This is a dictionary type allowing an Erlang RPC call to be made from Postfix. One use-case would be querying a Mnesia database of alias maps.
The easiest way to use this is from a Debian-based Linux distribution, as they enable dynamic loading of map types, thus not requiring one to maintain his own Postfix port.
Drop the dict_erlang.c and dict_erlang.h files in the src/global directory
in the Postfix source. Also copy the appropriate Makefile.in.[23].[36789] file
to the same directory according to your Postfix version, renaming it to just
Makefile.in. For Postfix 3.[36], copy the postfix-files.3.[36] file to the conf
directory in the Postfix source.
Note: the Makefiles above were tested with Postfix versions 2.7.0, 2.7.1, 2.8.5, 2.96, 3.3.0 and 3.6.4 (more specifically, the packages from Ubuntu 10.04, 10.10, 11.10, 12.04, 18.04 and 22.04). You may need to adapt it for different versions.
If you're on a Debian-based distribution, copy the files under debian to the
debian directory in the Postfix source (the control.x.y and rules.x.y
files should be renamed to control and rules to overwrite the standard
debian files). The postfix-erlang.files.2.x file should be renamed to
postfix-erlang.files for Postifx 2.x or ignored otherwise.
Then, change to the Postfix source directory and run
$ apt-get build-dep postfix
$ apt-get install erlang-dev
$ dpkg-buildpackage -b -uc -us
to generate the postfix-erlang package.
If you're using the stock Postfix, you'll need to edit the
src/global/mail_dict.c file and add the following code:
static const DICT_OPEN_INFO dict_open_info[] = {
....
+#ifdef HAS_ERLANG
+ DICT_TYPE_ERLANG, dict_erlang_open,
+#endif
0,
};
and then compile Postfix with
$ make makefiles CCARGS="-DHAS_ERLANG -I/path/to/erl_interface/include" \
AUXLIBS="-L/path/to/erl_interface/lib -lerl_interface_st -lei_st"
Point postfix to the Erlang map like you'd do with other dictionary types. For example,
virtual_alias_maps = proxy:erlang:/etc/postfix/virtual_alias_maps.cf
The configuration file requires four parameters:
nodes = mynode@myhost, mynode@myotherhost
cookie = chocolate
module = mydb
function = aliases
With this setup, postfix-erlang will connect to mynode@myhost using
chocolate as the magic cookie, and call mydb:aliases/1. The argument will
be passed to Erlang as a bit string. The specified function should return
{ok, [Bitstring, ...]} on success or not_found on failure. Currently there
is no way to choose different function arguments or alternative return formats.