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[1367] Added sections about DHCP in Reference Guide, fixed whitespaces.
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Tomek Mrugalski
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@ -1806,6 +1806,164 @@ then change those defaults with config set Resolver/forward_addresses[0]/address
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</chapter>
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<chapter id="dhcp4">
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<title>DHCPv4 Server</title>
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<para>Dynamic Host Configuration Protocol for IPv4 (DHCP or
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DHCPv4) and Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
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are protocols that allow one node (server) to provision
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configuration parameters to many hosts and devices (clients). To
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ease deployment in larger networks, additional nodes (relays) may
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be deployed that facilitate communication between servers and
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clients. Even though principles of both DHCPv4 and DHCPv6 are
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somewhat similar, these are two radically different
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protocols. BIND10 offers server implementations for both DHCPv4
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and DHCPv6.</para>
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<note>
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<para>
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As of December 2011, both DHCPv4 and DHCPv6 components are
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skeleton servers. That means that while they are capable of
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performing DHCP configuration, they are not fully functional
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yet. In particular, both do not have functional lease
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databases. This means that they will assign the same, fixed,
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hardcoded addresses to any client that will ask. See <xref
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linkend="dhcp4-limit"/> and <xref linkend="dhcp6-limit"/> for
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detailed description.
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</para>
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</note>
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<section>
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<title>Server Usage</title>
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<para>BIND10 provides experimental DHCPv4 server component since
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December 2011. It is currently described as skeleton server and
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can be described as an early prototype that is not yet fully
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functional. It is mature enough to conduct first tests in lab
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environment, but it has significant limitations. See <xref
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linkend="dhcp4-limit"/> for details.
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</para>
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<para>
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DHCPv4 server is implemented as <command>b10-dhcp4</command>
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daemon. As it is configurable yet, it is fully autonomous,
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i.e. it does not interact with <command>b10-cfgmgr</command>.
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To start DHCPv4 server, simply input:
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<screen>
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#<userinput>cd src/bin/dhcp4</userinput>
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#<userinput>./b10-dhcp4</userinput>
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</screen>
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Depending on your installation, <command>b10-dhcp4</command>
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binary may reside in src/bin/dhcp4 in your source code
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directory, in /usr/local/bin/b10-dhcp4 or other directory
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you specified during compilation.
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Afre start, server will detect available network interfaces
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and will attempt to open UDP sockets on all interfaces that
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are up, running, are not loopback and have IPv4 address
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assigned.
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Server will then listen to incoming traffic. Currently
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supported client messages are DISCOVER and REQUEST. Server
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will respond to them with OFFER and ACK, respectively.
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As DHCPv4 server opens privileged ports, it requires root
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access. Make sure you run this daemon as root.
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</para>
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</section>
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<section>
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<title>Server Configuration</title>
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<para>
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DHCPv4 server does not have lease database implemented yet
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or any support for configuration, so every time the same set
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of configuration options (including the same fixed address)
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will be assigned every time.
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</para>
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<para>
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At this stage of development, the only way to alter server
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configuration is to tweak its source code. To do so, please edit
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src/bin/dhcp4/dhcp4_srv.cc file and modify following parameters:
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<screen>
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const std::string HARDCODED_LEASE = "10.3.2.222"; // assigned lease
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const std::string HARDCODED_NETMASK = "255.255.255.0";
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const uint32_t HARDCODED_LEASE_TIME = 60; // in seconds
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const std::string HARDCODED_GATEWAY = "10.3.2.2";
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const std::string HARDCODED_DNS_SERVER = "8.8.8.8";
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const std::string HARDCODED_DOMAIN_NAME = "isc.example.org";
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const std::string HARDCODED_SERVER_ID = "10.3.1.1";</screen>
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Lease database and configuration support is planned for 2012.
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</para>
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</section>
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<section id="dhcp4-limit">
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<title>DHCPv4 Server Limitations</title>
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<para>
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During initial IPv4 node configuration, where server has to
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send packet to a node that does not have IPv4 address
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assigned yet, server requires certain tricks (or hacks) to
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transmit such packets. This is not implemented yet, therefore
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DHCPv4 server supports relayed traffic only.
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</para>
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</section>
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</chapter>
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<chapter id="dhcp6-srv">
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<title>DHCPv6 Server</title>
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<section id="dhcp6-limit">
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<title>DHCPv6 Server Limitations</title>
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<para>
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Relayed traffic is not supported.
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</para>
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</section>
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</chapter>
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<chapter id="libdhcp++">
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<title>libdhcp++ library</title>
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<para>libdhcp++ is a common library written in C++ that is
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handles many DHCP-related tasks, like DHCPv4 and DHCPv6 packets
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parsing, manipulation and assembly, option parsing, manipulation
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and assembly, network interface detection and socket operations.
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</para>
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<para>
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While this library is currently used by
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<command>b10-dhcp6</command> and <command>b10-dhcp4</command>
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only, it is designed to be portable, universal library useful
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for any kind of DHCP-related software.
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</para>
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<section>
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<title>Interface detection</title>
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<para>Both DHCPv4 and DHCPv6 components share network
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interface detection routines (see <xref
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linkend="libdhcp++"/> for details). Interface detection is
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currently only supported on Linux systems.</para>
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<para>For non-linux systems, there is currently stub
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implementation provided. As DHCP servers need to know
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available addresses, there was a simple mechanism implemented
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to provide that information. User is expected to create
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interfaces.txt file. Format of this file is simple. It
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contains list of interfaces along with available address on
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each interface. This mechanism is temporary and is going to be
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removed as soon as interface detection becomes available on
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non-linux systems. Example of interfaces.txt file looks as follows:
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<screen>
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# For DHCPv6, please specify link-local address (starts with fe80::)
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# If in doubt, check output of 'ifconfig -a' command.
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eth0 fe80::21e:8cff:fe9b:7349
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# For DHCPv4, please use following format:
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#eth0 192.0.2.5</screen>
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</para>
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</section>
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</chapter>
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<chapter id="statistics">
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<title>Statistics</title>
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