* don't hold spc mutex while sending data
* use send() for the banner to avoid SIGPIPE in case a client
connects and immediately goes away
* fix error path locking
* use kevent() instead of pollts() in the client. Apparently that
is the only sensible way for a library to support both multithreading
and signal-reentrancy in a race-free manner.
(can I catch all signals with one kevent instead of installing
NSIG different ones??)
* mark client comm descriptor non-blocking so that clients have
better signal-interruptibility (we now sleep in signal-accepting
kevent() instead of signal-masked recvfrom())
requests which have a 0-length response (such as copyin 0/0).
This change makes links(1) work against a rump kernel which contains
rumpnet_local. The presence of unix domain sockets caused links
to select() with 0 fds and a timeout, and because copyin never woke
up in the kernel the application blocked indefinitely.
dlsym(RTLD_NEXT) to lookup a host_syscall() function pointer which
is used instead of syscall() to communicate with the kernel server.
WARNING: popular opinion classifies this as "ugly code". if you
have a weak heart/mind/soul/sole meuniere, read max. 1 line of the
diff per day, preferably with food.
It's pretty much a placeholder for now. One plan for the future
is to require some sort of authentication for superuser clients.
The code will need a little massage then, though, to prevent DoS
attacks.
basics are there, but a few more tweaks are needed. The reason
I'm committing it now is that the code was mindnumbingly boring to
write (no wonder it took me almost 3 years to get it done), and I
might burn it if it's not in a safe place.
pooka