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([2a0d:3344:2712:7e10:4d59:d956:544f:d65c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47114461debsm15463165e9.18.2025.10.16.02.13.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Oct 2025 02:14:00 -0700 (PDT) Message-ID: <705f02b2-44c6-4012-a1f3-0040652acc36@redhat.com> Date: Thu, 16 Oct 2025 11:13:58 +0200 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 net-next 08/13] tcp: accecn: retransmit SYN/ACK without AccECN option or non-AccECN SYN/ACK To: chia-yu.chang@nokia-bell-labs.com, edumazet@google.com, linux-doc@vger.kernel.org, corbet@lwn.net, horms@kernel.org, dsahern@kernel.org, kuniyu@amazon.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 References: <20251013170331.63539-1-chia-yu.chang@nokia-bell-labs.com> <20251013170331.63539-9-chia-yu.chang@nokia-bell-labs.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20251013170331.63539-9-chia-yu.chang@nokia-bell-labs.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/13/25 7:03 PM, chia-yu.chang@nokia-bell-labs.com wrote: > From: Chia-Yu Chang > > If the TCP Server has not received an ACK to acknowledge its SYN/ACK > after the normal TCP timeout or it receives a second SYN with a > request for AccECN support, then either the SYN/ACK might just have > been lost, e.g. due to congestion, or a middlebox might be blocking > AccECN Options. To expedite connection setup in deployment scenarios > where AccECN path traversal might be problematic, the TCP Server SHOULD > retransmit the SYN/ACK, but with no AccECN Option. > > If this retransmission times out, to expedite connection setup, the TCP > Server SHOULD retransmit the SYN/ACK with (AE,CWR,ECE) = (0,0,0) > and no AccECN Option, but it remains in AccECN feedback mode. > > This follows Section 3.2.3.2.2 of AccECN spec (RFC9768). > > Signed-off-by: Chia-Yu Chang > --- > include/net/tcp_ecn.h | 14 ++++++++++---- > net/ipv4/tcp_output.c | 2 +- > 2 files changed, 11 insertions(+), 5 deletions(-) > > diff --git a/include/net/tcp_ecn.h b/include/net/tcp_ecn.h > index c66f0d944e1c..97a3a7f36aff 100644 > --- a/include/net/tcp_ecn.h > +++ b/include/net/tcp_ecn.h > @@ -651,10 +651,16 @@ static inline void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb) > static inline void > tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th) > { > - if (tcp_rsk(req)->accecn_ok) > - tcp_accecn_echo_syn_ect(th, tcp_rsk(req)->syn_ect_rcv); > - else if (inet_rsk(req)->ecn_ok) > - th->ece = 1; > + if (req->num_retrans < 1 || req->num_timeout < 1) { I think the above condition does not match the commit message. Should be: if (!req->num_retrans && !req->num_timeout) { /P