From 4f2673b3a2b6246729a1ff13b8945a040839dbd3 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Tue, 23 Mar 2021 01:51:44 +0200 Subject: net: bridge: add helper to replay port and host-joined mdb entries I have a system with DSA ports, and udhcpcd is configured to bring interfaces up as soon as they are created. I create a bridge as follows: ip link add br0 type bridge As soon as I create the bridge and udhcpcd brings it up, I also have avahi which automatically starts sending IPv6 packets to advertise some local services, and because of that, the br0 bridge joins the following IPv6 groups due to the code path detailed below: 33:33:ff:6d:c1:9c vid 0 33:33:00:00:00:6a vid 0 33:33:00:00:00:fb vid 0 br_dev_xmit -> br_multicast_rcv -> br_ip6_multicast_add_group -> __br_multicast_add_group -> br_multicast_host_join -> br_mdb_notify This is all fine, but inside br_mdb_notify we have br_mdb_switchdev_host hooked up, and switchdev will attempt to offload the host joined groups to an empty list of ports. Of course nobody offloads them. Then when we add a port to br0: ip link set swp0 master br0 the bridge doesn't replay the host-joined MDB entries from br_add_if, and eventually the host joined addresses expire, and a switchdev notification for deleting it is emitted, but surprise, the original addition was already completely missed. The strategy to address this problem is to replay the MDB entries (both the port ones and the host joined ones) when the new port joins the bridge, similar to what vxlan_fdb_replay does (in that case, its FDB can be populated and only then attached to a bridge that you offload). However there are 2 possibilities: the addresses can be 'pushed' by the bridge into the port, or the port can 'pull' them from the bridge. Considering that in the general case, the new port can be really late to the party, and there may have been many other switchdev ports that already received the initial notification, we would like to avoid delivering duplicate events to them, since they might misbehave. And currently, the bridge calls the entire switchdev notifier chain, whereas for replaying it should just call the notifier block of the new guy. But the bridge doesn't know what is the new guy's notifier block, it just knows where the switchdev notifier chain is. So for simplification, we make this a driver-initiated pull for now, and the notifier block is passed as an argument. To emulate the calling context for mdb objects (deferred and put on the blocking notifier chain), we must iterate under RCU protection through the bridge's mdb entries, queue them, and only call them once we're out of the RCU read-side critical section. There was some opportunity for reuse between br_mdb_switchdev_host_port, br_mdb_notify and the newly added br_mdb_queue_one in how the switchdev mdb object is created, so a helper was created. Suggested-by: Ido Schimmel Signed-off-by: Vladimir Oltean Acked-by: Nikolay Aleksandrov Signed-off-by: David S. Miller --- net/bridge/br_mdb.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 131 insertions(+), 17 deletions(-) (limited to 'net/bridge') diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c index 8846c5bcd075..95fa4af0e8dd 100644 --- a/net/bridge/br_mdb.c +++ b/net/bridge/br_mdb.c @@ -506,6 +506,134 @@ err: kfree(priv); } +static void br_switchdev_mdb_populate(struct switchdev_obj_port_mdb *mdb, + const struct net_bridge_mdb_entry *mp) +{ + if (mp->addr.proto == htons(ETH_P_IP)) + ip_eth_mc_map(mp->addr.dst.ip4, mdb->addr); +#if IS_ENABLED(CONFIG_IPV6) + else if (mp->addr.proto == htons(ETH_P_IPV6)) + ipv6_eth_mc_map(&mp->addr.dst.ip6, mdb->addr); +#endif + else + ether_addr_copy(mdb->addr, mp->addr.dst.mac_addr); + + mdb->vid = mp->addr.vid; +} + +static int br_mdb_replay_one(struct notifier_block *nb, struct net_device *dev, + struct switchdev_obj_port_mdb *mdb, + struct netlink_ext_ack *extack) +{ + struct switchdev_notifier_port_obj_info obj_info = { + .info = { + .dev = dev, + .extack = extack, + }, + .obj = &mdb->obj, + }; + int err; + + err = nb->notifier_call(nb, SWITCHDEV_PORT_OBJ_ADD, &obj_info); + return notifier_to_errno(err); +} + +static int br_mdb_queue_one(struct list_head *mdb_list, + enum switchdev_obj_id id, + const struct net_bridge_mdb_entry *mp, + struct net_device *orig_dev) +{ + struct switchdev_obj_port_mdb *mdb; + + mdb = kzalloc(sizeof(*mdb), GFP_ATOMIC); + if (!mdb) + return -ENOMEM; + + mdb->obj.id = id; + mdb->obj.orig_dev = orig_dev; + br_switchdev_mdb_populate(mdb, mp); + list_add_tail(&mdb->obj.list, mdb_list); + + return 0; +} + +int br_mdb_replay(struct net_device *br_dev, struct net_device *dev, + struct notifier_block *nb, struct netlink_ext_ack *extack) +{ + struct net_bridge_mdb_entry *mp; + struct switchdev_obj *obj, *tmp; + struct net_bridge *br; + LIST_HEAD(mdb_list); + int err = 0; + + ASSERT_RTNL(); + + if (!netif_is_bridge_master(br_dev) || !netif_is_bridge_port(dev)) + return -EINVAL; + + br = netdev_priv(br_dev); + + if (!br_opt_get(br, BROPT_MULTICAST_ENABLED)) + return 0; + + /* We cannot walk over br->mdb_list protected just by the rtnl_mutex, + * because the write-side protection is br->multicast_lock. But we + * need to emulate the [ blocking ] calling context of a regular + * switchdev event, so since both br->multicast_lock and RCU read side + * critical sections are atomic, we have no choice but to pick the RCU + * read side lock, queue up all our events, leave the critical section + * and notify switchdev from blocking context. + */ + rcu_read_lock(); + + hlist_for_each_entry_rcu(mp, &br->mdb_list, mdb_node) { + struct net_bridge_port_group __rcu **pp; + struct net_bridge_port_group *p; + + if (mp->host_joined) { + err = br_mdb_queue_one(&mdb_list, + SWITCHDEV_OBJ_ID_HOST_MDB, + mp, br_dev); + if (err) { + rcu_read_unlock(); + goto out_free_mdb; + } + } + + for (pp = &mp->ports; (p = rcu_dereference(*pp)) != NULL; + pp = &p->next) { + if (p->key.port->dev != dev) + continue; + + err = br_mdb_queue_one(&mdb_list, + SWITCHDEV_OBJ_ID_PORT_MDB, + mp, dev); + if (err) { + rcu_read_unlock(); + goto out_free_mdb; + } + } + } + + rcu_read_unlock(); + + list_for_each_entry(obj, &mdb_list, list) { + err = br_mdb_replay_one(nb, dev, SWITCHDEV_OBJ_PORT_MDB(obj), + extack); + if (err) + goto out_free_mdb; + } + +out_free_mdb: + list_for_each_entry_safe(obj, tmp, &mdb_list, list) { + list_del(&obj->list); + kfree(SWITCHDEV_OBJ_PORT_MDB(obj)); + } + + return err; +} +EXPORT_SYMBOL_GPL(br_mdb_replay); + static void br_mdb_switchdev_host_port(struct net_device *dev, struct net_device *lower_dev, struct net_bridge_mdb_entry *mp, @@ -515,18 +643,12 @@ static void br_mdb_switchdev_host_port(struct net_device *dev, .obj = { .id = SWITCHDEV_OBJ_ID_HOST_MDB, .flags = SWITCHDEV_F_DEFER, + .orig_dev = dev, }, - .vid = mp->addr.vid, }; - if (mp->addr.proto == htons(ETH_P_IP)) - ip_eth_mc_map(mp->addr.dst.ip4, mdb.addr); -#if IS_ENABLED(CONFIG_IPV6) - else - ipv6_eth_mc_map(&mp->addr.dst.ip6, mdb.addr); -#endif + br_switchdev_mdb_populate(&mdb, mp); - mdb.obj.orig_dev = dev; switch (type) { case RTM_NEWMDB: switchdev_port_obj_add(lower_dev, &mdb.obj, NULL); @@ -558,21 +680,13 @@ void br_mdb_notify(struct net_device *dev, .id = SWITCHDEV_OBJ_ID_PORT_MDB, .flags = SWITCHDEV_F_DEFER, }, - .vid = mp->addr.vid, }; struct net *net = dev_net(dev); struct sk_buff *skb; int err = -ENOBUFS; if (pg) { - if (mp->addr.proto == htons(ETH_P_IP)) - ip_eth_mc_map(mp->addr.dst.ip4, mdb.addr); -#if IS_ENABLED(CONFIG_IPV6) - else if (mp->addr.proto == htons(ETH_P_IPV6)) - ipv6_eth_mc_map(&mp->addr.dst.ip6, mdb.addr); -#endif - else - ether_addr_copy(mdb.addr, mp->addr.dst.mac_addr); + br_switchdev_mdb_populate(&mdb, mp); mdb.obj.orig_dev = pg->key.port->dev; switch (type) { -- cgit v1.2.3