS data. The parameter, "override-client-update", can be used to instruct the server to override client delegation requests. When this parameter is true, DHCPv6 will disregard requests for client delegation and generate a DDNS request to update both forward and reverse DNS data. In this case, the N-S-O flags in the server's response to the client will be 0-1-1 respectively.

(Note that the flag combination N=1, S=1 is prohibited according to RFC 4702. If such a combination is received from the client, the packet will be dropped by the DHCPv6 server.)

To override client delegation, issue the following commands:

> config set Dhcp6/dhcp-ddns/override-client-update true
> config commit

The third row in the table above describes the case in which the client requests that no DNS updates be done. The parameter, "override-no-update", can be used to instruct the server to disregard the client's wishes. When this parameter is true, DHCPv6 will generate DDNS udpate request to D2 even if the client requests no updates be done. The N-S-O flags in the server's response to the client will be 0-1-1.

To override client delegation, issue the following commands:

> config set Dhcp6/dhcp-ddns/override-no-update true
> config commit

18.2.16.3. DHCPv6 name generation for DDNS update requests

Each NameChangeRequest must of course include the fully qualified domain name whose DNS entries are to be affected. DHCPv6 can be configured to supply a portion or all of that name based upon what it receives from the client in the DHCP REQUEST.

The rules for determining the FQDN option are as follows:

  1. If configured to do so ignore the REQUEST contents and generate a FQDN using a configurable prefix and suffix.

  2. Otherwise, using is the domain name value from the client FQDN option as the candidate name:

    1. If the candidate name is a fully qualified domain name then use it.

    2. If the candidate name is a partial (i.e. unqualified) name then add a configurable suffix to the name and use the result as the FQDN.

    3. If the candidate name is a empty then generate a FQDN using a configurable prefix and suffix.

To instruct DHCPv6 to always generate a FQDN, set the parameter "replace-client-name" to true:

> config set Dhcp6/dhcp-ddns/replace-client-name true
> config commit

The prefix used when generating a FQDN is specified by the "generated-prefix" parameter. The default value is "myhost". To alter its value, simply set it to the desired string:

> config set Dhcp6/dhcp-ddns/generated-prefix "another.host"
> config commit

The suffix used when generating a FQDN or when qualifying a partial name is specified by the "qualifying-suffix" parameter. The default value is "example.com". To alter its value simply set it to the desired string:

> config set Dhcp6/dhcp-ddns/generated-prefix "our.net"
> config commit

When qualifying a partial name, DHCPv6 will construct a name with the format:

[candidate-name].[qualifying-suffix].

where candidate-name is the partial name supplied in the REQUEST. For example, if FQDN domain name value was "some-computer" and assuming the default value for qualifying-suffix, the generated FQDN would be:

some-computer.example.com.

When generating a the entire name, DHCPv6 will construct name of the format:

[generated-prefix]-[address-text].[qualifying-suffix].

where address-text is simply the lease IP address converted to a hyphenated string. For example, if lease address is 3001:1::70E and assuming default values for generated-prefix and qualifying-suffix, the generated FQDN would be:

myhost-3001-1--70E.example.com.

18.3. Server Identifier in DHCPv6

The DHCPv6 protocol uses a "server identifier" (also known as a DUID) for clients to be able to discriminate between several servers present on the same link. There are several types of DUIDs defined, but RFC 3315 instructs servers to use DUID-LLT if possible. This format consists of a link-layer (MAC) address and a timestamp. When started for the first time, the DHCPv6 server will automatically generate such a DUID and store the chosen value to a file. That file is read by the server and the contained value used whenever the server is subsequently started.

It is unlikely that this parameter should ever need to be changed. However, if such a need arises, stop the server, edit the file and restart the server. (The file is named b10-dhcp6-serverid and by default is stored in the "var" subdirectory of the directory in which BIND 10 is installed. This can be changed when BIND 10 is built by using "--localstatedir" on the "configure" command line.) The file is a text file that contains double digit hexadecimal values separated by colons. This format is similar to typical MAC address format. Spaces are ignored. No extra characters are allowed in this file.

18.4. Using specific relay agent for a subnet

The relay has to have an interface connected to the link on which the clients are being configured. Typically the relay has a global IPv6 address configured on that interface that belongs to the subnet that the server will assign addresses from. In such typical case, the server is able to use IPv6 address inserted by the relay (in link-addr field in RELAY-FORW message) to select appropriate subnet.

However, that is not always the case. The relay address may not match the subnet in certain deployments. This usually means that there is more than one subnet allocated for a given link. Two most common examples where this is the case are long lasting network renumbering (where both old and new address space is still being used) and a cable network. In a cable network both cable modems and the devices behind them are physically connected to the same link, yet they use distinct addressing. In such case, the DHCPv6 server needs additional information (like the value of interface-id option or IPv6 address inserted in the link-addr field in RELAY-FORW message) to properly select an appropriate subnet.

The following example assumes that there is a subnet 2001:db8:1::/64 that is accessible via relay that uses 3000::1 as its IPv6 address. The server will be able to select this subnet for any incoming packets that came from a relay that has an address in 2001:db8:1::/64 subnet. It will also select that subnet for a relay with address 3000::1.

> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64"
> config set Dhcp6/subnet6[0]/pool [ "2001:db8:1::2 - 2001:db8:1::ffff" ]
> config set Dhcp6/subnet6[0]/relay/ip-address "3000::1"
> config commit

18.5. Segregating IPv6 clients in a cable network

In certain cases, it is useful to mix relay address information, introduced in Section 18.4, “Using specific relay agent for a subnet” with client classification, explained in Section 18.2.15, “Limiting access to IPv6 subnet to certain classes”. One specific example is cable network, where typically modems get addresses from a different subnet than all devices connected behind them.

Let's assume that there is one CMTS (Cable Modem Termination System) with one CM MAC (a physical link that modems are connected to). We want the modems to get addresses from the 3000::/64 subnet, while everything connected behind modems should get addresses from another subnet (2001:db8:1::/64). The CMTS that acts as a relay an uses address 3000::1. The following configuration can serve that configuration:

> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[0]/subnet "3000::/64"
> config set Dhcp6/subnet6[0]/pool [ "3000::2 - 3000::ffff" ]
> config set Dhcp6/subnet6[0]/client-class "docsis3.0"
> config set Dhcp6/subnet6[0]/relay/ip-address "3000::1"
> config add Dhcp6/subnet6
> config set Dhcp6/subnet6[1]/subnet "2001:db8:1::/64"
> config set Dhcp6/subnet6[1]/pool [ "2001:db8:1::1 - 2001:db8:1::ffff" ]
> config set Dhcp6/subnet6[1]/relay/ip-address "3000::1"
> config commit

18.6. Supported Standards

The following standards and draft standards are currently supported:

  • RFC 3315: Supported messages are SOLICIT, ADVERTISE, REQUEST, RELEASE, RENEW, REBIND and REPLY.
  • RFC 3633: Supported options are IA_PD and IA_PREFIX. Also supported is the status code NoPrefixAvail.
  • RFC 3646: Supported option is DNS_SERVERS.
  • RFC 4704: Supported option is CLIENT_FQDN.

18.7. DHCPv6 Server Limitations

These are the current limitations and known problems with the DHCPv6 server software. Most of them are reflections of the early stage of development and should be treated as not implemented yet, rather than actual limitations.

  • On-line configuration has some limitations. Adding new subnets or modifying existing ones work, as is removing the last subnet from the list. However, removing non-last (e.g. removing subnet 1,2 or 3 if there are 4 subnets configured) will cause issues. The problem is caused by simplistic subnet-id assignment. The subnets are always numbered, starting from 1. That subnet-id is then used in leases that are stored in the lease database. Removing non-last subnet will cause the configuration information to mismatch data in the lease database. It is possible to manually update subnet-id fields in MySQL or PostgreSQL database, but it is awkward and error prone process. A better reconfiguration support is planned.

  • On startup, the DHCPv6 server does not get the full configuration from BIND 10. To remedy this, after starting BIND 10, modify any parameter and commit the changes, e.g.

    > config show Dhcp6/renew-timer
    Dhcp6/renew-timer	1000	integer	(default)
    > config set Dhcp6/renew-timer 1001
    > config commit

  • Temporary addresses are not supported.
  • The server will allocate, renew or rebind a maximum of one lease for a particular IA option (IA_NA or IA_PD) sent by a client. RFC 3315 and RFC 3633 allow for multiple addresses or prefixes to be allocated for a single IA.
  • Temporary addresses are not supported.
  • Confirmation (CONFIRM), duplication report (DECLINE), stateless configuration (INFORMATION-REQUEST) and client reconfiguration (RECONFIGURE) are not yet supported.
  • The server doesn't act upon expired leases. In particular, when a lease expires, the server doesn't request removal of the DNS records associated with it.


[2] The server comes with an in-memory database ("memfile") configured as the default database. This is used for internal testing and is not supported. In addition, it does not store lease information on disk: lease information will be lost if the server is restarted.

Chapter 19. The DHCP-DDNS Server

The DHCP-DDNS Server (known informally as D2) conducts the client side of the DDNS protocol (defined in RFC 2136) on behalf of the DHCPv4 and DHCPv6 servers. The DHCP servers construct DDNS update requests, known as NameChangeRequests (NCRs), based upon DHCP lease change events and then post these to D2. D2 attempts to match each such request to the appropriate DNS server(s) and carry out the necessary conversation with those servers to update the DNS data.

In order to match a request to appropriate DNS servers, D2 must have a catalog of servers from which to select. In fact, D2 has two such catalogs, one for forward DNS and one for reverse DNS; these catalogs are referred to as DDNS Domain Lists. Each list consists of one or more named DDNS Domains. Further, each DDNS Domain has a list of of one or more DNS servers that publish the DNS data for that domain.

When conducting forward domain matching, D2 will compare the FQDN in the request against the name of each forward DDNS Domain. The domain whose name matches the longest portion of the FQDN is considered the best match. For example, if the FQDN is "myhost.sample.example.com.", and there are two forward domains in the catalog: "sample.example.com." and "example.com.", the former is regarded as the best match. In some cases, it may not be possible to find a suitable match. Given the same two forward domains there would be no match for the FQDN, "bogus.net", so the request would be rejected. Finally, if there are no forward DDNS Domains defined, D2 will simply disregard the forward update portion of requests.

When conducting reverse domain matching, D2 constructs a reverse FQDN from the lease address in the request and compare that against the name of each reverse DDNS Domain. Again, the domain whose name matches the longest portion of the FQDN is considered the best match. For instance, if the lease address is "172.16.1.40" and there are two reverse domains in the catalog: "1.16.172.in-addr.arpa." and "16.172.in-addr.arpa", the former is the best match. As with forward matching, it is possible to not find a suitable match. Given the same two domains, there would be no match for the lease address, "192.168.1.50", and the request would be rejected. Finally, if there are no reverse DDNS Domains defined, D2 will simply disregard the reverse update portion of requests.

19.1. Starting and Stopping the DHCP-DDNS Server

b10-dhcp-ddns is the BIND 10 DHCP-DDNS server and, like other parts of BIND 10, is configured through the bindctl program.

After starting BIND 10 and entering bindctl, the first step in configuring the server is to add it to the list of running BIND 10 services.

> config add Init/components b10-dhcp-ddns
> config set Init/components/b10-dhcp-ddns/kind dispensable
> config commit

To remove b10-dhcp-ddns from the set of running services, the b10-dhcp-ddns is removed from list of Init components:

> config remove Init/components b10-dhcp-ddns
> config commit

Note that the server was only removed from the list, so BIND10 will not restart it, but the server itself is still running. Hence it is usually desired to stop it:

> DhcpDdns shutdown

Upon start up the module will load its configuration and begin listening for NCRs based on that configuration.

19.2. Configuring the DHCP-DDNS Server

Once the server is started, it can be configured. To view the current configuration, use the following command in bindctl:

> config show DhcpDdns

When starting b10-dhcp-ddns module for the first time, the default configuration will be available. It will look similar to this:

> config show DhcpDdns
DhcpDdns/interface  "eth0"  string  (default)
DhcpDdns/ip_address "127.0.0.1" string  (default)
DhcpDdns/port   53001   integer (default)
DhcpDdns/tsig_keys  []  list    (default)
DhcpDdns/forward_ddns/ddns_domains  []  list    (default)
DhcpDdns/reverse_ddns/ddns_domains  []  list    (default)

(While displayed, the parameter "interface" is not implemented, and will be removed in the near future.)

The configuration can be divided as follows, each of which is described in its own section:

  • General Server Parameters — values which control connectivity and global server behavior
  • TSIG Key Info — defines the TSIG keys used for secure traffic with DNS servers
  • Forward DDNS — defines the catalog of Forward DDNS Domains
  • Reverse DDNS — defines the catalog of Forward DDNS Domains

19.2.1. General Server Parameters

The DHCP-DDNS server must listen for requests on a known address and port. By default, it will listen at 127.0.0.1 on port 53001. This is governed by the parameters, "ip-address" and "port". Either value may be changed using config set/commit. For example to change the server to listen at 192.168.1.10 port 900:

> config set DhcpDdns/ip_address "192.168.1.10"
> config set DhcpDdns/port 900
> config commit

The server may be configured to listen over IPv4 or IPv6, therefore ip-address may an IPv4 or IPv6 address.

Warning

When the DHCP-DDNS server is configured to listen at an address other than the loopback address (127.0.0.1 or ::1), it is possible for a malicious attacker to send bogus NameChangeRequests to it and change entries in the DNS. For this reason, addresses other than the IPv4 or IPv6 loopback addresses should only be used for testing purposes. A future version of Kea will implement authentication to guard against such attacks.

Note

If the ip_address and port are changed, it will be necessary to change the corresponding values in the DHCP servers' "dhcp-ddns" configuration section.

19.2.2. TSIG Key List

Note

While this section may be displayed and edited using bindctl, the use of TSIG in actual communications between D2 and DNS servers is not yet implemented.

DDNS protocol can be conducted with or without TSIG as defined in RFC 2845. This configuration section allows the administrator to define the dictionary of TSIG keys to may be used. To use TSIG when working with a specific DDNS Domain that key must be defined in the TSIG Key List and referenced by name in that domain's entry in the DDNS catalog.

As one might gather from its name, this section is a list of TSIG keys. Each key has three parameters:

  • name — is a unique text label used to idenfity the this key within the list. It is this value that is used to specify which key (if any) should be used with a specific DNS server. So long as it is unique, its content is arbitrary. It cannot be blank.
  • algorithm — specifies which hashing algorithm should be used with this key. This value is not currently used.
  • secret — is used to specify the shared secret key code for this key. This value is not currently used.

By default, the TSIG Key list is empty:

> config show DhcpDdns/tsig_keys
DhcpDdns/tsig_keys  []  list  (default)

To create a new key in the list, one must first add a new key element:

> config add DhcpDdns/tsig_keys

Displaying the new element, reveals this:

> config show DhcpDdns/tsig_keys[0]
DhcpDdns/tsig_keys[0]/name  ""  string  (default)
DhcpDdns/tsig_keys[0]/algorithm "hmac_md5"  string  (modified)
DhcpDdns/tsig_keys[0]/secret  ""  string  (default)

Populating the key name and secret, while accepting the default value for alogorithm:

> config set DhcpDdns/tsig_keys[0]/name "key1.example.com"
> config set DhcpDdns/tsig_keys[0]/secret "123456789"
> config commit

19.2.3. Forward DDNS

The Forward DDNS section is used to configure D2's forward update behavior. Currently it contains a single parameter, the catalog of forward DDNS Domains:

> config show DhcpDdns/forward_ddns/
DhcpDdns/forward_ddns/ddns_domains  [] list  (default)

By default, this list is empty, which will cause the server to ignore the forward update portions of requests.

19.2.3.1. Adding Forward DDNS Domains

A forward DDNS Domain maps a forward DNS zone to a set of DNS servers which maintain the forward DNS data for that zone. You will need one forward DDNS Domain for each zone you wish to service. It may very well be that some or all of your zones are maintained by the same servers. You will still need one DDNS Domain per zone. Remember that matching a request to the appropriate server(s) is done by zone and a DDNS Domain only defines a single zone.

The section describes how to add Forward DDNS Domains. Repeat these steps for each Forward DDNS Domain desired. Each Forward DDNS Domain has the following parameters:

  • name — The fully qualified domain name (or zone) that this DDNS Domain can update. This is value used to compare against the request FQDN during forward matching. It must be unique within the catalog.
  • key_name — If TSIG is used with this domain's servers, this value should be the name of the key from within the TSIG Key List to use. If the value is blank (the default), TSIG will not be used in DDNS converations with this domain's servers. Currently TSIG has not been implemented, so this value is ignored.
  • dns_servers — A list of one or more DNS servers which can conduct the server side of the DDNS protocol for this domain. The servers are used in a first to last preference. In other words, when D2 begins to process a request for this domain it will pick the first server in this list and attempt to communicate with it. If that attempt fails, it will move to next one in the list and so on until the it achieves success or the list is exhausted.

To create a new forward DDNS Domain, one must first add a new domain element:

> config add DhcpDdns/forward_ddns/ddns_domains

Displaying the DDNS Domain reveals this:

> config show DhcpDdns/forward_ddns/ddns_domains[0]
DhcpDdns/forward_ddns/ddns_domains[0]/name  ""  string  (default)
DhcpDdns/forward_ddns/ddns_domains[0]/key_name  ""  string  (default)
DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers   []  list    (default)

To set the domain's name to "other.example.com":

> config set DhcpDdns/forward_ddns/ddns_domains[1]/name "other.example.com"
> config commit

It is permissable to add a domain without any servers. If that domain should be matched to a request, however, the request will fail. In order to make the domain useful though, we must add at least one DNS server to it.

19.2.3.1.1. Adding Forward DNS Servers

The section describes how to add DNS servers to a Forward DDNS Domain. Repeat them for as many servers as desired for a each domain.

Forward DNS Server entries represent actual DNS servers which support the server side of the DDNS protocol. Each Forward DNS Server has the following parameters:

  • hostname — The resolvable host name of the DNS server. This value is not yet implemented.
  • ip_address — The IP address at which the server listens for DDNS requests. This may be either an IPv4 or an IPv6 address.
  • port — The port on which the server listens for DDNS requests. It defaults to the standard DNS service port of 53.

To create a new forward DNS Server, one must first add a new server element to the domain:

> config add DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers

Displaying the DNS Server element should appear as follows:

> config show DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]
DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/hostname   ""  string  (default)
DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/ip_address ""  string  (default)
DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/port   53  integer(default)

As stated earlier, "hostname" is not yet supported so, the parameter "ip_address" must be set to the address of the DNS server. If for example the service is running at "172.88.99.10", then set it as follows:

> config set DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/ip_address "172.88.99.10"
> config commit

19.2.4. Reverse DDNS

The Reverse DDNS section is used to configure D2's reverse update behavior, and the concepts are the same as for the forward DDNS section. Currently it contains a single parameter, the catalog of reverse DDNS Domains:

> config show DhcpDdns/reverse_ddns/
DhcpDdns/reverse_ddns/ddns_domains  [] list  (default)

By default, this list is empty, which will cause the server to ignore the reverse update portions of requests.

19.2.4.1. Adding Reverse DDNS Domains

A reverse DDNS Domain maps a reverse DNS zone to a set of DNS servers which maintain the reverse DNS data for that zone. You will need one reverse DDNS Domain for each zone you wish to service. It may very well be that some or all of your zones are maintained by the same servers; even then, you will still need one DDNS Domain entry for each zone. Remember that matching a request to the appropriate server(s) is done by zone and a DDNS Domain only defines a single zone.

The section describes how to add Reverse DDNS Domains. Repeat these steps for each Reverse DDNS Domain desired. Each Reverse DDNS Domain has the following parameters:

  • name — The fully qualified reverse zone that this DDNS Domain can update. This is the value used during reverse matching which will compare it with a reversed version of the request's lease address. The zone name should follow the appropriate standards: for example, to to support the IPv4 subnet 172.16.1, the name should be. "1.16.172.in-addr.arpa.". Similarly, to support an IPv6 subent of 2001:db8:1, the name should be "1.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa." Whatever the name, it must be unique within the catalog.
  • key_name — If TSIG should be used with this domain's servers, then this value should be the name of the key from within the TSIG Key List to use. If the value is blank (the default), TSIG will not be used in DDNS converations with this domain's servers. Currently this value is not used as TSIG has not been implemented.
  • dns_servers — a list of one or more DNS servers which can conduct the server side of the DDNS protocol for this domain. Currently the servers are used in a first to last preference. In other words, when D2 begins to process a request for this domain it will pick the first server in this list and attempt to communicate with it. If that attempt fails, it will move to next one in the list and so on until the it achieves success or the list is exhausted.

To create a new reverse DDNS Domain, one must first add a new domain element:

> config add DhcpDdns/reverse_ddns/ddns_domains

Displaying the DDNS Domain reveals this:

> config show DhcpDdns/reverse_ddns/ddns_domains[0]
DhcpDdns/reverse_ddns/ddns_domains[0]/name  ""  string  (default)
DhcpDdns/reverse_ddns/ddns_domains[0]/key_name  ""  string  (default)
DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers   []  list    (default)

For domain supporting the subnet 2001:db8:1::, we would set the domain's name as follows:

> config set DhcpDdns/reverse_ddns/ddns_domains[1]/name "1.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa."
> config commit

It is permissable to add a domain without any servers. If that domain should be matched to a request, however, the request will fail. In order to make the domain useful though, we must add at least one DNS server to it.

19.2.4.1.1. Adding Reverse DNS Servers

The section describes how to add DNS servers to a Reverse DDNS Domain. Repeat them for as many servers as desired for a each domain.

Reverse DNS Server entries represents a actual DNS servers which support the server side of the DDNS protocol. Each Reverse DNS Server has the following parameters:

  • hostname — The resolvable host name of the DNS server. This value is currently ignored.
  • ip_address — The IP address at which the server listens for DDNS requests.
  • port — The port on which the server listens for DDNS requests. It defaults to the standard DNS service port of 53.

To create a new reverse DNS Server, one must first add a new server element to the domain:

> config add DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers

Displaying the DNS Server element should appear as follows:

> config show DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]
DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/hostname   ""  string  (default)
DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/ip_address ""  string  (default)
DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/port   53  integer(default)

As stated earlier, "hostname" is not yet supported so, the parameter "ip_address" must be set to the address of the DNS server. If for example the service is running at "172.88.99.10", then set it as follows:

> config set DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/ip_address "172.88.99.10"
> config commit

19.2.5. Example DHCP-DDNS Server Configuration

This section provides an example DHCP-DDNS server configuration based on a small example network. Let's suppose our example network has three domains, each with their own subnet.

Table 19.1. Our example network

DomainSubnetForward DNS ServersReverse DNS Servers
four.example.com192.0.2.0/24172.16.1.5, 172.16.2.5172.16.1.5, 172.16.2.5
six.example.com2001:db8:1::/643001:1::503001:1::51
example.com192.0.0.0/16172.16.2.5172.16.2.5


We need to construct three forward DDNS Domains:

Table 19.2. Forward DDNS Domains Needed

#DDNS Domain NameDNS Servers
1.four.example.com.172.16.1.5, 172.16.2.5
2.six.example.com.3001:1::50
3.example.com.172.16.2.5


As discussed earlier, FQDN to domain matching is based on the longest match. The FQDN, "myhost.four.example.com.", will match the first domain ("four.example.com") while "admin.example.com." will match the third domain ("example.com"). The FQDN, "other.example.net." will fail to match any domain and would be rejected.

The following series of commands in bindctl will create the Forward DDNS Domains.


> config add DhcpDdns/forward_ddns/ddns_domains
> config set DhcpDdns/forward_ddns/ddns_domains[0]/name "four.example.com."
> config add DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers
> config set DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/ip_address "172.16.1.5"
> config add DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers
> config set DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[1]/ip_address "172.16.2.5"
>
> config add DhcpDdns/forward_ddns/ddns_domains
> config set DhcpDdns/forward_ddns/ddns_domains[1]/name "six.example.com."
> config add DhcpDdns/forward_ddns/ddns_domains[1]/dns_servers
> config set DhcpDdns/forward_ddns/ddns_domains[1]/dns_servers[0]/ip_address "3001:1::50:"
>
> config add DhcpDdns/forward_ddns/ddns_domains
> config set DhcpDdns/forward_ddns/ddns_domains[2]/name "example.com."
> config add DhcpDdns/forward_ddns/ddns_domains[2]/dns_servers
> config set DhcpDdns/forward_ddns/ddns_domains[2]/dns_servers[0]/ip_address "172.16.2.5"
>
> config commit

Similarly, we need to construct the three reverse DDNS Domains:

Table 19.3. Reverse DDNS Domains Needed

#DDNS Domain NameDNS Servers
1.2.0.192.in-addr.arpa.172.16.1.5, 172.16.2.5
2.1.0.0.0.8.d.b.0.1.0.0.2.ip6.arpa.3001:1::50
3.0.182.in-addr.arpa.172.16.2.5


An address of "192.0.2.150" will match the first domain, "2001:db8:1::10" will match the second domain, and "192.0.50.77" the third domain.

The following series of commands in bindctl will create our Reverse DDNS Domains.


> config add DhcpDdns/reverse_ddns/ddns_domains
> config set DhcpDdns/reverse_ddns/ddns_domains[0]/name "2.0.192.in-addr.arpa."
> config add DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers
> config set DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/ip_address "172.16.1.5"
> config add DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers
> config set DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[1]/ip_address "172.16.2.5"
>
> config add DhcpDdns/reverse_ddns/ddns_domains
> config set DhcpDdns/reverse_ddns/ddns_domains[1]/name "1.0.0.0.8.d.b.0.1.0.0.2.ip6.arpa."
> config add DhcpDdns/reverse_ddns/ddns_domains[1]/dns_servers
> config set DhcpDdns/reverse_ddns/ddns_domains[1]/dns_servers[0]/ip_address "3001:1::50:"
>
> config add DhcpDdns/reverse_ddns/ddns_domains
> config set DhcpDdns/reverse_ddns/ddns_domains[2]/name "0.192.in-addr.arpa."
> config add DhcpDdns/reverse_ddns/ddns_domains[2]/dns_servers
> config set DhcpDdns/reverse_ddns/ddns_domains[2]/dns_servers[0]/ip_address "172.16.2.5"
>
> config commit

19.3. DHCP-DDNS Server Limitations

The following are the current limitations of the DHCP-DDNS Server.

  • Requests received from the DHCP servers are placed in a queue until they are processed. Currently all queued requests are lost when the server shuts down.
  • TSIG Authentication (RFC 2845) is not supported yet.

Chapter 20. libdhcp++ library

libdhcp++ is a common library written in C++ that handles many DHCP-related tasks, including:

  • DHCPv4 and DHCPv6 packets parsing, manipulation and assembly
  • Option parsing, manipulation and assembly
  • Network interface detection
  • Socket operations such as creation, data transmission and reception and socket closing.

While this library is currently used by BIND 10 DHCP, it is designed to be a portable, universal library, useful for any kind of DHCP-related software.

20.1. Interface detection and Socket handling

Both the DHCPv4 and DHCPv6 components share network interface detection routines. Interface detection is currently supported on Linux, all BSD family (FreeBSD, NetBSD, OpenBSD), Mac OS X and Solaris 11 systems.

DHCPv4 requires special raw socket processing to send and receive packets from hosts that do not have IPv4 address assigned yet. Support for this operation is implemented on Linux only, so it is likely that DHCPv4 component will not work in certain cases on systems other than Linux.

Chapter 21. Statistics

The b10-stats process is started by b10-init. It periodically collects statistics data from various modules and aggregates it.

This stats daemon provides commands to identify if it is running, show specified or all statistics data, and show specified or all statistics data schema. For example, using bindctl:

> Stats show
{
    "Auth": {
        "opcode.iquery": 0,
        "opcode.notify": 10,
        "opcode.query": 869617,
        ...
        "queries.tcp": 1749,
        "queries.udp": 867868
    },
    "Init": {
        "boot_time": "2011-01-20T16:59:03Z"
    },
    "Stats": {
        "boot_time": "2011-01-20T16:59:05Z",
        "last_update_time": "2011-01-20T17:04:05Z",
        "lname": "4d3869d9_a@jreed.example.net",
        "report_time": "2011-01-20T17:04:06Z",
        "timestamp": 1295543046.823504
    }
}
       

Chapter 22. Logging

22.1. Logging configuration

The logging system in BIND 10 is configured through the Logging module. All BIND 10 modules will look at the configuration in Logging to see what should be logged and to where.

22.1.1. Loggers

Within BIND 10, a message is logged through a component called a "logger". Different parts of BIND 10 log messages through different loggers, and each logger can be configured independently of one another.

In the Logging module, you can specify the configuration for zero or more loggers; any that are not specified will take appropriate default values.

The three most important elements of a logger configuration are the name (the component that is generating the messages), the severity (what to log), and the output_options (where to log).

22.1.1.1. name (string)

Each logger in the system has a name, the name being that of the component using it to log messages. For instance, if you want to configure logging for the resolver module, you add an entry for a logger named Resolver. This configuration will then be used by the loggers in the Resolver module, and all the libraries used by it.

If you want to specify logging for one specific library within the module, you set the name to module.library. For example, the logger used by the nameserver address store component has the full name of Resolver.nsas. If there is no entry in Logging for a particular library, it will use the configuration given for the module.

To illustrate this, suppose you want the cache library to log messages of severity DEBUG, and the rest of the resolver code to log messages of severity INFO. To achieve this you specify two loggers, one with the name Resolver and severity INFO, and one with the name Resolver.cache with severity DEBUG. As there are no entries for other libraries (e.g. the nsas), they will use the configuration for the module (Resolver), so giving the desired behavior.

One special case is that of a module name of * (asterisks), which is interpreted as any module. You can set global logging options by using this, including setting the logging configuration for a library that is used by multiple modules (e.g. *.config specifies the configuration library code in whatever module is using it).

If there are multiple logger specifications in the configuration that might match a particular logger, the specification with the more specific logger name takes precedence. For example, if there are entries for both * and Resolver, the resolver module — and all libraries it uses — will log messages according to the configuration in the second entry (Resolver). All other modules will use the configuration of the first entry (*). If there was also a configuration entry for Resolver.cache, the cache library within the resolver would use that in preference to the entry for Resolver.

One final note about the naming. When specifying the module name within a logger, use the name of the module as specified in bindctl, e.g. Resolver for the resolver module, Xfrout for the xfrout module, etc. When the message is logged, the message will include the name of the logger generating the message, but with the module name replaced by the name of the process implementing the module (so for example, a message generated by the Auth.cache logger will appear in the output with a logger name of b10-auth.cache).

22.1.1.2. severity (string)

This specifies the category of messages logged. Each message is logged with an associated severity which may be one of the following (in descending order of severity):

  • FATAL
  • ERROR
  • WARN
  • INFO
  • DEBUG

When the severity of a logger is set to one of these values, it will only log messages of that severity, and the severities above it. The severity may also be set to NONE, in which case all messages from that logger are inhibited.

22.1.1.3. output_options (list)

Each logger can have zero or more output_options. These specify where log messages are sent to. These are explained in detail below.

The other options for a logger are:

22.1.1.4. debuglevel (integer)

When a logger's severity is set to DEBUG, this value specifies what debug messages should be printed. It ranges from 0 (least verbose) to 99 (most verbose).

If severity for the logger is not DEBUG, this value is ignored.

22.1.1.5. additive (true or false)

If this is true, the output_options from the parent will be used. For example, if there are two loggers configured; Resolver and Resolver.cache, and additive is true in the second, it will write the log messages not only to the destinations specified for Resolver.cache, but also to the destinations as specified in the output_options in the logger named Resolver.

22.1.2. Output Options

The main settings for an output option are the destination and a value called output, the meaning of which depends on the destination that is set.

22.1.2.1. destination (string)

The destination is the type of output. It can be one of:

  • console
  • file
  • syslog

22.1.2.2. output (string)

Depending on what is set as the output destination, this value is interpreted as follows:

destination is console

The value of output must be one of stdout (messages printed to standard output) or stderr (messages printed to standard error).

Note: if output is set to stderr and a lot of messages are produced in a short time (e.g. if the logging level is set to DEBUG), you may occasionally see some messages jumbled up together. This is due to a combination of the way that messages are written to the screen and the unbuffered nature of the standard error stream. If this occurs, it is recommended that output be set to stdout.

destination is file

The value of output is interpreted as a file name; log messages will be appended to this file.

destination is syslog

The value of output is interpreted as the syslog facility (e.g. local0) that should be used for log messages.

The other options for output_options are:

22.1.2.2.1. flush (true of false)

Flush buffers after each log message. Doing this will reduce performance but will ensure that if the program terminates abnormally, all messages up to the point of termination are output.

22.1.2.2.2. maxsize (integer)

Only relevant when destination is file, this is maximum file size of output files in bytes. When the maximum size is reached, the file is renamed and a new file opened. (For example, a ".1" is appended to the name — if a ".1" file exists, it is renamed ".2", etc.)

If this is 0, no maximum file size is used.

Note

Due to a limitation of the underlying logging library (log4cplus), rolling over the log files (from ".1" to ".2", etc) may show odd results: There can be multiple small files at the timing of roll over. This can happen when multiple BIND 10 processes try to roll over the files simultaneously. Version 1.1.0 of log4cplus solved this problem, so if this or higher version of log4cplus is used to build BIND 10, it shouldn't happen. Even for older versions it is normally expected to happen rarely unless the log messages are produced very frequently by multiple different processes.

22.1.2.2.3. maxver (integer)

Maximum number of old log files to keep around when rolling the output file. Only relevant when destination is file.

22.1.3. Example session

In this example we want to set the global logging to write to the file /var/log/my_bind10.log, at severity WARN. We want the authoritative server to log at DEBUG with debuglevel 40, to a different file (/tmp/debug_messages).

Start bindctl.

["login success "]
> config show Logging
Logging/loggers	[]	list

By default, no specific loggers are configured, in which case the severity defaults to INFO and the output is written to stderr.

Let's first add a default logger:

> config add Logging/loggers
> config show Logging
Logging/loggers/	list	(modified)

The loggers value line changed to indicate that it is no longer an empty list:

> config show Logging/loggers
Logging/loggers[0]/name	""	string	(default)
Logging/loggers[0]/severity	"INFO"	string	(default)
Logging/loggers[0]/debuglevel	0	integer	(default)
Logging/loggers[0]/additive	false	boolean	(default)
Logging/loggers[0]/output_options	[]	list	(default)

The name is mandatory, so we must set it. We will also change the severity as well. Let's start with the global logger.

> config set Logging/loggers[0]/name *
> config set Logging/loggers[0]/severity WARN
> config show Logging/loggers
Logging/loggers[0]/name	"*"	string	(modified)
Logging/loggers[0]/severity	"WARN"	string	(modified)
Logging/loggers[0]/debuglevel	0	integer	(default)
Logging/loggers[0]/additive	false	boolean	(default)
Logging/loggers[0]/output_options	[]	list	(default)

Of course, we need to specify where we want the log messages to go, so we add an entry for an output option.

>  config add Logging/loggers[0]/output_options
>  config show Logging/loggers[0]/output_options
Logging/loggers[0]/output_options[0]/destination	"console"	string	(default)
Logging/loggers[0]/output_options[0]/output	"stdout"	string	(default)
Logging/loggers[0]/output_options[0]/flush	false	boolean	(default)
Logging/loggers[0]/output_options[0]/maxsize	0	integer	(default)
Logging/loggers[0]/output_options[0]/maxver	0	integer	(default)

These aren't the values we are looking for.

>  config set Logging/loggers[0]/output_options[0]/destination file
>  config set Logging/loggers[0]/output_options[0]/output /var/log/bind10.log
>  config set Logging/loggers[0]/output_options[0]/maxsize 204800
>  config set Logging/loggers[0]/output_options[0]/maxver 8

Which would make the entire configuration for this logger look like:

>  config show all Logging/loggers
Logging/loggers[0]/name	"*"	string	(modified)
Logging/loggers[0]/severity	"WARN"	string	(modified)
Logging/loggers[0]/debuglevel	0	integer	(default)
Logging/loggers[0]/additive	false	boolean	(default)
Logging/loggers[0]/output_options[0]/destination	"file"	string	(modified)
Logging/loggers[0]/output_options[0]/output	"/var/log/bind10.log"	string	(modified)
Logging/loggers[0]/output_options[0]/flush	false	boolean	(default)
Logging/loggers[0]/output_options[0]/maxsize	204800	integer	(modified)
Logging/loggers[0]/output_options[0]/maxver	8	integer	(modified)

That looks OK, so let's commit it before we add the configuration for the authoritative server's logger.

>  config commit

Now that we have set it, and checked each value along the way, adding a second entry is quite similar.

>  config add Logging/loggers
>  config set Logging/loggers[1]/name Auth
>  config set Logging/loggers[1]/severity DEBUG
>  config set Logging/loggers[1]/debuglevel 40
>  config add Logging/loggers[1]/output_options
>  config set Logging/loggers[1]/output_options[0]/destination file
>  config set Logging/loggers[1]/output_options[0]/output /tmp/auth_debug.log
>  config commit

And that's it. Once we have found whatever it was we needed the debug messages for, we can simply remove the second logger to let the authoritative server use the same settings as the rest.

>  config remove Logging/loggers[1]
>  config commit

And every module will now be using the values from the logger named *.

22.2. Logging Message Format

Each message written by BIND 10 to the configured logging destinations comprises a number of components that identify the origin of the message and, if the message indicates a problem, information about the problem that may be useful in fixing it.

Consider the message below logged to a file:

2011-06-15 13:48:22.034 ERROR [b10-resolver.asiolink]
    ASIODNS_OPENSOCK error 111 opening TCP socket to 127.0.0.1(53)

Note: the layout of messages written to the system logging file (syslog) may be slightly different. This message has been split across two lines here for display reasons; in the logging file, it will appear on one line.)

The log message comprises a number of components:

2011-06-15 13:48:22.034

The date and time at which the message was generated.

ERROR

The severity of the message.

[b10-resolver.asiolink]

The source of the message. This comprises two components: the BIND 10 process generating the message (in this case, b10-resolver) and the module within the program from which the message originated (which in the example is the asynchronous I/O link module, asiolink).

ASIODNS_OPENSOCK

The message identification. Every message in BIND 10 has a unique identification, which can be used as an index into the BIND 10 Messages Manual (http://bind10.isc.org/docs/bind10-messages.html) from which more information can be obtained.

error 111 opening TCP socket to 127.0.0.1(53)

A brief description of the cause of the problem. Within this text, information relating to the condition that caused the message to be logged will be included. In this example, error number 111 (an operating system-specific error number) was encountered when trying to open a TCP connection to port 53 on the local system (address 127.0.0.1). The next step would be to find out the reason for the failure by consulting your system's documentation to identify what error number 111 means.