The behavior of FRR may be extended or customized using
its built-in scripting capabilities.

Some configuration commands accept the name of a Lua script
to call to perform some task or make some decision. These
scripts have their environments populated with some set of
inputs, and are expected to populate some set of output
variables, which are read by FRR after the script completes.
The names and expected contents of these scripts are documented
alongside the commands that support them.
