net: bridge: convert multicast to generic rhashtable

The bridge multicast code currently uses a custom resizable hashtable
which predates the generic rhashtable interface. It has many
shortcomings compared and duplicates functionality that is presently
available via the generic rhashtable, so this patch removes the custom
rhashtable implementation in favor of the kernel's generic rhashtable.
The hash maximum is kept and the rhashtable's size is used to do a loose
check if it's reached in which case we revert to the old behaviour and
disable further bridge multicast processing. Also now we can support any
hash maximum, doesn't need to be a power of 2.

v3: add non-rcu br_mdb_get variant and use it where multicast_lock is
    held to avoid RCU splat, drop hash_max function and just set it
    directly

v2: handle when IGMP snooping is undefined, add br_mdb_init/uninit
    placeholders

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 73 insertions, 341 deletions

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 6bac0d6b7b94..83a5931a7784 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -37,6 +37,14 @@
 
 #include "br_private.h"
 
+static const struct rhashtable_params br_mdb_rht_params = {
+	.head_offset = offsetof(struct net_bridge_mdb_entry, rhnode),
+	.key_offset = offsetof(struct net_bridge_mdb_entry, addr),
+	.key_len = sizeof(struct br_ip),
+	.automatic_shrinking = true,
+	.locks_mul = 1,
+};
+
 static void br_multicast_start_querier(struct net_bridge *br,
 				       struct bridge_mcast_own_query *query);
 static void br_multicast_add_router(struct net_bridge *br,
@@ -54,7 +62,6 @@ static void br_ip6_multicast_leave_group(struct net_bridge *br,
 					 const struct in6_addr *group,
 					 __u16 vid, const unsigned char *src);
 #endif
-unsigned int br_mdb_rehash_seq;
 
 static inline int br_ip_equal(const struct br_ip *a, const struct br_ip *b)
 {
@@ -73,89 +80,58 @@ static inline int br_ip_equal(const struct br_ip *a, const struct br_ip *b)
 	return 0;
 }
 
-static inline int __br_ip4_hash(struct net_bridge_mdb_htable *mdb, __be32 ip,
-				__u16 vid)
-{
-	return jhash_2words((__force u32)ip, vid, mdb->secret) & (mdb->max - 1);
-}
-
-#if IS_ENABLED(CONFIG_IPV6)
-static inline int __br_ip6_hash(struct net_bridge_mdb_htable *mdb,
-				const struct in6_addr *ip,
-				__u16 vid)
+static struct net_bridge_mdb_entry *br_mdb_ip_get_rcu(struct net_bridge *br,
+						      struct br_ip *dst)
 {
-	return jhash_2words(ipv6_addr_hash(ip), vid,
-			    mdb->secret) & (mdb->max - 1);
+	return rhashtable_lookup(&br->mdb_hash_tbl, dst, br_mdb_rht_params);
 }
-#endif
 
-static inline int br_ip_hash(struct net_bridge_mdb_htable *mdb,
-			     struct br_ip *ip)
-{
-	switch (ip->proto) {
-	case htons(ETH_P_IP):
-		return __br_ip4_hash(mdb, ip->u.ip4, ip->vid);
-#if IS_ENABLED(CONFIG_IPV6)
-	case htons(ETH_P_IPV6):
-		return __br_ip6_hash(mdb, &ip->u.ip6, ip->vid);
-#endif
-	}
-	return 0;
-}
-
-static struct net_bridge_mdb_entry *__br_mdb_ip_get(
-	struct net_bridge_mdb_htable *mdb, struct br_ip *dst, int hash)
+struct net_bridge_mdb_entry *br_mdb_ip_get(struct net_bridge *br,
+					   struct br_ip *dst)
 {
-	struct net_bridge_mdb_entry *mp;
-
-	hlist_for_each_entry_rcu(mp, &mdb->mhash[hash], hlist[mdb->ver]) {
-		if (br_ip_equal(&mp->addr, dst))
-			return mp;
-	}
+	struct net_bridge_mdb_entry *ent;
 
-	return NULL;
-}
+	lockdep_assert_held_once(&br->multicast_lock);
 
-struct net_bridge_mdb_entry *br_mdb_ip_get(struct net_bridge_mdb_htable *mdb,
-					   struct br_ip *dst)
-{
-	if (!mdb)
-		return NULL;
+	rcu_read_lock();
+	ent = rhashtable_lookup(&br->mdb_hash_tbl, dst, br_mdb_rht_params);
+	rcu_read_unlock();
 
-	return __br_mdb_ip_get(mdb, dst, br_ip_hash(mdb, dst));
+	return ent;
 }
 
-static struct net_bridge_mdb_entry *br_mdb_ip4_get(
-	struct net_bridge_mdb_htable *mdb, __be32 dst, __u16 vid)
+static struct net_bridge_mdb_entry *br_mdb_ip4_get(struct net_bridge *br,
+						   __be32 dst, __u16 vid)
 {
 	struct br_ip br_dst;
 
+	memset(&br_dst, 0, sizeof(br_dst));
 	br_dst.u.ip4 = dst;
 	br_dst.proto = htons(ETH_P_IP);
 	br_dst.vid = vid;
 
-	return br_mdb_ip_get(mdb, &br_dst);
+	return br_mdb_ip_get(br, &br_dst);
 }
 
 #if IS_ENABLED(CONFIG_IPV6)
-static struct net_bridge_mdb_entry *br_mdb_ip6_get(
-	struct net_bridge_mdb_htable *mdb, const struct in6_addr *dst,
-	__u16 vid)
+static struct net_bridge_mdb_entry *br_mdb_ip6_get(struct net_bridge *br,
+						   const struct in6_addr *dst,
+						   __u16 vid)
 {
 	struct br_ip br_dst;
 
+	memset(&br_dst, 0, sizeof(br_dst));
 	br_dst.u.ip6 = *dst;
 	br_dst.proto = htons(ETH_P_IPV6);
 	br_dst.vid = vid;
 
-	return br_mdb_ip_get(mdb, &br_dst);
+	return br_mdb_ip_get(br, &br_dst);
 }
 #endif
 
 struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
 					struct sk_buff *skb, u16 vid)
 {
-	struct net_bridge_mdb_htable *mdb = rcu_dereference(br->mdb);
 	struct br_ip ip;
 
 	if (!br_opt_get(br, BROPT_MULTICAST_ENABLED))
@@ -164,6 +140,7 @@ struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
 	if (BR_INPUT_SKB_CB(skb)->igmp)
 		return NULL;
 
+	memset(&ip, 0, sizeof(ip));
 	ip.proto = skb->protocol;
 	ip.vid = vid;
 
@@ -180,47 +157,7 @@ struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
 		return NULL;
 	}
 
-	return br_mdb_ip_get(mdb, &ip);
-}
-
-static void br_mdb_free(struct rcu_head *head)
-{
-	struct net_bridge_mdb_htable *mdb =
-		container_of(head, struct net_bridge_mdb_htable, rcu);
-	struct net_bridge_mdb_htable *old = mdb->old;
-
-	mdb->old = NULL;
-	kfree(old->mhash);
-	kfree(old);
-}
-
-static int br_mdb_copy(struct net_bridge_mdb_htable *new,
-		       struct net_bridge_mdb_htable *old,
-		       int elasticity)
-{
-	struct net_bridge_mdb_entry *mp;
-	int maxlen;
-	int len;
-	int i;
-
-	for (i = 0; i < old->max; i++)
-		hlist_for_each_entry(mp, &old->mhash[i], hlist[old->ver])
-			hlist_add_head(&mp->hlist[new->ver],
-				       &new->mhash[br_ip_hash(new, &mp->addr)]);
-
-	if (!elasticity)
-		return 0;
-
-	maxlen = 0;
-	for (i = 0; i < new->max; i++) {
-		len = 0;
-		hlist_for_each_entry(mp, &new->mhash[i], hlist[new->ver])
-			len++;
-		if (len > maxlen)
-			maxlen = len;
-	}
-
-	return maxlen > elasticity ? -EINVAL : 0;
+	return br_mdb_ip_get_rcu(br, &ip);
 }
 
 void br_multicast_free_pg(struct rcu_head *head)
@@ -243,7 +180,6 @@ static void br_multicast_group_expired(struct timer_list *t)
 {
 	struct net_bridge_mdb_entry *mp = from_timer(mp, t, timer);
 	struct net_bridge *br = mp->br;
-	struct net_bridge_mdb_htable *mdb;
 
 	spin_lock(&br->multicast_lock);
 	if (!netif_running(br->dev) || timer_pending(&mp->timer))
@@ -255,10 +191,9 @@ static void br_multicast_group_expired(struct timer_list *t)
 	if (mp->ports)
 		goto out;
 
-	mdb = mlock_dereference(br->mdb, br);
-
-	hlist_del_rcu(&mp->hlist[mdb->ver]);
-	mdb->size--;
+	rhashtable_remove_fast(&br->mdb_hash_tbl, &mp->rhnode,
+			       br_mdb_rht_params);
+	hlist_del_rcu(&mp->mdb_node);
 
 	call_rcu_bh(&mp->rcu, br_multicast_free_group);
 
@@ -269,14 +204,11 @@ out:
 static void br_multicast_del_pg(struct net_bridge *br,
 				struct net_bridge_port_group *pg)
 {
-	struct net_bridge_mdb_htable *mdb;
 	struct net_bridge_mdb_entry *mp;
 	struct net_bridge_port_group *p;
 	struct net_bridge_port_group __rcu **pp;
 
-	mdb = mlock_dereference(br->mdb, br);
-
-	mp = br_mdb_ip_get(mdb, &pg->addr);
+	mp = br_mdb_ip_get(br, &pg->addr);
 	if (WARN_ON(!mp))
 		return;
 
@@ -319,53 +251,6 @@ out:
 	spin_unlock(&br->multicast_lock);
 }
 
-static int br_mdb_rehash(struct net_bridge_mdb_htable __rcu **mdbp, int max,
-			 int elasticity)
-{
-	struct net_bridge_mdb_htable *old = rcu_dereference_protected(*mdbp, 1);
-	struct net_bridge_mdb_htable *mdb;
-	int err;
-
-	mdb = kmalloc(sizeof(*mdb), GFP_ATOMIC);
-	if (!mdb)
-		return -ENOMEM;
-
-	mdb->max = max;
-	mdb->old = old;
-
-	mdb->mhash = kcalloc(max, sizeof(*mdb->mhash), GFP_ATOMIC);
-	if (!mdb->mhash) {
-		kfree(mdb);
-		return -ENOMEM;
-	}
-
-	mdb->size = old ? old->size : 0;
-	mdb->ver = old ? old->ver ^ 1 : 0;
-
-	if (!old || elasticity)
-		get_random_bytes(&mdb->secret, sizeof(mdb->secret));
-	else
-		mdb->secret = old->secret;
-
-	if (!old)
-		goto out;
-
-	err = br_mdb_copy(mdb, old, elasticity);
-	if (err) {
-		kfree(mdb->mhash);
-		kfree(mdb);
-		return err;
-	}
-
-	br_mdb_rehash_seq++;
-	call_rcu_bh(&mdb->rcu, br_mdb_free);
-
-out:
-	rcu_assign_pointer(*mdbp, mdb);
-
-	return 0;
-}
-
 static struct sk_buff *br_ip4_multicast_alloc_query(struct net_bridge *br,
 						    __be32 group,
 						    u8 *igmp_type)
@@ -589,111 +474,19 @@ static struct sk_buff *br_multicast_alloc_query(struct net_bridge *br,
 	return NULL;
 }
 
-static struct net_bridge_mdb_entry *br_multicast_get_group(
-	struct net_bridge *br, struct net_bridge_port *port,
-	struct br_ip *group, int hash)
-{
-	struct net_bridge_mdb_htable *mdb;
-	struct net_bridge_mdb_entry *mp;
-	unsigned int count = 0;
-	unsigned int max;
-	int elasticity;
-	int err;
-
-	mdb = rcu_dereference_protected(br->mdb, 1);
-	hlist_for_each_entry(mp, &mdb->mhash[hash], hlist[mdb->ver]) {
-		count++;
-		if (unlikely(br_ip_equal(group, &mp->addr)))
-			return mp;
-	}
-
-	elasticity = 0;
-	max = mdb->max;
-
-	if (unlikely(count > br->hash_elasticity && count)) {
-		if (net_ratelimit())
-			br_info(br, "Multicast hash table "
-				"chain limit reached: %s\n",
-				port ? port->dev->name : br->dev->name);
-
-		elasticity = br->hash_elasticity;
-	}
-
-	if (mdb->size >= max) {
-		max *= 2;
-		if (unlikely(max > br->hash_max)) {
-			br_warn(br, "Multicast hash table maximum of %d "
-				"reached, disabling snooping: %s\n",
-				br->hash_max,
-				port ? port->dev->name : br->dev->name);
-			err = -E2BIG;
-disable:
-			br_opt_toggle(br, BROPT_MULTICAST_ENABLED, false);
-			goto err;
-		}
-	}
-
-	if (max > mdb->max || elasticity) {
-		if (mdb->old) {
-			if (net_ratelimit())
-				br_info(br, "Multicast hash table "
-					"on fire: %s\n",
-					port ? port->dev->name : br->dev->name);
-			err = -EEXIST;
-			goto err;
-		}
-
-		err = br_mdb_rehash(&br->mdb, max, elasticity);
-		if (err) {
-			br_warn(br, "Cannot rehash multicast "
-				"hash table, disabling snooping: %s, %d, %d\n",
-				port ? port->dev->name : br->dev->name,
-				mdb->size, err);
-			goto disable;
-		}
-
-		err = -EAGAIN;
-		goto err;
-	}
-
-	return NULL;
-
-err:
-	mp = ERR_PTR(err);
-	return mp;
-}
-
 struct net_bridge_mdb_entry *br_multicast_new_group(struct net_bridge *br,
-						    struct net_bridge_port *p,
 						    struct br_ip *group)
 {
-	struct net_bridge_mdb_htable *mdb;
 	struct net_bridge_mdb_entry *mp;
-	int hash;
 	int err;
 
-	mdb = rcu_dereference_protected(br->mdb, 1);
-	if (!mdb) {
-		err = br_mdb_rehash(&br->mdb, BR_HASH_SIZE, 0);
-		if (err)
-			return ERR_PTR(err);
-		goto rehash;
-	}
-
-	hash = br_ip_hash(mdb, group);
-	mp = br_multicast_get_group(br, p, group, hash);
-	switch (PTR_ERR(mp)) {
-	case 0:
-		break;
+	mp = br_mdb_ip_get(br, group);
+	if (mp)
+		return mp;
 
-	case -EAGAIN:
-rehash:
-		mdb = rcu_dereference_protected(br->mdb, 1);
-		hash = br_ip_hash(mdb, group);
-		break;
-
-	default:
-		goto out;
+	if (atomic_read(&br->mdb_hash_tbl.nelems) >= br->hash_max) {
+		br_opt_toggle(br, BROPT_MULTICAST_ENABLED, false);
+		return ERR_PTR(-E2BIG);
 	}
 
 	mp = kzalloc(sizeof(*mp), GFP_ATOMIC);
@@ -703,11 +496,15 @@ rehash:
 	mp->br = br;
 	mp->addr = *group;
 	timer_setup(&mp->timer, br_multicast_group_expired, 0);
+	err = rhashtable_lookup_insert_fast(&br->mdb_hash_tbl, &mp->rhnode,
+					    br_mdb_rht_params);
+	if (err) {
+		kfree(mp);
+		mp = ERR_PTR(err);
+	} else {
+		hlist_add_head_rcu(&mp->mdb_node, &br->mdb_list);
+	}
 
-	hlist_add_head_rcu(&mp->hlist[mdb->ver], &mdb->mhash[hash]);
-	mdb->size++;
-
-out:
 	return mp;
 }
 
@@ -768,7 +565,7 @@ static int br_multicast_add_group(struct net_bridge *br,
 	    (port && port->state == BR_STATE_DISABLED))
 		goto out;
 
-	mp = br_multicast_new_group(br, port, group);
+	mp = br_multicast_new_group(br, group);
 	err = PTR_ERR(mp);
 	if (IS_ERR(mp))
 		goto err;
@@ -837,6 +634,7 @@ static int br_ip6_multicast_add_group(struct net_bridge *br,
 	if (ipv6_addr_is_ll_all_nodes(group))
 		return 0;
 
+	memset(&br_group, 0, sizeof(br_group));
 	br_group.u.ip6 = *group;
 	br_group.proto = htons(ETH_P_IPV6);
 	br_group.vid = vid;
@@ -1483,7 +1281,7 @@ static void br_ip4_multicast_query(struct net_bridge *br,
 		goto out;
 	}
 
-	mp = br_mdb_ip4_get(mlock_dereference(br->mdb, br), group, vid);
+	mp = br_mdb_ip4_get(br, group, vid);
 	if (!mp)
 		goto out;
 
@@ -1567,7 +1365,7 @@ static int br_ip6_multicast_query(struct net_bridge *br,
 		goto out;
 	}
 
-	mp = br_mdb_ip6_get(mlock_dereference(br->mdb, br), group, vid);
+	mp = br_mdb_ip6_get(br, group, vid);
 	if (!mp)
 		goto out;
 
@@ -1601,7 +1399,6 @@ br_multicast_leave_group(struct net_bridge *br,
 			 struct bridge_mcast_own_query *own_query,
 			 const unsigned char *src)
 {
-	struct net_bridge_mdb_htable *mdb;
 	struct net_bridge_mdb_entry *mp;
 	struct net_bridge_port_group *p;
 	unsigned long now;
@@ -1612,8 +1409,7 @@ br_multicast_leave_group(struct net_bridge *br,
 	    (port && port->state == BR_STATE_DISABLED))
 		goto out;
 
-	mdb = mlock_dereference(br->mdb, br);
-	mp = br_mdb_ip_get(mdb, group);
+	mp = br_mdb_ip_get(br, group);
 	if (!mp)
 		goto out;
 
@@ -1999,6 +1795,7 @@ void br_multicast_init(struct net_bridge *br)
 	timer_setup(&br->ip6_own_query.timer,
 		    br_ip6_multicast_query_expired, 0);
 #endif
+	INIT_HLIST_HEAD(&br->mdb_list);
 }
 
 static void __br_multicast_open(struct net_bridge *br,
@@ -2033,40 +1830,20 @@ void br_multicast_stop(struct net_bridge *br)
 
 void br_multicast_dev_del(struct net_bridge *br)
 {
-	struct net_bridge_mdb_htable *mdb;
 	struct net_bridge_mdb_entry *mp;
-	struct hlist_node *n;
-	u32 ver;
-	int i;
+	struct hlist_node *tmp;
 
 	spin_lock_bh(&br->multicast_lock);
-	mdb = mlock_dereference(br->mdb, br);
-	if (!mdb)
-		goto out;
-
-	br->mdb = NULL;
-
-	ver = mdb->ver;
-	for (i = 0; i < mdb->max; i++) {
-		hlist_for_each_entry_safe(mp, n, &mdb->mhash[i],
-					  hlist[ver]) {
-			del_timer(&mp->timer);
-			call_rcu_bh(&mp->rcu, br_multicast_free_group);
-		}
-	}
-
-	if (mdb->old) {
-		spin_unlock_bh(&br->multicast_lock);
-		rcu_barrier_bh();
-		spin_lock_bh(&br->multicast_lock);
-		WARN_ON(mdb->old);
+	hlist_for_each_entry_safe(mp, tmp, &br->mdb_list, mdb_node) {
+		del_timer(&mp->timer);
+		rhashtable_remove_fast(&br->mdb_hash_tbl, &mp->rhnode,
+				       br_mdb_rht_params);
+		hlist_del_rcu(&mp->mdb_node);
+		call_rcu_bh(&mp->rcu, br_multicast_free_group);
 	}
-
-	mdb->old = mdb;
-	call_rcu_bh(&mdb->rcu, br_mdb_free);
-
-out:
 	spin_unlock_bh(&br->multicast_lock);
+
+	rcu_barrier_bh();
 }
 
 int br_multicast_set_router(struct net_bridge *br, unsigned long val)
@@ -2176,7 +1953,6 @@ static void br_multicast_start_querier(struct net_bridge *br,
 
 int br_multicast_toggle(struct net_bridge *br, unsigned long val)
 {
-	struct net_bridge_mdb_htable *mdb;
 	struct net_bridge_port *port;
 	int err = 0;
 
@@ -2192,21 +1968,6 @@ int br_multicast_toggle(struct net_bridge *br, unsigned long val)
 	if (!netif_running(br->dev))
 		goto unlock;
 
-	mdb = mlock_dereference(br->mdb, br);
-	if (mdb) {
-		if (mdb->old) {
-			err = -EEXIST;
-rollback:
-			br_opt_toggle(br, BROPT_MULTICAST_ENABLED, false);
-			goto unlock;
-		}
-
-		err = br_mdb_rehash(&br->mdb, mdb->max,
-				    br->hash_elasticity);
-		if (err)
-			goto rollback;
-	}
-
 	br_multicast_open(br);
 	list_for_each_entry(port, &br->port_list, list)
 		__br_multicast_enable_port(port);
@@ -2271,45 +2032,6 @@ unlock:
 	return 0;
 }
 
-int br_multicast_set_hash_max(struct net_bridge *br, unsigned long val)
-{
-	int err = -EINVAL;
-	u32 old;
-	struct net_bridge_mdb_htable *mdb;
-
-	spin_lock_bh(&br->multicast_lock);
-	if (!is_power_of_2(val))
-		goto unlock;
-
-	mdb = mlock_dereference(br->mdb, br);
-	if (mdb && val < mdb->size)
-		goto unlock;
-
-	err = 0;
-
-	old = br->hash_max;
-	br->hash_max = val;
-
-	if (mdb) {
-		if (mdb->old) {
-			err = -EEXIST;
-rollback:
-			br->hash_max = old;
-			goto unlock;
-		}
-
-		err = br_mdb_rehash(&br->mdb, br->hash_max,
-				    br->hash_elasticity);
-		if (err)
-			goto rollback;
-	}
-
-unlock:
-	spin_unlock_bh(&br->multicast_lock);
-
-	return err;
-}
-
 int br_multicast_set_igmp_version(struct net_bridge *br, unsigned long val)
 {
 	/* Currently we support only version 2 and 3 */
@@ -2646,3 +2368,13 @@ void br_multicast_get_stats(const struct net_bridge *br,
 	}
 	memcpy(dest, &tdst, sizeof(*dest));
 }
+
+int br_mdb_hash_init(struct net_bridge *br)
+{
+	return rhashtable_init(&br->mdb_hash_tbl, &br_mdb_rht_params);
+}
+
+void br_mdb_hash_fini(struct net_bridge *br)
+{
+	rhashtable_destroy(&br->mdb_hash_tbl);
+}