From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 C431D51E44D; Fri, 18 Sep 2026 18:38:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789756731; cv=none; b=NJCj11vcF1DE1QX6ri7LL2pJQ9QJXpSIU0gKb1jE35MwLbPTweuAo1lhiojIOuQAv6TG7gg+J5axBJZCtTGUAzKZlbMJsWu5ne08EP90Kd3DV+I7OLgL227GIlFEQ52/U+N6okgCmYNcYDg+CEbI6XoCxgb2i37ajI/r10zvbfk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789756731; c=relaxed/simple; bh=9fFB322ofigbhZ4AsHIL6Rjd777i8DmaY1KKlXdI0h4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=tFNXh88NWp9okJ3uB5J+4pzyeYjPkEsHZqEgi0KdVy1ZUrf2cAH9OPH3ZYL9e5NTog9/jrvkVvvhhRt7qaIdjLminE3hW3LF76IDtW83q/bmUb0Rans7kteDe7DXeBy/cx3WiyBqMBzGjiV0MqPZsAkE41xGc78lVunyev/S2dw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WhZxrER2; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WhZxrER2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D6F5D1F00898; Fri, 18 Sep 2026 18:38:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789756720; bh=HYDkWofAVJqwkkU1bY6hCgIZKtFJ2cyzVvCbMtn/XgE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=WhZxrER2DvffppFwB5uP833/hiFEOC+Q5+20QlkGqkWNREoFWA7WQnmXVd+JoUBjh QOdENaTZ9rwlIYUYf2gJlD95VGPnQSzCWnT5ogqV6NrVKi/EjakXj/dj/QgumOQLEY K3+vdnYhQ6zKjKWU/d6scEkjKHunCEj05QZIhaCTOKK6Ts0Zfsar3TAKflppNJFGVg sbaQjZqSpsfFxrNLlbQ0FTI9v5nohoj34I03RIl2hUclqp9FLv3t1PcQ3VEQgFYIzN QC594049JRt3Wo2cYs7goSW+0hkK1CT5m0gwjM9hJvxk92rgithw1KFtmubBb64ZWE nPM2tNXd1pUxg== From: "Matthieu Baerts (NGI0)" Date: Fri, 18 Sep 2026 20:38:25 +0200 Subject: [PATCH net-next 1/4] mptcp: support MSG_ERRQUEUE on the parent socket Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260918-net-next-mptcp-msg_errqueue-v1-1-dd77e1738248@kernel.org> References: <20260918-net-next-mptcp-msg_errqueue-v1-0-dd77e1738248@kernel.org> In-Reply-To: <20260918-net-next-mptcp-msg_errqueue-v1-0-dd77e1738248@kernel.org> To: Mat Martineau , Geliang Tang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org, "Matthieu Baerts (NGI0)" , David Carlier X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4587; i=matttbe@kernel.org; h=from:subject:message-id; bh=6DCezqlDoG5LBUOfMLMJZ1aRCH4iRGtce+o1bVRCW28=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGLLWtmowMl+5LNmx4/HegP+5gUV/FC/Jz/GbviFfljfVj GOLdVV7RykLgxgXg6yYIot0W2T+zOdVvCVefhYwc1iZQIYwcHEKwERyQxn+O7xSs0yYInWTtzVL Nv+J7/e0lAsnQnlWnmn/+OLQatl3OxgZJlR4TRZnPdyZd+aUFXfertA5lQlHmRd42U/VLmzffXg jPwA= X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 From: David Carlier Splice pending err skbs from each subflow's error queue onto the parent msk's error queue at error-report time, so poll() and recvmsg(MSG_ERRQUEUE) on the parent socket observe TX timestamps through the standard inet ABI. The splice filters by SO_EE_ORIGIN: TIMESTAMPING events forward to the parent because they are tied to user-handed data, not to a specific path; subflow-level ICMP errors are dropped because the legacy RECVERR ABI cannot meaningfully convey their per-subflow peer identity to single-path-aware userspace. Such events will be carried by a future MPTCP_RECERR channel. Forwarded events all go through sock_queue_err_skb(), which re-homes skb->sk onto the parent and charges sk_rmem_alloc, so the parent's error queue stays bounded by sk_rcvbuf and is dropped under rmem pressure (sk_rmem_alloc + truesize >= sk_rcvbuf), matching tcp's sk_rcvbuf-gated tx-timestamp path and ip_icmp_error() / ipv6_icmp_error(). The MSG_ERRQUEUE branch of mptcp_recvmsg() forwards to inet_recv_error() directly, and poll() advertises EPOLLERR purely on the parent's sk_err / sk_error_queue, matching tcp_poll(). Signed-off-by: David Carlier Acked-by: Paolo Abeni Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/protocol.c | 55 +++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 46 insertions(+), 9 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index e89a69ab927c..15ae270ee6fd 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include @@ -919,21 +920,52 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) return moved; } +static bool mptcp_errqueue_skb_forwardable(const struct sk_buff *skb) +{ + /* Subflow-level ICMP errors are dropped: the legacy RECVERR ABI + * cannot convey their per-subflow peer identity. + */ + return SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_TIMESTAMPING; +} + +static bool __mptcp_subflow_splice_errqueue(struct sock *sk, struct sock *ssk) +{ + struct sk_buff *skb; + bool moved = false; + + while ((skb = skb_dequeue(&ssk->sk_error_queue))) { + /* sock_queue_err_skb() re-homes skb->sk onto the parent and + * charges sk_rmem_alloc, bounding the queue by sk_rcvbuf. + */ + if (!mptcp_errqueue_skb_forwardable(skb) || + sock_queue_err_skb(sk, skb)) { + kfree_skb(skb); + continue; + } + moved = true; + } + + return moved; +} + static bool __mptcp_subflow_error_report(struct sock *sk, struct sock *ssk) { + bool propagated = false; int ssk_state; + bool report; int err; + report = __mptcp_subflow_splice_errqueue(sk, ssk); + /* only propagate errors on fallen-back sockets or * on MPC connect */ if (sk->sk_state != TCP_SYN_SENT && !__mptcp_check_fallback(mptcp_sk(sk))) - return false; + goto out; err = sock_error(ssk); if (!err) - return false; - + goto out; /* We need to propagate only transition to CLOSE state. * Orphaned socket will see such state change via * subflow_sched_work_if_closed() and that path will properly @@ -943,11 +975,16 @@ static bool __mptcp_subflow_error_report(struct sock *sk, struct sock *ssk) if (ssk_state == TCP_CLOSE && !sock_flag(sk, SOCK_DEAD)) mptcp_set_state(sk, ssk_state); WRITE_ONCE(sk->sk_err, -err); + report = true; + propagated = true; - /* This barrier is coupled with smp_rmb() in mptcp_poll() */ - smp_wmb(); - sk_error_report(sk); - return true; +out: + if (report) { + /* This barrier is coupled with smp_rmb() in mptcp_poll() */ + smp_wmb(); + sk_error_report(sk); + } + return propagated; } void __mptcp_error_report(struct sock *sk) @@ -2385,7 +2422,6 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int target; long timeo; - /* MSG_ERRQUEUE is really a no-op till we support IP_RECVERR */ if (unlikely(flags & MSG_ERRQUEUE)) return inet_recv_error(sk, msg, len); @@ -4523,7 +4559,8 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock, /* This barrier is coupled with smp_wmb() in __mptcp_error_report() */ smp_rmb(); - if (READ_ONCE(sk->sk_err)) + if (READ_ONCE(sk->sk_err) || + !skb_queue_empty_lockless(&sk->sk_error_queue)) mask |= EPOLLERR; return mask; -- 2.55.0