[PATCH 5.10.y 1/3] mptcp: track and update contiguous data status

["Matthieu Baerts (NGI0)" <matttbe@kernel.org>]

From: Geliang Tang <geliang.tang@suse.com>

commit 0530020a7c8f2204e784f0dbdc882bbd961fdbde upstream.

This patch adds a new member allow_infinite_fallback in mptcp_sock,
which is initialized to 'true' when the connection begins and is set
to 'false' on any retransmit or successful MP_JOIN. Only do infinite
mapping fallback if there is a single subflow AND there have been no
retransmissions AND there have never been any MP_JOINs.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: e32d262c89e2 ("mptcp: handle consistently DSS corruption")
[ Conflicts in protocol.c, because commit 3e5014909b56 ("mptcp: cleanup
  MPJ subflow list handling") is not in this version. This commit is
  linked to a new feature, changing the context around. The new line
  can still be added at the same place.
  Conflicts in protocol.h, because commit 4f6e14bd19d6 ("mptcp: support
  TCP_CORK and TCP_NODELAY") is not in this version. This commit is
  linked to a new feature, changing the context around. The new line can
  still be added at the same place.
  Conflicts in subflow.c, because commit 0348c690ed37 ("mptcp: add the
  fallback check") is not in this version. This commit is linked to a
  new feature, changing the context around. The new line can still be
  added at the same place.
  Extra conflicts in v5.10, because the context has been changed. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 6 +++++-
 net/mptcp/protocol.h | 1 +
 net/mptcp/subflow.c  | 1 +
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 590e2c9bb67e..24a21ff0cb8a 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1810,9 +1810,11 @@ static void mptcp_worker(struct work_struct *work)
 		if (!mptcp_ext_cache_refill(msk))
 			break;
 	}
-	if (copied)
+	if (copied) {
 		tcp_push(ssk, msg.msg_flags, mss_now, tcp_sk(ssk)->nonagle,
 			 size_goal);
+		WRITE_ONCE(msk->allow_infinite_fallback, false);
+	}
 
 	dfrag->data_seq = orig_write_seq;
 	dfrag->offset = orig_offset;
@@ -1845,6 +1847,7 @@ static int __mptcp_init_sock(struct sock *sk)
 
 	msk->first = NULL;
 	inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss;
+	WRITE_ONCE(msk->allow_infinite_fallback, true);
 
 	mptcp_pm_data_init(msk);
 
@@ -2543,6 +2546,7 @@ bool mptcp_finish_join(struct sock *sk)
 	if (parent_sock && !sk->sk_socket)
 		mptcp_sock_graft(sk, parent_sock);
 	subflow->map_seq = READ_ONCE(msk->ack_seq);
+	WRITE_ONCE(msk->allow_infinite_fallback, false);
 	return true;
 }
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 44944e8f73c5..2330140d6b1c 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -213,6 +213,7 @@ struct mptcp_sock {
 	bool		rcv_data_fin;
 	bool		snd_data_fin_enable;
 	bool		use_64bit_ack; /* Set when we received a 64-bit DSN */
+	bool		allow_infinite_fallback;
 	spinlock_t	join_list_lock;
 	struct work_struct work;
 	struct sk_buff  *ooo_last_skb;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 843c61ebd421..0c020ca463f4 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1179,6 +1179,7 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
 	list_add_tail(&subflow->node, &msk->join_list);
 	spin_unlock_bh(&msk->join_list_lock);
 
+	WRITE_ONCE(msk->allow_infinite_fallback, false);
 	return err;
 
 failed:
-- 
2.45.2