BPF List
 help / color / mirror / Atom feed
From: Jakub Kicinski <kuba@kernel.org>
To: chia-yu.chang@nokia-bell-labs.com
Cc: shaojijie@huawei.com, shenjian15@huawei.com,
	linux-rdma@vger.kernel.org, eperezma@redhat.com,
	jasowang@redhat.com, virtualization@lists.linux.dev,
	mst@redhat.com, xuanzhuo@linux.alibaba.com, pabeni@redhat.com,
	edumazet@google.com, linux-doc@vger.kernel.org, corbet@lwn.net,
	horms@kernel.org, dsahern@kernel.org, kuniyu@google.com,
	bpf@vger.kernel.org, netdev@vger.kernel.org, dave.taht@gmail.com,
	jhs@mojatatu.com, stephen@networkplumber.org,
	xiyou.wangcong@gmail.com, jiri@resnulli.us, davem@davemloft.net,
	andrew+netdev@lunn.ch, donald.hunter@gmail.com, ast@fiberby.net,
	liuhangbin@gmail.com, shuah@kernel.org,
	linux-kselftest@vger.kernel.org, ij@kernel.org,
	ncardwell@google.com, koen.de_schepper@nokia-bell-labs.com,
	g.white@cablelabs.com, ingemar.s.johansson@ericsson.com,
	mirja.kuehlewind@ericsson.com, cheshire@apple.com,
	rs.ietf@gmx.at, Jason_Livingood@comcast.com,
	vidhi_goel@apple.com, Parav Pandit <parav@nvidia.com>
Subject: Re: [PATCH v5 net-next 1/2] net: update comments for SKB_GSO_TCP_ECN and SKB_GSO_TCP_ACCECN
Date: Tue, 11 Aug 2026 17:30:17 -0700	[thread overview]
Message-ID: <20260811173017.3d18dfdc@kernel.org> (raw)
In-Reply-To: <20260804213510.673084-2-chia-yu.chang@nokia-bell-labs.com>

On Tue,  4 Aug 2026 23:35:09 +0200 chia-yu.chang@nokia-bell-labs.com
wrote:
> This corresponds to discussions in virtio mailing list:
> https://lore.kernel.org/all/20250814120118.81787-1-chia-yu.chang@nokia-bell-labs.com/
> And it was suggested to clarify SKB_GSO_TCP_ECN and SKB_GSO_TCP_ACCECN.

> -	/* This indicates the tcp segment has CWR set. */
> +	/* For TX, this indicates that the first TCP segment has CWR set, and
> +	 * any subsequent segment in the same skb has CWR cleared. This flag
> +	 * must not be used in RX, because the connection to which the segment
> +	 * belongs is not tracked to use RFC3168 or AccECN. Using RFC3168 ECN
> +	 * offload may clear CWR and corrupt ACE signal (CWR is part of it).
> +	 * Instead, SKB_GSO_TCP_ACCECN shall be used to avoid CWR corruption.
> +	 */

I still can't wrap my head around this TBH.

SKB_GSO_TCP_ECN means RFC3168
SKB_GSO_TCP_ACCECN means AccECN

If the HW can correctly detect cwr on first frame and then no cwr 
and report that as ECN/RFC3168 - what's the problem? TSO will produce
the exact expected segment sequence.

Is the program that if we re-GRO that frame in SW we end up with
ECN+ACCECN on the same skb?

  reply	other threads:[~2026-08-12  0:30 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-04 21:35 [PATCH v5 net-next 0/2] ECN offload handling series chia-yu.chang
2026-08-04 21:35 ` [PATCH v5 net-next 1/2] net: update comments for SKB_GSO_TCP_ECN and SKB_GSO_TCP_ACCECN chia-yu.chang
2026-08-12  0:30   ` Jakub Kicinski [this message]
2026-08-12 10:33     ` Chia-Yu Chang (Nokia)
2026-08-04 21:35 ` [PATCH v5 net-next 2/2] net: hns3: fix GSO_ECN flag setting in the RX path chia-yu.chang
2026-08-06 11:47   ` Jijie Shao
2026-08-11 13:31   ` Jijie Shao
2026-08-12 10:35     ` Chia-Yu Chang (Nokia)

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20260811173017.3d18dfdc@kernel.org \
    --to=kuba@kernel.org \
    --cc=Jason_Livingood@comcast.com \
    --cc=andrew+netdev@lunn.ch \
    --cc=ast@fiberby.net \
    --cc=bpf@vger.kernel.org \
    --cc=cheshire@apple.com \
    --cc=chia-yu.chang@nokia-bell-labs.com \
    --cc=corbet@lwn.net \
    --cc=dave.taht@gmail.com \
    --cc=davem@davemloft.net \
    --cc=donald.hunter@gmail.com \
    --cc=dsahern@kernel.org \
    --cc=edumazet@google.com \
    --cc=eperezma@redhat.com \
    --cc=g.white@cablelabs.com \
    --cc=horms@kernel.org \
    --cc=ij@kernel.org \
    --cc=ingemar.s.johansson@ericsson.com \
    --cc=jasowang@redhat.com \
    --cc=jhs@mojatatu.com \
    --cc=jiri@resnulli.us \
    --cc=koen.de_schepper@nokia-bell-labs.com \
    --cc=kuniyu@google.com \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=linux-rdma@vger.kernel.org \
    --cc=liuhangbin@gmail.com \
    --cc=mirja.kuehlewind@ericsson.com \
    --cc=mst@redhat.com \
    --cc=ncardwell@google.com \
    --cc=netdev@vger.kernel.org \
    --cc=pabeni@redhat.com \
    --cc=parav@nvidia.com \
    --cc=rs.ietf@gmx.at \
    --cc=shaojijie@huawei.com \
    --cc=shenjian15@huawei.com \
    --cc=shuah@kernel.org \
    --cc=stephen@networkplumber.org \
    --cc=vidhi_goel@apple.com \
    --cc=virtualization@lists.linux.dev \
    --cc=xiyou.wangcong@gmail.com \
    --cc=xuanzhuo@linux.alibaba.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox