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([124.123.89.203]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1616980c3b7sm12992588c88.16.2026.10.08.03.06.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Oct 2026 03:06:31 -0700 (PDT) From: T S Rameshkumar X-Google-Original-From: T S Rameshkumar To: Petar Sakic Cc: Matthieu Baerts , Mat Martineau , Geliang Tang , netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mptcp: push queued data on passive TFO subflows becoming established Date: Thu, 8 Oct 2026 15:35:20 +0530 Message-Id: <20261008100520.104205-1-rameshkumar.t@phytecembedded.in> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Petar, Matthieu, Mat, Thanks for the feedback and confirmation! Indeed, since the bug predates e00b63056fb4 and exists back to when server-side Fast Open was originally introduced, the appropriate Fixes tag would be: Fixes: fb7084501a61 ("mptcp: add support for TCP_FASTOPEN sockopt") During our testing with simulated network latency in namespaces, we also found that when the 3rd ACK arrives: 1. check_fully_established() marks subflow->fully_established = true. 2. But within tcp_ack(), the underlying TCP state is still TCP_SYN_RECV until tcp_rcv_state_process() sets it to TCP_ESTABLISHED. 3. Therefore, invoking the push in subflow_state_change() ensures the subflow is recognized as active by __tcp_can_send() and immediately flushes the queued write buffer. I can send a [PATCH net v2] with the updated Fixes tag once maintainers review. Thanks, T S Rameshkumar