For me, this presents a few problems. I don't know where to get the SCM_CREDENTIALS constant, I have no idea what flags to use (does the Network module help with that?), I don't know how to get from a list of file descriptors or a tuple to a Ptr, and perhaps most importantly, I have no idea how to get the lengths of pid_t, uid_t, gid_t, and socklen_t.
The basic answer is that you can use tools like hsc2hs, c2hs or greencard. I also wrote this package that may be of help: http://hackage.haskell.org/package/bindings-posix You may want to look at the source code to see how to apply the idea to your needs. Note that this package uses a lot of macros I wrote myself (see package bindings-DSL), so you should not use them if you want to stick with standard tools. Best, Maurício