[Bridge] [PATCH 3/6] bridge: Avoid traffic disruption when Querier state changes

Joseph Huang Joseph.Huang at garmin.com
Tue May 4 18:22:56 UTC 2021


Modify br_mdb_notify so that switchdev mdb purge events are never sent
for mrouter ports, and when a non-mrouter port turns into an mrouter
port, all port groups associated with that port are deleted immediately.

Consider the following scenario:

                 +--------------------+
                 |                    |
+-----------+    |      Snooping   +--|    +------------+
| MC Source |----|      Bridge 1   |P1|----| Listener 1 |
+-----------|    |        +--+     +--|    +------------+
                 |        |P2|        |
                 +--------------------+
                           |
                           |
                 +--------------------+
                 |        |P3|        |
                 |        +--+     +--|    +---------------+
                 |      Snooping   |P4|----| Listener 2    |
                 |      Bridge 2   +--|    | Joins Group A |
                 |                    |    +---------------+
                 +--------------------+

Assuming initially Snooping Bridge 1 is the Querier, and Snooping Bridge
2 is a Non-Querier. After some Query/Report exchange, Snooping Bridge 1
would create an mdb group A and add P2 to the group, and starts a timer
on the port group A/P2.

Let's say Snooping Bridge 2 becomes the Querier for some reason (e.g.,
Snooping Bridge 2 rebooted) before the port group A/P2 expires. With
the patch 'bridge: Offload mrouter port forwarding to switchdev',
Snooping Bridge 1 detects that P2 has now become an mrouter port, and
will add it to the address database on the hardware switch chip (even
though it's already there when the port group A/P2 was added). This is
all fine until the timer on port group A/P2 expires, and then Snooping
Bridge 1 will purge P2 from the address database on the switch chip.
Now Listener 2 will not be able to receive multicast traffic from MC
Source anymore.

With this patch, immediately after a bridge port turns into an mrouter
port, the port's membership information is removed from the bridge' mdb,
but remains programmed in the address database on the hardware chip,
just to be consistent with the database/programming state as before
the Querier role change.  The hardware programming will be cleaned up
when the group expires (via br_multicast_group_change).

Signed-off-by: Joseph Huang <Joseph.Huang at garmin.com>
---
 net/bridge/br_mdb.c       | 17 +++++----
 net/bridge/br_multicast.c | 78 ++++++++++++++++++++++++++++++++-------
 net/bridge/br_private.h   |  3 +-
 3 files changed, 75 insertions(+), 23 deletions(-)

diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index e8684d798ec3..c121b780450b 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -708,16 +708,17 @@ void br_mdb_switchdev_port(struct net_bridge_mdb_entry *mp,
 void br_mdb_notify(struct net_device *dev,
 		   struct net_bridge_mdb_entry *mp,
 		   struct net_bridge_port_group *pg,
-		   int type)
+		   int type, bool swdev_notify)
 {
 	struct net *net = dev_net(dev);
 	struct sk_buff *skb;
 	int err = -ENOBUFS;
 
-	if (pg) {
-		br_mdb_switchdev_port(mp, pg->key.port, type);
-	} else {
-		br_mdb_switchdev_host(dev, mp, type);
+	if (swdev_notify) {
+		if (pg)
+			br_mdb_switchdev_port(mp, pg->key.port, type);
+		else
+			br_mdb_switchdev_host(dev, mp, type);
 	}
 
 	skb = nlmsg_new(rtnl_mdb_nlmsg_size(pg), GFP_ATOMIC);
@@ -1011,7 +1012,7 @@ static int br_mdb_add_group(struct net_bridge *br, struct net_bridge_port *port,
 		}
 
 		br_multicast_host_join(mp, false);
-		br_mdb_notify(br->dev, mp, NULL, RTM_NEWMDB);
+		br_mdb_notify(br->dev, mp, NULL, RTM_NEWMDB, true);
 
 		return 0;
 	}
@@ -1042,7 +1043,7 @@ static int br_mdb_add_group(struct net_bridge *br, struct net_bridge_port *port,
 	rcu_assign_pointer(*pp, p);
 	if (entry->state == MDB_TEMPORARY)
 		mod_timer(&p->timer, now + br->multicast_membership_interval);
-	br_mdb_notify(br->dev, mp, p, RTM_NEWMDB);
+	br_mdb_notify(br->dev, mp, p, RTM_NEWMDB, true);
 	/* if we are adding a new EXCLUDE port group (*,G) it needs to be also
 	 * added to all S,G entries for proper replication, if we are adding
 	 * a new INCLUDE port (S,G) then all of *,G EXCLUDE ports need to be
@@ -1176,7 +1177,7 @@ static int __br_mdb_del(struct net_bridge *br, struct br_mdb_entry *entry,
 	if (entry->ifindex == mp->br->dev->ifindex && mp->host_joined) {
 		br_multicast_host_leave(mp, false);
 		err = 0;
-		br_mdb_notify(br->dev, mp, NULL, RTM_DELMDB);
+		br_mdb_notify(br->dev, mp, NULL, RTM_DELMDB, true);
 		if (!mp->ports && netif_running(br->dev))
 			mod_timer(&mp->timer, jiffies);
 		goto unlock;
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 5ed0d5efef09..d7fbe1f3af18 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -506,7 +506,7 @@ static void br_multicast_fwd_src_handle(struct net_bridge_group_src *src)
 		sg_mp = br_mdb_ip_get(src->br, &sg_key.addr);
 		if (!sg_mp)
 			return;
-		br_mdb_notify(src->br->dev, sg_mp, sg, RTM_NEWMDB);
+		br_mdb_notify(src->br->dev, sg_mp, sg, RTM_NEWMDB, true);
 	}
 }
 
@@ -617,7 +617,12 @@ void br_multicast_del_pg(struct net_bridge_mdb_entry *mp,
 	br_multicast_eht_clean_sets(pg);
 	hlist_for_each_entry_safe(ent, tmp, &pg->src_list, node)
 		br_multicast_del_group_src(ent, false);
-	br_mdb_notify(br->dev, mp, pg, RTM_DELMDB);
+	/* don't notify switchdev if mrouter port
+	 * switchdev will be notified when group expires via
+	 * br_multicast_group_change
+	 */
+	br_mdb_notify(br->dev, mp, pg, RTM_DELMDB,
+		      hlist_unhashed(&pg->key.port->rlist));
 	if (!br_multicast_is_star_g(&mp->addr)) {
 		rhashtable_remove_fast(&br->sg_port_tbl, &pg->rhnode,
 				       br_sg_port_rht_params);
@@ -688,7 +693,7 @@ static void br_multicast_port_group_expired(struct timer_list *t)
 
 		if (WARN_ON(!mp))
 			goto out;
-		br_mdb_notify(br->dev, mp, pg, RTM_NEWMDB);
+		br_mdb_notify(br->dev, mp, pg, RTM_NEWMDB, true);
 	}
 out:
 	spin_unlock(&br->multicast_lock);
@@ -1228,7 +1233,7 @@ void br_multicast_host_join(struct net_bridge_mdb_entry *mp, bool notify)
 		if (br_multicast_is_star_g(&mp->addr))
 			br_multicast_star_g_host_state(mp);
 		if (notify)
-			br_mdb_notify(mp->br->dev, mp, NULL, RTM_NEWMDB);
+			br_mdb_notify(mp->br->dev, mp, NULL, RTM_NEWMDB, true);
 	}
 
 	if (br_group_is_l2(&mp->addr))
@@ -1246,7 +1251,7 @@ void br_multicast_host_leave(struct net_bridge_mdb_entry *mp, bool notify)
 	if (br_multicast_is_star_g(&mp->addr))
 		br_multicast_star_g_host_state(mp);
 	if (notify)
-		br_mdb_notify(mp->br->dev, mp, NULL, RTM_DELMDB);
+		br_mdb_notify(mp->br->dev, mp, NULL, RTM_DELMDB, true);
 }
 
 static struct net_bridge_port_group *
@@ -1294,7 +1299,7 @@ __br_multicast_add_group(struct net_bridge *br,
 	rcu_assign_pointer(*pp, p);
 	if (blocked)
 		p->flags |= MDB_PG_FLAGS_BLOCKED;
-	br_mdb_notify(br->dev, mp, p, RTM_NEWMDB);
+	br_mdb_notify(br->dev, mp, p, RTM_NEWMDB, true);
 
 found:
 	if (igmpv2_mldv1)
@@ -2436,7 +2441,7 @@ static int br_ip4_multicast_igmp3_report(struct net_bridge *br,
 			break;
 		}
 		if (changed)
-			br_mdb_notify(br->dev, mdst, pg, RTM_NEWMDB);
+			br_mdb_notify(br->dev, mdst, pg, RTM_NEWMDB, true);
 unlock_continue:
 		spin_unlock_bh(&br->multicast_lock);
 	}
@@ -2575,7 +2580,7 @@ static int br_ip6_multicast_mld2_report(struct net_bridge *br,
 			break;
 		}
 		if (changed)
-			br_mdb_notify(br->dev, mdst, pg, RTM_NEWMDB);
+			br_mdb_notify(br->dev, mdst, pg, RTM_NEWMDB, true);
 unlock_continue:
 		spin_unlock_bh(&br->multicast_lock);
 	}
@@ -2660,26 +2665,71 @@ br_multicast_update_query_timer(struct net_bridge *br,
 	mod_timer(&query->timer, jiffies + br->multicast_querier_interval);
 }
 
-static void br_port_mc_router_state_change(struct net_bridge_port *p,
+static void br_port_mc_router_state_change(struct net_bridge_port *port,
 					   bool is_mc_router)
 {
 	struct switchdev_attr attr = {
-		.orig_dev = p->dev,
+		.orig_dev = port->dev,
 		.id = SWITCHDEV_ATTR_ID_PORT_MROUTER,
 		.flags = SWITCHDEV_F_DEFER,
 		.u.mrouter = is_mc_router,
 	};
 	struct net_bridge_mdb_entry *mp;
+	struct net_bridge *br = port->br;
 	struct hlist_node *n;
 
-	switchdev_port_attr_set(p->dev, &attr, NULL);
+	switchdev_port_attr_set(port->dev, &attr, NULL);
 
 	/* Add/delete the router port to/from all multicast group
 	 * called whle br->multicast_lock is held
 	 */
-	hlist_for_each_entry_safe(mp, n, &p->br->mdb_list, mdb_node) {
-		br_mdb_switchdev_port(mp, p, is_mc_router ?
-				      RTM_NEWMDB : RTM_DELMDB);
+	hlist_for_each_entry_safe(mp, n, &br->mdb_list, mdb_node) {
+		struct net_bridge_port_group __rcu **pp;
+		struct net_bridge_port_group *p;
+		int port_group_exists = 0;
+
+		if (is_mc_router) {
+			for (pp = &mp->ports;
+				(p = mlock_dereference(*pp, br)) != NULL;
+				pp = &p->next) {
+				if (p->key.port == port) {
+					port_group_exists = 1;
+					if (!(p->flags & MDB_PG_FLAGS_PERMANENT))
+						br_multicast_del_pg(mp, p, pp);
+				}
+
+				if ((unsigned long)p->key.port < (unsigned long)port)
+					break;
+			}
+
+			if (port_group_exists)
+				continue;
+
+			br_mdb_switchdev_port(mp, port, RTM_NEWMDB);
+		} else {
+			for (pp = &mp->ports;
+				(p = mlock_dereference(*pp, br)) != NULL;
+				pp = &p->next) {
+				if (p->key.port == port) {
+					port_group_exists = 1;
+					break;
+				}
+
+				if ((unsigned long)p->key.port < (unsigned long)port)
+					break;
+			}
+
+			if (port_group_exists)
+				continue;
+
+			p = br_multicast_new_port_group(port, &mp->addr, *pp, 0,
+							NULL, MCAST_EXCLUDE, RTPROT_KERNEL);
+			if (unlikely(!p))
+				continue;
+			rcu_assign_pointer(*pp, p);
+			br_mdb_notify(br->dev, mp, p, RTM_NEWMDB, false);
+			mod_timer(&p->timer, jiffies + br->multicast_membership_interval);
+		}
 	}
 }
 
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 5cba9d228b9c..9aa51508ba83 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -832,7 +832,8 @@ void br_mdb_hash_fini(struct net_bridge *br);
 void br_mdb_switchdev_port(struct net_bridge_mdb_entry *mp,
 			   struct net_bridge_port *p, int type);
 void br_mdb_notify(struct net_device *dev, struct net_bridge_mdb_entry *mp,
-		   struct net_bridge_port_group *pg, int type);
+		   struct net_bridge_port_group *pg, int type,
+		   bool swdev_notify);
 void br_rtr_notify(struct net_device *dev, struct net_bridge_port *port,
 		   int type);
 void br_multicast_del_pg(struct net_bridge_mdb_entry *mp,
-- 
2.17.1



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