[PATCH 6.1.y] mptcp: pm: update add_addr counters after connect

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

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 the selftests, in the same context, because the next line
  with 'run_tests' has been updated later by a few commits like commit
  e571fb09c893 ("selftests: mptcp: add speed env var"). We don't need to
  touch this line, nor to backport the long refactoring series. ]
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 7d9b41d7445b..3e2cbf0e6ce9 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -685,6 +685,7 @@ static void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
 	unsigned int add_addr_accept_max;
 	struct mptcp_addr_info remote;
 	unsigned int subflows_max;
+	bool sf_created = false;
 	int i, nr;
 
 	add_addr_accept_max = mptcp_pm_get_add_addr_accept_max(msk);
@@ -710,15 +711,18 @@ 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);
+	}
 }
 
 void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index e9744e31e6a0..51f68bb6bdb8 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -2343,10 +2343,10 @@ remove_tests()
 	if reset "remove invalid addresses"; then
 		pm_nl_set_limits $ns1 3 3
 		pm_nl_add_endpoint $ns1 10.0.12.1 flags signal
-		pm_nl_add_endpoint $ns1 10.0.3.1 flags signal
 		# broadcast IP: no packet for this address will be received on ns1
 		pm_nl_add_endpoint $ns1 224.0.0.1 flags signal
-		pm_nl_set_limits $ns2 3 3
+		pm_nl_add_endpoint $ns1 10.0.3.1 flags signal
+		pm_nl_set_limits $ns2 2 2
 		run_tests $ns1 $ns2 10.0.1.1 0 -3 0 speed_10
 		chk_join_nr 1 1 1
 		chk_add_nr 3 3
-- 
2.43.0