netdev - Re: [PATCH net-next v4 4/4] net: gro: move L3 flush checks to tcp_gro

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Message-ID: <494e8cac-e87a-4bc4-8a77-1801a703fd86@gmail.com>
Date: Tue, 26 Mar 2024 13:35:01 +0100
From: Richard Gobert <richardbgobert@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, dsahern@...nel.org,
 xeb@...l.ru, shuah@...nel.org, idosch@...dia.com, amcohen@...dia.com,
 petrm@...dia.com, jbenc@...hat.com, bpoirier@...dia.com,
 b.galvani@...il.com, liujian56@...wei.com, horms@...nel.org,
 linyunsheng@...wei.com, therbert@...gle.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v4 4/4] net: gro: move L3 flush checks to
 tcp_gro_receive

Willem de Bruijn wrote:
> In v3 we discussed how the flush on network layer differences (like
> TTL or ToS) currently only affect the TCP GRO path, but should apply
> more broadly.
> 
> We agreed that it is fine to leave that to a separate patch series.
> 
> But seeing this patch, it introduces a lot of churn, but also makes
> it harder to address that issue for UDP, as it now moves network
> layer checks directly to the TCP code.
Currently the logic of flush_id is scattered in tcp_gro_receive and
{inet,ipv6}_gro_receive with conditionals rewriting ->flush and ->flush_id,
so IMO the code should be more concise when it's in one place - in addition
to not doing checks against non relevant packets.

With this patch, the fix will probably be simple, most likely just calling
gro_network_flush from skb_gro_receive or from the relevant flow in
udp_gro_receive_segment. Since this bug fix should be simple and it being
not relevant to the optimization, I'd like to solve it in another series
and properly test that new flow. Do you agree?