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Johnathan Corgan
87f0678ce0
start_service switched dnsmasq's .fips forwarding to the gateway's port
before the gateway ran. A gateway that then failed, on a config it could
not parse or on a NAT or route error after binding, left every LAN
client's .fips lookups going to a port nothing held, until someone
started the gateway by hand; procd gives up respawning after five
failures and says nothing.
procd now runs the init script's supervise command, which starts the
gateway, switches dnsmasq to its port once the gateway's own process holds
a socket bound there, and switches it back to the daemon's port when the
gateway exits for any reason, passing procd's SIGTERM on so the gateway can
clean up. Ownership is checked by matching a socket inode for the port in
/proc/net/udp{,6} against the gateway's open descriptors, so a port held by
something else, such as an mDNS responder on 5353, is never mistaken for the
gateway. supervise records the gateway's pid in /var/run/fips-gateway.pid,
and an exiting instance skips the swap back only when the gateway named
there, the one procd started in its place, holds the port. Every change to
the dnsmasq entry is made under one lock, so a stopping and a starting
gateway cannot interleave. stop_service still swaps back as before. The
exit status is the gateway's, so procd's respawn behaves as it did.
procd sends SIGTERM to the supervise shell and, five seconds later, SIGKILL
to that shell alone, so a gateway slow to stop would outlive it, holding its
port. supervise kills the gateway three seconds after passing the SIGTERM
on, and stops its watcher as soon as the gateway is gone.
A new scenario runs the command start_service hands procd against stub
gateways that hold their socket themselves and exit before binding, fail
after binding, are stopped by SIGTERM, or ignore it, against a port taken by
another process, and against a swap back with a process other than the
successor holding the port, and checks dnsmasq ends on the daemon's port
each time.