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 60A9D63B9 for ; Tue, 3 Feb 2026 09:07:38 +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=1770109658; cv=none; b=rzcOAMt6d+ODWVpC5Ju6zeMCNo4jc+6ixROW/PDG9IZ2h9dHNulVDfUFS9y/Y3HTqUo6qSTU3vkW6i1Pwszsbz2FtLUs/l5FMZbhcHaA5TZKyKZV48Jwo037DWMI5gb35OomFKwkR+5vZa1OU+SHXRp01QbjEMkespwF2KOq4Rk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770109658; c=relaxed/simple; bh=giGXWo+4vd/WgnjKgtn9V+E3elOMsFGEc8drcvYhYas=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=Cnp5uXTdiyC8oMaEnPb0orjNtIMFfztDJ5TYxAJICuj4FR0DFTOgqe6nrGBmdctPTY4Sp5Scry/j6R7WlyHsuDbjvHCRCUl4HM1HkHyXjlohsVN0Vq0BVgaHPHlNoH7GJzAn0xzO2hdmDzmLBri7UGMdLURRF319DdMT8LBZ/WY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BhuD73vc; 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="BhuD73vc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82302C19421; Tue, 3 Feb 2026 09:07:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770109658; bh=giGXWo+4vd/WgnjKgtn9V+E3elOMsFGEc8drcvYhYas=; h=Date:Subject:To:References:From:In-Reply-To:From; b=BhuD73vcQrRoZnqFCdg1lFlk/1uSeEicVe+s59VSYlBwy/yjYncKciiNxat4nYwhs xLrSoq6JPD04WrIX+zcEJpRL6M0MwefzBy4UbuiKuh1oeQx4Tl12GLOn41Nu8ilIC2 AZtAjVCdwbUSL59LQKMYI4hdg5IR00dOo/zaGD576i2UhiV3i3NSYXPPQJQWHSRDOS 1B3eywAa72nqBG6Vq9vSTpDg3TSzUBRGemJikOjdZhzHyWDvWlxyv67DQKt5530eVg VRihYTEf1AMpD2EBxSVqhxy2krUXGihJojuZ8rv7rEn8pAKcMKxcN7ovogqF2DQl5U SMeMXu3MVNrAA== Message-ID: <6eb6a640-8837-4970-b58f-e2ad5eef9b0e@kernel.org> Date: Tue, 3 Feb 2026 10:07:35 +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-next 2/3] mptcp: implement .splice_eof Content-Language: en-GB, fr-BE To: Geliang Tang , mptcp@lists.linux.dev References: <9e3dddfc65f24c1a11e5f0353b497f1d4f1c6f82.1770023932.git.tanggeliang@kylinos.cn> <5866364b-87b9-4abd-9eed-5437e6c56ffb@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Geliang, Thank you for your reply! On 03/02/2026 07:36, Geliang Tang wrote: > Hi Matt, > > On Mon, 2026-02-02 at 11:07 +0100, Matthieu Baerts wrote: >> Hi Geliang, >> >> Thank you for looking at that! >> >> On 02/02/2026 10:21, Geliang Tang wrote: >>> From: Geliang Tang >>> >>> This patch implements the .splice_eof interface for MPTCP, namely >>> mptcp_splice_eof(), which sequentially calls do_tcp_splice_eof() >>> for >>> each subflow. >> >> Can you please explain what this hook is supposed to do / used for >> please? > > do_tcp_splice_eof() ensures that any remaining data in the TCP send > queue is flushed immediately when a sendfile() operation reaches end- > of-file (EOF). OK, so if I understand correctly, it means that without .splice_eof() support, the queue is not flushed immediately when a sendfile() operation reaches end-of-file (EOF). But that's OK, it will be flushed, eventually with a small delay but the most important is that all data will be transferred. Is that correct? If it is, can you please reflect that in the commit message? I think it is essential to mention it is not linked to the 'splice()' syscall, it is an improvement, and nothing was broken before. >> And also why the solution is to call do_tcp_splice_eof() on each >> subflow? > > MPTCP operates over multiple TCP subflows. When splicing data through > an MPTCP socket, each subflow may have pending data in its send buffer > that needs to be properly finalized. So here calls do_tcp_splice_eof() > on each subflow. Can you also please add a note about that in the commit message? >> Also, I'm a bit confused: why is this needed? Does it fix something >> or >> is it a new feature or an optimisation? > > It is not a fix, but a new feature, to keep consistent with TCP. Since > TCP handles the splice EOF notification but MPTCP didn't. > >> >>> Suggested-by: Matthieu Baerts >>> Signed-off-by: Geliang Tang >>> --- >>>  net/mptcp/protocol.c | 16 ++++++++++++++++ >>>  1 file changed, 16 insertions(+) >>> >>> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c >>> index c88882062c40..5635d196cb9f 100644 >>> --- a/net/mptcp/protocol.c >>> +++ b/net/mptcp/protocol.c >>> @@ -4018,6 +4018,20 @@ static int mptcp_connect(struct sock *sk, >>> struct sockaddr_unsized *uaddr, >>>   return 0; >>>  } >>>   >>> +static void mptcp_splice_eof(struct socket *sock) >>> +{ >>> + struct mptcp_subflow_context *subflow; >>> + struct sock *sk = sock->sk, *ssk; >>> + >>> + lock_sock(sk); >>> + mptcp_for_each_subflow(mptcp_sk(sk), subflow) { >>> + ssk = mptcp_subflow_tcp_sock(subflow); >>> + >>> + do_tcp_splice_eof(ssk); >> >> Is it fine to call this on closed subflows? e.g. if the initial >> subflow >> has been closed. (I didn't check, maybe that's OK) > > Good point. I will add this check in v2: > > if (ssk->sk_state == TCP_CLOSE) > continue; > >> >>> + } >>> + release_sock(sk); >>> +} >>> + >>>  static struct proto mptcp_prot = { >>>   .name = "MPTCP", >>>   .owner = THIS_MODULE, >>> @@ -4049,6 +4063,7 @@ static struct proto mptcp_prot = { >>>   .obj_size = sizeof(struct mptcp_sock), >>>   .slab_flags = SLAB_TYPESAFE_BY_RCU, >>>   .no_autobind = true, >>> + .splice_eof = mptcp_splice_eof, >>>  }; >>>   >>>  static int mptcp_bind(struct socket *sock, struct sockaddr_unsized >>> *uaddr, int addr_len) >>> @@ -4540,6 +4555,7 @@ static const struct proto_ops >>> mptcp_stream_ops = { >>>   .set_rcvlowat    = mptcp_set_rcvlowat, >>>   .read_sock    = mptcp_read_sock, >>>   .splice_read    = mptcp_splice_read, >>> + .splice_eof    = inet_splice_eof, >> >> Is this line required? Will it not call inet_splice_eof() by default? >> (I >> didn't check) > > Yes, this is required. > > sock_splice_eof() needs to call the .splice_eof interface from struct > proto_ops. To maintain consistency with regular TCP behavior, the > .splice_eof interface of mptcp_stream_ops is set to inet_splice_eof > too. inet_splice_eof() will switch to the protocol-specific > implementation (sk->sk_prot->splice_eof), which for MPTCP is > mptcp_splice_eof(). OK. Then be careful that inet_splice_eof() will call inet_send_prepare() which will call sock_rps_record_flow(sk). mptcp_rps_record_subflows() should be called on each subflow, probably from mptcp_splice_eof(). Cheers, Matt -- Sponsored by the NGI0 Core fund.