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From: T S Rameshkumar <rameshsv06@gmail.com>
To: Petar Sakic <petar.sakic@ink.fish>
Cc: Matthieu Baerts <matttbe@kernel.org>,
	Mat Martineau <martineau@kernel.org>,
	Geliang Tang <geliang@kernel.org>,
	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	[thread overview]
Message-ID: <20261008100520.104205-1-rameshkumar.t@phytecembedded.in> (raw)
In-Reply-To: <CAFPPu1gU2Y-D+d4i3F0MoNkYK+e1U+=X3qf6QycjfKBw+8snPg@mail.gmail.com>

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

  reply	other threads:[~2026-10-08 10:06 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-08  8:59 Bug report mptcp: passive TFO: data written by the server before the MPC third ACK is never sent Petar Sakic
2026-10-08 10:05 ` T S Rameshkumar [this message]
  -- strict thread matches above, loose matches on Subject: below --
2026-10-08  9:52 [PATCH] mptcp: push queued data on passive TFO subflows becoming established T S Rameshkumar
2026-10-08  9:59 ` Petar Sakic

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