dhcp-relay

dhcp-relay is intended as a replacement for ISC dhcrelay and specifically it's OpenBSD descendant.

The motivation for this was the lack of support in dhcrelay for interfaces on multiple IP subnets. dhcrelay assumed a single primary address on an interface and would only relay DHCP requests as that one DHCP gateway. dhcp-relay is designed to support this, but also aims to be a better implementation of this part of the DHCP protocol.

Usage

usage: dhcp-relay [-vd] [-C circuit] [-R remote] [-H hoplim] -i interface
	destination ...

Improvements over dhcrelay

• dhcp-relay supports acting as a DHCP gateway for all the IP subnets configured on the specified interface, not just the first network.
• The BPF filter used on the interface is restricted to accepting broadcast and multicast Ethernet packets, what the RFC calls "locally delivered datagrams". This stops the relay intercepting unicast packets, eg, DHCP INFORM packets from clients sent directly to their server, or packets from other DHCP relays.
• The ability to list extra "helper" servers that can send messages via the relay to the client network, but are not sent client requests.

Missing dhcrelay features

• Support for operating on enc(4) interfaces

To do

• Add all missing dhcrelay features
• Support use in a DHCP relay chain
• Get this into OpenBSD so I can stop using git