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 882F335961 for ; Wed, 10 Sep 2025 03:24:07 +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=1757474647; cv=none; b=hBVWYn7z2r5nCfSclWxTbGsUnE1DEJgMj0TR74/XLi+6HymE6n1B63fNruNftM8EBLfaHkux2xIzfbCRnmnn63IsQha+orXNyXKBxB4F2UpwVIgVu4/Rhigi5VmmYTPk/CHU6KaMYZE58V5VdcxUKh2/gClX7SwM7oW4e2LEZwo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757474647; c=relaxed/simple; bh=jboUkeT6qKgGzNYvWXQ7xzhk7Sr7Qqrd+DTmZUf1TMc=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References: Content-Type:MIME-Version; b=jOxTtyupIQvAFn85MaURdLNh+yr589XtP0ScFv+9RjLTAwmne7+3hQgVxqqDtpGFdGfH+l+1g0xbolEmqbtoSnjkjZjKazJJpyLq2A+Q1u8LGpG8m4AJhd2ipAWcLC7IG9/X+QRJ5ZK3NdJuWP9q4uCzr+GFsbL9Rn6GUx6pdBY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MsGKhLNj; 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="MsGKhLNj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74177C4CEF0; Wed, 10 Sep 2025 03:24:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757474647; bh=jboUkeT6qKgGzNYvWXQ7xzhk7Sr7Qqrd+DTmZUf1TMc=; h=Subject:From:To:Date:In-Reply-To:References:From; b=MsGKhLNjqlwHuJSXyLNJR3H2uq247X69qQT6VzjiZtuqbMvYtfJgnxpFUChVW/9Tw 5ZpEBf6Yc+ZgdsbU5WWdxGAawA1xJIYvAGillv4P/CbQhCX0cu5dtVhCFhPOrCAl0H T4AhH0aM5ks6VTXW5McdnrOQqM/CIrN3z8Bsm1L5sdwS77HPsKVffmb0iuieGl60xd EB+yD4mu1Xe4QwKxRVmHw7w4UpsuzcjDNVS7FF8bIbXYomoWtL/PBG9gMkL/kYFghp zWRXghTbGHfI4OPQAwSnXVdTznrcIt74bHSbyW1GsqGWZ4uFC0de4nblgEIJa4nauZ +GfCBfXYjYwjA== Message-ID: Subject: Re: [PATCH mptcp-net v2 1/5] mptcp: propagate shutdown to subflows when possible From: Geliang Tang To: Matthieu Baerts , mptcp@lists.linux.dev Date: Wed, 10 Sep 2025 11:24:02 +0800 In-Reply-To: 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> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.56.0-1 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Matt, On Sat, 2025-09-06 at 15:42 +0200, Matthieu Baerts wrote: > 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..9feb9f437c2bdfff392249e > > > 7ad0 > > > 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. I mean not to modify mptcp_check_data_fin and mptcp_check_data_fin_ack, but to check TCP_CLOSE in mptcp_worker(), something like: @@ -2749,6 +2749,9 @@ static void mptcp_worker(struct work_struct *work) mptcp_check_data_fin_ack(sk); mptcp_check_data_fin(sk); + if (sk->sk_state == TCP_CLOSE) + mptcp_shutdown_subflows(msk); + if (test_and_clear_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags)) __mptcp_close_subflow(sk); Another option is to call mptcp_shutdown_subflows in mptcp_close_wake_up, which one do you think is better? Thanks, -Geliang > > Cheers, > Matt