dhcpd-unnumbered

what is dhcpd-unnumbered

dhcpd-unnumbered is a very light weight ipv4 dhcp server designed for unnumbered l3 tap interfaces

how does it work

• it listens for dhcp requests on all interfaces (so dynamic tap interfaces can come and go without changes)
• incoming requests are matched to their interface
• the interface is checked against a regex. only matching interfaces are handled (default tap.*_0), not matching are ignored completely
• if tap matches
  • routes for that tap are looked up,
  • if client requested a specific IP and still owns this IP, that IP is offered
  • if client did not request an IP (aka DHCP discover) the first non-private IP is being offered
  • some options can also be specified via a file (<ifname>.options)

In addition to listening on all interfaces, it can also dynamically bind a socket in each VRF matching a regex (bindRegex). These sockets will be created and torn down as the interfaces come and go.

NOTES:

• dhcp offers will supply a fake /24, clients are let to believe that they live in a shared /24 subnet
• dhcp will include/offer a gateway IP using the first IP in the clients "fake" /24
• the dhcp can/will include a hostname different options can be supported around this:
  • static hostname (every client gets the same hostname)
  • dynamic hostname: hostname is generated from its IP, with the dots replaced with -
  • hostname override: dhcpd-unnumbered can dynamically pick up a file reading the hostname from it. completely customized hostnames can be offered through this
• dhcpd-unnumbered can also offer a tftp next-host IP for pxebooting clients
• Options in a .options file take precedence over command line and inferred settings. See options/options.go.

usage:

dhcpd-unnumbered --help