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[80.230.34.155]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435e131ce70sm36590005f8f.27.2026.02.01.01.01.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 01 Feb 2026 01:01:21 -0800 (PST) Date: Sun, 1 Feb 2026 04:01:16 -0500 From: "Michael S. Tsirkin" To: chia-yu.chang@nokia-bell-labs.com Cc: tariqt@nvidia.com, linux-rdma@vger.kernel.org, shaojijie@huawei.com, shenjian15@huawei.com, salil.mehta@huawei.com, mbloch@nvidia.com, saeedm@nvidia.com, leon@kernel.org, eperezma@redhat.com, brett.creeley@amd.com, jasowang@redhat.com, virtualization@lists.linux.dev, xuanzhuo@linux.alibaba.com, pabeni@redhat.com, edumazet@google.com, parav@nvidia.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, kuba@kernel.org, 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 Subject: Re: [PATCH v1 net-next 1/3] net: update commnets for SKB_GSO_TCP_ECN and SKB_GSO_TCP_ACCECN Message-ID: <20260201040043-mutt-send-email-mst@kernel.org> References: <20260131225510.2946-1-chia-yu.chang@nokia-bell-labs.com> <20260131225510.2946-2-chia-yu.chang@nokia-bell-labs.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260131225510.2946-2-chia-yu.chang@nokia-bell-labs.com> On Sat, Jan 31, 2026 at 11:55:08PM +0100, chia-yu.chang@nokia-bell-labs.com wrote: > From: Chia-Yu Chang > > No functional changes. > > Co-developed-by: Ilpo Järvinen > Signed-off-by: Ilpo Järvinen > Signed-off-by: Chia-Yu Chang Subject: comments? > --- > include/linux/skbuff.h | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index e6bfe5d0c525..30a8dc4233ba 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -671,7 +671,13 @@ enum { > /* This indicates the skb is from an untrusted source. */ > SKB_GSO_DODGY = 1 << 1, > > - /* This indicates the tcp segment has CWR set. */ > + /* For Tx, this indicates the first TCP segment has CWR set, and any > + * subsequent segment in the same skb has CWR cleared. However, because > + * the connection to which the segment belongs is not tracked to use > + * RFC3168 or AccECN (RFC9768), and using RFC3168 ECN offload may clear > + * ACE signal (CWR is one of it). Therefore, this cannot be used on Rx. > + * Instead, SKB_GSO_TCP_ACCECN shall be used to avoid CWR corruption. > + */ > SKB_GSO_TCP_ECN = 1 << 2, > > __SKB_GSO_TCP_FIXEDID = 1 << 3, > @@ -706,6 +712,14 @@ enum { > > SKB_GSO_FRAGLIST = 1 << 18, > > + /* For TX, this indicates the TCP segment uses the CWR flag as part of > + * ACE signal, and the CWR flag is not modified in the skb. For RX, any > + * CWR flagged segment must use SKB_GSO_TCP_ACCECN to ensure CWR flag > + * is not cleared by any RFC3168 ECN offload, and thus keeping ACE > + * signal of AccECN segments. This is particularly used for Rx of > + * virtio_net driver in order to tell latter GSO Tx in a forwarding > + * scenario that it is NOT ok to clean CWR flag from the 2nd segment. > + */ > SKB_GSO_TCP_ACCECN = 1 << 19, > > /* These indirectly map onto the same netdev feature. > -- > 2.34.1