Found while setting up the live check, which is the only place it could
have shown: every unit test passes without it.
spawn_restored_listeners re-parsed the listeners and spawned them, but
never bound their sockets. Binding is not part of parsing -- it happens in
bind_and_drop_priv, once, at startup -- so listen() would have failed on an
unbound socket and the port would have stayed shut while the policy
recorded it as reopened. LP-5 would have been a promise the server did not
keep, and the operator's only clue a log line.
bind() is now split out of bind_and_drop_priv and called on its own here.
It cannot be the whole of bind_and_drop_priv, because that also drops
privileges, which must happen once at startup and never again.
That split has a consequence worth stating: a listener on a port below 1024
cannot be bound again once privileges are gone. Ports 143 and 110 are the
realistic cases. Rather than leave such a listener parsed, spawned and
silently dead, the bind errors are read back and those listeners are
reported as needing a restart -- which is the "cannot be recreated" case
LP-5 already anticipated, and it stays saved for another try.
Re-parsing is also narrowed to the listeners being restored, so putting one
back cannot bind a port another listener already holds.
jcoffey-dev
3f689529c7