Use ALLOW_NEW_SOURCES and BLOCK_OLD_SOURCES to signal a join or leave

with SSM MLDv2 by default.
This is current practice and complies with RFC 4604, as well as being
required by production IPv6 networks in Japan.
The behaviour may be disabled by setting the net.inet6.mld.use_allow
sysctl/tunable to 0.

Requested by:	Hideki Yamamoto
MFC after:	1 week

2 files changed, 60 insertions, 16 deletions

diff --git a/sys/netinet6/mld6.c b/sys/netinet6/mld6.c
index 8759ade..cade0d2 100644
--- a/sys/netinet6/mld6.c
+++ b/sys/netinet6/mld6.c
@@ -132,7 +132,8 @@ static struct mbuf *
 static int	mld_v2_enqueue_filter_change(struct ifqueue *,
 		    struct in6_multi *);
 static int	mld_v2_enqueue_group_record(struct ifqueue *,
-		    struct in6_multi *, const int, const int, const int);
+		    struct in6_multi *, const int, const int, const int,
+		    const int);
 static int	mld_v2_input_query(struct ifnet *, const struct ip6_hdr *,
 		    struct mbuf *, const int, const int);
 static int	mld_v2_merge_state_changes(struct in6_multi *,
@@ -236,6 +237,11 @@ SYSCTL_INT(_net_inet6_mld, OID_AUTO, v1enable, CTLFLAG_RW,
     &mld_v1enable, 0, "Enable fallback to MLDv1");
 TUNABLE_INT("net.inet6.mld.v1enable", &mld_v1enable);
 
+static int	mld_use_allow = 1;
+SYSCTL_INT(_net_inet6_mld, OID_AUTO, use_allow, CTLFLAG_RW,
+    &mld_use_allow, 0, "Use ALLOW/BLOCK for RFC 4604 SSM joins/leaves");
+TUNABLE_INT("net.inet6.mld.use_allow", &mld_use_allow);
+
 /*
  * Packed Router Alert option structure declaration.
  */
@@ -461,6 +467,8 @@ mld_domifattach(struct ifnet *ifp)
 	mli = mli_alloc_locked(ifp);
 	if (!(ifp->if_flags & IFF_MULTICAST))
 		mli->mli_flags |= MLIF_SILENT;
+	if (mld_use_allow)
+		mli->mli_flags |= MLIF_USEALLOW;
 
 	MLD_UNLOCK();
 
@@ -1550,7 +1558,8 @@ mld_v2_process_group_timers(struct mld_ifinfo *mli,
 			int retval;
 
 			retval = mld_v2_enqueue_group_record(qrq, inm, 0, 1,
-			    (inm->in6m_state == MLD_SG_QUERY_PENDING_MEMBER));
+			    (inm->in6m_state == MLD_SG_QUERY_PENDING_MEMBER),
+			    0);
 			CTR2(KTR_MLD, "%s: enqueue record = %d",
 			    __func__, retval);
 			inm->in6m_state = MLD_REPORTING_MEMBER;
@@ -2025,7 +2034,7 @@ mld_initial_join(struct in6_multi *inm, struct mld_ifinfo *mli,
 			ifq = &inm->in6m_scq;
 			_IF_DRAIN(ifq);
 			retval = mld_v2_enqueue_group_record(ifq, inm, 1,
-			    0, 0);
+			    0, 0, (mli->mli_flags & MLIF_USEALLOW));
 			CTR2(KTR_MLD, "%s: enqueue record = %d",
 			    __func__, retval);
 			if (retval <= 0) {
@@ -2118,7 +2127,8 @@ mld_handle_state_change(struct in6_multi *inm, struct mld_ifinfo *mli)
 
 	_IF_DRAIN(&inm->in6m_scq);
 
-	retval = mld_v2_enqueue_group_record(&inm->in6m_scq, inm, 1, 0, 0);
+	retval = mld_v2_enqueue_group_record(&inm->in6m_scq, inm, 1, 0, 0,
+	    (mli->mli_flags & MLIF_USEALLOW));
 	CTR2(KTR_MLD, "%s: enqueue record = %d", __func__, retval);
 	if (retval <= 0)
 		return (-retval);
@@ -2203,7 +2213,8 @@ mld_final_leave(struct in6_multi *inm, struct mld_ifinfo *mli)
 				in6m_acquire_locked(inm);
 
 				retval = mld_v2_enqueue_group_record(
-				    &inm->in6m_scq, inm, 1, 0, 0);
+				    &inm->in6m_scq, inm, 1, 0, 0,
+				    (mli->mli_flags & MLIF_USEALLOW));
 				KASSERT(retval != 0,
 				    ("%s: enqueue record = %d", __func__,
 				     retval));
@@ -2250,6 +2261,10 @@ mld_final_leave(struct in6_multi *inm, struct mld_ifinfo *mli)
  * it was recorded for a Group-Source query, and will be omitted if
  * it is not both in-mode and recorded.
  *
+ * If use_block_allow is non-zero, state change reports for initial join
+ * and final leave, on an inclusive mode group with a source list, will be
+ * rewritten to use the ALLOW_NEW and BLOCK_OLD record types, respectively.
+ *
  * The function will attempt to allocate leading space in the packet
  * for the IPv6+ICMP headers to be prepended without fragmenting the chain.
  *
@@ -2260,7 +2275,7 @@ mld_final_leave(struct in6_multi *inm, struct mld_ifinfo *mli)
 static int
 mld_v2_enqueue_group_record(struct ifqueue *ifq, struct in6_multi *inm,
     const int is_state_change, const int is_group_query,
-    const int is_source_query)
+    const int is_source_query, const int use_block_allow)
 {
 	struct mldv2_record	 mr;
 	struct mldv2_record	*pmr;
@@ -2308,10 +2323,16 @@ mld_v2_enqueue_group_record(struct ifqueue *ifq, struct in6_multi *inm,
 		 * If the mode did not change, and there are non-ASM
 		 * listeners or source filters present,
 		 * we potentially need to issue two records for the group.
-		 * If we are transitioning to MCAST_UNDEFINED, we need
-		 * not send any sources.
 		 * If there are ASM listeners, and there was no filter
 		 * mode transition of any kind, do nothing.
+		 *
+		 * If we are transitioning to MCAST_UNDEFINED, we need
+		 * not send any sources. A transition to/from this state is
+		 * considered inclusive with some special treatment.
+		 *
+		 * If we are rewriting initial joins/leaves to use
+		 * ALLOW/BLOCK, and the group's membership is inclusive,
+		 * we need to send sources in all cases.
 		 */
 		if (mode != inm->in6m_st[0].iss_fmode) {
 			if (mode == MCAST_EXCLUDE) {
@@ -2321,9 +2342,26 @@ mld_v2_enqueue_group_record(struct ifqueue *ifq, struct in6_multi *inm,
 			} else {
 				CTR1(KTR_MLD, "%s: change to INCLUDE",
 				    __func__);
-				type = MLD_CHANGE_TO_INCLUDE_MODE;
-				if (mode == MCAST_UNDEFINED)
-					record_has_sources = 0;
+				if (use_block_allow) {
+					/*
+					 * XXX
+					 * Here we're interested in state
+					 * edges either direction between
+					 * MCAST_UNDEFINED and MCAST_INCLUDE.
+					 * Perhaps we should just check
+					 * the group state, rather than
+					 * the filter mode.
+					 */
+					if (mode == MCAST_UNDEFINED) {
+						type = MLD_BLOCK_OLD_SOURCES;
+					} else {
+						type = MLD_ALLOW_NEW_SOURCES;
+					}
+				} else {
+					type = MLD_CHANGE_TO_INCLUDE_MODE;
+					if (mode == MCAST_UNDEFINED)
+						record_has_sources = 0;
+				}
 			}
 		} else {
 			if (record_has_sources) {
@@ -2436,9 +2474,12 @@ mld_v2_enqueue_group_record(struct ifqueue *ifq, struct in6_multi *inm,
 	 * If we are appending to an existing packet, we need to obtain
 	 * a pointer to the group record after m_append(), in case a new
 	 * mbuf was allocated.
+	 *
 	 * Only append sources which are in-mode at t1. If we are
-	 * transitioning to MCAST_UNDEFINED state on the group, do not
-	 * include source entries.
+	 * transitioning to MCAST_UNDEFINED state on the group, and
+	 * use_block_allow is zero, do not include source entries.
+	 * Otherwise, we need to include this source in the report.
+	 *
 	 * Only report recorded sources in our filter set when responding
 	 * to a group-source query.
 	 */
@@ -2460,7 +2501,8 @@ mld_v2_enqueue_group_record(struct ifqueue *ifq, struct in6_multi *inm,
 			now = im6s_get_mode(inm, ims, 1);
 			CTR2(KTR_MLD, "%s: node is %d", __func__, now);
 			if ((now != mode) ||
-			    (now == mode && mode == MCAST_UNDEFINED)) {
+			    (now == mode &&
+			     (!use_block_allow && mode == MCAST_UNDEFINED))) {
 				CTR1(KTR_MLD, "%s: skip node", __func__);
 				continue;
 			}
@@ -2550,7 +2592,8 @@ mld_v2_enqueue_group_record(struct ifqueue *ifq, struct in6_multi *inm,
 			    __func__, ip6_sprintf(ip6tbuf, &ims->im6s_addr));
 			now = im6s_get_mode(inm, ims, 1);
 			if ((now != mode) ||
-			    (now == mode && mode == MCAST_UNDEFINED)) {
+			    (now == mode &&
+			     (!use_block_allow && mode == MCAST_UNDEFINED))) {
 				CTR1(KTR_MLD, "%s: skip node", __func__);
 				continue;
 			}
@@ -2961,7 +3004,7 @@ mld_v2_dispatch_general_query(struct mld_ifinfo *mli)
 		case MLD_AWAKENING_MEMBER:
 			inm->in6m_state = MLD_REPORTING_MEMBER;
 			retval = mld_v2_enqueue_group_record(&mli->mli_gq,
-			    inm, 0, 0, 0);
+			    inm, 0, 0, 0, 0);
 			CTR2(KTR_MLD, "%s: enqueue record = %d",
 			    __func__, retval);
 			break;
diff --git a/sys/netinet6/mld6_var.h b/sys/netinet6/mld6_var.h
index efd01ab..e62ec23 100644
--- a/sys/netinet6/mld6_var.h
+++ b/sys/netinet6/mld6_var.h
@@ -55,6 +55,7 @@ struct mld_ifinfo {
 	struct ifqueue	 mli_gq;	/* queue of general query responses */
 };
 #define MLIF_SILENT	0x00000001	/* Do not use MLD on this ifp */
+#define MLIF_USEALLOW	0x00000002	/* Use ALLOW/BLOCK for joins/leaves */
 
 #define MLD_RANDOM_DELAY(X)		(arc4random() % (X) + 1)
 #define MLD_MAX_STATE_CHANGES		24 /* Max pending changes per group */