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Dynamic Host Configuration Protocol for IPv4 (DHCPv4) server daemon.

The main driving force behind this was OpenBSD's Google Summer of Code 2014.

Tested on OpenBSD/amd64 and OpenBSD/sparc64 both directly and through a relay agent (HP A5800 Switch) with a variety of clients:

  • Windows XP, 7, Phone
  • dhcpcd 5.5.6 on Android
  • dhcpcd 6.4.2 on Linux
  • udhcpc 1.14.3 on Samsung TV
  • udhcpc 1.11.2 on Ubiquiti airOS 5.5
  • udhcpc 0.9.9 on Ubiquiti airOS 4.0
  • OpenBSD dhclient
  • Intel UNDI Boot Agent PXE-2.0, 2.1
  • iPXE 1.0.0+ (09c5) inside QEMU 2.0.0
  • Cisco IP Phone 7941 (requires DHCP option 150 to be faked)
  • RouterBOOT on a big-endian MIPS board
  • Xerox WorkCentre 3220
  • dhcdrop
  • sdhcp
  • Sony PlayStation 3
  • Pioneer VSX-921K
  • TP-link TL-WR841N
  • TP-link TL-WR741N (makes 6 DHCPDISCOVERs before SELECTING)
  • some Belkin router (without the backdoor) (gets a lease, then releases it, then re-discovers asking for the same one, all with xid 0x1)
  • Sony Bravia TV (option 57 violates (RFC 2132); they probably wanted to write 9216 (0x2400) bytes and copied the length (0x02) byte on the left, which makes it look like 548 (0x0224) bytes, which of course is illegal)
  • Linksys WRP400

What we need now:

  • a proper configuration file parser (Grégoire Duchêne was working on that in another GSoC project) integrated into dhcpctl + the format documented
  • maybe transaction support will be needed to keep the reload process sane
  • re-check all cases when a dynamic range overlaps some static host entries
  • Support other operating systems. I have working code for Windows + Linux but need to put it all together. My previous DHCP server manipulated ARP instead of sending stuff on BPF. Then it's valgrind time :-)
  • DHCPv6 support. We need to understand the bloody RFC and support a small subset. Certainly no rush at any cost. RFC 4361 will be required as the identifiers seem to make sense between address families (and not just for tracking stolen laptops).
  • Lease on-disk-dumper and multicast-syncer. I was sort of hoping it would be a separate process, but we'll see. Likely to happen after the parser.
  • Some address-liveness awareness code, most likely ICMP before DHCPOFFERs. Maybe ARP snooping over dynamic ranges? Would require another 2MB bitmap.
  • On commit/expiry/release is a cool feature in ISC DHCP 4.3. We could use such a mechanism to implement DDNS registration; command with environment variables containing lease information would do whatever you want it to.

Compiling on Linux:

Remember, it's a work in progress. Your minimal Debian installation will need:

$ apt-get install git libc6-dev libbsd-dev libevent-dev libpcap-dev gcc make pkg-config
$ git clone
$ cd dhcpd && ./configure
$ cd dhcpd && make
$ cd ../dhcpctl && make
$ useradd -r -d /var/empty dhcp
$ mkdir -p /var/empty

The development is mainly done on OpenBSD and Gentoo. Patches welcome, but please try to keep them small. No autotools!


Dynamic Host Configuration Protocol (DHCP) daemon; main driving force behind this was OpenBSD's Google Summer of Code 2014.




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