Our documentation is saying that the in-kernel PM is only using fullmesh
endpoints to establish subflows to announced addresses when at least one
endpoint has a fullmesh flag. But this was not totally correct: only
fullmesh endpoints were used if at least one endpoint *from the same
address family as the received ADD_ADDR* has the fullmesh flag.

This is confusing, and it seems clearer not to have differences
depending on the address family.

So, now, when at least one MPTCP endpoint has a fullmesh flag, the local
addresses are picked from all fullmesh endpoints, which might be 0 if
there are no endpoints for the correct address family.

One selftest needs to be adapted for this behaviour change.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_kernel.c                           | 10 +++-------
 tools/testing/selftests/net/mptcp/mptcp_join.sh |  6 +++++-
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c
index 054d85045381..40a0572b3149 100644
--- a/net/mptcp/pm_kernel.c
+++ b/net/mptcp/pm_kernel.c
@@ -609,15 +609,11 @@ fill_local_addresses_vec(struct mptcp_sock *msk, struct mptcp_addr_info *remote,
 			 struct mptcp_pm_local *locals)
 {
 	bool c_flag_case = remote->id && mptcp_pm_add_addr_c_flag_case(msk);
-	int i;
 
 	/* If there is at least one MPTCP endpoint with a fullmesh flag */
-	if (mptcp_pm_get_endp_fullmesh_max(msk)) {
-		i = fill_local_addresses_vec_fullmesh(msk, remote, locals,
-						      c_flag_case);
-		if (i)
-			return i;
-	}
+	if (mptcp_pm_get_endp_fullmesh_max(msk))
+		return fill_local_addresses_vec_fullmesh(msk, remote, locals,
+							 c_flag_case);
 
 	/* If there is at least one MPTCP endpoint with a laminar flag */
 	if (mptcp_pm_get_endp_laminar_max(msk))
diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 78a1aa4ecff2..e7a498dd5a46 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -2952,7 +2952,11 @@ mixed_tests()
 		pm_nl_add_endpoint $ns1 10.0.1.1 flags signal
 		speed=slow \
 			run_tests $ns1 $ns2 dead:beef:2::1
-		chk_join_nr 1 1 1
+		if mptcp_lib_kallsyms_has "mptcp_pm_get_endp_fullmesh_max$"; then
+			chk_join_nr 0 0 0
+		else
+			chk_join_nr 1 1 1
+		fi
 	fi
 
 	# fullmesh still tries to create all the possibly subflows with

-- 
2.51.0