[PATCH mptcp-next v8 0/8] Reduce the differences between TCP and MPTCP for TLS usage

[PATCH mptcp-next v8 0/8] Reduce the differences between TCP and MPTCP for TLS usage

[Geliang Tang]

From: Geliang Tang <tanggeliang@kylinos.cn>

v8:
 - check MPTCP_SYNC_SEQ in mptcp_inq_hint:
       if (hint_val >= INT_MAX) {
               if (test_bit(MPTCP_SYNC_SEQ, &msk->cb_flags))
                       return 0;
               return INT_MAX;
       }
 - rename mptcp_sock_rate_check_app_limited to
   mptcp_rate_check_app_limited.

v7:
 - Patch 1 is a new one to fix the existing issue Sashiko mentioned -
   using atomic64_t for msk->ack_seq.
 - Fix the map_subflow_seq setting in fallback mode in patch 4.
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1787537436.git.tanggeliang@kylinos.cn/

v6:
 - Memory ordering for MPTCP_SYNC_SEQ: Add smp_wmb() before set_bit() in
   subflow_set_remote_key() and smp_rmb() after test_and_clear_bit() in
   __mptcp_move_skb() and mptcp_release_cb() to prevent data races on
   weakly-ordered architectures, ensuring ack_seq updates are visible
   before the flag is set and readers see the updated sequence after
   observing the flag.
 - Lockdep nested locking: Use lock_sock_fast_nested(ssk) instead of
   lock_sock_fast(ssk) in mptcp_sock_rate_check_app_limited() to suppress
   false positive recursive locking warnings when acquiring subflow socket
   locks while holding the parent MPTCP socket lock.
 - Receive window advertisement order: Swap mptcp_rcv_space_adjust() and
   mptcp_cleanup_rbuf() in mptcp_read_complete() to expand the receive
   buffer before evaluating window updates, ensuring ACKs advertise the
   new (larger) window size instead of delaying the advertisement until
   the next cycle.
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1787446274.git.tanggeliang@kylinos.cn/

v5:
 - only patch 3 changed.
 - Fallback offset underflow: Initialize MPTCP sequence space to 0 in
   mptcp_propagate_state() when mp_opt == NULL, ensuring SKB's map_seq
   starts from 0 to match msk->copied_seq and prevent offset calculation
   underflow in fallback mode.
 - Stale peek_seq: Move peek_seq recomputation into the mptcp_move_skbs()
   continue path and add another recomputation after sk_wait_data(),
   ensuring peek_seq stays synchronized with msk->copied_seq updates from
   MPTCP_SYNC_SEQ processing in both paths.
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1787368526.git.tanggeliang@kylinos.cn/

v4:
 - mptcp_recvmsg: move the peek_seq recompute from after sk_wait_data()
   to before the mptcp_move_skbs() continue check.
   mptcp_move_skbs() -> __mptcp_move_skb() may shift the head skb's
   map_seq to the IASN frame via __mptcp_sync_rcv_sequence(); if
   'continue' then exits the loop, the recompute is skipped, and the
   next __mptcp_recvmsg_mskq() computes offset with peek_seq in the old
   frame minus map_seq in the new frame. The underflow makes the offset
   test fail and the skb is skipped (and mptcp_recv_skb() actually frees
   the TFO skb via mptcp_eat_recv_skb()).
 - Make all three MPTCP_SYNC_SEQ bit accesses atomic:
   - subflow_set_remote_key:   __set_bit            -> set_bit
   - __mptcp_move_skb:         __test_and_clear_bit -> test_and_clear_bit
   - mptcp_release_cb:         __test_and_clear_bit -> test_and_clear_bit
   The flag is set in BH under mptcp_data_lock() (msk slock held) and
   cleared in user context under lock_sock() slow path (only owned=1,
   slock not held). The non-atomic RMW on the two sides races, which can
   lose the IASN sync.
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1787295147.git.tanggeliang@kylinos.cn/

v3:
 - Patch 2, handle "offset" in __mptcp_sync_rcv_sequence().
 - Patch 3, update __mptcp_move_skb() in response to Sashiko comments:

 	if (__test_and_clear_bit(MPTCP_SYNC_SEQ, &msk->cb_flags))
		msk->copied_seq += mptcp_iasn(msk);

 - Patch 4, replace after64() to after() in mptcp_prune_ofo_queue(). The
   pre-existing issue raised by Sashiko regarding changing the type of
   ack_seq to atomic64_t is not addressed in this series.
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1786445142.git.tanggeliang@kylinos.cn/

v2:
 - Patch 3, updated in response to Sashiko comments:

        if (unlikely(msk->rcvd_dummy_seq)) {
                msk->copied_seq += mptcp_iasn(msk);
                __mptcp_sync_rcv_sequence(sk);
                /* Release cb() would otherwise re-base copied_seq
                 * again.
                 */
                test_and_clear_bit(MPTCP_SYNC_SEQ, &msk->cb_flags);
        }

        /* Skip the already peeked data. */
        if (offset >= skb->len) {
                *last = skb;
                continue;
        }
 - Patch 5, replaced with Paolo's patch.
 - Patch 6, 7, new patches addressing app-limited conditions.
 - The patch "trim the duplicated skb head at receive enqueue" has been
   dropped, as it is no longer needed after Paolo updated the "mptcp:
   out-of-order queue pruning" series.
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1786158416.git.tanggeliang@kylinos.cn/

v1:
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1785150300.git.tanggeliang@kylinos.cn/

The goal of this series is to reduce the differences between TCP and MPTCP
for TLS usage, in preparation for adding TLS over MPTCP support in the
future.

In previous versions [1], a struct tls_prot_ops was defined to represent
the interface differences between TCP and MPTCP, which contained the
following callbacks:

	struct sk_buff *(*recv_skb)(struct sock *sk, u32 *off);
	bool (*lock_is_held)(struct sock *sk);
	void (*read_done)(struct sock *sk, size_t len);
	u32 (*get_skb_seq)(struct sk_buff *skb);
	int (*skb_get_header)(const struct sk_buff *skb, int offset,
	                      void *to, int len);
	bool (*epollin_ready)(const struct sock *sk);
	void (*check_app_limited)(struct sock *sk);

In reality, some of these callbacks are unnecessary. This series aims to
eliminate the get_skb_seq(), skb_get_header(), and lock_is_held()
callbacks.

The first four patches come from Paolo's "mptcp: address stall under memory
pressure" series v5 [2], with only minor cleanup from my side.

They remove the CB offset field and sync the MPTCP skb CB layout with the
TCP one, so that we can obtain the TCP or MPTCP sequence number in a
unified way, e.g.:

	struct tls_skb_cb {
	    u32 seq;
	};

	#define TLS_SKB_CB(__skb) ((struct tls_skb_cb *)&((__skb)->cb[0]))

This eliminates the need for a separate get_skb_seq() callback.

Building on the removal of the CB offset field, I also added patch 5 that
trims the duplicated skb head at receive enqueue. With that in place, KTLS
can retrieve the record header via skb_copy_bits() directly, so there is no
longer any need for a dedicated MPTCP helper like mptcp_skb_get_header().
The skb_get_header() callback can thus be removed.

Patch 6 defers sk_data_ready to the worker, which avoids recursive locking
when TLS calls back into MPTCP under mptcp_data_lock(). With this change,
the lock_is_held() callback is no longer needed and can be removed.

[1]
https://patchwork.kernel.org/project/mptcp/cover/cover.1782123118.git.tanggeliang@kylinos.cn/
[2]
https://patchwork.kernel.org/project/mptcp/cover/cover.1778446731.git.pabeni@redhat.com/

Geliang Tang (3):
  mptcp: use atomic64_t for msk->ack_seq
  mptcp: track app-limited state in mptcp_sendmsg
  selftests: mptcp: sockopt: check app_limited

Paolo Abeni (5):
  mptcp: drop the mptcp_ooo_try_coalesce() helper
  mptcp: drop the cant_coalesce CB field
  mptcp: remove CB offset field
  mptcp: sync mptcp skb cb layout with tcp one
  mptcp: defer read_sock cleanup to mptcp_worker

 include/net/tcp.h                             |   1 +
 include/trace/events/mptcp.h                  |   4 +-
 net/ipv4/tcp.c                                |   9 +-
 net/mptcp/fastopen.c                          |  17 +-
 net/mptcp/options.c                           |   5 +-
 net/mptcp/protocol.c                          | 288 +++++++++++-------
 net/mptcp/protocol.h                          |  24 +-
 net/mptcp/sockopt.c                           |   2 +-
 net/mptcp/subflow.c                           |  26 +-
 .../selftests/net/mptcp/mptcp_sockopt.c       |   1 +
 10 files changed, 250 insertions(+), 127 deletions(-)

-- 
2.53.0

[PATCH mptcp-next v8 1/8] mptcp: use atomic64_t for msk->ack_seq

[Geliang Tang]

From: Geliang Tang <tanggeliang@kylinos.cn>

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 <tanggeliang@kylinos.cn>
---
 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 = RB_EMPTY_ROOT(&msk->out_of_order_queue);
 		__entry->ooo_space = ofo_empty ? 0 :
 				     MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq -
-				     msk->ack_seq;
+				     atomic64_read(&msk->ack_seq);
 
 		__entry->rcvbuf = sk->sk_rcvbuf;
 		__entry->rcv_wnd = atomic64_read(&msk->rcv_wnd_sent) -
-				   msk->ack_seq;
+				   atomic64_read(&msk->ack_seq);
 		__entry->scaling_ratio = msk->scaling_ratio;
 		__entry->sport = ntohs(inet->inet_sport);
 		__entry->dport = 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;
 
 	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);
 
 	return true;
@@ -1539,7 +1540,7 @@ void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
 			 */
 			subflow = mptcp_subflow_ctx(ssk);
 			msk = mptcp_sk(subflow->conn);
-			ack_seq = READ_ONCE(msk->ack_seq);
+			ack_seq = atomic64_read(&msk->ack_seq);
 			if (mpext->ack64) {
 				put_unaligned_be64(ack_seq, ptr);
 				ptr += 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 = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq;
 	struct mptcp_sock *msk = mptcp_sk(sk);
 	struct sk_buff *tail;
+	u64 ack_seq;
 
 	mptcp_borrow_fwdmem(sk, skb);
 
-	if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) {
+	ack_seq = atomic64_read(&msk->ack_seq);
+	if (MPTCP_SKB_CB(skb)->map_seq == 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)
 		}
 
 		msk->bytes_received += copy_len;
-		WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len);
+		atomic64_add(copy_len, &msk->ack_seq);
 		tail = 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;
 	}
 
 	/* Partial packet */
-	if (after64(MPTCP_SKB_CB(skb)->end_seq, msk->ack_seq)) {
-		copy_len = MPTCP_SKB_CB(skb)->end_seq - msk->ack_seq;
-		MPTCP_SKB_CB(skb)->offset += msk->ack_seq -
+	if (after64(MPTCP_SKB_CB(skb)->end_seq, ack_seq)) {
+		copy_len = MPTCP_SKB_CB(skb)->end_seq - ack_seq;
+		MPTCP_SKB_CB(skb)->offset += ack_seq -
 					     MPTCP_SKB_CB(skb)->map_seq;
-		MPTCP_SKB_CB(skb)->map_seq += msk->ack_seq -
+		MPTCP_SKB_CB(skb)->map_seq += 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 = READ_ONCE(msk->rcv_data_fin_seq);
 
-		if (READ_ONCE(msk->ack_seq) == rcv_data_fin_seq) {
+		if (atomic64_read(&msk->ack_seq) == rcv_data_fin_seq) {
 			if (seq)
 				*seq = rcv_data_fin_seq;
 
@@ -710,7 +712,7 @@ static void mptcp_check_data_fin(struct sock *sk)
 	 */
 
 	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);
 
 		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 = (struct sock *)msk;
 	struct sk_buff *skb, *tail;
+	u64 end_seq, ack_seq;
 	bool moved = false;
 	struct rb_node *p;
-	u64 end_seq;
 
 	p = rb_first(&msk->out_of_order_queue);
 	pr_debug("msk=%p empty=%d\n", msk, RB_EMPTY_ROOT(&msk->out_of_order_queue));
 	while (p) {
+		ack_seq = atomic64_read(&msk->ack_seq);
 		skb = 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;
 
 		p = rb_next(p);
 		rb_erase(&skb->rbnode, &msk->out_of_order_queue);
 
-		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 = MPTCP_SKB_CB(skb)->end_seq;
 		tail = skb_peek_tail(&sk->sk_receive_queue);
 		if (!tail || !mptcp_ooo_try_coalesce(msk, tail, skb)) {
-			int delta = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq;
+			int delta = ack_seq - MPTCP_SKB_CB(skb)->map_seq;
 
 			/* skip overlapping data, if any */
 			pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%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 += delta;
 			MPTCP_SKB_CB(skb)->map_seq += delta;
 			__skb_queue_tail(&sk->sk_receive_queue, skb);
 		}
-		msk->bytes_received += end_seq - msk->ack_seq;
-		WRITE_ONCE(msk->ack_seq, end_seq);
+		msk->bytes_received += end_seq - ack_seq;
+		atomic64_set(&msk->ack_seq, end_seq);
 		moved = true;
 	}
 	return moved;
@@ -1072,7 +1074,7 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk)
 
 static void mptcp_subflow_joined(struct mptcp_sock *msk, struct sock *ssk)
 {
-	mptcp_subflow_ctx(ssk)->map_seq = READ_ONCE(msk->ack_seq);
+	mptcp_subflow_ctx(ssk)->map_seq = atomic64_read(&msk->ack_seq);
 	msk->allow_infinite_fallback = 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)
 
 	skb = skb_peek(&sk->sk_receive_queue);
 	if (skb) {
-		u64 hint_val = READ_ONCE(msk->ack_seq) - MPTCP_SKB_CB(skb)->map_seq;
+		u64 hint_val = atomic64_read(&msk->ack_seq) -
+			       MPTCP_SKB_CB(skb)->map_seq;
 
 		if (hint_val >= INT_MAX)
 			return INT_MAX;
@@ -3678,7 +3681,7 @@ static int mptcp_disconnect(struct sock *sk, int flags)
 	mptcp_init_rtt_est(msk);
 
 	/* for fallback's sake */
-	WRITE_ONCE(msk->ack_seq, 0);
+	atomic64_set(&msk->ack_seq, 0);
 	atomic64_set(&msk->rcv_wnd_sent, 0);
 
 	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, struct mptcp_info *info)
 	mptcp_data_lock(sk);
 	info->mptcpi_last_ack_recv = jiffies_to_msecs(now - msk->last_ack_recv);
 	info->mptcpi_snd_una = msk->snd_una;
-	info->mptcpi_rcv_nxt = msk->ack_seq;
+	info->mptcpi_rcv_nxt = atomic64_read(&msk->ack_seq);
 	info->mptcpi_bytes_acked = 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 *msk,
 	subflow->map_seq = subflow->iasn;
 
 	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);
 	atomic64_set(&msk->rcv_wnd_sent, subflow->iasn);
 }
@@ -1198,7 +1198,8 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
 		data_len--;
 	}
 
-	map_seq = mptcp_expand_seq(READ_ONCE(msk->ack_seq), mpext->data_seq, mpext->dsn64);
+	map_seq = mptcp_expand_seq(atomic64_read(&msk->ack_seq),
+				   mpext->data_seq, mpext->dsn64);
 	WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);
 
 	if (subflow->map_valid) {
@@ -1386,7 +1387,7 @@ static bool subflow_check_data_avail(struct sock *ssk)
 		if (unlikely(!READ_ONCE(msk->can_ack)))
 			goto fallback;
 
-		old_ack = READ_ONCE(msk->ack_seq);
+		old_ack = atomic64_read(&msk->ack_seq);
 		ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
 		pr_debug("msk ack_seq=%llx subflow ack_seq=%llx\n", old_ack,
 			 ack_seq);
-- 
2.53.0

[PATCH mptcp-next v8 2/8] mptcp: drop the mptcp_ooo_try_coalesce() helper

[Geliang Tang]

From: Paolo Abeni <pabeni@redhat.com>

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 <geliang@kernel.org>
Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 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, struct sk_buff *to,
 {
 	int limit = READ_ONCE(sk->sk_rcvbuf);
 
-	if (unlikely(MPTCP_SKB_CB(to)->cant_coalesce) ||
+	if (MPTCP_SKB_CB(from)->map_seq != 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;
 }
 
-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 != 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 = list_last_entry(&msk->backlog_list, struct sk_buff, list);
 
-	if (tail && MPTCP_SKB_CB(skb)->map_seq == MPTCP_SKB_CB(tail)->end_seq &&
-	    ssk == tail->sk &&
+	if (tail && ssk == tail->sk &&
 	    __mptcp_try_coalesce(sk, tail, skb, &fragstolen, &delta)) {
 		skb->truesize -= delta;
 		kfree_skb_partial(skb, fragstolen);
@@ -904,7 +895,7 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk)
 
 		end_seq = MPTCP_SKB_CB(skb)->end_seq;
 		tail = 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 = ack_seq - MPTCP_SKB_CB(skb)->map_seq;
 
 			/* skip overlapping data, if any */
-- 
2.53.0

[PATCH mptcp-next v8 3/8] mptcp: drop the cant_coalesce CB field

[Geliang Tang]

From: Paolo Abeni <pabeni@redhat.com>

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 <geliang@kernel.org>
Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 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 mptcp_subflow_context *subf
 	MPTCP_SKB_CB(skb)->end_seq = 0;
 	MPTCP_SKB_CB(skb)->offset = 0;
 	MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp;
-	MPTCP_SKB_CB(skb)->cant_coalesce = 1;
 
 	mptcp_data_lock(sk);
 	DEBUG_NET_WARN_ON_ONCE(sock_owned_by_user_nocheck(sk));
 
+	mptcp_sk(sk)->rcvd_dummy_seq = 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, struct sk_buff *to,
 	int limit = READ_ONCE(sk->sk_rcvbuf);
 
 	if (MPTCP_SKB_CB(from)->map_seq != 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 = MPTCP_SKB_CB(skb)->map_seq + copy_len;
 	MPTCP_SKB_CB(skb)->offset = offset;
 	MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp;
-	MPTCP_SKB_CB(skb)->cant_coalesce = 0;
 
 	__skb_unlink(skb, &ssk->sk_receive_queue);
 
@@ -438,6 +436,28 @@ static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset,
 	skb_dst_drop(skb);
 }
 
+void __mptcp_sync_rcv_sequence(struct sock *sk)
+{
+	struct mptcp_sock *msk = 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 = false;
+	skb = skb_peek_tail(&sk->sk_receive_queue);
+	if (!skb)
+		return;
+
+	ack_seq = atomic64_read(&msk->ack_seq);
+	offset = MPTCP_SKB_CB(skb)->offset;
+	MPTCP_SKB_CB(skb)->map_seq = ack_seq - skb->len + offset;
+	MPTCP_SKB_CB(skb)->end_seq = ack_seq;
+}
+
 static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb)
 {
 	u64 copy_len = 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 sk_buff *skb)
 
 	mptcp_borrow_fwdmem(sk, skb);
 
+	/* 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 = atomic64_read(&msk->ack_seq);
 	if (MPTCP_SKB_CB(skb)->map_seq == 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);
+		}
 	}
 }
 
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
 
 struct mptcp_skb_cb {
 	u64 map_seq;
 	u64 end_seq;
 	u32 offset;
 	u8  has_rxtstamp;
-	u8  cant_coalesce;
 };
 
 #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);
 
+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 *msk,
 				   struct mptcp_subflow_context *subflow,
 				   const struct mptcp_options_received *mp_opt)
 {
+	struct sock *sk = (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);
+	}
 }
 
 static void mptcp_propagate_state(struct sock *sk, struct sock *ssk,
-- 
2.53.0

[PATCH mptcp-next v8 4/8] mptcp: remove CB offset field

[Geliang Tang]

From: Paolo Abeni <pabeni@redhat.com>

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 <geliang@kernel.org>
Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/fastopen.c |  15 ++++--
 net/mptcp/protocol.c | 115 +++++++++++++++++++++----------------------
 net/mptcp/protocol.h |   9 +++-
 net/mptcp/subflow.c  |   9 ++++
 4 files changed, 83 insertions(+), 65 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 mptcp_subflow_context *subf
 	subflow->ssn_offset += skb->len;
 	has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp;
 
-	/* Only the sequence delta is relevant */
-	MPTCP_SKB_CB(skb)->map_seq = -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 = -(u64)skb->len;
 	MPTCP_SKB_CB(skb)->end_seq = 0;
-	MPTCP_SKB_CB(skb)->offset = 0;
 	MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp;
 
 	mptcp_data_lock(sk);
 	DEBUG_NET_WARN_ON_ONCE(sock_owned_by_user_nocheck(sk));
 
-	mptcp_sk(sk)->rcvd_dummy_seq = true;
+	msk = mptcp_sk(sk);
+	msk->rcvd_dummy_seq = true;
+	msk->copied_seq = MPTCP_SKB_CB(skb)->map_seq;
+	msk->tfo_skb_len = 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 += skb->len;
+	msk->bytes_received += skb->len;
 
 	sk->sk_data_ready(sk);
 
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index c23046b1e51b..d5fc88337054 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -29,7 +29,7 @@
 #include "protocol.h"
 #include "mib.h"
 
-static unsigned int mptcp_inq_hint(const struct sock *sk);
+static unsigned int mptcp_inq_hint(struct sock *sk);
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/mptcp.h>
@@ -168,7 +168,6 @@ static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to,
 	int limit = READ_ONCE(sk->sk_rcvbuf);
 
 	if (MPTCP_SKB_CB(from)->map_seq != 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);
 }
 
-static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset,
-			   int copy_len)
+static void mptcp_init_skb(struct sock *ssk, struct sk_buff *skb, int offset)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 	bool has_rxtstamp = 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 = mptcp_subflow_get_mapped_dsn(subflow);
-	MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + copy_len;
-	MPTCP_SKB_CB(skb)->offset = offset;
+	MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow) -
+				     offset;
+	MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + skb->len;
 	MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp;
 
 	__skb_unlink(skb, &ssk->sk_receive_queue);
@@ -440,8 +438,6 @@ void __mptcp_sync_rcv_sequence(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
 	struct sk_buff *skb;
-	u64 ack_seq;
-	u32 offset;
 
 	if (likely(!msk->rcvd_dummy_seq))
 		return;
@@ -452,10 +448,8 @@ void __mptcp_sync_rcv_sequence(struct sock *sk)
 	if (!skb)
 		return;
 
-	ack_seq = atomic64_read(&msk->ack_seq);
-	offset = MPTCP_SKB_CB(skb)->offset;
-	MPTCP_SKB_CB(skb)->map_seq = ack_seq - skb->len + offset;
-	MPTCP_SKB_CB(skb)->end_seq = ack_seq;
+	MPTCP_SKB_CB(skb)->map_seq = mptcp_iasn(msk) - skb->len;
+	MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + skb->len;
 }
 
 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 sk_buff *skb)
 
 	mptcp_borrow_fwdmem(sk, skb);
 
+	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 += 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 sk_buff *skb)
 	/* Partial packet */
 	if (after64(MPTCP_SKB_CB(skb)->end_seq, ack_seq)) {
 		copy_len = MPTCP_SKB_CB(skb)->end_seq - ack_seq;
-		MPTCP_SKB_CB(skb)->offset += ack_seq -
-					     MPTCP_SKB_CB(skb)->map_seq;
-		MPTCP_SKB_CB(skb)->map_seq += ack_seq -
-					      MPTCP_SKB_CB(skb)->map_seq;
 		goto insert;
 	}
 
@@ -861,7 +857,7 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 		if (offset < skb->len) {
 			size_t len = skb->len - offset;
 
-			mptcp_init_skb(ssk, skb, offset, len);
+			mptcp_init_skb(ssk, skb, offset);
 
 			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=%llx ack seq=%llx delta=%d\n",
 				 MPTCP_SKB_CB(skb)->map_seq, ack_seq,
 				 delta);
-			MPTCP_SKB_CB(skb)->offset += delta;
-			MPTCP_SKB_CB(skb)->map_seq += delta;
 			__skb_queue_tail(&sk->sk_receive_queue, skb);
 		}
 		msk->bytes_received += end_seq - ack_seq;
@@ -2203,33 +2197,24 @@ static void mptcp_eat_recv_skb(struct sock *sk, struct sk_buff *skb)
 }
 
 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 = mptcp_sk(sk);
 	struct sk_buff *skb, *tmp;
-	int total_data_len = 0;
 	int copied = 0;
 
 	skb_queue_walk_safe(&sk->sk_receive_queue, skb, tmp) {
-		u32 delta, offset = MPTCP_SKB_CB(skb)->offset;
+		u64 offset = *seq - MPTCP_SKB_CB(skb)->map_seq;
 		u32 data_len = skb->len - offset;
 		u32 count;
 		int err;
 
-		if (flags & MSG_PEEK) {
-			/* skip already peeked skbs */
-			if (total_data_len + data_len <= copied_total) {
-				total_data_len += data_len;
-				*last = skb;
-				continue;
-			}
-
-			/* skip the already peeked data in the current skb */
-			delta = copied_total - total_data_len;
-			offset += delta;
-			data_len -= delta;
+		/* Skip the already peeked data. */
+		if (offset >= skb->len) {
+			*last = skb;
+			continue;
 		}
 
 		count = min_t(size_t, len - copied, data_len);
@@ -2248,14 +2233,12 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg,
 		}
 
 		copied += count;
+		*seq += count;
 
 		if (!(flags & MSG_PEEK)) {
 			msk->bytes_consumed += count;
-			if (count < data_len) {
-				MPTCP_SKB_CB(skb)->offset += count;
-				MPTCP_SKB_CB(skb)->map_seq += count;
+			if (count < data_len)
 				break;
-			}
 
 			mptcp_eat_recv_skb(sk, skb);
 		} else {
@@ -2408,26 +2391,26 @@ static bool mptcp_move_skbs(struct sock *sk)
 	return enqueued;
 }
 
-static unsigned int mptcp_inq_hint(const struct sock *sk)
+static unsigned int mptcp_inq_hint(struct sock *sk)
 {
 	const struct mptcp_sock *msk = mptcp_sk(sk);
-	const struct sk_buff *skb;
+	u64 hint_val;
 
-	skb = skb_peek(&sk->sk_receive_queue);
-	if (skb) {
-		u64 hint_val = atomic64_read(&msk->ack_seq) -
-			       MPTCP_SKB_CB(skb)->map_seq;
-
-		if (hint_val >= INT_MAX)
-			return INT_MAX;
-
-		return (unsigned int)hint_val;
+	/* Avoid races vs ack_seq updates. */
+	mptcp_data_lock(sk);
+	hint_val = atomic64_read(&msk->ack_seq) - msk->copied_seq;
+	mptcp_data_unlock(sk);
+	if (hint_val >= INT_MAX) {
+		if (test_bit(MPTCP_SYNC_SEQ, &msk->cb_flags))
+			return 0;
+		return INT_MAX;
 	}
 
-	if (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN))
+	if (!hint_val &&
+	    (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN)))
 		return 1;
 
-	return 0;
+	return (unsigned int)hint_val;
 }
 
 static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
@@ -2436,6 +2419,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 	struct mptcp_sock *msk = mptcp_sk(sk);
 	struct scm_timestamping_internal tss;
 	int copied = 0, cmsg_flags = 0;
+	u64 peek_seq, *seq;
 	int target;
 	long timeo;
 
@@ -2454,6 +2438,11 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 
 	len = min_t(size_t, len, INT_MAX);
 	target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
+	seq = &msk->copied_seq;
+	if (flags & MSG_PEEK) {
+		peek_seq = msk->copied_seq;
+		seq = &peek_seq;
+	}
 
 	if (unlikely(msk->recvmsg_inq))
 		cmsg_flags = MPTCP_CMSG_INQ;
@@ -2463,7 +2452,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 		int err, bytes_read;
 
 		bytes_read = __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 +2462,11 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 
 		copied += bytes_read;
 
-		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 = msk->copied_seq + copied;
 			continue;
+		}
 
 		/* only the MPTCP socket status is relevant here. The exit
 		 * conditions mirror closely tcp_recvmsg()
@@ -2518,6 +2510,10 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 			err = copied ? : err;
 			goto out_err;
 		}
+
+		/* Recompute peek offset after eventual seq resync. */
+		if (flags & MSG_PEEK)
+			peek_seq = msk->copied_seq + copied;
 	}
 
 	mptcp_cleanup_rbuf(msk, copied);
@@ -3695,11 +3691,13 @@ static int mptcp_disconnect(struct sock *sk, int flags)
 	msk->bytes_retrans = 0;
 	msk->rcvspace_init = 0;
 	msk->fastclosing = 0;
+	msk->tfo_skb_len = 0;
 	mptcp_init_rtt_est(msk);
 
 	/* for fallback's sake */
 	atomic64_set(&msk->ack_seq, 0);
 	atomic64_set(&msk->rcv_wnd_sent, 0);
+	msk->copied_seq = 0;
 
 	WRITE_ONCE(sk->sk_shutdown, 0);
 	sk_error_report(sk);
@@ -3929,6 +3927,7 @@ static void mptcp_release_cb(struct sock *sk)
 			 * the flag
 			 */
 			smp_rmb();
+			msk->copied_seq += mptcp_iasn(msk);
 			__mptcp_sync_rcv_sequence(sk);
 		}
 	}
@@ -4593,7 +4592,7 @@ static struct sk_buff *mptcp_recv_skb(struct sock *sk, u32 *off)
 		mptcp_move_skbs(sk);
 
 	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
-		offset = MPTCP_SKB_CB(skb)->offset;
+		offset = msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq;
 		if (offset < skb->len) {
 			*off = offset;
 			return skb;
@@ -4635,11 +4634,9 @@ static int __mptcp_read_sock(struct sock *sk, read_descriptor_t *desc,
 		copied += count;
 
 		msk->bytes_consumed += count;
-		if (count < data_len) {
-			MPTCP_SKB_CB(skb)->offset += count;
-			MPTCP_SKB_CB(skb)->map_seq += count;
+		msk->copied_seq += count;
+		if (count < data_len)
 			break;
-		}
 
 		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;
 };
 
@@ -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_sock *msk);
 int mptcp_sched_get_send(struct mptcp_sock *msk);
 int mptcp_sched_get_retrans(struct mptcp_sock *msk);
 
+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 *msk,
 	atomic64_set(&msk->rcv_wnd_sent, subflow->iasn);
 
 	if (!sock_owned_by_user(sk)) {
+		/* User space could have already read partially the TFO skb */
+		msk->copied_seq += subflow->iasn;
 		__mptcp_sync_rcv_sequence(sk);
 	} else {
 		/* Ensure ack_seq is visible before setting the flag */
@@ -520,6 +522,13 @@ static void mptcp_propagate_state(struct sock *sk, struct sock *ssk,
 		WRITE_ONCE(msk->snd_una, subflow->idsn + 1);
 		WRITE_ONCE(msk->wnd_end, subflow->idsn + 1 + tcp_sk(ssk)->snd_wnd);
 		subflow_set_remote_key(msk, subflow, mp_opt);
+	} else {
+		/* Fallback: initialize sequence space to 0 (no remote key) */
+		subflow->map_seq = 0;
+		/* ensure mptcp_subflow_get_map_offset() returns 0 */
+		subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq -
+					   subflow->ssn_offset;
+		atomic64_set(&msk->ack_seq, 0);
 	}
 
 	if (!sock_owned_by_user(sk)) {
-- 
2.53.0

[PATCH mptcp-next v8 5/8] mptcp: sync mptcp skb cb layout with tcp one

[Geliang Tang]

From: Paolo Abeni <pabeni@redhat.com>

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 <geliang@kernel.org>
Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 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 mptcp_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 = -(u64)skb->len;
+	MPTCP_SKB_CB(skb)->map_seq64 = -(u64)skb->len;
+	MPTCP_SKB_CB(skb)->map_seq = MPTCP_SKB_CB(skb)->map_seq64;
 	MPTCP_SKB_CB(skb)->end_seq = 0;
+	MPTCP_SKB_CB(skb)->flags = 0;
 	MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp;
 
 	mptcp_data_lock(sk);
@@ -57,7 +59,7 @@ void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subf
 
 	msk = mptcp_sk(sk);
 	msk->rcvd_dummy_seq = true;
-	msk->copied_seq = MPTCP_SKB_CB(skb)->map_seq;
+	msk->copied_seq = MPTCP_SKB_CB(skb)->map_seq64;
 	msk->tfo_skb_len = 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 d5fc88337054..d0425ba96ad5 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -172,7 +172,7 @@ static bool __mptcp_try_coalesce(struct sock *sk, struct sk_buff *to,
 	    !skb_try_coalesce(to, from, fragstolen, delta))
 		return false;
 
-	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 = MPTCP_SKB_CB(from)->end_seq;
@@ -254,8 +254,8 @@ static void mptcp_prune_ofo_queue(struct sock *sk,
 		struct sk_buff *skb = rb_to_skb(node);
 
 		/* 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;
 
 		pruned = true;
@@ -301,15 +301,19 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb)
 {
 	struct sock *sk = (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;
 
 	seq = MPTCP_SKB_CB(skb)->map_seq;
-	end_seq = MPTCP_SKB_CB(skb)->end_seq;
+	end_seq = MPTCP_SKB_CB(skb)->map_seq64 + skb->len;
 	max_seq = atomic64_read(&msk->rcv_wnd_sent);
 
-	pr_debug("msk=%p seq=%llx limit=%llx empty=%d\n", msk, seq, max_seq,
+	pr_debug("msk=%p seq=%x limit=%llx empty=%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)
 	}
 
 	/* 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 = &msk->ooo_last_skb->rbnode;
 		p = &parent->rb_right;
@@ -357,18 +361,18 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb)
 	while (*p) {
 		parent = *p;
 		skb1 = rb_to_skb(parent);
-		if (before64(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
+		if (before(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
 			p = &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 = skb_rb_next(skb)) != 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 sk_buff *skb, int offset)
 
 	/* 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 = mptcp_subflow_get_mapped_dsn(subflow) -
-				     offset;
+	MPTCP_SKB_CB(skb)->map_seq64 = mptcp_subflow_get_mapped_dsn(subflow) -
+				       offset;
+	MPTCP_SKB_CB(skb)->map_seq = (u32)MPTCP_SKB_CB(skb)->map_seq64;
 	MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + skb->len;
+	MPTCP_SKB_CB(skb)->flags = 0;
 	MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp;
 
 	__skb_unlink(skb, &ssk->sk_receive_queue);
@@ -448,13 +454,14 @@ void __mptcp_sync_rcv_sequence(struct sock *sk)
 	if (!skb)
 		return;
 
-	MPTCP_SKB_CB(skb)->map_seq = mptcp_iasn(msk) - skb->len;
+	MPTCP_SKB_CB(skb)->map_seq64 = mptcp_iasn(msk) - skb->len;
+	MPTCP_SKB_CB(skb)->map_seq = (u32)MPTCP_SKB_CB(skb)->map_seq64;
 	MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + skb->len;
 }
 
 static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb)
 {
-	u64 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq;
+	u32 copy_len = MPTCP_SKB_CB(skb)->end_seq - MPTCP_SKB_CB(skb)->map_seq;
 	struct mptcp_sock *msk = 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);
 
 	ack_seq = atomic64_read(&msk->ack_seq);
-	if (MPTCP_SKB_CB(skb)->map_seq == ack_seq) {
+	if (MPTCP_SKB_CB(skb)->map_seq64 == 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;
 	}
 
 	/* Partial packet */
-	if (after64(MPTCP_SKB_CB(skb)->end_seq, ack_seq)) {
-		copy_len = MPTCP_SKB_CB(skb)->end_seq - ack_seq;
+	if (after64(MPTCP_SKB_CB(skb)->map_seq64 + skb->len, ack_seq)) {
+		copy_len = MPTCP_SKB_CB(skb)->end_seq - (u32)ack_seq;
 		goto insert;
 	}
 
@@ -894,40 +901,40 @@ static bool __mptcp_ofo_queue(struct mptcp_sock *msk)
 {
 	struct sock *sk = (struct sock *)msk;
 	struct sk_buff *skb, *tail;
-	u64 end_seq, ack_seq;
+	u32 seq_delta, ack_seq;
 	bool moved = false;
 	struct rb_node *p;
 
 	p = rb_first(&msk->out_of_order_queue);
 	pr_debug("msk=%p empty=%d\n", msk, RB_EMPTY_ROOT(&msk->out_of_order_queue));
 	while (p) {
-		ack_seq = atomic64_read(&msk->ack_seq);
+		ack_seq = (u32)atomic64_read(&msk->ack_seq);
 		skb = 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;
 
 		p = rb_next(p);
 		rb_erase(&skb->rbnode, &msk->out_of_order_queue);
 
-		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;
 		}
 
-		end_seq = MPTCP_SKB_CB(skb)->end_seq;
+		seq_delta = MPTCP_SKB_CB(skb)->end_seq - ack_seq;
 		tail = skb_peek_tail(&sk->sk_receive_queue);
 		if (!tail || !mptcp_try_coalesce(sk, tail, skb)) {
 			int delta = ack_seq - MPTCP_SKB_CB(skb)->map_seq;
 
 			/* skip overlapping data, if any */
-			pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%d\n",
+			pr_debug("uncoalesced seq=%x ack seq=%x delta=%d\n",
 				 MPTCP_SKB_CB(skb)->map_seq, ack_seq,
 				 delta);
 			__skb_queue_tail(&sk->sk_receive_queue, skb);
 		}
-		msk->bytes_received += end_seq - ack_seq;
-		atomic64_set(&msk->ack_seq, end_seq);
+		msk->bytes_received += seq_delta;
+		atomic64_add(seq_delta, &msk->ack_seq);
 		moved = true;
 	}
 	return moved;
@@ -2206,7 +2213,7 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg,
 	int copied = 0;
 
 	skb_queue_walk_safe(&sk->sk_receive_queue, skb, tmp) {
-		u64 offset = *seq - MPTCP_SKB_CB(skb)->map_seq;
+		u32 offset = (u32)(*seq) - MPTCP_SKB_CB(skb)->map_seq;
 		u32 data_len = skb->len - offset;
 		u32 count;
 		int err;
@@ -4592,7 +4599,7 @@ static struct sk_buff *mptcp_recv_skb(struct sock *sk, u32 *off)
 		mptcp_move_skbs(sk);
 
 	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
-		offset = msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq;
+		offset = (u32)msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq;
 		if (offset < skb->len) {
 			*off = offset;
 			return skb;
@@ -4843,11 +4850,23 @@ static int mptcp_napi_poll(struct napi_struct *napi, int budget)
 	return work_done;
 }
 
+#define CHK_CB_FIELD(mptcp_field, tcp_field)	\
+	({					\
+		BUILD_BUG_ON(offsetof(struct mptcp_skb_cb, mptcp_field) !=    \
+			     offsetof(struct tcp_skb_cb, tcp_field));	      \
+		BUILD_BUG_ON(offsetofend(struct mptcp_skb_cb, mptcp_field) != \
+			     offsetofend(struct tcp_skb_cb, tcp_field));      \
+	})
+
 void __init mptcp_proto_init(void)
 {
 	struct mptcp_delegated_action *delegated;
 	int cpu;
 
+	CHK_CB_FIELD(map_seq, seq);
+	CHK_CB_FIELD(end_seq, end_seq);
+	CHK_CB_FIELD(flags, tcp_flags);
+
 	mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo;
 
 	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
 
 struct mptcp_skb_cb {
-	u64 map_seq;
-	u64 end_seq;
+	u32 map_seq;
+	u32 end_seq;
+	u32 unused;
+	u16 flags;
 	u8  has_rxtstamp;
+	u64 map_seq64;
 };
 
 #define MPTCP_SKB_CB(__skb)	((struct mptcp_skb_cb *)&((__skb)->cb[0]))
-- 
2.53.0

[PATCH mptcp-next v8 6/8] mptcp: defer read_sock cleanup to mptcp_worker

[Geliang Tang]

From: Paolo Abeni <pabeni@redhat.com>

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 <geliang@kernel.org>
Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 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 d0425ba96ad5..623edce84b8b 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3141,6 +3141,15 @@ static void mptcp_backlog_purge(struct sock *sk)
 	sk_mem_reclaim(sk);
 }
 
+static void mptcp_read_complete(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	mptcp_rcv_space_adjust(msk, msk->read_copied);
+	mptcp_cleanup_rbuf(msk, msk->read_copied);
+	msk->read_copied = 0;
+}
+
 static void mptcp_do_fastclose(struct sock *sk)
 {
 	struct mptcp_subflow_context *subflow, *tmp;
@@ -3217,6 +3226,9 @@ static void mptcp_worker(struct work_struct *work)
 	if (test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
 		__mptcp_retrans(sk);
 
+	if (test_and_clear_bit(MPTCP_WORK_READ_COMPLETE, &msk->flags))
+		mptcp_read_complete(sk);
+
 	fail_tout = 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);
@@ -4595,9 +4607,6 @@ static struct sk_buff *mptcp_recv_skb(struct sock *sk, u32 *off)
 	struct sk_buff *skb;
 	u32 offset;
 
-	if (!list_empty(&msk->backlog_list))
-		mptcp_move_skbs(sk);
-
 	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
 		offset = (u32)msk->copied_seq - MPTCP_SKB_CB(skb)->map_seq;
 		if (offset < skb->len) {
@@ -4612,6 +4621,7 @@ 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)
@@ -4653,11 +4663,14 @@ static int __mptcp_read_sock(struct sock *sk, read_descriptor_t *desc,
 	if (noack)
 		goto out;
 
-	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 += 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
 
 /* 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;
-- 
2.53.0

[PATCH mptcp-next v8 7/8] mptcp: track app-limited state in mptcp_sendmsg

[Geliang Tang]

From: Geliang Tang <tanggeliang@kylinos.cn>

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 <tanggeliang@kylinos.cn>
---
 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 670c20876f26..f5cbb5a8a288 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)
 
 /* 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);
 
 /* 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 msghdr *msg, int *copied,
 }
 
 /* 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 = tcp_sk(sk);
+	struct sock *sk = (struct sock *)tp;
 
 	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 =
 			(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);
 
 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 623edce84b8b..8d72a62e0618 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2050,6 +2050,21 @@ static void mptcp_rps_record_subflows(const struct mptcp_sock *msk)
 	}
 }
 
+static void mptcp_rate_check_app_limited(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_subflow_context *subflow;
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow;
+
+		slow = 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 = mptcp_sk(sk);
@@ -2080,6 +2095,9 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
 
+	/* is sending application-limited? */
+	mptcp_rate_check_app_limited(sk);
+
 	if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
 		ret = sk_stream_wait_connect(sk, &timeo);
 		if (ret)
-- 
2.53.0

[PATCH mptcp-next v8 8/8] selftests: mptcp: sockopt: check app_limited

[Geliang Tang]

From: Geliang Tang <tanggeliang@kylinos.cn>

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 == 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 <tanggeliang@kylinos.cn>
---
 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/testing/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 += 1; /* sequence advances due to FIN */
 
 	assert(s.mptcpi_rcv_delta == (uint64_t)total);
+	assert(s.tcp_info.tcpi_delivery_rate_app_limited == 1);
 	close(fd);
 }
 
-- 
2.53.0

Re: [PATCH mptcp-next v8 6/8] mptcp: defer read_sock cleanup to mptcp_worker

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] Data Race
- [Medium] Lockdep Warning
--

--- Patch [6]: [PATCH mptcp-next v8 6/8] mptcp: defer read_sock cleanup to mptcp_worker ---
commit 428fada46f89f37bf4a52466b0f6ca0c4349248e
Author: Paolo Abeni <pabeni@redhat.com>

mptcp: defer read_sock cleanup to mptcp_worker

This commit defers MPTCP read socket cleanup to mptcp_worker() to prevent lock
recursion on sk_lock.slock. It introduces a new MPTCP_WORK_READ_COMPLETE bit,
allowing __mptcp_read_sock() to schedule cleanup asynchronously when invoked in
BH scope during TLS data processing.

> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index d0425ba96ad54..623edce84b8ba 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -3141,6 +3141,15 @@ static void mptcp_backlog_purge(struct sock *sk)
>  	sk_mem_reclaim(sk);
>  }
>  
> +static void mptcp_read_complete(struct sock *sk)
> +{
> +	struct mptcp_sock *msk = mptcp_sk(sk);
> +
> +	mptcp_rcv_space_adjust(msk, msk->read_copied);
> +	mptcp_cleanup_rbuf(msk, msk->read_copied);
> +	msk->read_copied = 0;

[Severity: High]
Could this result in a data race on msk->read_copied?

mptcp_read_complete() is called from mptcp_worker(), which holds lock_sock(sk)
but not the mptcp_data_lock() spinlock.

Meanwhile, __mptcp_read_sock() increments msk->read_copied in BH context where
it holds mptcp_data_lock() but not lock_sock(sk).

If both run concurrently, updates to msk->read_copied could be lost or
inconsistent.

> +}

[ ... ]

> @@ -4612,6 +4621,7 @@ 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)

[Severity: Medium]
Will this trigger a lockdep warning when invoked in BH scope?

Since __mptcp_read_sock() is now intended to run in BH scope without holding
lock_sock(sk), the existing msk_owned_by_me(msk) assertion at the beginning of
the function might fail when called from the TLS data path.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1787644449.git.tanggeliang@kylinos.cn?part=6

Re: [PATCH mptcp-next v8 1/8] mptcp: use atomic64_t for msk->ack_seq

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Torn reads on locklessly accessed `u64` variables (`bytes_received`, `bytes_consumed`, `write_seq`, `snd_nxt`) on 32-bit architectures.
--

--- Patch [1]: [PATCH mptcp-next v8 1/8] mptcp: use atomic64_t for msk->ack_seq ---
commit 6ecb7c718880f7f40ce17752ce61e7a9dfad9bea
Author: Geliang Tang <geliang@kernel.org>

mptcp: use atomic64_t for msk->ack_seq

This commit converts msk->ack_seq from u64 to atomic64_t to guarantee
tear-free accesses on all architectures. It also caches the atomic64_read()
value in local variables in __mptcp_move_skb() and __mptcp_ofo_queue()
to avoid inconsistent repeated reads.

> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index f22d64ab1c53b..88bdb65a9e87e 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -464,7 +466,7 @@ static bool __mptcp_move_skb(struct sock *sk, struct sk_buff *skb)
>  		}
>  
>  		msk->bytes_received += copy_len;
> -		WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len);
> +		atomic64_add(copy_len, &msk->ack_seq);

[Severity: High]
This isn't a bug introduced by this patch, but since it explicitly sets out
to fix 32-bit torn reads for msk->ack_seq, should the other 64-bit socket
state variables also be converted?

For example, msk->bytes_received is updated here using a plain non-atomic +=
operation, and it is read locklessly in mptcp_data_avail():

net/mptcp/protocol.h:mptcp_data_avail() {
	...
	return READ_ONCE(msk->bytes_received) - READ_ONCE(msk->bytes_consumed);
}

Similarly, write_seq and snd_nxt are read locklessly:

net/mptcp/protocol.h:mptcp_stream_memory_free() {
	...
	notsent_bytes = READ_ONCE(msk->write_seq) - READ_ONCE(msk->snd_nxt);
}

A torn read on these 64-bit variables can produce a massively incorrect
value. When a counter crosses a 4GB boundary (e.g., transitioning from
0x00000000FFFFFFFF to 0x0000000100000000), a concurrent 32-bit read might see
0x00000001FFFFFFFF. In mptcp_poll(), this could lead to incorrectly
calculated data_avail or notsent_bytes, causing spurious EPOLLIN/EPOLLOUT
events or missing events that permanently stall the connection.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1787644449.git.tanggeliang@kylinos.cn?part=1

Re: [PATCH mptcp-next v8 4/8] mptcp: remove CB offset field

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] mptcp_inq_hint() can return arbitrarily large, bogus values to userspace (via FIONREAD) due to a missing sequence sync check when the unread data length evaluates to less than INT_MAX, enabling a remotely triggerable Denial of Service.
--

--- Patch [4]: [PATCH mptcp-next v8 4/8] mptcp: remove CB offset field ---
commit f21bf73a134ec25916ac8358db183f0eea8d9925
Author: Paolo Abeni <pabeni@redhat.com>

mptcp: remove CB offset field

This commit introduces a new msk-level field to track the bytes already
consumed inside each skb, similar to TCP, instead of using a CB offset
field. It synchronizes sequence spaces and simplifies hint calculations
and buffer moves.

> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c

[ ... ]

> @@ -2408,26 +2391,26 @@ static bool mptcp_move_skbs(struct sock *sk)
>  	return enqueued;
>  }
>  
> -static unsigned int mptcp_inq_hint(const struct sock *sk)
> +static unsigned int mptcp_inq_hint(struct sock *sk)
>  {
>  	const struct mptcp_sock *msk = mptcp_sk(sk);
> -	const struct sk_buff *skb;
> +	u64 hint_val;
>  
> -	skb = skb_peek(&sk->sk_receive_queue);
> -	if (skb) {
> -		u64 hint_val = atomic64_read(&msk->ack_seq) -
> -			       MPTCP_SKB_CB(skb)->map_seq;
> -
> -		if (hint_val >= INT_MAX)
> -			return INT_MAX;
> -
> -		return (unsigned int)hint_val;
> +	/* Avoid races vs ack_seq updates. */
> +	mptcp_data_lock(sk);
> +	hint_val = atomic64_read(&msk->ack_seq) - msk->copied_seq;
> +	mptcp_data_unlock(sk);
> +	if (hint_val >= INT_MAX) {
> +		if (test_bit(MPTCP_SYNC_SEQ, &msk->cb_flags))
> +			return 0;
> +		return INT_MAX;
>  	}

[Severity: High]
Does this logic allow un-synced sequence lengths smaller than INT_MAX to
leak into userspace?

If a server application is actively reading data in recvmsg() (holding the
socket lock) and a remote attacker sends a third ACK with MP_CAPABLE, the
softirq defers updating copied_seq by setting the MPTCP_SYNC_SEQ bit.

Because the test_bit(MPTCP_SYNC_SEQ, ...) check is nested inside the
if (hint_val >= INT_MAX) block, an attacker could bypass the sync check by
crafting a sender_key such that the resulting hint_val is just under INT_MAX.

Could this return an arbitrarily large hint_val to userspace via FIONREAD
(TCP_INQ), potentially leading to massive application-level memory allocations
and rapid memory exhaustion?

>  
> -	if (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN))
> +	if (!hint_val &&
> +	    (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN)))
>  		return 1;
>  
> -	return 0;
> +	return (unsigned int)hint_val;
>  }
>  
>  static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1787644449.git.tanggeliang@kylinos.cn?part=4

Re: [PATCH mptcp-next v8 0/8] Reduce the differences between TCP and MPTCP for TLS usage

[MPTCP CI]

Hi Geliang,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Success! ✅
- KVM Validation: normal (only selftest_mptcp_join): Success! ✅
- KVM Validation: debug (except selftest_mptcp_join): Success! ✅
- KVM Validation: debug (only selftest_mptcp_join): Success! ✅
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/32825688610

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/415f8a01f452
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1151323


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)