From nobody Mon Aug 24 21:27:14 2026 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 E906332B99F for ; Mon, 24 Aug 2026 02:20:59 +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=1787538061; cv=none; b=s/4J73bJu+tCQekVbZ1gIIFpTwOURNKmaUf5G+feITNJS0rl9tVaav9EBC5eLAqscsrcagy3xTk/cfr7eu2eVDw4T4fRwDHSXSnDUFuKKX7JFWVeXfEOTv7/cfFOlKNyB4j5Jo4K4hh8NP56LzON/oChcZkw/WrTbhbGl1saGj0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787538061; c=relaxed/simple; bh=hc8M+nH0e7ZArtQvpcrEv6zSYi91EvJPoY7ULkTnj7o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PvplNDKoOZGzipfa4nJKHUEeepAyR0nM3nsccQUZx5bfZ13gcqcbFAiuFzPx0MdmcQKLrcFn5J6nmIEknX11JkDINZpUdOWwr0dcwgiQrL5EaAQ2CvJFqYNZSxF9UOTu7qDCon9zg5+o5Fs36yNXyGRkpNj/kyKCS29vxUpelb4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ge7PAmAA; 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="ge7PAmAA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BBA0C1F000E9; Mon, 24 Aug 2026 02:20:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787538059; bh=bqnu+YbO6DFJnR6Kz15ZvsBkeY9Xo3GHguirfyIfc2U=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ge7PAmAAZqHffhaXM7bXcOHBLeNArpiYSE3PSjMqwgQH09yQW8fbviFJ6pYob87Ew OCFgkKvhDJTzPiSZ7g+MBCn2DomnZBjQYRRzcaH4xLu3gwc+J7bG6/5WoYTEimoP2Z TqFveNY0bV7J2fM6M6MU6aP0XdeC646mBzZVSY7Epttmlqpos7sWRyO99aVuw596VA CaC4b/k9pOoibWUxZ4NpVfFCLV62CogRwAn4Q9Xsnx9n5PMN+eD9IKGavkhq0mMlfm b3BTr2xOZ/pzl4KVKKvQI+IKsOZRRFR/B0VrHbFd76cfxS2Dp6r7esUuZeEyblU3gl 7bFqvJfzeZ95Q== From: Geliang Tang To: mptcp@lists.linux.dev Cc: Geliang Tang Subject: [PATCH mptcp-next v7 1/8] mptcp: use atomic64_t for msk->ack_seq Date: Mon, 24 Aug 2026 10:20:36 +0800 Message-ID: <5c649d995c212b9b6f72f109a09e89c5e4f67ce8.1787537436.git.tanggeliang@kylinos.cn> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Geliang Tang msk->ack_seq is updated in process context without mptcp_data_lock() and read concurrently in softirq via mptcp_write_options(). On 32-bit architectures, 64-bit READ_ONCE/WRITE_ONCE compiles to two 32-bit accesses, so a torn read could produce a corrupted MPTCP Data ACK. Convert msk->ack_seq from u64 to atomic64_t to guarantee tear-free accesses on all architectures. Also cache atomic64_read() in a local variable in __mptcp_move_skb() and __mptcp_ofo_queue() to avoid inconsistent repeated reads. Signed-off-by: Geliang Tang --- include/trace/events/mptcp.h | 4 ++-- net/mptcp/options.c | 5 +++-- net/mptcp/protocol.c | 43 +++++++++++++++++++----------------- net/mptcp/protocol.h | 2 +- net/mptcp/sockopt.c | 2 +- net/mptcp/subflow.c | 7 +++--- 6 files changed, 34 insertions(+), 29 deletions(-) diff --git a/include/trace/events/mptcp.h b/include/trace/events/mptcp.h index 22882bd03459..517b8129a95d 100644 --- a/include/trace/events/mptcp.h +++ b/include/trace/events/mptcp.h @@ -224,11 +224,11 @@ TRACE_EVENT(mptcp_rcvbuf_grow, ofo_empty =3D RB_EMPTY_ROOT(&msk->out_of_order_queue); __entry->ooo_space =3D ofo_empty ? 0 : MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq - - msk->ack_seq; + atomic64_read(&msk->ack_seq); =20 __entry->rcvbuf =3D sk->sk_rcvbuf; __entry->rcv_wnd =3D atomic64_read(&msk->rcv_wnd_sent) - - msk->ack_seq; + atomic64_read(&msk->ack_seq); __entry->scaling_ratio =3D msk->scaling_ratio; __entry->sport =3D ntohs(inet->inet_sport); __entry->dport =3D ntohs(inet->inet_dport); diff --git a/net/mptcp/options.c b/net/mptcp/options.c index f87707110c75..16abb8c6485c 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -1169,7 +1169,8 @@ bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk= , u64 data_fin_seq, bool us return false; =20 WRITE_ONCE(msk->rcv_data_fin_seq, - mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit)); + mptcp_expand_seq(atomic64_read(&msk->ack_seq), + data_fin_seq, use_64bit)); WRITE_ONCE(msk->rcv_data_fin, 1); =20 return true; @@ -1539,7 +1540,7 @@ void mptcp_write_options(struct tcphdr *th, __be32 *p= tr, struct tcp_sock *tp, */ subflow =3D mptcp_subflow_ctx(ssk); msk =3D mptcp_sk(subflow->conn); - ack_seq =3D READ_ONCE(msk->ack_seq); + ack_seq =3D atomic64_read(&msk->ack_seq); if (mpext->ack64) { put_unaligned_be64(ack_seq, ptr); ptr +=3D 2; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index f22d64ab1c53..88bdb65a9e87 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -451,10 +451,12 @@ static bool __mptcp_move_skb(struct sock *sk, struct = sk_buff *skb) u64 copy_len =3D MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; struct mptcp_sock *msk =3D mptcp_sk(sk); struct sk_buff *tail; + u64 ack_seq; =20 mptcp_borrow_fwdmem(sk, skb); =20 - if (MPTCP_SKB_CB(skb)->map_seq =3D=3D msk->ack_seq) { + ack_seq =3D atomic64_read(&msk->ack_seq); + if (MPTCP_SKB_CB(skb)->map_seq =3D=3D ack_seq) { /* in sequence */ insert: if (!mptcp_try_rmem_schedule(sk, skb)) { @@ -464,7 +466,7 @@ static bool __mptcp_move_skb(struct sock *sk, struct sk= _buff *skb) } =20 msk->bytes_received +=3D copy_len; - WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len); + atomic64_add(copy_len, &msk->ack_seq); tail =3D skb_peek_tail(&sk->sk_receive_queue); if (tail && mptcp_try_coalesce(sk, tail, skb)) return true; @@ -472,17 +474,17 @@ static bool __mptcp_move_skb(struct sock *sk, struct = sk_buff *skb) skb_set_owner_r(skb, sk); __skb_queue_tail(&sk->sk_receive_queue, skb); return true; - } else if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) { + } else if (after64(MPTCP_SKB_CB(skb)->map_seq, ack_seq)) { mptcp_data_queue_ofo(msk, skb); return false; } =20 /* Partial packet */ - if (after64(MPTCP_SKB_CB(skb)->end_seq, msk->ack_seq)) { - copy_len =3D MPTCP_SKB_CB(skb)->end_seq - msk->ack_seq; - MPTCP_SKB_CB(skb)->offset +=3D msk->ack_seq - + if (after64(MPTCP_SKB_CB(skb)->end_seq, ack_seq)) { + copy_len =3D MPTCP_SKB_CB(skb)->end_seq - ack_seq; + MPTCP_SKB_CB(skb)->offset +=3D ack_seq - MPTCP_SKB_CB(skb)->map_seq; - MPTCP_SKB_CB(skb)->map_seq +=3D msk->ack_seq - + MPTCP_SKB_CB(skb)->map_seq +=3D ack_seq - MPTCP_SKB_CB(skb)->map_seq; goto insert; } @@ -569,7 +571,7 @@ static bool mptcp_pending_data_fin(struct sock *sk, u64= *seq) (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2))) { u64 rcv_data_fin_seq =3D READ_ONCE(msk->rcv_data_fin_seq); =20 - if (READ_ONCE(msk->ack_seq) =3D=3D rcv_data_fin_seq) { + if (atomic64_read(&msk->ack_seq) =3D=3D rcv_data_fin_seq) { if (seq) *seq =3D rcv_data_fin_seq; =20 @@ -710,7 +712,7 @@ static void mptcp_check_data_fin(struct sock *sk) */ =20 if (mptcp_pending_data_fin(sk, &rcv_data_fin_seq)) { - WRITE_ONCE(msk->ack_seq, msk->ack_seq + 1); + atomic64_inc(&msk->ack_seq); WRITE_ONCE(msk->rcv_data_fin, 0); =20 WRITE_ONCE(sk->sk_shutdown, sk->sk_shutdown | RCV_SHUTDOWN); @@ -879,22 +881,22 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) { struct sock *sk =3D (struct sock *)msk; struct sk_buff *skb, *tail; + u64 end_seq, ack_seq; bool moved =3D false; struct rb_node *p; - u64 end_seq; =20 p =3D rb_first(&msk->out_of_order_queue); pr_debug("msk=3D%p empty=3D%d\n", msk, RB_EMPTY_ROOT(&msk->out_of_order_q= ueue)); while (p) { + ack_seq =3D atomic64_read(&msk->ack_seq); skb =3D rb_to_skb(p); - if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) + if (after64(MPTCP_SKB_CB(skb)->map_seq, ack_seq)) break; =20 p =3D rb_next(p); rb_erase(&skb->rbnode, &msk->out_of_order_queue); =20 - if (unlikely(!after64(MPTCP_SKB_CB(skb)->end_seq, - msk->ack_seq))) { + if (unlikely(!after64(MPTCP_SKB_CB(skb)->end_seq, ack_seq))) { mptcp_drop(sk, skb); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); continue; @@ -903,18 +905,18 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) end_seq =3D MPTCP_SKB_CB(skb)->end_seq; tail =3D skb_peek_tail(&sk->sk_receive_queue); if (!tail || !mptcp_ooo_try_coalesce(msk, tail, skb)) { - int delta =3D msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq; + int delta =3D ack_seq - MPTCP_SKB_CB(skb)->map_seq; =20 /* skip overlapping data, if any */ pr_debug("uncoalesced seq=3D%llx ack seq=3D%llx delta=3D%d\n", - MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq, + MPTCP_SKB_CB(skb)->map_seq, ack_seq, delta); MPTCP_SKB_CB(skb)->offset +=3D delta; MPTCP_SKB_CB(skb)->map_seq +=3D delta; __skb_queue_tail(&sk->sk_receive_queue, skb); } - msk->bytes_received +=3D end_seq - msk->ack_seq; - WRITE_ONCE(msk->ack_seq, end_seq); + msk->bytes_received +=3D end_seq - ack_seq; + atomic64_set(&msk->ack_seq, end_seq); moved =3D true; } return moved; @@ -1072,7 +1074,7 @@ void mptcp_data_ready(struct sock *sk, struct sock *s= sk) =20 static void mptcp_subflow_joined(struct mptcp_sock *msk, struct sock *ssk) { - mptcp_subflow_ctx(ssk)->map_seq =3D READ_ONCE(msk->ack_seq); + mptcp_subflow_ctx(ssk)->map_seq =3D atomic64_read(&msk->ack_seq); msk->allow_infinite_fallback =3D false; mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC); } @@ -2396,7 +2398,8 @@ static unsigned int mptcp_inq_hint(const struct sock = *sk) =20 skb =3D skb_peek(&sk->sk_receive_queue); if (skb) { - u64 hint_val =3D READ_ONCE(msk->ack_seq) - MPTCP_SKB_CB(skb)->map_seq; + u64 hint_val =3D atomic64_read(&msk->ack_seq) - + MPTCP_SKB_CB(skb)->map_seq; =20 if (hint_val >=3D INT_MAX) return INT_MAX; @@ -3678,7 +3681,7 @@ static int mptcp_disconnect(struct sock *sk, int flag= s) mptcp_init_rtt_est(msk); =20 /* for fallback's sake */ - WRITE_ONCE(msk->ack_seq, 0); + atomic64_set(&msk->ack_seq, 0); atomic64_set(&msk->rcv_wnd_sent, 0); =20 WRITE_ONCE(sk->sk_shutdown, 0); diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 3d250e8204d5..4074fea9ba85 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -292,7 +292,7 @@ struct mptcp_sock { u64 bytes_sent; u64 snd_nxt; u64 bytes_received; - u64 ack_seq; + atomic64_t ack_seq; atomic64_t rcv_wnd_sent; u64 rcv_data_fin_seq; u64 bytes_retrans; diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c index 922f6ae5c80c..666827eb2c9a 100644 --- a/net/mptcp/sockopt.c +++ b/net/mptcp/sockopt.c @@ -1101,7 +1101,7 @@ void mptcp_diag_fill_info(struct mptcp_sock *msk, str= uct mptcp_info *info) mptcp_data_lock(sk); info->mptcpi_last_ack_recv =3D jiffies_to_msecs(now - msk->last_ack_recv); info->mptcpi_snd_una =3D msk->snd_una; - info->mptcpi_rcv_nxt =3D msk->ack_seq; + info->mptcpi_rcv_nxt =3D atomic64_read(&msk->ack_seq); info->mptcpi_bytes_acked =3D msk->bytes_acked; mptcp_data_unlock(sk); } diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 2d7ccb01d234..6345c6ac43b2 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -491,7 +491,7 @@ static void subflow_set_remote_key(struct mptcp_sock *m= sk, subflow->map_seq =3D subflow->iasn; =20 WRITE_ONCE(msk->remote_key, subflow->remote_key); - WRITE_ONCE(msk->ack_seq, subflow->iasn); + atomic64_set(&msk->ack_seq, subflow->iasn); WRITE_ONCE(msk->can_ack, true); 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="eC+md8Ll" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A2031F00A3A; Mon, 24 Aug 2026 02:21:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787538061; bh=WPiQ0Gp8ihIXG5nHE174mBCKN5G5kCI9bi6cIdQDlWY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=eC+md8LlRRp5xuXsy6rm2t0faheMpTTjhRtW6tFERqGLXx7S5zuW1QelQviYSuBng SwWvriog/FriLf3mQRP94mG4ocDVxiZiRrQLc8k6wFdQMYO3tDi8PfI7yq3wsk7uGR 2vgO0/QNXValXMJOntEe0O5arzSJuhkUzozDKWWmb9HAzEGirH+z0ZGDg3JEoAEBIA oNE8uygdGRF1/Hhtar6XWw/l7ilJbvE2g7cDmsQ5iZCPP9T12hZsKck+GJ2VRyZJD5 gR/i7buoeKx8wpzOAhl1KiIr8WMRv2zbwavgfjtQ4Gx5MkA4LqsFcLT+HJGbftdwMl o6TzaOt+SZX5g== From: Geliang Tang To: mptcp@lists.linux.dev Cc: Paolo Abeni , Geliang Tang Subject: [PATCH mptcp-next v7 2/8] mptcp: drop the mptcp_ooo_try_coalesce() helper Date: Mon, 24 Aug 2026 10:20:37 +0800 Message-ID: <95bc8d7ca9cdeb86b36d76667aa2c468b106d669.1787537436.git.tanggeliang@kylinos.cn> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Paolo Abeni It's used to save an additional comparison for in-order skbs, but is also a barrier to remove CB offset. Remove the helper, let __mptcp_try_coalesce() always perform the sequence check and remove duplicate checks from the callers. Co-developed-by: Geliang Tang Signed-off-by: Geliang Tang Signed-off-by: Paolo Abeni --- net/mptcp/protocol.c | 21 ++++++--------------- 1 file changed, 6 insertions(+), 15 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 88bdb65a9e87..1682a90951f0 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -167,7 +167,8 @@ static bool __mptcp_try_coalesce(struct sock *sk, struc= t sk_buff *to, { int limit =3D READ_ONCE(sk->sk_rcvbuf); =20 - if (unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || + if (MPTCP_SKB_CB(from)->map_seq !=3D MPTCP_SKB_CB(to)->end_seq || + unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || MPTCP_SKB_CB(from)->offset || ((to->len + from->len) > (limit >> 3)) || !skb_try_coalesce(to, from, fragstolen, delta)) @@ -200,15 +201,6 @@ static bool mptcp_try_coalesce(struct sock *sk, struct= sk_buff *to, return true; } =20 -static bool mptcp_ooo_try_coalesce(struct mptcp_sock *msk, struct sk_buff = *to, - struct sk_buff *from) -{ - if (MPTCP_SKB_CB(from)->map_seq !=3D MPTCP_SKB_CB(to)->end_seq) - return false; - - return mptcp_try_coalesce((struct sock *)msk, to, from); -} - /* "inspired" by tcp_rcvbuf_grow(), main difference: * - mptcp does not maintain a msk-level window clamp * - returns true when the receive buffer is actually updated @@ -348,7 +340,7 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk= , struct sk_buff *skb) /* with 2 subflows, adding at end of ooo queue is quite likely * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup. */ - if (mptcp_ooo_try_coalesce(msk, msk->ooo_last_skb, skb)) { + if (mptcp_try_coalesce(sk, msk->ooo_last_skb, skb)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL); return; @@ -394,7 +386,7 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk= , struct sk_buff *skb) MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); goto merge_right; } - } else if (mptcp_ooo_try_coalesce(msk, skb1, skb)) { + } else if (mptcp_try_coalesce(sk, skb1, skb)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE); return; } @@ -779,8 +771,7 @@ static void __mptcp_add_backlog(struct sock *sk, if (!list_empty(&msk->backlog_list)) tail =3D list_last_entry(&msk->backlog_list, struct sk_buff, list); =20 - if (tail && MPTCP_SKB_CB(skb)->map_seq =3D=3D MPTCP_SKB_CB(tail)->end_seq= && - ssk =3D=3D tail->sk && + if (tail && ssk =3D=3D tail->sk && __mptcp_try_coalesce(sk, tail, skb, &fragstolen, &delta)) { skb->truesize -=3D delta; kfree_skb_partial(skb, fragstolen); @@ -904,7 +895,7 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) =20 end_seq =3D MPTCP_SKB_CB(skb)->end_seq; tail =3D skb_peek_tail(&sk->sk_receive_queue); - if (!tail || !mptcp_ooo_try_coalesce(msk, tail, skb)) { + if (!tail || !mptcp_try_coalesce(sk, tail, skb)) { int delta =3D ack_seq - MPTCP_SKB_CB(skb)->map_seq; =20 /* skip overlapping data, if any */ --=20 2.53.0 From nobody Mon Aug 24 21:27:14 2026 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 5B2CD30E83F for ; 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="LFb5m7JT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9EC71F00A3F; Mon, 24 Aug 2026 02:21:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787538064; bh=yBtlQqMlfMKTCHO5Gvh9mCm8QAf6U3B0AMoWcIczy/E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LFb5m7JTbHDkJ9uNdqDKpUdOgJHNMw59pvqXVAT+sVvE8hZwyO2oENT4wr1Oj5Efn UiFshvDITxAY5twJtLjMCZwsn3uEo3jmrC1fiZIVNbDkutHufuJPB4bJ+W+Neh/e/c cQpN6q7g/9jbhrcygdtey4E+yvLXcstzF+y3M3X/f4s9tkRErsEyUia8OpqEIZoynr sKSSHM9c/Y3K146X4n+qX5sF9JYIkOfQCHZZ1P/1d+zUE5qN3D2eKUHIMdsFvRKH6v lcxsu0wmbgfazUwgtC3CIrlkdanXzmtR3GCpzDhSO30A+gwUtdmHYCdpofPSm1JUa3 BTEbNmqzOWHBg== From: Geliang Tang To: mptcp@lists.linux.dev Cc: Paolo Abeni , Geliang Tang Subject: [PATCH mptcp-next v7 3/8] mptcp: drop the cant_coalesce CB field Date: Mon, 24 Aug 2026 10:20:38 +0800 Message-ID: <4264936e47e1cec65918ffec433f11ad233a9046.1787537436.git.tanggeliang@kylinos.cn> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Paolo Abeni Such field is used to ensure in-sequence processing in case of fastopen. Instead let's perform synchronization of the fastopen skb sequence when the IASN becomes available with the 3rd ack. When the `cant_coalesce` field has been introduced, commit f03afb3aeb9d ("mptcp: drop __mptcp_fastopen_gen_msk_ackseq()") noted that updating the already queued skb for passive fastopen socket at 3rd ack time would be difficult and race prone. The main point is that such update don't need to be synchronously performed at 3rd ack time, but is sufficient to perform it before the next segment is introduced into the msk. To such extent, add an explicit test in __mptcp_move_skb(). Performance wise this trades a conditional in the fast path - in __mptcp_try_coalesce() - with a similar one in __mptcp_move_skb() and a couple more in slow paths. After this change the user-space will always observe consistent sequence numbers in the receive queue, even in the TFO dummy mapping case. There is still a potential race in mptcp_inq_hint() that will be addressed by a later patch in the series. Co-developed-by: Geliang Tang Signed-off-by: Geliang Tang Signed-off-by: Paolo Abeni --- net/mptcp/fastopen.c | 2 +- net/mptcp/protocol.c | 37 +++++++++++++++++++++++++++++++++++-- net/mptcp/protocol.h | 4 +++- net/mptcp/subflow.c | 10 ++++++++++ 4 files changed, 49 insertions(+), 4 deletions(-) diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c index f717750906ff..d6895c2200cc 100644 --- a/net/mptcp/fastopen.c +++ b/net/mptcp/fastopen.c @@ -49,11 +49,11 @@ void mptcp_fastopen_subflow_synack_set_params(struct mp= tcp_subflow_context *subf MPTCP_SKB_CB(skb)->end_seq =3D 0; MPTCP_SKB_CB(skb)->offset =3D 0; MPTCP_SKB_CB(skb)->has_rxtstamp =3D has_rxtstamp; - MPTCP_SKB_CB(skb)->cant_coalesce =3D 1; =20 mptcp_data_lock(sk); DEBUG_NET_WARN_ON_ONCE(sock_owned_by_user_nocheck(sk)); =20 + mptcp_sk(sk)->rcvd_dummy_seq =3D true; mptcp_borrow_fwdmem(sk, skb); skb_set_owner_r(skb, sk); __skb_queue_tail(&sk->sk_receive_queue, skb); diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 1682a90951f0..c23046b1e51b 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -168,7 +168,6 @@ static bool __mptcp_try_coalesce(struct sock *sk, struc= t sk_buff *to, int limit =3D READ_ONCE(sk->sk_rcvbuf); =20 if (MPTCP_SKB_CB(from)->map_seq !=3D MPTCP_SKB_CB(to)->end_seq || - unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || MPTCP_SKB_CB(from)->offset || ((to->len + from->len) > (limit >> 3)) || !skb_try_coalesce(to, from, fragstolen, delta)) @@ -430,7 +429,6 @@ static void mptcp_init_skb(struct sock *ssk, struct sk_= buff *skb, int offset, MPTCP_SKB_CB(skb)->end_seq =3D MPTCP_SKB_CB(skb)->map_seq + copy_len; MPTCP_SKB_CB(skb)->offset =3D offset; MPTCP_SKB_CB(skb)->has_rxtstamp =3D has_rxtstamp; - MPTCP_SKB_CB(skb)->cant_coalesce =3D 0; =20 __skb_unlink(skb, &ssk->sk_receive_queue); =20 @@ -438,6 +436,28 @@ static void mptcp_init_skb(struct sock *ssk, struct sk= _buff *skb, int offset, skb_dst_drop(skb); } =20 +void __mptcp_sync_rcv_sequence(struct sock *sk) +{ + struct mptcp_sock *msk =3D mptcp_sk(sk); + struct sk_buff *skb; + u64 ack_seq; + u32 offset; + + if (likely(!msk->rcvd_dummy_seq)) + return; + + /* User space can have already received the TFO skb. */ + msk->rcvd_dummy_seq =3D false; + skb =3D skb_peek_tail(&sk->sk_receive_queue); + if (!skb) + return; + + ack_seq =3D atomic64_read(&msk->ack_seq); + offset =3D MPTCP_SKB_CB(skb)->offset; + MPTCP_SKB_CB(skb)->map_seq =3D ack_seq - skb->len + offset; + MPTCP_SKB_CB(skb)->end_seq =3D ack_seq; +} + static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) { u64 copy_len =3D MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; @@ -447,6 +467,12 @@ static bool __mptcp_move_skb(struct sock *sk, struct s= k_buff *skb) =20 mptcp_borrow_fwdmem(sk, skb); =20 + /* Be sure to sync the eventual fastopen dummy mapping before any other + * skb lands into the msk. + */ + if (unlikely(msk->rcvd_dummy_seq)) + __mptcp_sync_rcv_sequence(sk); + ack_seq =3D atomic64_read(&msk->ack_seq); if (MPTCP_SKB_CB(skb)->map_seq =3D=3D ack_seq) { /* in sequence */ @@ -3898,6 +3924,13 @@ static void mptcp_release_cb(struct sock *sk) __mptcp_error_report(sk); if (__test_and_clear_bit(MPTCP_SYNC_SNDBUF, &msk->cb_flags)) __mptcp_sync_sndbuf(sk); + if (test_and_clear_bit(MPTCP_SYNC_SEQ, &msk->cb_flags)) { + /* Ensure we see the updated ack_seq after seeing + * the flag + */ + smp_rmb(); + __mptcp_sync_rcv_sequence(sk); + } } } =20 diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 4074fea9ba85..18ae5d78c3f1 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -126,13 +126,13 @@ #define MPTCP_FLUSH_JOIN_LIST 5 #define MPTCP_SYNC_STATE 6 #define MPTCP_SYNC_SNDBUF 7 +#define MPTCP_SYNC_SEQ 8 =20 struct mptcp_skb_cb { u64 map_seq; u64 end_seq; u32 offset; u8 has_rxtstamp; - u8 cant_coalesce; }; =20 #define MPTCP_SKB_CB(__skb) ((struct mptcp_skb_cb *)&((__skb)->cb[0])) @@ -313,6 +313,7 @@ struct mptcp_sock { u32 token; unsigned long flags; unsigned long cb_flags; + bool rcvd_dummy_seq; bool recovery; /* closing subflow write queue reinjected */ bool can_ack; bool fully_established; @@ -1172,6 +1173,7 @@ void mptcp_event_pm_listener(const struct sock *ssk, enum mptcp_event_type event); bool mptcp_userspace_pm_active(const struct mptcp_sock *msk); =20 +void __mptcp_sync_rcv_sequence(struct sock *sk); void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context= *subflow, struct request_sock *req); int mptcp_pm_genl_fill_addr(struct sk_buff *msg, diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 6345c6ac43b2..e3f77257f030 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -476,6 +476,8 @@ static void subflow_set_remote_key(struct mptcp_sock *m= sk, struct mptcp_subflow_context *subflow, const struct mptcp_options_received *mp_opt) { + struct sock *sk =3D (struct sock *)msk; + /* active MPC subflow will reach here multiple times: * at subflow_finish_connect() time and at 4th ack time */ @@ -494,6 +496,14 @@ static void subflow_set_remote_key(struct mptcp_sock *= msk, atomic64_set(&msk->ack_seq, subflow->iasn); WRITE_ONCE(msk->can_ack, true); atomic64_set(&msk->rcv_wnd_sent, subflow->iasn); + + if (!sock_owned_by_user(sk)) { + __mptcp_sync_rcv_sequence(sk); + } else { + /* Ensure ack_seq is visible before setting the flag */ + smp_wmb(); + set_bit(MPTCP_SYNC_SEQ, &msk->cb_flags); + } } =20 static void mptcp_propagate_state(struct sock *sk, struct sock *ssk, --=20 2.53.0 From nobody Mon Aug 24 21:27:14 2026 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 A726C34AB14 for ; Mon, 24 Aug 2026 02:21:06 +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=1787538068; cv=none; b=dNmuy44WtQBh4Ii6zEE+mgRRqsSHQMujATj8bbUYMmHTOi5WQPdVj+3W19LKVwbYBi+ZCcJCabk0agVm3W+fDXaX9kYAGt8HMfOlzloCVC3qjp8pM/GM4KBsbWA8FPK0BUrTuB81YWp+KuzE2qAG7sing7FGgSXgTqT3/MITeSE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787538068; c=relaxed/simple; bh=cOhhGdH2cPjNpF3dgHVIXXq00dkV64F2yOKXwo8Qn/4=; 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charset="utf-8" From: Paolo Abeni Instead, use a new msk-level field to track the bytes already consumed inside each skb, carrying the amount of bytes already copied to user-space, alike what TCP is already doing. The newly introduce `copied_seq` field is always accessed under the msk socket lock, delegating the synchronization with IASN to the msk release CB, when the socket is owned by the user-space at remote key reception time. Such synchronization preserves any partial progress (copy) made on the TFO packet. Note that the explicit synchronization in __mptcp_move_skb() is needed to ensure that the TFO skb in the receive queue got its map_seq synched before the next skb lands into the receive queue when spooling the backlog at mptcp_release_cb() time, as the release CB synchronization will happen later. Prior to this patch, the TFO skb dummy mapping was always ignored, now it affects the `copied_seq` initial update: be sure to extends the sign correctly of such mapping initialization time. Overall this simplify a bit the __mptcp_recvmsg_mskq(), mptcp_inq_hint() and the __mptcp_move_skb() code and will also make possible the next patch. Initialize MPTCP sequence space to 0 in mptcp_propagate_state() when mp_opt is NULL, ensuring SKB's map_seq starts from 0 to match msk->copied_seq and prevent offset calculation underflow in fallback mode. Co-developed-by: Geliang Tang Signed-off-by: Geliang Tang Signed-off-by: Paolo Abeni --- net/mptcp/fastopen.c | 15 ++++-- net/mptcp/protocol.c | 114 ++++++++++++++++++++----------------------- net/mptcp/protocol.h | 9 +++- net/mptcp/subflow.c | 9 ++++ 4 files changed, 81 insertions(+), 66 deletions(-) diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c index d6895c2200cc..421a50a85547 100644 --- a/net/mptcp/fastopen.c +++ b/net/mptcp/fastopen.c @@ -9,6 +9,7 @@ void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context= *subflow, struct request_sock *req) { + struct mptcp_sock *msk; struct sock *sk, *ssk; struct sk_buff *skb; struct tcp_sock *tp; @@ -44,20 +45,24 @@ void mptcp_fastopen_subflow_synack_set_params(struct mp= tcp_subflow_context *subf subflow->ssn_offset +=3D skb->len; has_rxtstamp =3D TCP_SKB_CB(skb)->has_rxtstamp; =20 - /* Only the sequence delta is relevant */ - MPTCP_SKB_CB(skb)->map_seq =3D -skb->len; + /* The TFO segment data sits before the IASN; before receiving + * the remote key, IASN is assumed being 0. + */ + MPTCP_SKB_CB(skb)->map_seq =3D -(u64)skb->len; MPTCP_SKB_CB(skb)->end_seq =3D 0; - MPTCP_SKB_CB(skb)->offset =3D 0; MPTCP_SKB_CB(skb)->has_rxtstamp =3D has_rxtstamp; =20 mptcp_data_lock(sk); DEBUG_NET_WARN_ON_ONCE(sock_owned_by_user_nocheck(sk)); =20 - mptcp_sk(sk)->rcvd_dummy_seq =3D true; + msk =3D mptcp_sk(sk); + msk->rcvd_dummy_seq =3D true; + msk->copied_seq =3D MPTCP_SKB_CB(skb)->map_seq; + msk->tfo_skb_len =3D skb->len; mptcp_borrow_fwdmem(sk, skb); skb_set_owner_r(skb, sk); __skb_queue_tail(&sk->sk_receive_queue, skb); - mptcp_sk(sk)->bytes_received +=3D skb->len; + msk->bytes_received +=3D skb->len; =20 sk->sk_data_ready(sk); =20 diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index c23046b1e51b..a9faae858a21 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -29,7 +29,7 @@ #include "protocol.h" #include "mib.h" =20 -static unsigned int mptcp_inq_hint(const struct sock *sk); +static unsigned int mptcp_inq_hint(struct sock *sk); =20 #define CREATE_TRACE_POINTS #include @@ -168,7 +168,6 @@ static bool __mptcp_try_coalesce(struct sock *sk, struc= t sk_buff *to, int limit =3D READ_ONCE(sk->sk_rcvbuf); =20 if (MPTCP_SKB_CB(from)->map_seq !=3D MPTCP_SKB_CB(to)->end_seq || - MPTCP_SKB_CB(from)->offset || ((to->len + from->len) > (limit >> 3)) || !skb_try_coalesce(to, from, fragstolen, delta)) return false; @@ -415,8 +414,7 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk= , struct sk_buff *skb) skb_set_owner_r(skb, sk); } =20 -static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offs= et, - int copy_len) +static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offs= et) { struct mptcp_subflow_context *subflow =3D mptcp_subflow_ctx(ssk); bool has_rxtstamp =3D TCP_SKB_CB(skb)->has_rxtstamp; @@ -425,9 +423,9 @@ static void mptcp_init_skb(struct sock *ssk, struct sk_= buff *skb, int offset, * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq * value */ - MPTCP_SKB_CB(skb)->map_seq =3D mptcp_subflow_get_mapped_dsn(subflow); - MPTCP_SKB_CB(skb)->end_seq =3D MPTCP_SKB_CB(skb)->map_seq + copy_len; - MPTCP_SKB_CB(skb)->offset =3D offset; + MPTCP_SKB_CB(skb)->map_seq =3D mptcp_subflow_get_mapped_dsn(subflow) - + offset; + MPTCP_SKB_CB(skb)->end_seq =3D MPTCP_SKB_CB(skb)->map_seq + skb->len; MPTCP_SKB_CB(skb)->has_rxtstamp =3D has_rxtstamp; =20 __skb_unlink(skb, &ssk->sk_receive_queue); @@ -440,8 +438,6 @@ void __mptcp_sync_rcv_sequence(struct sock *sk) { struct mptcp_sock *msk =3D mptcp_sk(sk); struct sk_buff *skb; - u64 ack_seq; - u32 offset; =20 if (likely(!msk->rcvd_dummy_seq)) return; @@ -452,10 +448,8 @@ void __mptcp_sync_rcv_sequence(struct sock *sk) if (!skb) return; =20 - ack_seq =3D atomic64_read(&msk->ack_seq); - offset =3D MPTCP_SKB_CB(skb)->offset; - MPTCP_SKB_CB(skb)->map_seq =3D ack_seq - skb->len + offset; - MPTCP_SKB_CB(skb)->end_seq =3D ack_seq; + MPTCP_SKB_CB(skb)->map_seq =3D mptcp_iasn(msk) - skb->len; + MPTCP_SKB_CB(skb)->end_seq =3D MPTCP_SKB_CB(skb)->map_seq + skb->len; } =20 static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) @@ -467,6 +461,12 @@ static bool __mptcp_move_skb(struct sock *sk, struct s= k_buff *skb) =20 mptcp_borrow_fwdmem(sk, skb); =20 + if (test_and_clear_bit(MPTCP_SYNC_SEQ, &msk->cb_flags)) { + /* Ensure we see the updated ack_seq after seeing the flag */ + smp_rmb(); + msk->copied_seq +=3D mptcp_iasn(msk); + } + /* Be sure to sync the eventual fastopen dummy mapping before any other * skb lands into the msk. */ @@ -500,10 +500,6 @@ static bool __mptcp_move_skb(struct sock *sk, struct s= k_buff *skb) /* Partial packet */ if (after64(MPTCP_SKB_CB(skb)->end_seq, ack_seq)) { copy_len =3D MPTCP_SKB_CB(skb)->end_seq - ack_seq; - MPTCP_SKB_CB(skb)->offset +=3D ack_seq - - MPTCP_SKB_CB(skb)->map_seq; - MPTCP_SKB_CB(skb)->map_seq +=3D ack_seq - - MPTCP_SKB_CB(skb)->map_seq; goto insert; } =20 @@ -861,7 +857,7 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp= _sock *msk, if (offset < skb->len) { size_t len =3D skb->len - offset; =20 - mptcp_init_skb(ssk, skb, offset, len); + mptcp_init_skb(ssk, skb, offset); =20 if (own_msk) { mptcp_subflow_lend_fwdmem(subflow, skb); @@ -928,8 +924,6 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) pr_debug("uncoalesced seq=3D%llx ack seq=3D%llx delta=3D%d\n", MPTCP_SKB_CB(skb)->map_seq, ack_seq, delta); - MPTCP_SKB_CB(skb)->offset +=3D delta; - MPTCP_SKB_CB(skb)->map_seq +=3D delta; __skb_queue_tail(&sk->sk_receive_queue, skb); } msk->bytes_received +=3D end_seq - ack_seq; @@ -2203,33 +2197,24 @@ static void mptcp_eat_recv_skb(struct sock *sk, str= uct sk_buff *skb) } =20 static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg, - size_t len, int flags, int copied_total, + size_t len, int flags, u64 *seq, struct scm_timestamping_internal *tss, int *cmsg_flags, struct sk_buff **last) { struct mptcp_sock *msk =3D mptcp_sk(sk); struct sk_buff *skb, *tmp; - int total_data_len =3D 0; int copied =3D 0; =20 skb_queue_walk_safe(&sk->sk_receive_queue, skb, tmp) { - u32 delta, offset =3D MPTCP_SKB_CB(skb)->offset; + u64 offset =3D *seq - MPTCP_SKB_CB(skb)->map_seq; u32 data_len =3D skb->len - offset; u32 count; int err; =20 - if (flags & MSG_PEEK) { - /* skip already peeked skbs */ - if (total_data_len + data_len <=3D copied_total) { - total_data_len +=3D data_len; - *last =3D skb; - continue; - } - - /* skip the already peeked data in the current skb */ - delta =3D copied_total - total_data_len; - offset +=3D delta; - data_len -=3D delta; + /* Skip the already peeked data. */ + if (offset >=3D skb->len) { + *last =3D skb; + continue; } =20 count =3D min_t(size_t, len - copied, data_len); @@ -2248,14 +2233,12 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, st= ruct msghdr *msg, } =20 copied +=3D count; + *seq +=3D count; =20 if (!(flags & MSG_PEEK)) { msk->bytes_consumed +=3D count; - if (count < data_len) { - MPTCP_SKB_CB(skb)->offset +=3D count; - MPTCP_SKB_CB(skb)->map_seq +=3D count; + if (count < data_len) break; - } =20 mptcp_eat_recv_skb(sk, skb); } else { @@ -2408,26 +2391,23 @@ static bool mptcp_move_skbs(struct sock *sk) return enqueued; } =20 -static unsigned int mptcp_inq_hint(const struct sock *sk) +static unsigned int mptcp_inq_hint(struct sock *sk) { const struct mptcp_sock *msk =3D mptcp_sk(sk); - const struct sk_buff *skb; + u64 hint_val; =20 - skb =3D skb_peek(&sk->sk_receive_queue); - if (skb) { - u64 hint_val =3D atomic64_read(&msk->ack_seq) - - MPTCP_SKB_CB(skb)->map_seq; - - if (hint_val >=3D INT_MAX) - return INT_MAX; - - return (unsigned int)hint_val; - } + /* Avoid races vs ack_seq updates. */ + mptcp_data_lock(sk); + hint_val =3D atomic64_read(&msk->ack_seq) - msk->copied_seq; + mptcp_data_unlock(sk); + if (hint_val >=3D INT_MAX) + return INT_MAX; =20 - if (sk->sk_state =3D=3D TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN)) + if (!hint_val && + (sk->sk_state =3D=3D TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN))) return 1; =20 - return 0; + return (unsigned int)hint_val; } =20 static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, @@ -2436,6 +2416,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msgh= dr *msg, size_t len, struct mptcp_sock *msk =3D mptcp_sk(sk); struct scm_timestamping_internal tss; int copied =3D 0, cmsg_flags =3D 0; + u64 peek_seq, *seq; int target; long timeo; =20 @@ -2454,6 +2435,11 @@ static int mptcp_recvmsg(struct sock *sk, struct msg= hdr *msg, size_t len, =20 len =3D min_t(size_t, len, INT_MAX); target =3D sock_rcvlowat(sk, flags & MSG_WAITALL, len); + seq =3D &msk->copied_seq; + if (flags & MSG_PEEK) { + peek_seq =3D msk->copied_seq; + seq =3D &peek_seq; + } =20 if (unlikely(msk->recvmsg_inq)) cmsg_flags =3D MPTCP_CMSG_INQ; @@ -2463,7 +2449,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msgh= dr *msg, size_t len, int err, bytes_read; =20 bytes_read =3D __mptcp_recvmsg_mskq(sk, msg, len - copied, flags, - copied, &tss, &cmsg_flags, + seq, &tss, &cmsg_flags, &last); if (unlikely(bytes_read < 0)) { if (!copied) @@ -2473,8 +2459,11 @@ static int mptcp_recvmsg(struct sock *sk, struct msg= hdr *msg, size_t len, =20 copied +=3D bytes_read; =20 - if (!list_empty(&msk->backlog_list) && mptcp_move_skbs(sk)) + if (!list_empty(&msk->backlog_list) && mptcp_move_skbs(sk)) { + if (flags & MSG_PEEK) + peek_seq =3D msk->copied_seq + copied; continue; + } =20 /* only the MPTCP socket status is relevant here. The exit * conditions mirror closely tcp_recvmsg() @@ -2518,6 +2507,10 @@ static int mptcp_recvmsg(struct sock *sk, struct msg= hdr *msg, size_t len, err =3D copied ? : err; goto out_err; } + + /* Recompute peek offset after eventual seq resync. */ + if (flags & MSG_PEEK) + peek_seq =3D msk->copied_seq + copied; } =20 mptcp_cleanup_rbuf(msk, copied); @@ -3695,11 +3688,13 @@ static int mptcp_disconnect(struct sock *sk, int fl= ags) msk->bytes_retrans =3D 0; msk->rcvspace_init =3D 0; msk->fastclosing =3D 0; + msk->tfo_skb_len =3D 0; mptcp_init_rtt_est(msk); =20 /* for fallback's sake */ atomic64_set(&msk->ack_seq, 0); atomic64_set(&msk->rcv_wnd_sent, 0); + msk->copied_seq =3D 0; =20 WRITE_ONCE(sk->sk_shutdown, 0); sk_error_report(sk); @@ -3929,6 +3924,7 @@ static void mptcp_release_cb(struct sock *sk) * the flag */ smp_rmb(); + msk->copied_seq +=3D mptcp_iasn(msk); __mptcp_sync_rcv_sequence(sk); } } @@ -4593,7 +4589,7 @@ static struct sk_buff *mptcp_recv_skb(struct sock *sk= , u32 *off) mptcp_move_skbs(sk); =20 while ((skb =3D skb_peek(&sk->sk_receive_queue)) !=3D NULL) { - offset =3D MPTCP_SKB_CB(skb)->offset; + offset =3D msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq; if (offset < skb->len) { *off =3D offset; return skb; @@ -4635,11 +4631,9 @@ static int __mptcp_read_sock(struct sock *sk, read_d= escriptor_t *desc, copied +=3D count; =20 msk->bytes_consumed +=3D count; - if (count < data_len) { - MPTCP_SKB_CB(skb)->offset +=3D count; - MPTCP_SKB_CB(skb)->map_seq +=3D count; + msk->copied_seq +=3D count; + if (count < data_len) break; - } =20 mptcp_eat_recv_skb(sk, skb); if (!desc->count) diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 18ae5d78c3f1..18c59cedfe1b 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -131,7 +131,6 @@ struct mptcp_skb_cb { u64 map_seq; u64 end_seq; - u32 offset; u8 has_rxtstamp; }; =20 @@ -292,6 +291,7 @@ struct mptcp_sock { u64 bytes_sent; u64 snd_nxt; u64 bytes_received; + u64 copied_seq; atomic64_t ack_seq; atomic64_t rcv_wnd_sent; u64 rcv_data_fin_seq; @@ -311,6 +311,7 @@ struct mptcp_sock { u32 last_ack_recv; unsigned long timer_ival; u32 token; + u32 tfo_skb_len; unsigned long flags; unsigned long cb_flags; bool rcvd_dummy_seq; @@ -865,6 +866,12 @@ struct sock *mptcp_subflow_get_retrans(struct mptcp_so= ck *msk); int mptcp_sched_get_send(struct mptcp_sock *msk); int mptcp_sched_get_retrans(struct mptcp_sock *msk); =20 +static inline u64 mptcp_iasn(const struct mptcp_sock *msk) +{ + return atomic64_read(&msk->ack_seq) - msk->bytes_received + + msk->tfo_skb_len; +} + static inline u64 mptcp_data_avail(const struct mptcp_sock *msk) { return READ_ONCE(msk->bytes_received) - READ_ONCE(msk->bytes_consumed); diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index e3f77257f030..7fc526d0deae 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -498,6 +498,8 @@ static void subflow_set_remote_key(struct mptcp_sock *m= sk, atomic64_set(&msk->rcv_wnd_sent, subflow->iasn); =20 if (!sock_owned_by_user(sk)) { + /* User space could have already read partially the TFO skb */ + msk->copied_seq +=3D subflow->iasn; 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Mon, 24 Aug 2026 02:21:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787538068; bh=OGhmsvJNh5U841FecUDd6a6snvzYrhDOJKOeqcEPqzQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Qh9QcfSQ9HKdzr+BwiJx+C2uHB4DDmhXgb2sFEr6Avj5SBD1E20H5bLP4GkEL+Oe3 vNg9cY7wSE+OnXe0C0L10AWPRTdlFhRb8O78tP1Ug4FCZjWFp5m+dtPnONLMplMbZ9 KkSS6yvZJEspiH4xDckQWuGMGKdGkRTP1tsZ1EimPR8TWefyVxWWoKIjvqcJ4oJ+2v 49jB/hJczYrskwZvn3ThNc5ECNq8ni3VozTiJX35x5wZrfdyO/0Mj2ank9x0z0prWZ +lpP8qR9vXTNJLz+zQAw85MSpEMkrv9GFbh55O0np9fdzQU/n6I/azjuxeKRP0fPBy 6EqaG/vz1HhFg== From: Geliang Tang To: mptcp@lists.linux.dev Cc: Paolo Abeni , Geliang Tang Subject: [PATCH mptcp-next v7 5/8] mptcp: sync mptcp skb cb layout with tcp one Date: Mon, 24 Aug 2026 10:20:40 +0800 Message-ID: X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Paolo Abeni The MPTCP protocol uses a significantly different CB layout WRT TCP, as it includes different information and use 64 bits for the sequence numbers. As the msk-level rcvbuf buffer size is limited by the core socket code the INT_MAX; after validating the incoming skb vs the current receive window, we can safely use 32 bits for MPTCP-level sequence number. This allow updating the MPTCP CB layout so that fields with a corresponding TCP-level data use the same area inside the CB itself. Add build time check to ensure the latter invariant. Co-developed-by: Geliang Tang Signed-off-by: Geliang Tang Signed-off-by: Paolo Abeni --- net/mptcp/fastopen.c | 6 ++-- net/mptcp/protocol.c | 81 +++++++++++++++++++++++++++----------------- net/mptcp/protocol.h | 7 ++-- 3 files changed, 59 insertions(+), 35 deletions(-) diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c index 421a50a85547..0d339dd454f9 100644 --- a/net/mptcp/fastopen.c +++ b/net/mptcp/fastopen.c @@ -48,8 +48,10 @@ void mptcp_fastopen_subflow_synack_set_params(struct mpt= cp_subflow_context *subf /* The TFO segment data sits before the IASN; before receiving * the remote key, IASN is assumed being 0. */ - MPTCP_SKB_CB(skb)->map_seq =3D -(u64)skb->len; + MPTCP_SKB_CB(skb)->map_seq64 =3D -(u64)skb->len; + MPTCP_SKB_CB(skb)->map_seq =3D MPTCP_SKB_CB(skb)->map_seq64; MPTCP_SKB_CB(skb)->end_seq =3D 0; + MPTCP_SKB_CB(skb)->flags =3D 0; MPTCP_SKB_CB(skb)->has_rxtstamp =3D has_rxtstamp; =20 mptcp_data_lock(sk); @@ -57,7 +59,7 @@ void mptcp_fastopen_subflow_synack_set_params(struct mptc= p_subflow_context *subf =20 msk =3D mptcp_sk(sk); msk->rcvd_dummy_seq =3D true; - msk->copied_seq =3D MPTCP_SKB_CB(skb)->map_seq; + msk->copied_seq =3D MPTCP_SKB_CB(skb)->map_seq64; msk->tfo_skb_len =3D skb->len; mptcp_borrow_fwdmem(sk, skb); skb_set_owner_r(skb, sk); diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index a9faae858a21..71f61dde3b10 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -172,7 +172,7 @@ static bool __mptcp_try_coalesce(struct sock *sk, struc= t sk_buff *to, !skb_try_coalesce(to, from, fragstolen, delta)) return false; =20 - pr_debug("colesced seq %llx into %llx new len %d new end seq %llx\n", + pr_debug("colesced seq %x into %x new len %d new end seq %x\n", MPTCP_SKB_CB(from)->map_seq, MPTCP_SKB_CB(to)->map_seq, to->len, MPTCP_SKB_CB(from)->end_seq); MPTCP_SKB_CB(to)->end_seq =3D MPTCP_SKB_CB(from)->end_seq; @@ -254,8 +254,8 @@ static void mptcp_prune_ofo_queue(struct sock *sk, struct sk_buff *skb =3D rb_to_skb(node); =20 /* Stop pruning if the incoming skb would land in OoO tail. */ - if (after64(MPTCP_SKB_CB(in_skb)->map_seq, - MPTCP_SKB_CB(skb)->map_seq)) + if (after(MPTCP_SKB_CB(in_skb)->map_seq, + MPTCP_SKB_CB(skb)->map_seq)) break; =20 pruned =3D true; @@ -301,15 +301,19 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *m= sk, struct sk_buff *skb) { struct sock *sk =3D (struct sock *)msk; struct rb_node **p, *parent; - u64 seq, end_seq, max_seq; + u64 end_seq, max_seq; struct sk_buff *skb1; + u32 seq; =20 seq =3D MPTCP_SKB_CB(skb)->map_seq; - end_seq =3D MPTCP_SKB_CB(skb)->end_seq; + end_seq =3D MPTCP_SKB_CB(skb)->map_seq64 + skb->len; max_seq =3D atomic64_read(&msk->rcv_wnd_sent); =20 - pr_debug("msk=3D%p seq=3D%llx limit=3D%llx empty=3D%d\n", msk, seq, max_s= eq, + pr_debug("msk=3D%p seq=3D%x limit=3D%llx empty=3D%d\n", msk, seq, max_seq, RB_EMPTY_ROOT(&msk->out_of_order_queue)); + /* Use the full sequence space to perform the admission checks, to + * protect vs possible wrap-arounds. + */ if (after64(end_seq, max_seq)) { /* out of window */ mptcp_drop(sk, skb); @@ -345,7 +349,7 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk= , struct sk_buff *skb) } =20 /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */ - if (!before64(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) { + if (!before(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL); parent =3D &msk->ooo_last_skb->rbnode; p =3D &parent->rb_right; @@ -357,18 +361,18 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *m= sk, struct sk_buff *skb) while (*p) { parent =3D *p; skb1 =3D rb_to_skb(parent); - if (before64(seq, MPTCP_SKB_CB(skb1)->map_seq)) { + if (before(seq, MPTCP_SKB_CB(skb1)->map_seq)) { p =3D &parent->rb_left; continue; } - if (before64(seq, MPTCP_SKB_CB(skb1)->end_seq)) { - if (!after64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) { + if (before(seq, MPTCP_SKB_CB(skb1)->end_seq)) { + if (!after(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) { /* All the bits are present. Drop. */ mptcp_drop(sk, skb); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); return; } - if (after64(seq, MPTCP_SKB_CB(skb1)->map_seq)) { + if (after(seq, MPTCP_SKB_CB(skb1)->map_seq)) { /* partial overlap: * | skb | * | skb1 | @@ -399,7 +403,7 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk= , struct sk_buff *skb) merge_right: /* Remove other segments covered by skb. */ while ((skb1 =3D skb_rb_next(skb)) !=3D NULL) { - if (before64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) + if (before((u32)end_seq, MPTCP_SKB_CB(skb1)->end_seq)) break; rb_erase(&skb1->rbnode, &msk->out_of_order_queue); mptcp_drop(sk, skb1); @@ -421,11 +425,13 @@ static void mptcp_init_skb(struct sock *ssk, struct s= k_buff *skb, int offset) =20 /* the skb map_seq accounts for the skb offset: * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq - * value + * value; note that end seq number is only available in 32bits format. */ - MPTCP_SKB_CB(skb)->map_seq =3D mptcp_subflow_get_mapped_dsn(subflow) - - offset; + MPTCP_SKB_CB(skb)->map_seq64 =3D mptcp_subflow_get_mapped_dsn(subflow) - + offset; + MPTCP_SKB_CB(skb)->map_seq =3D (u32)MPTCP_SKB_CB(skb)->map_seq64; MPTCP_SKB_CB(skb)->end_seq =3D MPTCP_SKB_CB(skb)->map_seq + skb->len; + MPTCP_SKB_CB(skb)->flags =3D 0; MPTCP_SKB_CB(skb)->has_rxtstamp =3D has_rxtstamp; =20 __skb_unlink(skb, &ssk->sk_receive_queue); @@ -448,13 +454,14 @@ void __mptcp_sync_rcv_sequence(struct sock *sk) if (!skb) return; =20 - MPTCP_SKB_CB(skb)->map_seq =3D mptcp_iasn(msk) - skb->len; + MPTCP_SKB_CB(skb)->map_seq64 =3D mptcp_iasn(msk) - skb->len; + MPTCP_SKB_CB(skb)->map_seq =3D (u32)MPTCP_SKB_CB(skb)->map_seq64; MPTCP_SKB_CB(skb)->end_seq =3D MPTCP_SKB_CB(skb)->map_seq + skb->len; } =20 static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb) { - u64 copy_len =3D MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; + u32 copy_len =3D MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq; struct mptcp_sock *msk =3D mptcp_sk(sk); struct sk_buff *tail; u64 ack_seq; @@ -474,7 +481,7 @@ static bool __mptcp_move_skb(struct sock *sk, struct sk= _buff *skb) __mptcp_sync_rcv_sequence(sk); =20 ack_seq =3D atomic64_read(&msk->ack_seq); - if (MPTCP_SKB_CB(skb)->map_seq =3D=3D ack_seq) { + if (MPTCP_SKB_CB(skb)->map_seq64 =3D=3D ack_seq) { /* in sequence */ insert: if (!mptcp_try_rmem_schedule(sk, skb)) { @@ -492,14 +499,14 @@ static bool __mptcp_move_skb(struct sock *sk, struct = sk_buff *skb) skb_set_owner_r(skb, sk); __skb_queue_tail(&sk->sk_receive_queue, skb); return true; - } else if (after64(MPTCP_SKB_CB(skb)->map_seq, ack_seq)) { + } else if (after64(MPTCP_SKB_CB(skb)->map_seq64, ack_seq)) { mptcp_data_queue_ofo(msk, skb); return false; } =20 /* Partial packet */ - if (after64(MPTCP_SKB_CB(skb)->end_seq, ack_seq)) { - copy_len =3D MPTCP_SKB_CB(skb)->end_seq - ack_seq; + if (after64(MPTCP_SKB_CB(skb)->map_seq64 + skb->len, ack_seq)) { + copy_len =3D MPTCP_SKB_CB(skb)->end_seq - (u32)ack_seq; goto insert; } =20 @@ -894,40 +901,40 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk) { struct sock *sk =3D (struct sock *)msk; struct sk_buff *skb, *tail; - u64 end_seq, ack_seq; + u32 seq_delta, ack_seq; bool moved =3D false; struct rb_node *p; =20 p =3D rb_first(&msk->out_of_order_queue); pr_debug("msk=3D%p empty=3D%d\n", msk, RB_EMPTY_ROOT(&msk->out_of_order_q= ueue)); while (p) { - ack_seq =3D atomic64_read(&msk->ack_seq); + ack_seq =3D (u32)atomic64_read(&msk->ack_seq); skb =3D rb_to_skb(p); - if (after64(MPTCP_SKB_CB(skb)->map_seq, ack_seq)) + if (after(MPTCP_SKB_CB(skb)->map_seq, ack_seq)) break; =20 p =3D rb_next(p); rb_erase(&skb->rbnode, &msk->out_of_order_queue); =20 - if (unlikely(!after64(MPTCP_SKB_CB(skb)->end_seq, ack_seq))) { + if (unlikely(!after(MPTCP_SKB_CB(skb)->end_seq, ack_seq))) { mptcp_drop(sk, skb); MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA); continue; } =20 - end_seq =3D MPTCP_SKB_CB(skb)->end_seq; + seq_delta =3D MPTCP_SKB_CB(skb)->end_seq - ack_seq; tail =3D skb_peek_tail(&sk->sk_receive_queue); if (!tail || !mptcp_try_coalesce(sk, tail, skb)) { int delta =3D ack_seq - MPTCP_SKB_CB(skb)->map_seq; =20 /* skip overlapping data, if any */ - pr_debug("uncoalesced seq=3D%llx ack seq=3D%llx delta=3D%d\n", + pr_debug("uncoalesced seq=3D%x ack seq=3D%x delta=3D%d\n", MPTCP_SKB_CB(skb)->map_seq, ack_seq, delta); __skb_queue_tail(&sk->sk_receive_queue, skb); } - msk->bytes_received +=3D end_seq - ack_seq; - atomic64_set(&msk->ack_seq, end_seq); + msk->bytes_received +=3D seq_delta; + atomic64_add(seq_delta, &msk->ack_seq); moved =3D true; } return moved; @@ -2206,7 +2213,7 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, stru= ct msghdr *msg, int copied =3D 0; =20 skb_queue_walk_safe(&sk->sk_receive_queue, skb, tmp) { - u64 offset =3D *seq - MPTCP_SKB_CB(skb)->map_seq; + u32 offset =3D (u32)(*seq) - MPTCP_SKB_CB(skb)->map_seq; u32 data_len =3D skb->len - offset; u32 count; int err; @@ -4589,7 +4596,7 @@ static struct sk_buff *mptcp_recv_skb(struct sock *sk= , u32 *off) mptcp_move_skbs(sk); =20 while ((skb =3D skb_peek(&sk->sk_receive_queue)) !=3D NULL) { - offset =3D msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq; + offset =3D (u32)msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq; if (offset < skb->len) { *off =3D offset; return skb; @@ -4840,11 +4847,23 @@ static int mptcp_napi_poll(struct napi_struct *napi= , int budget) return work_done; } =20 +#define CHK_CB_FIELD(mptcp_field, tcp_field) \ + ({ \ + BUILD_BUG_ON(offsetof(struct mptcp_skb_cb, mptcp_field) !=3D \ + offsetof(struct tcp_skb_cb, tcp_field)); \ + BUILD_BUG_ON(offsetofend(struct mptcp_skb_cb, mptcp_field) !=3D \ + offsetofend(struct tcp_skb_cb, tcp_field)); \ + }) + void __init mptcp_proto_init(void) { struct mptcp_delegated_action *delegated; int cpu; =20 + CHK_CB_FIELD(map_seq, seq); + CHK_CB_FIELD(end_seq, end_seq); + CHK_CB_FIELD(flags, tcp_flags); + mptcp_prot.h.hashinfo =3D tcp_prot.h.hashinfo; =20 if (percpu_counter_init(&mptcp_sockets_allocated, 0, GFP_KERNEL)) diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 18c59cedfe1b..13cbc14870d2 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -129,9 +129,12 @@ #define MPTCP_SYNC_SEQ 8 =20 struct mptcp_skb_cb { - u64 map_seq; 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charset="utf-8" From: Paolo Abeni When MPTCP carries TLS, the data path runs under mptcp_data_lock(). Reaching sk->sk_data_ready(sk) synchronously ends up at tls_strp_check_rcv() -> mptcp_recv_skb() -> mptcp_move_skbs(), which calls mptcp_data_lock() on the same sk and recurses on sk_lock.slock. The TLS path is not the only constraint: before the mptcp_recv_skb() calls, the TLS code would also reach __mptcp_read_sock(), which calls mptcp_rcv_space_adjust() and mptcp_cleanup_rbuf(). Both require holding the msk socket lock in process context, while the mptcp/TLS caller is in BH scope. Fix this by deferring sk->sk_data_ready(sk) to mptcp_worker() via a new MPTCP_WORK_READ_COMPLETE bit, reusing the existing mptcp_schedule_work()/ mptcp_cancel_work() infrastructure. The wakeup bit is consumed after the SOCK_DEAD && TCP_CLOSE destroy branch, so a socket that reaches the destroy path drops the pending wakeup rather than running it post-free. Co-developed-by: Geliang Tang Signed-off-by: Geliang Tang Signed-off-by: Paolo Abeni --- net/mptcp/protocol.c | 25 +++++++++++++++++++------ net/mptcp/protocol.h | 2 ++ 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 71f61dde3b10..3ce61eb96001 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -3138,6 +3138,15 @@ static void mptcp_backlog_purge(struct sock *sk) sk_mem_reclaim(sk); } =20 +static void mptcp_read_complete(struct sock *sk) +{ + struct mptcp_sock *msk =3D mptcp_sk(sk); + + mptcp_rcv_space_adjust(msk, msk->read_copied); + mptcp_cleanup_rbuf(msk, msk->read_copied); + msk->read_copied =3D 0; +} + static void mptcp_do_fastclose(struct sock *sk) { struct mptcp_subflow_context *subflow, *tmp; @@ -3214,6 +3223,9 @@ static void mptcp_worker(struct work_struct *work) if (test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags)) __mptcp_retrans(sk); =20 + if (test_and_clear_bit(MPTCP_WORK_READ_COMPLETE, &msk->flags)) + mptcp_read_complete(sk); + fail_tout =3D msk->first ? READ_ONCE(mptcp_subflow_ctx(msk->first)->fail_= tout) : 0; if (fail_tout && time_after(jiffies, fail_tout)) mptcp_mp_fail_no_response(msk); @@ -4592,9 +4604,6 @@ static struct sk_buff *mptcp_recv_skb(struct sock *sk= , u32 *off) struct sk_buff *skb; u32 offset; =20 - if (!list_empty(&msk->backlog_list)) - mptcp_move_skbs(sk); - while ((skb =3D skb_peek(&sk->sk_receive_queue)) !=3D NULL) { offset =3D (u32)msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq; if (offset < skb->len) { @@ -4609,6 +4618,7 @@ static struct sk_buff *mptcp_recv_skb(struct sock *sk= , u32 *off) /* * Note: * - It is assumed that the socket was locked by the caller. + * - Can be invoked in BH scope. */ static int __mptcp_read_sock(struct sock *sk, read_descriptor_t *desc, sk_read_actor_t recv_actor, bool noack) @@ -4650,11 +4660,14 @@ static int __mptcp_read_sock(struct sock *sk, read_= descriptor_t *desc, if (noack) goto out; =20 - mptcp_rcv_space_adjust(msk, copied); - + /* The backlog flushing is only needed when some data is actually + * moved and will take place in the workers's release callback. + */ if (copied > 0) { mptcp_recv_skb(sk, &offset); - mptcp_cleanup_rbuf(msk, copied); + msk->read_copied +=3D copied; + set_bit(MPTCP_WORK_READ_COMPLETE, &msk->flags); + mptcp_schedule_work(sk); } out: return copied; diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 13cbc14870d2..2b3a32166d8b 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -117,6 +117,7 @@ #define MPTCP_FALLBACK_DONE 2 #define MPTCP_WORK_CLOSE_SUBFLOW 3 #define MPTCP_RTX_DISABLED 4 +#define MPTCP_WORK_READ_COMPLETE 5 =20 /* MPTCP socket release cb flags */ #define MPTCP_PUSH_PENDING 1 @@ -312,6 +313,7 @@ struct mptcp_sock { u32 last_data_sent; u32 last_data_recv; u32 last_ack_recv; + int read_copied; unsigned long timer_ival; u32 token; u32 tfo_skb_len; --=20 2.53.0 From nobody Mon Aug 24 21:27:14 2026 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 18CE132B99F for ; Mon, 24 Aug 2026 02:21:13 +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=1787538074; cv=none; b=amJTg63O3IkCLEJIcrtH3hfA3Q4cj0Hci7Z74ET3tmniV/liqyJitXQPpCRKQ2goYyG1qTA5pGerrLdZTvKAUz19c8RV68y35IEf//GqWuVDLeG97n3U2L194J4VPV1RHJnLAnmRszoECTlp+8eE8RqfLMq/HOhWvq9iqSAiUZM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787538074; c=relaxed/simple; bh=gefA6gEz31+Uw4ngU+Ksxa3WCW754+oez2UJr3ERQ1I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uTJsBBqZ9xhZGx5NEGiSp5JhsFcqVYrYXTY8miRUgAEaRjldiK0GhMgkr97gKVXXbgAnDakeLD41Bq2ItrcY8N03N787qn0CmBgbh3EA121G38MEbaOS+8MmepyMRI1vqsn7Ni6V3U30ecj2uWk27gKcO/C+9fkwXQm5+ermwSI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dcyUIGfY; 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="dcyUIGfY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ADF741F00A3F; Mon, 24 Aug 2026 02:21:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787538073; bh=Ai5bTq+o0O8e+IVJ74sRMEel2Q6KAidqVN8lXrAdvZs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dcyUIGfYO5wuBREdyNRv91p56TkUwb+AAQ965icWzrXwzjAbcS+s7blOqsWACc3wK Af55fQ7YMMpLUDARceJADrYiWcmjGk1TgIT4TS3HFFmwdd4k0srWT1NtVCUy2BHVxG YzQ8O6mJvnyv5G2GWE73O4uSHRlSTJrbXfVxLoS4SY4QCHWQrtbfFdIWYLY1SK+RIe bqdjwyHOhXayR4Fo/2PnnxyIObx8XnRRZQ1a+Jw5dOlgwuu7A29RtJ1m8WNoq+fblr Y6dn+wbZM911qdvJKaQmb9EmSe4JpspEjyAsd5mZi8yIFqhhmutekt7dVG+YtAoJte UEt7/ZjcvmK/g== From: Geliang Tang To: mptcp@lists.linux.dev Cc: Geliang Tang Subject: [PATCH mptcp-next v7 7/8] mptcp: track app-limited state in mptcp_sendmsg Date: Mon, 24 Aug 2026 10:20:42 +0800 Message-ID: <393ff662e4bd9b57beaf3be701f7385a24a07d99.1787537436.git.tanggeliang@kylinos.cn> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Geliang Tang The application-limited accounting in TCP is updated by tcp_rate_check_app_limited(), which currently takes a struct sock * and internally calls tcp_sk(). MPTCP needs to apply the same accounting to each subflow individually - every subflow is an independent TCP socket with its own tp->app_limited / delivered state - so wrapping the call as a struct sock * -> tcp_sk() helper is awkward at the call site. Split the existing function: keep the logic as tcp_sock_rate_check_app_limited(struct tcp_sock *tp), and turn tcp_rate_check_app_limited(struct sock *) into a thin wrapper so the exported API is unchanged for other TCP users. Then add mptcp_sock_rate_check_app_limited() that walks every subflow of the mptcp_sock and runs tcp_sock_rate_check_app_limited() under each subflow's socket lock. Invoke it from mptcp_sendmsg() right after the send-side setup, so the delivery-rate app_limited state stays in sync with what the application actually has to send across each subflow. With this in place, TCP_INFO.tcpi_delivery_rate_app_limited is reported correctly for MPTCP connections instead of being left at 0. Signed-off-by: Geliang Tang --- include/net/tcp.h | 1 + net/ipv4/tcp.c | 9 +++++++-- net/mptcp/protocol.c | 18 ++++++++++++++++++ 3 files changed, 26 insertions(+), 2 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index 2c5b889530b5..9d436816411b 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -849,6 +849,7 @@ static inline int tcp_bound_to_half_wnd(struct tcp_sock= *tp, int pktsize) =20 /* tcp.c */ void tcp_get_info(struct sock *, struct tcp_info *); +void tcp_sock_rate_check_app_limited(struct tcp_sock *tp); void tcp_rate_check_app_limited(struct sock *sk); =20 /* Read 'sendfile()'-style from a TCP socket */ diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 1452c40e22d4..f0f843fd1897 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1096,9 +1096,9 @@ int tcp_sendmsg_fastopen(struct sock *sk, struct msgh= dr *msg, int *copied, } =20 /* If a gap is detected between sends, mark the socket application-limited= . */ -void tcp_rate_check_app_limited(struct sock *sk) +void tcp_sock_rate_check_app_limited(struct tcp_sock *tp) { - struct tcp_sock *tp =3D tcp_sk(sk); + struct sock *sk =3D (struct sock *)tp; =20 if (/* We have less than one packet to send. */ tp->write_seq - tp->snd_nxt < tp->mss_cache && @@ -1111,6 +1111,11 @@ void tcp_rate_check_app_limited(struct sock *sk) tp->app_limited =3D (tp->delivered + tcp_packets_in_flight(tp)) ? : 1; } + +void tcp_rate_check_app_limited(struct sock *sk) +{ + tcp_sock_rate_check_app_limited(tcp_sk(sk)); +} EXPORT_SYMBOL_GPL(tcp_rate_check_app_limited); =20 int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 3ce61eb96001..22566a0ef3c5 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2050,6 +2050,21 @@ static void mptcp_rps_record_subflows(const struct m= ptcp_sock *msk) } } =20 +static void mptcp_sock_rate_check_app_limited(struct sock *sk) +{ + struct mptcp_sock *msk =3D mptcp_sk(sk); + struct mptcp_subflow_context *subflow; + + mptcp_for_each_subflow(msk, subflow) { + struct sock *ssk =3D mptcp_subflow_tcp_sock(subflow); + bool slow; + + slow =3D lock_sock_fast_nested(ssk); + tcp_sock_rate_check_app_limited(tcp_sk(ssk)); + unlock_sock_fast(ssk, slow); + } +} + static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) { struct mptcp_sock *msk =3D mptcp_sk(sk); @@ -2080,6 +2095,9 @@ static int mptcp_sendmsg(struct sock *sk, struct msgh= dr *msg, size_t len) =20 timeo =3D sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT); =20 + /* is sending application-limited? */ + mptcp_sock_rate_check_app_limited(sk); + if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) { ret =3D sk_stream_wait_connect(sk, &timeo); if (ret) --=20 2.53.0 From nobody Mon Aug 24 21:27:14 2026 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 9DF00282F0A for ; Mon, 24 Aug 2026 02:21:14 +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=1787538075; cv=none; b=TPkAnEbaeJLJBXNG9shab52zjw4VM/clzmxLi9Vn+aPtEJ08RFgC222yJv7G7YLoKeG9HtcyN+jWdKAXVheEVQJI5ElvJWtzRGsoITBeihNoyY8pYaovzYgoRIXcZfUXdLaV3141zk/WS1WGIaqyC5lV/3GJYXhjipm6g6mlKl4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787538075; c=relaxed/simple; bh=JxT3qeiSHuBS12KtGnTPLFRzVxKd0fvCXwqrRkI3nnM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=X+9vRDpoJWypfOp7dM6d2FVYfFCXhn0RBcHHWLhig03RuTg5BDA02J6DG4RULI4ZTicBgJZ+suuBgDlzqXYwbkYH7VTSXFp5gndW6v7HR0S+Kt0pP9M/Pq+UiSAp74rYjcM88xZb4D31TpX6lLuCwaBN2O8crsj+kxx3mM6FlY4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IomZVF8m; 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="IomZVF8m" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D8FD1F000E9; Mon, 24 Aug 2026 02:21:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787538074; bh=xNNDwMcimuhvgxiiYj/oGzahS6NB1VtBfCB7+LyvfjA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=IomZVF8mJC6HHj7K5Os7pOl6opMUZZ07bCt//7g5suSakfPa7otDNd+Qi2uXbFAQ1 KN4oEURul09YlxWIFZhctT7/bGDjzFJI0QBIbub/4LRloM7IdYbJivff5k9uyUHXs/ zFl5YFhz1JXlljHXaDnoJ6jWbTKm4reni0vZHY42jmgoh4ANN0WwmzbdIgU3wcCzZT zjCvhkUGYbwgUxkTqk/7yR10tjKOkOA1qj8Z5Itm0Z0HK81yKk71FzCCSrI2BexkhX lwliY4SXyQPhMD6/eeAz46xQdlScYcGeIlH+jEOBmGiTqEEGU8I4ZZZXnUd/jkRtix yNdnxryXqM5qg== From: Geliang Tang To: mptcp@lists.linux.dev Cc: Geliang Tang Subject: [PATCH mptcp-next v7 8/8] selftests: mptcp: sockopt: check app_limited Date: Mon, 24 Aug 2026 10:20:43 +0800 Message-ID: X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Geliang Tang connect_one_server() in mptcp_sockopt exchanges only a few packets between the client and server, then closes the socket. After such a small transfer the application has nothing further to send, so the connection is, by definition, application-limited. Extend the TCP_INFO readback at the end of the function to assert s.tcp_info.tcpi_delivery_rate_app_limited =3D=3D 1. Without the preceding commit, mptcp_sendmsg() never updates the per-subflow app-limited state, and this field stays at 0 - the assertion would fail. With it in place, the value is forced to 1, turning this into a regression guard for the subflow-side application-limited accounting. Signed-off-by: Geliang Tang --- tools/testing/selftests/net/mptcp/mptcp_sockopt.c | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c b/tools/test= ing/selftests/net/mptcp/mptcp_sockopt.c index d68515b7903b..8d712bdb4325 100644 --- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c +++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c @@ -640,6 +640,7 @@ static void connect_one_server(int fd, int pipefd) total +=3D 1; /* sequence advances due to FIN */ =20 assert(s.mptcpi_rcv_delta =3D=3D (uint64_t)total); + assert(s.tcp_info.tcpi_delivery_rate_app_limited =3D=3D 1); close(fd); } =20 --=20 2.53.0