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Mon, 24 Nov 2025 13:06:36 -0800 (PST) Received: from [192.168.88.32] ([212.105.153.231]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-477bf3af0ecsm217044555e9.9.2025.11.24.13.06.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Nov 2025 13:06:35 -0800 (PST) Message-ID: <0c7e9f23-ea1a-48dd-957a-956dfb3d6dc4@redhat.com> Date: Mon, 24 Nov 2025 22:06:35 +0100 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mptcp-net] mptcp: clear scheduled subflows on retransmit To: Matthieu Baerts , mptcp@lists.linux.dev Cc: dcaratti@redhat.com References: <30e5325f37026b870cd0d0765d5d47c8a68fced9.1763676964.git.pabeni@redhat.com> From: Paolo Abeni In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: j5lEHACG5H2BuM0yHo3gDXug4XGA7TFRGGNNat61xJQ_1764018397 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/24/25 7:18 PM, Matthieu Baerts wrote: > On 20/11/2025 23:16, Paolo Abeni wrote: >> When __mptcp_retrans() kicks-in, it schedules one or more subflow for >> retransmission, but such subflows could be actually left alone if there >> is no more data to retransmit and/or in case of concurrent fallback. >> >> Scheduled subflows could be processed much later in time, i.e. when new >> data will be transmitted, leading to bad subflow selection. >> >> Explicitly clear all scheduled subflows before leaving the retransmission >> function. >> >> Fixes: ee2708aedad0 ("mptcp: use get_retrans wrapper") >> Signed-off-by: Paolo Abeni >> --- >> net/mptcp/protocol.c | 13 +++++++++++-- >> 1 file changed, 11 insertions(+), 2 deletions(-) >> >> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c >> index 6f4220c8b5bb..3b327e9ccb78 100644 >> --- a/net/mptcp/protocol.c >> +++ b/net/mptcp/protocol.c >> @@ -2763,7 +2763,7 @@ static void __mptcp_retrans(struct sock *sk) >> } >> >> if (!mptcp_send_head(sk)) >> - return; >> + goto clear_scheduled; >> >> goto reset_timer; >> } >> @@ -2794,7 +2794,7 @@ static void __mptcp_retrans(struct sock *sk) >> if (__mptcp_check_fallback(msk)) { >> spin_unlock_bh(&msk->fallback_lock); >> release_sock(ssk); >> - return; >> + goto clear_scheduled; >> } >> >> while (info.sent < info.limit) { >> @@ -2826,6 +2826,15 @@ static void __mptcp_retrans(struct sock *sk) >> >> if (!mptcp_rtx_timer_pending(sk)) >> mptcp_reset_rtx_timer(sk); >> + >> +clear_scheduled: >> + /* If no rtx data was available or in case of fallback, there > > When reading this comment, it sounds like a "return" could be added > before this new label (clear_scheduled). Is it always needed to clear > this flag or only in these two cases? No, we can't add a return before 'clear_scheduled:'. At least the 'goto reset_timer;' under the 'if (!dfrag) {' conditional above could reach there with one or more subflows scheduled. Cheers, Paolo