If the subflow is considered as "staled", it is better to avoid it to
send an ACK carrying an ADD_ADDR or RM_ADDR. Another subflow, if any,
will then be selected.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_netlink.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index db586a5b3866f66a24431d7f2cab566f89102885..618289aac0ab7f558d55d8b2ebb00dc62fc72f88 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -781,7 +781,7 @@ bool mptcp_pm_nl_is_init_remote_addr(struct mptcp_sock *msk,
 
 void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
 {
-	struct mptcp_subflow_context *subflow;
+	struct mptcp_subflow_context *subflow, *alt = NULL;
 
 	msk_owned_by_me(msk);
 	lockdep_assert_held(&msk->pm.lock);
@@ -792,10 +792,18 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
 
 	mptcp_for_each_subflow(msk, subflow) {
 		if (__mptcp_subflow_active(subflow)) {
-			mptcp_pm_send_ack(msk, subflow, false, false);
-			break;
+			if (!subflow->stale) {
+				mptcp_pm_send_ack(msk, subflow, false, false);
+				return;
+			}
+
+			if (!alt)
+				alt = subflow;
 		}
 	}
+
+	if (alt)
+		mptcp_pm_send_ack(msk, alt, false, false);
 }
 
 int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,

-- 
2.45.2