Bite the bullet, and make the IPv6 SSM and MLDv2 mega-commit:

import from p4 bms_netdev.  Summary of changes:

 * Connect netinet6/in6_mcast.c to build.
   The legacy KAME KPIs are mostly preserved.
 * Eliminate now dead code from ip6_output.c.
   Don't do mbuf bingo, we are not going to do RFC 2292 style
   CMSG tricks for multicast options as they are not required
   by any current IPv6 normative reference.
 * Refactor transports (UDP, raw_ip6) to do own mcast filtering.
   SCTP, TCP unaffected by this change.
 * Add ip6_msource, in6_msource structs to in6_var.h.
 * Hookup mld_ifinfo state to in6_ifextra, allocate from
   domifattach path.
 * Eliminate IN6_LOOKUP_MULTI(), it is no longer referenced.
   Kernel consumers which need this should use in6m_lookup().
 * Refactor IPv6 socket group memberships to use a vector (like IPv4).
 * Update ifmcstat(8) for IPv6 SSM.
 * Add witness lock order for IN6_MULTI_LOCK.
 * Move IN6_MULTI_LOCK out of lower ip6_output()/ip6_input() paths.
 * Introduce IP6STAT_ADD/SUB/INC/DEC as per rwatson's IPv4 cleanup.
 * Update carp(4) for new IPv6 SSM KPIs.
 * Virtualize ip6_mrouter socket.
   Changes mostly localized to IPv6 MROUTING.
 * Don't do a local group lookup in MROUTING.
 * Kill unused KAME prototypes in6_purgemkludge(), in6_restoremkludge().
 * Preserve KAME DAD timer jitter behaviour in MLDv1 compatibility mode.
 * Bump __FreeBSD_version to 800084.
 * Update UPDATING.

NOTE WELL:
 * This code hasn't been tested against real MLDv2 queriers
   (yet), although the on-wire protocol has been verified in Wireshark.
 * There are a few unresolved issues in the socket layer APIs to
   do with scope ID propagation.
 * There is a LOR present in ip6_output()'s use of
   in6_setscope() which needs to be resolved. See comments in mld6.c.
   This is believed to be benign and can't be avoided for the moment
   without re-introducing an indirect netisr.

This work was mostly derived from the IGMPv3 implementation, and
has been sponsored by a third party.

1 files changed, 8 insertions, 21 deletions

diff --git a/sys/netinet6/ip6_input.c b/sys/netinet6/ip6_input.c
index 5654c94..69ac45c 100644
--- a/sys/netinet6/ip6_input.c
+++ b/sys/netinet6/ip6_input.c
@@ -555,25 +555,12 @@ passin:
 	}
 
 	/*
-	 * Multicast check
+	 * Multicast check. Assume packet is for us to avoid
+	 * prematurely taking locks.
 	 */
 	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
-		struct in6_multi *in6m = 0;
-
+		ours = 1;
 		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_mcast);
-		/*
-		 * See if we belong to the destination multicast group on the
-		 * arrival interface.
-		 */
-		IN6_LOOKUP_MULTI(ip6->ip6_dst, m->m_pkthdr.rcvif, in6m);
-		if (in6m)
-			ours = 1;
-		else if (!ip6_mrouter) {
-			V_ip6stat.ip6s_notmember++;
-			V_ip6stat.ip6s_cantforward++;
-			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
-			goto bad;
-		}
 		deliverifp = m->m_pkthdr.rcvif;
 		goto hbhcheck;
 	}
@@ -823,7 +810,8 @@ passin:
 	/*
 	 * Forward if desirable.
 	 */
-	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
+	if (V_ip6_mrouter &&
+	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
 		/*
 		 * If we are acting as a multicast router, all
 		 * incoming multicast packets are passed to the
@@ -832,13 +820,12 @@ passin:
 		 * ip6_mforward() returns a non-zero value, the packet
 		 * must be discarded, else it may be accepted below.
 		 */
-		if (ip6_mrouter && ip6_mforward &&
+		if (ip6_mforward &&
 		    ip6_mforward(ip6, m->m_pkthdr.rcvif, m)) {
-			V_ip6stat.ip6s_cantforward++;
+			IP6STAT_INC(ip6s_cantforward);
+			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
 			goto bad;
 		}
-		if (!ours)
-			goto bad;
 	} else if (!ours) {
 		ip6_forward(m, srcrt);
 		goto out;