MFC r345003:
Add NULL pointer check to nat64_output(). It is possible that a processed packet was originated by local host, in this case m->m_pkthdr.rcvif is NULL. Check and set it to V_loif to avoid NULL pointer dereference in IP input code, since it is expected that packet has valid receiving interface when netisr processes it. Obtained from: Yandex LLC Sponsored by: Yandex LLC