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

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Message-ID: <20250410101824.GA6272@breakpoint.cc>
Date: Thu, 10 Apr 2025 12:18:24 +0200
From: Florian Westphal <fw@...len.de>
To: Huajian Yang <huajianyang@...micro.com>
Cc: pablo@...filter.org, fw@...len.de, 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:
> --- a/net/bridge/netfilter/nf_conntrack_bridge.c
> +++ b/net/bridge/netfilter/nf_conntrack_bridge.c
> @@ -61,18 +61,14 @@ static int nf_br_ip_fragment(struct net *net, struct sock *sk,
>  		struct sk_buff *frag;
>  
>  		if (first_len - hlen > mtu ||
> -		    skb_headroom(skb) < ll_rs)
> -			goto blackhole;

I would prefer to keep blackhole logic for the mtu tests,
i.e.
  if (first_len - hlen > mtu)
      goto blackhole;

same for the frag->len test in the skb_walk_frags loop.
>From what I understood the problem is only because of
the lower devices' headroom requirement.