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 8CB9A10785 for ; Sun, 4 Jan 2026 03:30:39 +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=1767497439; cv=none; b=RktgmC2Hr1vwfOHTl3nxg5q7+QR1A+v3UT0KPF+gBlPwCBTFN846QpDMDolUNT3MCnF427uEhFCGco5UkhQTI2YyIPkQjli77hNPNwCSkbV42bvwjEZ92qeq0ZRR0llKcz4CFIh1ZrIBwiZFfr/ythMFkIgbmkL8yKC1kkwOzrQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767497439; c=relaxed/simple; bh=gbzhv4xmxkUX5AzIrCczY+cuOLJl+ommidtSiDR/UUQ=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References: Content-Type:MIME-Version; b=ZshJN5NIQVlbkiprSkhaHcbPcSqD7tZ2CcOk2SEApQVg+2yrK4MvcfkNf4oKCtkK3Jo5kWvwvL1Bd6erW3b8+7r40w6ztc8R47L2eETXqFQY/uKHbNgyyXWJJnCZLdR7Uq+CpnX6dL5V2o/c8coxqwmdypWp5mRKANqZbQqSfKo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sHBow9M5; 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="sHBow9M5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12C89C4CEF7; Sun, 4 Jan 2026 03:30:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767497439; bh=gbzhv4xmxkUX5AzIrCczY+cuOLJl+ommidtSiDR/UUQ=; h=Subject:From:To:Date:In-Reply-To:References:From; b=sHBow9M5FZCZzl2SvS4weum98QJIf53qlcLNYJdpbNR+VT31FHn5HIOIon2JwNTbQ 3nI3Ar4uufKDlGltvUVMz9mftpHqu3iqlJCeNXaho9cYHODcXA8rlv97kdQwGNAivg WqxNqjPdk1MUxFKAnZnJ/RkZY3bKZw6xJ2vbk6vZnGluelIw0DLLMrRb8tHfL2/+Jt WodPJoAGXnq0YOIEXxoTWvqsoFtIETO0knujlEGN7EZyvYW+ANh3AYMGeSDjccS8H4 Ee6VRoD1TmrfAtXf/bTLo7YiPmiWbriPurCHtQ+Pn8A8MuIiIq0zpIv05NNvvu2Uy0 piWBcmQwsHYqQ== Message-ID: Subject: Re: [PATCH mptcp-next 03/11] mptcp: only reset subflow errors when propagated From: Geliang Tang To: "Matthieu Baerts (NGI0)" , MPTCP Upstream Date: Sun, 04 Jan 2026 11:30:30 +0800 In-Reply-To: <20251226-mptcp-issue-603-v1-3-bb30e331b839@kernel.org> References: <20251226-mptcp-issue-603-v1-0-bb30e331b839@kernel.org> <20251226-mptcp-issue-603-v1-3-bb30e331b839@kernel.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.56.2-4 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 Fri, 2025-12-26 at 07:40 +0100, Matthieu Baerts (NGI0) wrote: > Some subflow socket errors need to be reported to the MPTCP socket: > the > initial subflow connect (MP_CAPABLE), and the ones from the fallback > sockets. The others are not propagated. > > The issue is that sock_error() was used to retrieve the error, which > was > also resetting the sk_err field. Because of that, when notifying the > userspace about subflow close events later on from the MPTCP worker, > the > ssk->sk_err field was always 0. > > Now, the error (sk_err) is only reset when propagating it to the msk. > > Fixes: 15cc10453398 ("mptcp: deliver ssk errors to msk") > Signed-off-by: Matthieu Baerts (NGI0) > --- > Note: I guess we could also duplicate the error in > mptcp_subflow_context > struct before scheduling the worker, and use this field in > mptcp_event_put_token_and_ssk(), but I don't see why we should always > reset ssk->sk_err in __mptcp_subflow_error_report() in all cases. > --- >  net/mptcp/protocol.c | 5 ++--- >  1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index 1d68648b5194..5d6c987089c6 100644 > --- a/net/mptcp/protocol.c > +++ b/net/mptcp/protocol.c > @@ -817,10 +817,9 @@ static bool __mptcp_ofo_queue(struct mptcp_sock > *msk) >   >  static bool __mptcp_subflow_error_report(struct sock *sk, struct > sock *ssk) >  { > - int err = sock_error(ssk); >   int ssk_state; >   > - if (!err) > + if (!READ_ONCE(ssk->sk_err)) >   return false; Your fix works. I'm wondering if swapping the order of 'if (sk- >sk_state != TCP_SYN_SENT && !__mptcp_check_fallback(mptcp_sk(sk)))' and 'if (!err)' would be a bit simpler, i.e.: int err = sock_error(ssk); int ssk_state; if (sk->sk_state != TCP_SYN_SENT && !__mptcp_check_fallback(mptcp_sk(sk))) return false; if (!err) return false; WDYT? Thanks, -Geliang >   >   /* only propagate errors on fallen-back sockets or > @@ -837,7 +836,7 @@ static bool __mptcp_subflow_error_report(struct > sock *sk, struct sock *ssk) >   ssk_state = inet_sk_state_load(ssk); >   if (ssk_state == TCP_CLOSE && !sock_flag(sk, SOCK_DEAD)) >   mptcp_set_state(sk, ssk_state); > - WRITE_ONCE(sk->sk_err, -err); > + WRITE_ONCE(sk->sk_err, -sock_error(ssk)); >   >   /* This barrier is coupled with smp_rmb() in mptcp_poll() */ >   smp_wmb();