netdev - Re: [PATCH net-next v2 06/14] net: bridge: mcast: track active state, IPv6 address availability

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Message-ID: <20260208160840.GF154003@shredder>
Date: Sun, 8 Feb 2026 18:08:40 +0200
From: Ido Schimmel <idosch@...dia.com>
To: Linus Lüssing <linus.luessing@...3.blue>
Cc: bridge@...ts.linux.dev, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Simon Horman <horms@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	"David S . Miller" <davem@...emloft.net>,
	Kuniyuki Iwashima <kuniyu@...gle.com>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Xiao Liang <shaw.leon@...il.com>
Subject: Re: [PATCH net-next v2 06/14] net: bridge: mcast: track active
 state, IPv6 address availability

On Fri, Feb 06, 2026 at 03:52:12AM +0100, Linus Lüssing wrote:
> 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@...3.blue>

Reviewed-by: Ido Schimmel <idosch@...dia.com>

> ---
>  net/bridge/br_multicast.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> index 0fc29875db9c..a1cde2ba2a3e 100644
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -1125,6 +1125,7 @@ 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 address is configured on the bridge

an IPv6 link-local address

>   *
>   * And is unset otherwise.
>   *
> @@ -1222,10 +1223,12 @@ 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);
> -- 
> 2.51.0
>