This is an attempt to write a proper, liberally licensed DHCP server library in Erlang.

It is written as a extendable library, allowing to delegate the relevant calls on discover / request and release without burdening the implementation with the bookkeeping details required by DHCP.

Running it is pretty simple:

• Start the dhcp app.
• Implement a handler.
• Register the handler via a call to dhcp_server:register_handler/2

The handler

The handler is a module implementing the dhcp_handler behaviour it has to export the functions, a handler is created for every release request (identified by xid and chaddr):

init/0

The initialising function it takes no parameters but has to return a tupel of the form: {ok, state(), server_id()} where the server_id() is the IP address used to identify the server.

discover/3

Discover is called on a discover request, it takes three parameters:

• ReplyPkg - a minimal reply package with the values from the request already set.
• RequestPkg - the original request package.
• State - The state of the handler.

The function has to return either:

• {ok, ReplyPkg} where ReplyPkg was filled 'manually'.
• {ok, {offer, IP, Netmask[, GWs], ReplyPkg}, State} - where IP and Netmask are IP addresses to offer, GWs can either be omitted, be a single IP or a list of IP's and ReplyPkg is either the original package or has modification as additional options set on it.
• {ok, State} - if no offer is send in reply.
• {error, Reason} - an error that shuts down the related FSM.

request/3

A request in reply to the offer, it is already checked if the requested IP is equal to the offered IP, the parameters passed are in accordance with the discover function:

• ReplyPkg - a minimal reply package with the values from the request already set.
• RequestPkg - the original request package.
• State - The state of the handler.

The funcion has to return:

• {ok, ReplyPkg} where ReplyPkg was filled 'manually'.
• {ok, {ack, [IP, Netmask[, GWs]], ReplyPkg}, State} - where IP and Netmask are IP addresses to offer, GWs can either be omitted, be a single IP or a list of IP's and ReplyPkg is either the original package or has modification as additional options set on it, all fiends but The ReplyPkg are optional.
• {ok, {nck, ReplyPkg}, State} - The request is denied, details can be set in the ReplyPkg.
• {error, Reason} - an error that shuts down the related FSM.

release/2

Only for informative reasons, the function does not have to return a package, it is passed it's state and the release package and can return either:

• {ok, State} - return normal.
• {error, Reason} - an error that shuts down the related FSM.

Configuration

There are three configuration options that can adjust the behavior of the FSM, namely the timeouts.

• initial_timeout - the timeout in seconds until the FSM quits when no initial discover or request is received.
• offer_timeout - the timeout in seconds before a offer has to be accepted or declined.