selftests: mptcp: join: skip mixed tests if not supported

Selftests are supposed to run on any kernels, including the old ones not
supporting all MPTCP features.

One of them is the support of a mix of subflows in v4 and v6 by the
in-kernel PM introduced by commit b9d69db ("mptcp: let the
in-kernel PM use mixed IPv4 and IPv6 addresses").

It looks like there is no external sign we can use to predict the
expected behaviour. Instead of accepting different behaviours and thus
not really checking for the expected behaviour, we are looking here for
a specific kernel version. That's not ideal but it looks better than
removing the test because it cannot support older kernel versions.

Link: multipath-tcp/mptcp_net-next#368
Fixes: ad34937 ("selftests: mptcp: add test-cases for mixed v4/v6 subflows")
Cc: stable@vger.kernel.org
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: matttbe

tools/testing/selftests/net/mptcp/mptcp_join.sh

@@ -2637,7 +2637,8 @@ v4mapped_tests()
 
 mixed_tests()
 {
-	if reset "IPv4 sockets do not use IPv6 addresses"; then
+	if reset "IPv4 sockets do not use IPv6 addresses" &&
+	   continue_if mptcp_lib_kversion_ge 6.3; then
 		pm_nl_set_limits $ns1 0 1
 		pm_nl_set_limits $ns2 1 1
 		pm_nl_add_endpoint $ns1 dead:beef:2::1 flags signal
@@ -2646,7 +2647,8 @@ mixed_tests()
 	fi
 
 	# Need an IPv6 mptcp socket to allow subflows of both families
-	if reset "simult IPv4 and IPv6 subflows"; then
+	if reset "simult IPv4 and IPv6 subflows" &&
+	   continue_if mptcp_lib_kversion_ge 6.3; then
 		pm_nl_set_limits $ns1 0 1
 		pm_nl_set_limits $ns2 1 1
 		pm_nl_add_endpoint $ns1 10.0.1.1 flags signal
@@ -2655,7 +2657,8 @@ mixed_tests()
 	fi
 
 	# cross families subflows will not be created even in fullmesh mode
-	if reset "simult IPv4 and IPv6 subflows, fullmesh 1x1"; then
+	if reset "simult IPv4 and IPv6 subflows, fullmesh 1x1" &&
+	   continue_if mptcp_lib_kversion_ge 6.3; then
 		pm_nl_set_limits $ns1 0 4
 		pm_nl_set_limits $ns2 1 4
 		pm_nl_add_endpoint $ns2 dead:beef:2::2 flags subflow,fullmesh
@@ -2666,7 +2669,8 @@ mixed_tests()
 
 	# fullmesh still tries to create all the possibly subflows with
 	# matching family
-	if reset "simult IPv4 and IPv6 subflows, fullmesh 2x2"; then
+	if reset "simult IPv4 and IPv6 subflows, fullmesh 2x2" &&
+	   continue_if mptcp_lib_kversion_ge 6.3; then
 		pm_nl_set_limits $ns1 0 4
 		pm_nl_set_limits $ns2 2 4
 		pm_nl_add_endpoint $ns1 10.0.2.1 flags signal