linux-kernel - Re: [PATCH net-next v3] net: bridge: locally receive all multicast packets if IFF

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Message-ID: <Z_34arGmvmWVHbPu@shredder>
Date: Tue, 15 Apr 2025 09:10:50 +0300
From: Ido Schimmel <idosch@...dia.com>
To: Shengyu Qu <wiagn233@...look.com>
Cc: razor@...ckwall.org, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
	bridge@...ts.linux.dev, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Felix Fietkau <nbd@....name>
Subject: Re: [PATCH net-next v3] net: bridge: locally receive all multicast
 packets if IFF_ALLMULTI is set

On Mon, Apr 14, 2025 at 06:56:01PM +0800, Shengyu Qu wrote:
> 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 <nbd@....name>
> Closes:https://github.com/openwrt/openwrt/issues/15857#issuecomment-2662851243
> Signed-off-by: Shengyu Qu <wiagn233@...look.com>

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