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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4463d5ee9ecsm1107145f8f.16.2026.04.27.14.10.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Apr 2026 14:10:12 -0700 (PDT) From: David Carlier To: mptcp@lists.linux.dev Cc: Matthieu Baerts , Mat Martineau , Geliang Tang , Paolo Abeni , David Carlier Subject: [PATCH mptcp-next v4 3/4] mptcp: support MSG_ERRQUEUE on the parent socket Date: Mon, 27 Apr 2026 22:10:05 +0100 Message-ID: X-Mailer: git-send-email 2.53.0 In-Reply-To: References: <20260421223338.52743-1-devnexen@gmail.com> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 ICMP, tx timestamp, and zerocopy completion notifications through the standard inet ABI. If sock_queue_err_skb() on the parent fails (rmem-limited), the skb is left on the subflow queue and retried on the next error report, avoiding silent loss. Suggested-by: Paolo Abeni Signed-off-by: David Carlier --- net/mptcp/protocol.c | 33 ++++++++++++++++++++++++++++----- 1 file changed, 28 insertions(+), 5 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 0db50e3715c3..131fb6ddfcd9 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -815,21 +815,39 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) return moved; } +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))) { + if (sock_queue_err_skb(sk, skb)) { + skb_queue_head(&ssk->sk_error_queue, skb); + break; + } + moved = true; + } + + return moved; +} + static bool __mptcp_subflow_error_report(struct sock *sk, struct sock *ssk) { 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 @@ -839,6 +857,11 @@ 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; + +out: + if (!report) + return false; /* This barrier is coupled with smp_rmb() in mptcp_poll() */ smp_wmb(); @@ -2295,7 +2318,6 @@ 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); @@ -4340,7 +4362,8 @@ 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; -- 2.53.0