svn commit: r307083 - head/sys/netinet

[Jonathan T. Looney]

Author: jtl
Date: Wed Oct 12 02:30:33 2016
New Revision: 307083
URL: https://svnweb.freebsd.org/changeset/base/307083

Log:
  Currently, when tcp_input() receives a packet on a session that matches a
  TCPCB, it checks (so->so_options & SO_ACCEPTCONN) to determine whether or
  not the socket is a listening socket. However, this causes the code to
  access a different cacheline. If we first check if the socket is in the
  LISTEN state, we can avoid accessing so->so_options when processing packets
  received for ESTABLISHED sessions.
  
  If INVARIANTS is defined, the code still needs to access both variables to
  check that so->so_options is consistent with the state.
  
  Reviewed by:	gallatin
  MFC after:	1 week
  Sponsored by:	Netflix

Modified:
  head/sys/netinet/tcp_input.c

Modified: head/sys/netinet/tcp_input.c
==============================================================================
--- head/sys/netinet/tcp_input.c	Wed Oct 12 02:16:42 2016	(r307082)
+++ head/sys/netinet/tcp_input.c	Wed Oct 12 02:30:33 2016	(r307083)
@@ -1071,11 +1071,11 @@ relocked:
 	 * state) we look into the SYN cache if this is a new connection
 	 * attempt or the completion of a previous one.
 	 */
-	if (so->so_options & SO_ACCEPTCONN) {
+	KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN),
+	    ("%s: so accepting but tp %p not listening", __func__, tp));
+	if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) {
 		struct in_conninfo inc;
 
-		KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but "
-		    "tp not listening", __func__));
 		bzero(&inc, sizeof(inc));
 #ifdef INET6
 		if (isipv6) {