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From: Eric Dumazet <edumazet@google.com>
Date: Tue, 26 Mar 2024 15:46:35 +0100
Message-ID: <CANn89iJkDbzLKmUGRHNFpfiaO8z19i44qgqkBA9Updt4QsRkyg@mail.gmail.com>
Subject: Re: [PATCH net-next v4 4/4] net: gro: move L3 flush checks to tcp_gro_receive
To: Richard Gobert <richardbgobert@gmail.com>
Cc: davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, 
	willemdebruijn.kernel@gmail.com, netdev@vger.kernel.org, 
	linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
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On Tue, Mar 26, 2024 at 3:43=E2=80=AFPM Richard Gobert <richardbgobert@gmai=
l.com> wrote:
>
> Eric Dumazet wrote:
> > On Mon, Mar 25, 2024 at 7:27=E2=80=AFPM Richard Gobert <richardbgobert@=
gmail.com> wrote:
> >>
> >> {inet,ipv6}_gro_receive functions perform flush checks (ttl, flags,
> >> iph->id, ...) against all packets in a loop. These flush checks are us=
ed
> >> currently only in tcp flows in GRO.
> >
> > I think this is a bug.
> >
> > GRO should not aggregate packets if their ttl/tos fields do not match.
>
> AFAIU, the only UDP flow where ttl/flush_id need to be checked is when
> udp_gro_receive_segment calls skb_gro_receive - could you confirm / point
> out if there are any other flows to which these flush checks may be
> relevant?
>
> As I've discussed with Willem in v3 I prefer to fix this bug in a separat=
e
> series.

I do not understand this patch 4/4 then.

Why bother moving stuff in net/ipv4/tcp_offload.c if we plan to move
it back to where it belongs ?