Added the ability to get/set the IP_RECVTOS socket option on UDP endpoints. If
enabled, TOS from the incoming Network Header passed as ancillary data in the
ControlMessages.
Test:
* Added unit test to udp_test.go that tests getting/setting as well as
verifying that we receive expected TOS from incoming packet.
* Added a syscall test
PiperOrigin-RevId: 287029703
If the socket is bound to ANY and connected to a loopback address,
getsockname() has to return the loopback address. Without this fix,
getsockname() returns ANY.
PiperOrigin-RevId: 283647781