[Bridge] [PATCH v2] net: bridge: sync fdb to new unicast-filtering ports

Wolfgang Bumiller w.bumiller at proxmox.com
Fri Jul 2 08:26:05 UTC 2021

Since commit 2796d0c648c9 ("bridge: Automatically manage
port promiscuous mode.")
bridges with `vlan_filtering 1` and only 1 auto-port don't
set IFF_PROMISC for unicast-filtering-capable ports.

Normally on port changes `br_manage_promisc` is called to
update the promisc flags and unicast filters if necessary,
but it cannot distinguish between *new* ports and ones
losing their promisc flag, and new ports end up not
receiving the MAC address list.

Fix this by calling `br_fdb_sync_static` in `br_add_if`
after the port promisc flags are updated and the unicast
filter was supposed to have been filled.

Fixes: 2796d0c648c9 ("bridge: Automatically manage port promiscuous mode.")
Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
Changes to v1:
  * Added unsync to error case.
  * Improved error message
  * Added `Fixes` tag to commit message

 net/bridge/br_if.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index f7d2f472ae24..2fd03a9742c8 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -652,6 +652,18 @@ int br_add_if(struct net_bridge *br, struct net_device *dev,
 	list_add_rcu(&p->list, &br->port_list);
+	if (!br_promisc_port(p) && (p->dev->priv_flags & IFF_UNICAST_FLT)) {
+		/* When updating the port count we also update all ports'
+		 * promiscuous mode.
+		 * A port leaving promiscuous mode normally gets the bridge's
+		 * fdb synced to the unicast filter (if supported), however,
+		 * `br_port_clear_promisc` does not distinguish between
+		 * non-promiscuous ports and *new* ports, so we need to
+		 * sync explicitly here.
+		 */
+		if (br_fdb_sync_static(br, p))
+			netdev_err(dev, "failed to sync bridge static fdb addresses to this port\n");
+	}
@@ -701,6 +713,7 @@ int br_add_if(struct net_bridge *br, struct net_device *dev,
 	return 0;
+	br_fdb_unsync_static(br, p);
 	br_fdb_delete_by_port(br, p, 0, 1);

More information about the Bridge mailing list