From nobody Fri Jan 9 07:02:00 2026 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 511961DFDB8 for ; Fri, 26 Dec 2025 06:40:40 +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=1766731240; cv=none; b=A9KyJieGjqlu4FdlwGdxnGQ0aOOrb1ptRHH1fVrMu8T/uJ1crl7CN8FOPhR7ftd/f5cdmIQl8sumTiZOPWKLL/WoBFBFP0U85635AsHERRuou81p+WtsxAP81/NiziAN5nqIDlCPNj/3kkPvKlOsaDWueMe1/w4gDW5VY/JSQvc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766731240; c=relaxed/simple; bh=gtUybE9wszvo+9x8LDu2L+Gz8Vg2wf3Wvn6frsIYIjg=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=olJG41EWI8RVitlfB9PsiP42F+TU8SHvuVOjXsiri8LLwY5dXAnv5qI9CYesi6N1ptUXFd40eEY8cUNxc5HTH21mKCTR+EPwVLGPuuXmGovO8c53fqVwtWfBk+hknRe4RKUgQrSUnGk2CMluvuLTb9PcEiE87ZkhuZrwSrBnm64= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OPousf47; 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="OPousf47" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9ACAC113D0; Fri, 26 Dec 2025 06:40:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766731240; bh=gtUybE9wszvo+9x8LDu2L+Gz8Vg2wf3Wvn6frsIYIjg=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=OPousf47zbGRLSQzyD3IGBnTjXg16b//4ow7afQK/Nxuue9c+tsGC7Nm3EVLNF2SJ IwoJ4xkCSYMipdKTvLcDEOeHScCksSDKyd0f7udyQC1ieZ1tjTqAKxE5rzQZju5qfh 2MVd2Tpj3NXDWQFhr9kW6Ovyf5XOzDHfnETxg4zeqV8xSImG3JzDNKdYX8Y9e46/Xj AjvW4P2SzpYp5i5cfjIjhzDoKy1kAJEXekRqywIJW5cYrnT9LA+yVkiwruGJI/xUCl RakUMdnvK7JDLynCyetpTapBu4Yhn30O7etVhXVBBfO1T6GhhZRCdlDGKsEw1ELU3L dQPdkpXKCXdmQ== From: "Matthieu Baerts (NGI0)" Date: Fri, 26 Dec 2025 07:40:17 +0100 Subject: [PATCH mptcp-next 03/11] mptcp: only reset subflow errors when propagated Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251226-mptcp-issue-603-v1-3-bb30e331b839@kernel.org> References: <20251226-mptcp-issue-603-v1-0-bb30e331b839@kernel.org> In-Reply-To: <20251226-mptcp-issue-603-v1-0-bb30e331b839@kernel.org> To: MPTCP Upstream Cc: "Matthieu Baerts (NGI0)" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=1891; i=matttbe@kernel.org; h=from:subject:message-id; bh=gtUybE9wszvo+9x8LDu2L+Gz8Vg2wf3Wvn6frsIYIjg=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGDL9dO+IKJet+Lq96GRkbq3RGlGOh1VdfB/bzlg9u/7l9 5Ww/kvGHaUsDGJcDLJiiizSbZH5M59X8ZZ4+VnAzGFlAhnCwMUpABMR0mP476lv1RXjeYzLYtnU 7eunWvzmVk/3Tjg2uU6LU5z7++0GeUaG4y67uE0/fz1z5omK/ORL/J/zdfZ4iZy4x3XS0e1BfeR 7LgA= X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 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) =20 static bool __mptcp_subflow_error_report(struct sock *sk, struct sock *ssk) { - int err =3D sock_error(ssk); int ssk_state; =20 - if (!err) + if (!READ_ONCE(ssk->sk_err)) return false; =20 /* only propagate errors on fallen-back sockets or @@ -837,7 +836,7 @@ static bool __mptcp_subflow_error_report(struct sock *s= k, struct sock *ssk) ssk_state =3D inet_sk_state_load(ssk); if (ssk_state =3D=3D 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)); =20 /* This barrier is coupled with smp_rmb() in mptcp_poll() */ smp_wmb(); --=20 2.51.0