[PATCH net-next v4 06/14] net: bridge: mcast: track active state, IPv6 address availability

Linus Lüssing
2026-03-07T04:46:14Z

If we are the only potential MLD querier but don't have an IPv6
link-local address configured on our bridge interface then we can't
create a valid MLD query and in turn can't reliably receive MLD reports
and can't build a complete MDB. Hence disable the new multicast active
state variable then. Or reenable it if an IPv6 link-local address
became available.

No functional change for the fast/data path yet.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
---
net/bridge/br_multicast.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 64aac9c415e2..2eebfb7c5ff9 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1125,6 +1125,8 @@ static void br_multicast_notify_active(struct net_bridge_mcast *brmctx,
* The multicast active state is set, per protocol family, if:
*
* - an IGMP/MLD querier is present
+ * - for own IPv6 MLD querier: an IPv6 link-local address is configured on the
+ * bridge
*
* And is unset otherwise.
*
@@ -1223,10 +1225,12 @@ static struct sk_buff *br_ip6_multicast_alloc_query(struct net_bridge_mcast *brm
&ip6h->daddr, 0, &ip6h->saddr)) {
kfree_skb(skb);
br_opt_toggle(brmctx->br, BROPT_HAS_IPV6_ADDR, false);
+ br_multicast_update_active(brmctx);
return NULL;
}

br_opt_toggle(brmctx->br, BROPT_HAS_IPV6_ADDR, true);
+ br_multicast_update_active(brmctx);
ipv6_eth_mc_map(&ip6h->daddr, eth->h_dest);

hopopt = (u8 *)(ip6h + 1);
--
2.53.0