netdev - Re: [PATCH net v2] net: clear the dst when changing skb protocol

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Message-ID: <20250609150037.1cc762e0@kernel.org>
Date: Mon, 9 Jun 2025 15:00:37 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: Maciej Żenczykowski <maze@...gle.com>,
 davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
 pabeni@...hat.com, andrew+netdev@...n.ch, horms@...nel.org, Daniel Borkmann
 <daniel@...earbox.net>, martin.lau@...ux.dev, john.fastabend@...il.com,
 eddyz87@...il.com, sdf@...ichev.me, haoluo@...gle.com, willemb@...gle.com,
 william.xuanziyang@...wei.com, alan.maguire@...cle.com,
 bpf@...r.kernel.org, shuah@...nel.org, linux-kselftest@...r.kernel.org,
 yonghong.song@...ux.dev
Subject: Re: [PATCH net v2] net: clear the dst when changing skb protocol

On Mon, 09 Jun 2025 09:50:30 -0400 Willem de Bruijn wrote:
> > > +       if (ret)
> > > +               return ret;
> > > +
> > >         bpf_compute_data_pointers(skb);
> > > -       return ret;  
> 
> I wonder whether that unconditional call to bpf_compute_data_pointers
> even if ret was there for a reason.
> 
> From reviewing the bpf_skb_proto_xlat error paths, it does seem safe
> to remove it. The cases where an error may be returned after the skb
> is modified only modify the skb in terms of headroom, not headlen.

I should have mentioned, I looked around and also concluded this
unconditional recompute was purely aesthetic.