Do not offload IGMP/MLD messages as it could lead to IGMP/MLD Reports
being unintentionally flooded to Hosts. Instead, let the bridge decide
where to send these IGMP/MLD messages.
Consider the case where the local host is sending out reports in response
to a remote querier like the following:
mcast-listener-process (IP_ADD_MEMBERSHIP)
\
br0
/ \
swp1 swp2
| |
QUERIER SOME-OTHER-HOST
In the above setup, br0 will want to br_forward() reports for
mcast-listener-process's group(s) via swp1 to QUERIER; but since the
source hwdom is 0, the report is eligible for tx offloading, and is
flooded by hardware to both swp1 and swp2, reaching SOME-OTHER-HOST as
well. (Example and illustration provided by Tobias.)
Fixes: 472111920f1c ("net: bridge: switchdev: allow the TX data plane forwarding to be offloaded")
Signed-off-by: Joseph Huang <Joseph.Huang@xxxxxxxxxx>
---
v1: https://lore.kernel.org/netdev/20250701193639.836027-1-Joseph.Huang@xxxxxxxxxx/
v2: Updated commit message.
---
net/bridge/br_switchdev.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c
index 95d7355a0407..757c34bf5931 100644
--- a/net/bridge/br_switchdev.c
+++ b/net/bridge/br_switchdev.c
@@ -18,7 +18,8 @@ static bool nbp_switchdev_can_offload_tx_fwd(const struct net_bridge_port *p,
return false;
return (p->flags & BR_TX_FWD_OFFLOAD) &&
- (p->hwdom != BR_INPUT_SKB_CB(skb)->src_hwdom);
+ (p->hwdom != BR_INPUT_SKB_CB(skb)->src_hwdom) &&
+ !br_multicast_igmp_type(skb);
}
bool br_switchdev_frame_uses_tx_fwd_offload(struct sk_buff *skb)
--
2.49.0
