[RFC PATCH v2 net-next 09/16] net: dsa: replay port and local fdb entries when joining the bridge

Vladimir Oltean
2021-03-18T23:20:00Z

From: Vladimir Oltean <vladimir.oltean@nxp.com>

When a DSA port joins a LAG that already had an FDB entry pointing to it:

ip link set bond0 master br0
bridge fdb add dev bond0 00:01:02:03:04:05 master static
ip link set swp0 master bond0

the DSA port will have no idea that this FDB entry is there, because it
missed the switchdev event emitted at its creation.

Ido Schimmel pointed this out during a discussion about challenges with
switchdev offloading of stacked interfaces between the physical port and
the bridge, and recommended to just catch that condition and deny the
CHANGEUPPER event:
https://lore.kernel.org/netdev/20210210105949.GB287766@shredder.lan/

But in fact, we might need to deal with the hard thing anyway, which is
to replay all FDB addresses relevant to this port, because it isn't just
static FDB entries, but also local addresses (ones that are not
forwarded but terminated by the bridge). There, we can't just say 'oh
yeah, there was an upper already so I'm not joining that'.

So, similar to the logic for replaying MDB entries, add a function that
must be called by individual switchdev drivers and replays local FDB
entries as well as ones pointing towards a bridge port. This time, we
use the atomic switchdev notifier block, since that's what FDB entries
expect for some reason.

Reported-by: Ido Schimmel <idosch@idosch.org>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
include/linux/if_bridge.h | 9 +++++++
include/net/switchdev.h | 1 +
net/bridge/br_fdb.c | 52 +++++++++++++++++++++++++++++++++++++++
net/dsa/dsa_priv.h | 1 +
net/dsa/port.c | 4 +++
net/dsa/slave.c | 2 +-
6 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
index 4c25dafb013d..89596134e88f 100644
--- a/include/linux/if_bridge.h
+++ b/include/linux/if_bridge.h
@@ -147,6 +147,8 @@ void br_fdb_clear_offload(const struct net_device *dev, u16 vid);
bool br_port_flag_is_set(const struct net_device *dev, unsigned long flag);
u8 br_port_get_stp_state(const struct net_device *dev);
clock_t br_get_ageing_time(struct net_device *br_dev);
+int br_fdb_replay(struct net_device *br_dev, struct net_device *dev,
+ struct notifier_block *nb);
#else
static inline struct net_device *
br_fdb_find_port(const struct net_device *br_dev,
@@ -175,6 +177,13 @@ static inline clock_t br_get_ageing_time(struct net_device *br_dev)
{
return 0;
}
+
+static inline int br_fdb_replay(struct net_device *br_dev,
+ struct net_device *dev,
+ struct notifier_block *nb)
+{
+ return -EINVAL;
+}
#endif

#endif
diff --git a/include/net/switchdev.h b/include/net/switchdev.h
index b7fc7d0f54e2..7688ec572757 100644
--- a/include/net/switchdev.h
+++ b/include/net/switchdev.h
@@ -205,6 +205,7 @@ struct switchdev_notifier_info {

struct switchdev_notifier_fdb_info {
struct switchdev_notifier_info info; /* must be first */
+ struct list_head list;
const unsigned char *addr;
u16 vid;
u8 added_by_user:1,
diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index b7490237f3fc..49125cc196ac 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -726,6 +726,58 @@ static inline size_t fdb_nlmsg_size(void)
+ nla_total_size(sizeof(u8)); /* NFEA_ACTIVITY_NOTIFY */
}

+static int br_fdb_replay_one(struct notifier_block *nb,
+ struct net_bridge_fdb_entry *fdb,
+ struct net_device *dev)
+{
+ struct switchdev_notifier_fdb_info item;
+ int err;
+
+ item.addr = fdb->key.addr.addr;
+ item.vid = fdb->key.vlan_id;
+ item.added_by_user = test_bit(BR_FDB_ADDED_BY_USER, &fdb->flags);
+ item.offloaded = test_bit(BR_FDB_OFFLOADED, &fdb->flags);
+ item.info.dev = dev;
+
+ err = nb->notifier_call(nb, SWITCHDEV_FDB_ADD_TO_DEVICE, &item);
+ return notifier_to_errno(err);
+}
+
+int br_fdb_replay(struct net_device *br_dev, struct net_device *dev,
+ struct notifier_block *nb)
+{
+ struct net_bridge_fdb_entry *fdb;
+ struct net_bridge *br;
+ int err = 0;
+
+ if (!netif_is_bridge_master(br_dev))
+ return -EINVAL;
+
+ if (!netif_is_bridge_port(dev))
+ return -EINVAL;
+
+ br = netdev_priv(br_dev);
+
+ rcu_read_lock();
+
+ hlist_for_each_entry_rcu(fdb, &br->fdb_list, fdb_node) {
+ struct net_device *dst_dev;
+
+ dst_dev = fdb->dst ? fdb->dst->dev : br->dev;
+ if (dst_dev != br_dev && dst_dev != dev)
+ continue;
+
+ err = br_fdb_replay_one(nb, fdb, dst_dev);
+ if (err)
+ break;
+ }
+
+ rcu_read_unlock();
+
+ return err;
+}
+EXPORT_SYMBOL(br_fdb_replay);
+
static void fdb_notify(struct net_bridge *br,
const struct net_bridge_fdb_entry *fdb, int type,
bool swdev_notify)
diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index b14c43cb88bb..92282de54230 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -262,6 +262,7 @@ static inline bool dsa_tree_offloads_bridge_port(struct dsa_switch_tree *dst,

/* slave.c */
extern const struct dsa_device_ops notag_netdev_ops;
+extern struct notifier_block dsa_slave_switchdev_notifier;
extern struct notifier_block dsa_slave_switchdev_blocking_notifier;

void dsa_slave_mii_bus_init(struct dsa_switch *ds);
diff --git a/net/dsa/port.c b/net/dsa/port.c
index 6670612f96c6..9850051071f2 100644
--- a/net/dsa/port.c
+++ b/net/dsa/port.c
@@ -205,6 +205,10 @@ static int dsa_port_switchdev_sync(struct dsa_port *dp,
if (err && err != -EOPNOTSUPP)
return err;

+ err = br_fdb_replay(br, brport_dev, &dsa_slave_switchdev_notifier);
+ if (err && err != -EOPNOTSUPP)
+ return err;
+
return 0;
}

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index b974d8f84a2e..c51e52418a62 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -2392,7 +2392,7 @@ static struct notifier_block dsa_slave_nb __read_mostly = {
.notifier_call = dsa_slave_netdevice_event,
};

-static struct notifier_block dsa_slave_switchdev_notifier = {
+struct notifier_block dsa_slave_switchdev_notifier = {
.notifier_call = dsa_slave_switchdev_event,
};

--
2.25.1