If multicast snooping is enabled, multicast packets may not always end up on the local bridge interface, if the host is not a member of the multicast group. Similar to how IFF_PROMISC allows all packets to be received locally, let IFF_ALLMULTI allow all multicast packets to be received.
OpenWrt uses a user space daemon for DHCPv6/RA/NDP handling, and in relay mode it sets the ALLMULTI flag in order to receive all relevant queries on the network. This works for normal network interfaces and non-snooping bridges, but not snooping bridges (unless multicast routing is enabled). Reported-by: Felix Fietkau <n...@nbd.name> Closes:https://github.com/openwrt/openwrt/issues/15857#issuecomment-2662851243 Signed-off-by: Shengyu Qu <wiagn...@outlook.com> --- Changes since v1: - Move to net-next - Changed code according to Nikolay's advice Changes since v2: - Fix alignment - Remove redundant parenthesis - Add more infomation in commit message --- net/bridge/br_input.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c index 232133a0fd21..5f6ac9bf1527 100644 --- a/net/bridge/br_input.c +++ b/net/bridge/br_input.c @@ -189,7 +189,8 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) && br_multicast_querier_exists(brmctx, eth_hdr(skb), mdst)) { if ((mdst && mdst->host_joined) || - br_multicast_is_router(brmctx, skb)) { + br_multicast_is_router(brmctx, skb) || + br->dev->flags & IFF_ALLMULTI) { local_rcv = true; DEV_STATS_INC(br->dev, multicast); } -- 2.43.0
