ahcpd8

Usage

Overview

AHCP is a configuration protocol that can replace DHCP on networks without transitive connectivity, such as mesh networks.

Options

-m multicast-address

Specify the link-local multicast address to be used by AHCP. The default is ff02::cca6:c0f9:e182:5359.

-p port

Specify the UDP port number to be used by AHCP. The default is 5359.

-n

Operate as a forwarder: participate in the flooding protocol, but don't actually perform any configuration.

-4

Only attempt to configure IPv4 addresses.

-6

Only attempt to configure IPv6 addresses.

-N

Do not configure DNS.

-t time

Specify the time, in seconds, for which leases are requested. The default is slightly over one hour. Must be between five minutes and a year.

-s script

Specify the configuration script to run. The default is /etc/ahcp/ahcp-config.sh.

-d level

Set the debug level to level (default 1).

-i filename

Specify the filename containing this host's unique id. The default is /var/lib/ahcp-unique-id. If it doesn't exist, it will be created by ahcpd.

-c filename

Specify the name of the configuration file.

-C statement

Specify a configuration statement directly on the command line.

-D

Daemonise at startup.

-L logfile

Specify a file to log random ``how do you do?'' messages to. This defaults to standard error if not daemonising, and to /var/log/ahcpd.log otherwise.

-I pidfile

Specify a file to write our process id to. The default is /var/run/ahcpd.pid.

Configuration file format

The configuration is a sequence of lines, each of which starts with one of the keywords below. Blank lines are ignored. Comments are introduced with an octothorp ``#'' and terminate at the end of the line.

The following keywords are recognised:

mode server|client|forwarder

Specifies whether the daemon operates as a server, a client, or a forwarder. If omitted, the default is to operate as a client, unless the -n flag is present on the command line. If present, this must be the first line in the configuration file.

prefix prefix

Specifies a prefix to use for configuring clients. This keyword is only valid in server configurations, and may be specified twice, once for IPv4 and once for IPv6.

lease-dir directory

Specifies a directory to store lease files. This keyword is only valid in server configurations.

name-server address

Specifies the address of a DNS server to configure clients with. This keyword is only valid in server configurations, and may be repeated multiple times.

ntp-server address

Specifies the address of an NTP server to configure clients with. This keyword is only valid in server configurations, and may be repeated multiple times.

Files

/var/lib/ahcp-unique-id

An 8-byte long file containing this host's unique id. If it doesn't exist, a new unique id will be generated from an interface's MAC address.

/etc/ahcp/ahcp-config.sh

The script that performs the actual configuration. It will be passed one argument, which is either start or stop.

/etc/ahcp/ahcp-local.sh

If this is an executable script, it will be called by ahcp-config.sh just after configuring or deconfiguring. It will be passed one argument, which is either start or stop.

Signals

Notes

Since the AHCP protocol is designed for mesh networks, it doesn't have any provisions for setting routing parameters such as a default gateway, the IPv4 network mask and the IPv6 list of on-link prefixes; these are expected to be provided by a full-fledged routing protocol for mesh nodes, and by router advertisements for ordinary nodes.

The AHCP server should use NTP to synchronise its clock. If a server instance of ahcpd doesn't detect time synchronisation, it will only give out leases for a short period of time, and be extremely conservative about releasing them. Note that an SNTP client is not enough — ahcpd actually checks with the kernel for time synchronisation, so real NTP is necessary.