Support for SMP
---------------

It's actually going to be quite easy to modify rws so that it supports
SMP - even though the underlying threading library is lightweight user
threads. The plan is as follows, I'm just waiting for the patch!

Support should probably go directly into pthrlib/src/pthr_server.c so
that it can benefit all pthrlib-based servers.

At start up, based on some command line flag and/or autodetection of
the number of CPUs, the server should fork N times where N is the
number of CPUs. This results in N+1 processes. Process 0 (the parent)
will have the listening socket. Processes 1-N will be connected by
Unix domain sockets back to process 0. Processes 1-N will have special
modified listen threads listening on their respective Unix domain
socket. (NB. Use the socketpair function to create each Unix domain
socket).

When process 0 receives a connection, based on some hashing function
of the peername, it should decide which of the 1-N processes will
handle the request. The important thing is that the hashing function
must always assign the same client to the same process, which is why
the hash should be based on the peername.

When a new client connection arrives at process 0, let's say it
decides to pass this to process n (1 <= n <= N). It should pass the
file descriptor over the corresponding Unix domain socket to process n
using the sendmsg(2) function (see cmsg(3) for details). Process n
will receive the file descriptor and can then continue to handle the
request.

This method should scale up over small numbers of processors (eg. up
to 8).