coredhcp

coredhcp

Fast, multithreaded, modular and extensible DHCP server written in Go

This is still a work-in-progress

Example configuration

In CoreDHCP almost everything is implemented as a plugin. The order of plugins in the configuration matters: every request is evaluated calling each plugin in order, until one breaks the evaluation and responds to, or drops, the request.

The following configuration runs a DHCPv6-only server, listening on all the interfaces, using a custom server ID and DNS, and reading the leases from a text file.

server6:
    # this server will listen on all the available interfaces, on the default
    # DHCPv6 server port, and will join the default multicast groups. For more
    # control, see the `listen` directive in cmds/coredhcp/config.yml.example .
    plugins:
        - server_id: LL 00:de:ad:be:ef:00
        - file: "leases.txt"
        - dns: 8.8.8.8 8.8.4.4 2001:4860:4860::8888 2001:4860:4860::8844

For more complex examples, like how to listen on specific interfaces and configure other plugins, see config.yml.example.

Build and run

An example server is located under cmds/coredhcp/, so enter that directory first. To build a server with a custom set of plugins, see the "Server with custom plugins" section below.

Once you have a working configuration in config.yml (see config.yml.example), you can build and run the server:

$ cd cmds/coredhcp
$ go build
$ sudo ./coredhcp
INFO[2019-01-05T22:28:07Z] Registering plugin "file"
INFO[2019-01-05T22:28:07Z] Registering plugin "server_id"
INFO[2019-01-05T22:28:07Z] Loading configuration
INFO[2019-01-05T22:28:07Z] Found plugin: `server_id` with 2 args, `[LL 00:de:ad:be:ef:00]`
INFO[2019-01-05T22:28:07Z] Found plugin: `file` with 1 args, `[leases.txt]`
INFO[2019-01-05T22:28:07Z] Loading plugins...
INFO[2019-01-05T22:28:07Z] Loading plugin `server_id`
INFO[2019-01-05T22:28:07Z] plugins/server_id: loading `server_id` plugin
INFO[2019-01-05T22:28:07Z] plugins/server_id: using ll 00:de:ad:be:ef:00
INFO[2019-01-05T22:28:07Z] Loading plugin `file`
INFO[2019-01-05T22:28:07Z] plugins/file: reading leases from leases.txt
INFO[2019-01-05T22:28:07Z] plugins/file: loaded 1 leases from leases.txt
INFO[2019-01-05T22:28:07Z] Starting DHCPv6 listener on [::]:547
INFO[2019-01-05T22:28:07Z] Waiting
2019/01/05 22:28:07 Server listening on [::]:547
2019/01/05 22:28:07 Ready to handle requests
...

Then try it with the local test client, that is located under cmds/client/:

$ cd cmds/client
$ go build
$ sudo ./client
INFO[2019-01-05T22:29:21Z] &{ReadTimeout:3s WriteTimeout:3s LocalAddr:[::1]:546 RemoteAddr:[::1]:547}
INFO[2019-01-05T22:29:21Z] DHCPv6Message
  messageType=SOLICIT
  transactionid=0x6d30ff
  options=[
    OptClientId{cid=DUID{type=DUID-LLT hwtype=Ethernet hwaddr=00:11:22:33:44:55}}
    OptRequestedOption{options=[DNS Recursive Name Server, Domain Search List]}
    OptElapsedTime{elapsedtime=0}
    OptIANA{IAID=[250 206 176 12], t1=3600, t2=5400, options=[]}
  ]
...

Docker

There is a Dockerfile and a docker-compose.yml.

Docker compose expects a configuration file under /etc/coredhcp/config.yaml, and it is mapped to ./etc/coredhcp/config.yaml when using docker compose. You can adjust the exported volume in docker-compose.yml to point to a different configuration file on the host file system.

There is an example configuration file config.yml.example that you can use as a starting point.

Plugins

CoreDHCP is heavily based on plugins: even the core functionalities are implemented as plugins. Therefore, knowing how to write one is the key to add new features to CoreDHCP.

Core plugins can be found under the plugins directory. Additional plugins can also be found in the coredhcp/plugins repository.

Server with custom plugins

To build a server with a custom set of plugins you can use the coredhcp-generator tool. Head there for documentation on how to use it.

How to write a plugin

The best way to learn is to read the comments and source code of the example plugin, which guides you through the implementation of a simple plugin that prints a packet every time it is received by the server.

Authors

• Andrea Barberio
• Anatole Denis
• Pablo Mazzini