From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EDE5C2ECEA9 for ; Sat, 6 Sep 2025 13:42:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757166154; cv=none; b=qfCHgzDS1xXiiWuz8EpuXurTMOParYkACOy3wT0Yj1OG6x4VrF/NlGcpVo6hi0I4zEqxzeJl/RYEiltN/quL4zwXSEuOjG6NhmHM095e4urtqfaY+4QGy942bl8hFOWi4JZUl9dZraFMi8MR24xqnw5sqVo/+9yJKrpcc+1zWN4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757166154; c=relaxed/simple; bh=SwbNg3VR+w3ZzRrLiuvlUK28gJqMniv7lW8dxgX0JVs=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=ehKpN7tFmSVSWTcB7RoNYL8JvYBa5CCm5qCIF1ugpp/ZygGuQ/hrQpD+A+Hasia+IJQamvZHtsW6x90j4sFe6uZx08rcLaPjOlQtFQGkTjjGeJPq/V1uj1FsYFhOt1kYButE0VoegP14ImjESSAOnhEdg6Jjj4WeRUluTkUHGv4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F/7toklB; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="F/7toklB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0AB99C4CEE7; Sat, 6 Sep 2025 13:42:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757166153; bh=SwbNg3VR+w3ZzRrLiuvlUK28gJqMniv7lW8dxgX0JVs=; h=Date:Subject:To:References:From:In-Reply-To:From; b=F/7toklBdbkbUYzcfZ4/j8iGKvocHkpUEpbvRLVshL27rJajI+TvUnuI+X5AC2gXF 7Ut5VtWG0odLpRXPtXZJB/EvunwGMM4PMGN329wSEfgtqfs8LC/7su4Y3ASIW9wrNF BdfLu2RKj7tfXDQrwKe9lj84nQSAqzGVEXnIvtp9jPCaKeJy229UCGh9Ka/Fn2ZVPS 4059VilYPcDblEbkEnIwY+7zvE5LP5eGxTYNGvwHitdcXGgnhxMH6S9c4nxuDBr9h8 AYctMPCgwdYUJm7/m2Rf8RS1P8x3MvB3s6VnwOev7cru+N0GxVwXkS0OP5E1vr6EKW QoVu0qaGCbq2Q== Message-ID: Date: Sat, 6 Sep 2025 15:42:30 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH mptcp-net v2 1/5] mptcp: propagate shutdown to subflows when possible Content-Language: en-GB, fr-BE To: Geliang Tang , mptcp@lists.linux.dev References: <20250905-sft-mptcp-disc-err-v2-0-dfb3b6b4a877@kernel.org> <20250905-sft-mptcp-disc-err-v2-1-dfb3b6b4a877@kernel.org> <9f2a05ac6034fb33f579302a0ede2ec13eb6c915.camel@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Geliang, On 06/09/2025 02:45, Geliang Tang wrote: > On Fri, 2025-09-05 at 20:18 +0200, Matthieu Baerts (NGI0) wrote: >> When the MPTCP DATA FIN have been ACKed, there is no more MPTCP >> related >> metadata to exchange, and all subflows can be safely shutdown. >> >> Before this patch, the subflows were actually terminated at 'close()' >> time. That's certainly fine most of the time, but not when the >> userspace >> 'shutdown()' a connection, without close()ing it. When doing so, the >> subflows were staying in LAST_ACK state on one side -- and >> consequently >> in FIN_WAIT2 on the other side -- until the 'close()' of the MPTCP >> socket. >> >> Now, when the DATA FIN have been ACKed, all subflows are shutdown. A >> consequence of this is that the TCP 'FIN' flag can be set earlier >> now, >> but the end result is the same. This affects the packetdrill tests >> looking at the end of the MPTCP connections, but for a good reason. >> >> Fixes: 3721b9b64676 ("mptcp: Track received DATA_FIN sequence number >> and add related helpers") >> Fixes: 16a9a9da1723 ("mptcp: Add helper to process acks of DATA_FIN") >> Signed-off-by: Matthieu Baerts (NGI0) >> --- >>  net/mptcp/protocol.c | 16 ++++++++++++++++ >>  1 file changed, 16 insertions(+) >> >> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c >> index >> 1c26acf6c4145896ecbb5c7f7004121c66a20649..9feb9f437c2bdfff392249e7ad0 >> 0edd09ba67ac3 100644 >> --- a/net/mptcp/protocol.c >> +++ b/net/mptcp/protocol.c >> @@ -372,6 +372,20 @@ static void mptcp_close_wake_up(struct sock *sk) >>   sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); >>  } >>   >> +static void mptcp_shutdown_subflows(struct mptcp_sock *msk) >> +{ >> + struct mptcp_subflow_context *subflow; >> + >> + mptcp_for_each_subflow(msk, subflow) { >> + struct sock *ssk = mptcp_subflow_tcp_sock(subflow); >> + bool slow; >> + >> + slow = lock_sock_fast(ssk); >> + tcp_shutdown(ssk, SEND_SHUTDOWN); >> + unlock_sock_fast(ssk, slow); >> + } >> +} >> + >>  /* called under the msk socket lock */ >>  static bool mptcp_pending_data_fin_ack(struct sock *sk) >>  { >> @@ -396,6 +410,7 @@ static void mptcp_check_data_fin_ack(struct sock >> *sk) >>   break; >>   case TCP_CLOSING: >>   case TCP_LAST_ACK: >> + mptcp_shutdown_subflows(msk); >>   mptcp_set_state(sk, TCP_CLOSE); >>   break; >>   } >> @@ -564,6 +579,7 @@ static bool mptcp_check_data_fin(struct sock *sk) >>   mptcp_set_state(sk, TCP_CLOSING); >>   break; >>   case TCP_FIN_WAIT2: >> + mptcp_shutdown_subflows(msk); > > I think we should not directly call mptcp_shutdown_subflows() within > mptcp_check_data_fin() and mptcp_check_data_fin_ack(), but should > instead call it after these functions return and the sk state is > TCP_CLOSE. This ensures that the original purpose of these two > functions remains unchanged. Thank you for the review. I'm not sure to understand what you mean about the "original purpose": they both set the appropriated actions when DATA_FIN have been received. Here, I do want to shut the subflows down when the DATA_FIN ACK are received, so that's the good spot, no? Note that commit 3721b9b64676 ("mptcp: Track received DATA_FIN sequence number and add related helpers") already had a hint of what should have been done: see the "Close subflows now?" comment, later removed in commit e16163b6e2b7 ("mptcp: refactor shutdown and close"). Or maybe do you mean their original name "check_data_fin(_ack)" is confusing? The "check" here is not just to check if the DATA_FIN (ACK) was set, but to check actions related to them. Cheers, Matt -- Sponsored by the NGI0 Core fund.