From: Nico Schottelius
Subject: Unix IPC, socket/AF_UNIX; bind on r/o devices?
Date: 09 May 2005 09:51:27 GMT
To: comp.unix.programmer

Hello!

Situation:
   - everything mounted readonly (as when starting the system)
   - one process with n children, which may have n children (recursive)
   - all the children and children of children should be able to talk to the
     first parent

Problem:
   - Using bind() will fail, because
      a) socket cannot created
      b) the existing socket cannot be reused

Other possibilities not working:
   - shared memory is not an option, as one need
     -lrt, which needs -lpthread, which is problematic to link statically

   - pipes: handling the pipes from parent to child of child of child
     would be hard to program
   
   - socketpair: should be the same problematic as it's with pipes

   - fifos: one would have to create the fifos before and two fifos
     for each child; possible, but very unelegant; and one would have
     to memorize, which child is connected to which fifo; again possible,
     but somehow unelegant
   
   - signaling: one could implement communication with some kind of
     morse code with signals, but that won't be a good solution

Questions:
   - Is there any way, case b) (socket already existing) can be solved in
     a way that I tell bind() to use an existing socket?
   - What would be the best solution to talk bidirectional to clients
     in this scenario?

I appreciate any hint, as I really like the socket mechanism and would
like to keep it.


Thanks in advance,

Nico