On 23/03/2021 01:51, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.olt...@nxp.com>
>
> 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 <ido...@idosch.org>
> Signed-off-by: Vladimir Oltean <vladimir.olt...@nxp.com>
> ---
> include/linux/if_bridge.h | 9 +++
> include/net/switchdev.h | 1 +
> net/bridge/br_mdb.c | 148 +++++++++++++++++++++++++++++++++-----
> 3 files changed, 141 insertions(+), 17 deletions(-)
>
Absolutely the same comments here as for the fdb version.
The code looks correct.
Acked-by: Nikolay Aleksandrov <niko...@nvidia.com>
> diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
> index ebd16495459c..f6472969bb44 100644
> --- a/include/linux/if_bridge.h
> +++ b/include/linux/if_bridge.h
> @@ -69,6 +69,8 @@ bool br_multicast_has_querier_anywhere(struct net_device
> *dev, int proto);
> bool br_multicast_has_querier_adjacent(struct net_device *dev, int proto);
> bool br_multicast_enabled(const struct net_device *dev);
> bool br_multicast_router(const struct net_device *dev);
> +int br_mdb_replay(struct net_device *br_dev, struct net_device *dev,
> + struct notifier_block *nb, struct netlink_ext_ack *extack);
> #else
> static inline int br_multicast_list_adjacent(struct net_device *dev,
> struct list_head *br_ip_list)
> @@ -93,6 +95,13 @@ static inline bool br_multicast_router(const struct
> net_device *dev)
> {
> return false;
> }
> +static inline int br_mdb_replay(struct net_device *br_dev,
> + struct net_device *dev,
> + struct notifier_block *nb,
> + struct netlink_ext_ack *extack)
> +{
> + return -EOPNOTSUPP;
> +}
> #endif
>
> #if IS_ENABLED(CONFIG_BRIDGE) && IS_ENABLED(CONFIG_BRIDGE_VLAN_FILTERING)
> diff --git a/include/net/switchdev.h b/include/net/switchdev.h
> index b7fc7d0f54e2..8c3218177136 100644
> --- a/include/net/switchdev.h
> +++ b/include/net/switchdev.h
> @@ -68,6 +68,7 @@ enum switchdev_obj_id {
> };
>
> struct switchdev_obj {
> + struct list_head list;
> struct net_device *orig_dev;
> enum switchdev_obj_id id;
> u32 flags;
> 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 @@ static void br_mdb_complete(struct net_device *dev, int
> err, void *priv)
> 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) {
>
n
