Fabrice Bellet authored Apr 05, 2016 and Olivier Crête committed Apr 11, 2017

With this patch, we don't create a new GSource for udp-turn socket,
because it would duplicate the packets already received on the base UDP
socket, as the underlying GSocket is the same. This is a race condition,
because an UDP packet arriving on the base socket, may randomly be
handled by the GSource callback created for the base socket (udp-bsd) of
the callback created for the udp-turn socket. Moreover this callback
already knows how to parse UDP datagrams received from a known turn
server.

This patch also prevents a subtle bug, when a STUN request is received
directly from a peer, is handled by the udp turn socket. If the agent
already has a valid permission for this remote candidate, established
for another pair, it will happily send the STUN reply through the turn
relay. This generates a source address mismatch on the peer agent, when
it'll receive the STUN response from the turn relay instead of the
initial address the request has been sent to.

Differential Revision: https://phabricator.freedesktop.org/D932