MFC r313168 (by pkelsey):
Fix VIMAGE-related bugs in TFO. The autokey callout vnet context was
not being initialized, and the per-vnet fastopen context was only
being initialized for the default vnet.

PR: 216613

MFC r303978; Fix kernel build with TCP_RFC7413 option

The current in_pcb.h includes route.h, which includes sockaddr structures.
Including <sys/socketvar.h> should require <sys/socket.h>; add it in
the appropriate place.

PR: 211385
Submitted by: Sergey Kandaurov and iron at mail.ua
Reviewed by: gnn
Approved by: gnn (mentor)