linux-kernel - Re: [PATCH] net: Move specific fragmented packet to slow

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Message-ID: <aAEMPbbOGZDRygwr@strlen.de>
Date: Thu, 17 Apr 2025 16:12:13 +0200
From: Florian Westphal <fw@...len.de>
To: Huajian Yang <huajianyang@...micro.com>
Cc: pablo@...filter.org, kadlec@...filter.org, razor@...ckwall.org,
	idosch@...dia.com, davem@...emloft.net, dsahern@...nel.org,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	horms@...nel.org, netfilter-devel@...r.kernel.org,
	coreteam@...filter.org, bridge@...ts.linux.dev,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: Move specific fragmented packet to slow_path
 instead of dropping it

Huajian Yang <huajianyang@...micro.com> wrote:
> The config NF_CONNTRACK_BRIDGE will change the bridge forwarding for
> fragmented packets.
> 
> The original bridge does not know that it is a fragmented packet and
> forwards it directly, after NF_CONNTRACK_BRIDGE is enabled, function
> nf_br_ip_fragment and br_ip6_fragment will check the headroom.
> 
> In original br_forward, insufficient headroom of skb may indeed exist,
> but there's still a way to save the skb in the device driver after
> dev_queue_xmit.So droping the skb will change the original bridge
> forwarding in some cases.

Fixes: 3c171f496ef5 ("netfilter: bridge: add connection tracking system")
Reviewed-by: Florian Westphal <fw@...len.de>

This should probably be routed via Pablo.

Pablo, feel free to route this via nf-next if you think its not an
urgent fix, its been like this since bridge conntrack was added.