ProFTPD third parties module and packages development
-----------------------------------------------------

Upstream provides `prxs' as a useful tool to build your own proftpd DSO modules.
The resulting shared library can be loaded in the /usr/lib/proftpd directory to
allow proftpd finding the additional module.
This could be done with a command like

    prxs -c -i -d mod_foo.c

The resulting module mod_foo.so is strictly binary-dependent on the specific
version of proftpd you used to build it by prxs. If you prefer creating
a deb source package Debian proftpd-dev package provides 

    /usr/share/proftpd/proftpd-substvars

which can be used to introduce a dependency on ${proftpd:Depends} in 
your debian/control for foo binary package. You have to add its contents 
to a debian/<foo>.substvars or debian/substvars with a command like

    cat /usr/share/proftpd/proftpd-substvars >>debian/<foo>.substvars

just before calling dh_gencontrol or dpkg-gencontrol.