- Have a real pty_exec ? (not needed for now, slirp.telnetd seems to do a
  sterling job)

- PPP - I have no time/need for this, so it's pretty low priority.  I will
  accept patches though.

- Don't die if the link goes down.  Let the user "continue" once the link is
  back up again.  Once the link dies, should create a UNIX-domain socket in
  the user's home directory, and (blocked) listen() (don't read any further
  sockets, let TCP's flow control kick in), when a new slirp is started it
  should check for this socket, and try and connect.  If successfull, the
  new slirp should write the tty that the old slirp should now use, and
  simply continue (might have problems with controlling tty, etc.).  Should
  timeout, so that a clumsy user that just turns off the modem doesn't leave
  a process running "forever".

- Emulate ICMP packets.  ICMP ECHO-REQUEST to the remote-host should send an
  ECHO-REPLY, others whould emulate with a UDP packet to port 7 (echo), and
  send an ICMP ECHO-REPLY back when the UDP packet comes back.  All other
  ICMP packet types should be emulated/dumped as appropriate.

- Fix the on-the-fly config stuff.  It's *ugly* and doesn't work too well
  (CR/LF are stuffed, etc)  The command-line options should be updated too.

- Add support for BOOTP, for auto-configuration.

- Add support for "r"-commands.  Either fudge a way to do it by exec()ing
  the real suid-binary, or have slirp installed suid-root and bind() a port
  < 1024 if the source port was < 1024.  The later is more general, but
  needs to be suid-root (a problem in itself) and would probably contain
  security bugs.

- Fix all bugs.

- Port to all OS's.
