Author: jtl
Date: Fri Apr 20 15:44:29 2018
New Revision: 332829
URL: https://svnweb.freebsd.org/changeset/base/332829

Log:
  MFC r307083:
   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.
  
  Sponsored by: Netflix, Inc.

Modified:
  stable/11/sys/netinet/tcp_input.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/netinet/tcp_input.c
==============================================================================
--- stable/11/sys/netinet/tcp_input.c   Fri Apr 20 15:41:33 2018        
(r332828)
+++ stable/11/sys/netinet/tcp_input.c   Fri Apr 20 15:44:29 2018        
(r332829)
@@ -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) {
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