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Date: Thu, 10 Apr 2025 12:18:24 +0200
From: Florian Westphal <fw@strlen.de>
To: Huajian Yang <huajianyang@asrmicro.com>
Cc: pablo@netfilter.org, fw@strlen.de, kadlec@netfilter.org,
	razor@blackwall.org, idosch@nvidia.com, davem@davemloft.net,
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Subject: Re: [PATCH] net: Move specific fragmented packet to slow_path
 instead of dropping it
Message-ID: <20250410101824.GA6272@breakpoint.cc>
References: <20250410075726.8599-1-huajianyang@asrmicro.com>
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In-Reply-To: <20250410075726.8599-1-huajianyang@asrmicro.com>
User-Agent: Mutt/1.10.1 (2018-07-13)

Huajian Yang <huajianyang@asrmicro.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.