> I have also added a new subroutine, fsocreate(), that creates a socket
> a la socreate(9) and sticks it into a process's file descriptor table.
> I use it in both gre(4) and sys_socket().  gre sticks the sockets it owns
> into process 0's file table, so it's clear which socket belongs to who.

why you want to use file descriptors, rather than pointers?
using process 0's file table for gre sounds weird to me.

YAMAMOTO Takashi