tinydhcpd

tinydhcpd is (going to be) a tiny DHCPv4 server, aiming for compliance with RFC2131 and implementation of most common DHCP options.

• Getting started
  • Building
  • Running
• Why another DHCP server?
  • Goals

Getting started

Building

To compile and run tinydhcpd, you need the following:

• Linux with epoll & close_range support (>5.9)
• libconfig++
• libcap
• Meson & (optionally) Ninja
• A compiler supporting C++20 designated initializers (GCC 8 or later, Clang 10 or later)

To install the necessary dependencies, you can use the following commands:

Ubuntu:

# apt install build-essential libconfig++-dev libcap-dev meson ninja-build 

Gentoo:

# emerge libconfig libcap meson ninja

Fedora:

# dnf install gcc-c++ libconfig-devel libcap-devel meson ninja-build

To compile, execute the following in the root of the repository:

$ meson <build_dir_name>
$ cd <build_dir_name>
$ meson compile

The executable can then be found in the specified build directory.

Running

By default, tinydhcpd looks for a file called tinydhcpd.conf in /etc/tinydhcpd/. An example configuration file can be found here.

Currently, the following commandline options are available:

-a, --address <address>      Listen on address <address>
-i, --interface <iface>      Bind to interface <iface>
-c, --configfile <file>      Use <file> instead of the default config file
-d, --debug                  Change log level to DEBUG
-f, --foreground             Don't fork to background

Why another DHCP server?

Most DHCP servers these days come bundled with a DNS server of some sort (e.g. dnsmasq and the ISC's DHCP server implementation) to allow for tight integration between DNS and IP allocation. That unfortunately also means that they are big pieces of software, which can become a problem on small embedded systems, and their complex dependencies can lead to build failures or crashes when built against a non-standard configuration (e.g. for aarch64 with musl-libc).

The inability to properly cross-compile and/or use the above programs strictly for DHCP motivated me to write my own little DHCP server, which only does DHCP and nothing else.

Goals

• Implement a standards-conform DHCP server
• Allow for easy cross-compilation
• Explicitly support smaller/alternative libc implementations (like musl-libc)
• Ideally minimize executable size (as of July 2022, the size-optimized stripped binary clocks in at just 80kB)