SO_RCVSIZE
SO_SNDSIZE
TCP_NODELAY
TCP_MAXSEG

There is a problem, though. Right now, we identify a connection by a
triple of (local port, remote IP, remote port). However, some apps
(iperf, at least), set these options before calling connect(). Thus,
we don't know these things yet. To fix this, we could either:
  Delay notification of sockopt changes until after connect() is
    called for the socket
  Use something else (ie. (pid,fd)) as the ID for connections.
We should probably talk about this (at least Jon and I) at the
next meeting.