netdev - Re: [PATCH net] netfilter: nf_reject: don't leak dst refcount for loopback packets

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Message-ID: <20250821074726.7cc3f294@kernel.org>
Date: Thu, 21 Aug 2025 07:47:26 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Pablo Neira Ayuso <pablo@...filter.org>
Cc: Florian Westphal <fw@...len.de>, netdev@...r.kernel.org, Paolo Abeni
 <pabeni@...hat.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH net] netfilter: nf_reject: don't leak dst refcount for
 loopback packets

On Wed, 20 Aug 2025 16:04:47 +0200 Florian Westphal wrote:
> > > Quick question: does inconditional route lookup work for br_netfilter?  
> > 
> > Never mind, it should be fine, the fake dst get attached to the skb.  
> 
> Good point, this changes behaviour for br_netfilter case, we no
> longer call nf_reject_fill_skb_dst() then due to the fake dst.
> 
> I don't think br_netfilter is supposed to do anything (iptables
> -j REJECT doesn't work in PRE_ROUTING), and we should not encourage
> use of br_netfilter with nftables.
> 
> What about adding a followup patch, targetting nf, that adds:
> 
> if (hook == NF_INET_PRE_ROUTING && nf_bridge_info_exists(oldskb))
> 	return;
> 
> ?
> 
> After all, there is no guarantee that we have the needed routing
> info on a bridge in the first place.

Pablo, are you okay with that plan? Would be great to ship this to
Linus and therefore net-next today, given the checks recently added
there..