dhcp server

Pre-Alpha. This page describes behavior that may change.

DHCP server plugin serving leases to LAN clients per RFC 2131/2132. Address pool with bitmap allocation, lease tracking with expiry timers, full DISCOVER/OFFER/REQUEST/ACK/NAK/RELEASE/DECLINE state machine, static MAC-to-IP mappings, subnet matching for multi-handler dispatch, and support for multiple named address ranges per subnet.

Configuration

service {
    dhcp-server {
        enabled true;
        listen-interface eth1;

        shared-network lan {
            subnet 192.168.1.0/24 {
                range {
                    start 192.168.1.100;
                    stop 192.168.1.200;
                }
                lease-time 86400;
                default-router 192.168.1.1;
                dns-server 8.8.8.8;
                dns-server 8.8.4.4;
                domain-name example.com;

                static-mapping printer {
                    mac-address aa:bb:cc:dd:ee:ff;
                    ip-address 192.168.1.10;
                }
            }
        }
    }
}

Multiple named ranges

A subnet can define multiple named address ranges for segmented allocation:

shared-network lan {
    subnet 192.168.1.0/24 {
        range clients {
            start 192.168.1.100;
            stop 192.168.1.199;
        }
        range servers {
            start 192.168.1.200;
            stop 192.168.1.250;
        }
    }
}

Each range has an independent bitmap pool. Address allocation prefers the client's last-assigned range.

Configuration reference

Path	Type	Default	Description
`dhcp-server/enabled`	boolean	false	Enable the DHCP server.
`dhcp-server/listen-interface`	leaf-list	--	Interfaces to serve DHCP on.
`dhcp-server/shared-network/<name>/subnet/<prefix>/range/start`	string	--	First allocatable address.
`dhcp-server/shared-network/<name>/subnet/<prefix>/range/stop`	string	--	Last allocatable address.
`dhcp-server/shared-network/<name>/subnet/<prefix>/lease-time`	uint32	86400	Lease duration in seconds (60-604800).
`dhcp-server/shared-network/<name>/subnet/<prefix>/default-router`	string	--	Default gateway (option 3).
`dhcp-server/shared-network/<name>/subnet/<prefix>/dns-server`	leaf-list	--	DNS servers (option 6).
`dhcp-server/shared-network/<name>/subnet/<prefix>/domain-name`	string	--	Domain name (option 15).
`dhcp-server/shared-network/<name>/subnet/<prefix>/static-mapping/<name>/mac-address`	string	--	Client MAC address.
`dhcp-server/shared-network/<name>/subnet/<prefix>/static-mapping/<name>/ip-address`	string	--	Fixed IP for this client.

Behaviour

The server binds to the specified interfaces using SO_BINDTODEVICE (Linux). For each DHCPDISCOVER, it finds the matching subnet by comparing the giaddr (relay agent) or the receiving interface's address against configured subnets. Addresses are allocated from the bitmap pool, preferring the client's previously-assigned address if still available.

Static mappings take priority over the dynamic pool. A client whose MAC matches a static mapping always receives that fixed address regardless of the pool state.

Leases are tracked with expiry timers. Expired leases return their address to the pool. The server handles RELEASE and DECLINE messages to free addresses early.