From: YonglongLi <liyonglong@chinatelecom.cn>

commit 40eec1795cc27b076d49236649a29507c7ed8c2d upstream.

The creation of new subflows can fail for different reasons. If no
subflow have been created using the received ADD_ADDR, the related
counters should not be updated, otherwise they will never be decremented
for events related to this ID later on.

For the moment, the number of accepted ADD_ADDR is only decremented upon
the reception of a related RM_ADDR, and only if the remote address ID is
currently being used by at least one subflow. In other words, if no
subflow can be created with the received address, the counter will not
be decremented. In this case, it is then important not to increment
pm.add_addr_accepted counter, and not to modify pm.accept_addr bit.

Note that this patch does not modify the behaviour in case of failures
later on, e.g. if the MP Join is dropped or rejected.

The "remove invalid addresses" MP Join subtest has been modified to
validate this case. The broadcast IP address is added before the "valid"
address that will be used to successfully create a subflow, and the
limit is decreased by one: without this patch, it was not possible to
create the last subflow, because:

- the broadcast address would have been accepted even if it was not
  usable: the creation of a subflow to this address results in an error,

- the limit of 2 accepted ADD_ADDR would have then been reached.

Fixes: 01cacb00b35c ("mptcp: add netlink-based PM")
Cc: stable@vger.kernel.org
Co-developed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: YonglongLi <liyonglong@chinatelecom.cn>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240607-upstream-net-20240607-misc-fixes-v1-3-1ab9ddfa3d00@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Conflicts in pm_netlink.c because commit 12a18341b5c3 ("mptcp: send
  ADD_ADDR echo before create subflows") is not present in this version,
  and it changes the context, but not the block that needs to be moved.
  Conflicts in the selftests, because many features modifying the whole
  file have been added later, e.g. commit ae7bd9ccecc3 ("selftests:
  mptcp: join: option to execute specific tests"). The same
  modifications have been reported to the old code: simply moving one
  line, and changing the limits. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_netlink.c                          | 16 ++++++++++------
 tools/testing/selftests/net/mptcp/mptcp_join.sh |  4 ++--
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index d78ef96a88cc..7b312aa03e6b 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -608,6 +608,7 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 	struct mptcp_addr_info remote;
 	unsigned int subflows_max;
 	bool reset_port = false;
+	bool sf_created = false;
 	int i, nr;
 
 	add_addr_accept_max = mptcp_pm_get_add_addr_accept_max(msk);
@@ -632,16 +633,19 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 	 */
 	nr = fill_local_addresses_vec(msk, addrs);
 
-	msk->pm.add_addr_accepted++;
-	if (msk->pm.add_addr_accepted >= add_addr_accept_max ||
-	    msk->pm.subflows >= subflows_max)
-		WRITE_ONCE(msk->pm.accept_addr, false);
-
 	spin_unlock_bh(&msk->pm.lock);
 	for (i = 0; i < nr; i++)
-		__mptcp_subflow_connect(sk, &addrs[i], &remote);
+		if (__mptcp_subflow_connect(sk, &addrs[i], &remote) == 0)
+			sf_created = true;
 	spin_lock_bh(&msk->pm.lock);
 
+	if (sf_created) {
+		msk->pm.add_addr_accepted++;
+		if (msk->pm.add_addr_accepted >= add_addr_accept_max ||
+		    msk->pm.subflows >= subflows_max)
+			WRITE_ONCE(msk->pm.accept_addr, false);
+	}
+
 	/* be sure to echo exactly the received address */
 	if (reset_port)
 		remote.port = 0;
diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 3cf4f9f05956..e725285298a0 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1306,10 +1306,10 @@ remove_tests()
 	reset
 	ip netns exec $ns1 ./pm_nl_ctl limits 3 3
 	ip netns exec $ns1 ./pm_nl_ctl add 10.0.12.1 flags signal
-	ip netns exec $ns1 ./pm_nl_ctl add 10.0.3.1 flags signal
 	# broadcast IP: no packet for this address will be received on ns1
 	ip netns exec $ns1 ./pm_nl_ctl add 224.0.0.1 flags signal
-	ip netns exec $ns2 ./pm_nl_ctl limits 3 3
+	ip netns exec $ns1 ./pm_nl_ctl add 10.0.3.1 flags signal
+	ip netns exec $ns2 ./pm_nl_ctl limits 2 2
 	run_tests $ns1 $ns2 10.0.1.1 0 -3 0 slow
 	chk_join_nr "remove invalid addresses" 1 1 1
 	chk_add_nr 3 3
-- 
2.43.0