bridge: mcast: Delete empty MDB entry when port group creation fails

When a port group cannot be created for a new group, the MDB entry that
was created for it is left with no ports and is not joined by the host.
Its timer is never armed, so the entry is never deleted, but it is
counted towards mcast_hash_max. When this maximum is reached, the bridge
disables multicast snooping.

Since commit b57e8d870d52 ("net: bridge: Maintain number of MDB entries
in net_bridge_mcast_port"), port group creation also fails when the port
reached its mcast_max_groups limit. A host behind such a port can
therefore disable snooping by sending reports for new groups, which is
what the limit is meant to prevent. The RTM_NEWMDB path has the same
problem.

Fix by deleting the entry after a failure if it is unused. Delete it
immediately rather than arming its timer, so that it stops counting
towards the maximum right away.

Fixes: b57e8d870d52 ("net: bridge: Maintain number of MDB entries in net_bridge_mcast_port")
Reported-by: Yunlong Ma <yunlong_ma@buaa.edu.cn>
Closes: https://lore.kernel.org/netdev/2f5b61e2.1e71a.1a11fcb3809.Coremail.yunlong_ma@buaa.edu.cn/
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Tested-by: Gabriel Goller <g.goller@proxmox.com>
Reviewed-by: Gabriel Goller <g.goller@proxmox.com>
Link: https://patch.msgid.link/20261016101407.2030133-2-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions