Since one can access all processes that are running in a sub-hurd from
the main system (say, using gdb), one could have a special program,
that listens to the messages that process sends.
Now say that you wish to allow network communication to be allowed
from the sub-hurd, you'd attach this `proxy server' to the network
stack process that is running within the sub-hurd. The proxy server
would then listen, and forward all communication (at the same time
maybe sending modified messages) to the real network stack process
(the one in the main hurd).
This method might serve, but it would take substantial work to build
useful kinds of communication on top of this mechanism. Would someone
like to try implementing that?
This is work that any of you could do
without waiting for anyone else to do anything.