selftests: mptcp: add IPv4-mapped IPv6 testcases

Here, we make sure we support IPv4-mapped in IPv6 addresses in different
contexts:

- a v4-mapped address is received by the PM and can be used as v4.
- a v4 address is received by the PM and can be used even with a v4
  mapped socket.

We also make sure we don't try to establish subflows between v4 and v6
addresses, e.g. if a real v6 address ends with a valid v4 address.

Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -790,6 +790,81 @@ chk_join_nr "remove subflow and signal IPv6" 2 2 2
 chk_add_nr 1 1
 chk_rm_nr 1 1
 
+# subflow IPv4-mapped to IPv4-mapped
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl add "::ffff:10.0.3.2" flags subflow
+run_tests $ns1 $ns2 "::ffff:10.0.1.1"
+chk_join_nr "single subflow IPv4-mapped" 1 1 1
+
+# signal address IPv4-mapped with IPv4-mapped sk
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 1 1
+ip netns exec $ns1 ./pm_nl_ctl add "::ffff:10.0.2.1" flags signal
+run_tests $ns1 $ns2 "::ffff:10.0.1.1"
+chk_join_nr "signal address IPv4-mapped" 1 1 1
+chk_add_nr 1 1
+
+# subflow v4-map-v6
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
+run_tests $ns1 $ns2 "::ffff:10.0.1.1"
+chk_join_nr "single subflow v4-map-v6" 1 1 1
+
+# signal address v4-map-v6
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 1 1
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.2.1 flags signal
+run_tests $ns1 $ns2 "::ffff:10.0.1.1"
+chk_join_nr "signal address v4-map-v6" 1 1 1
+chk_add_nr 1 1
+
+# subflow v6-map-v4
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl add "::ffff:10.0.3.2" flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "single subflow v6-map-v4" 1 1 1
+
+# signal address v6-map-v4
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 1 1
+ip netns exec $ns1 ./pm_nl_ctl add "::ffff:10.0.2.1" flags signal
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "signal address v6-map-v4" 1 1 1
+chk_add_nr 1 1
+
+# no subflow IPv6 to v4 address
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl add dead:beef:2::2 flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "no JOIN with diff families v4-v6" 0 0 0
+
+# no subflow IPv6 to v4 address even if v6 has a valid v4 at the end
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl add dead:beef:2::10.0.3.2 flags subflow
+run_tests $ns1 $ns2 10.0.1.1
+chk_join_nr "no JOIN with diff families v4-v6-2" 0 0 0
+
+# no subflow IPv4 to v6 address, no need to slow down too then
+reset
+ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl limits 0 1
+ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
+run_tests $ns1 $ns2 dead:beef:1::1
+chk_join_nr "no JOIN with diff families v6-v4" 0 0 0
+
 # single subflow, backup
 reset
 ip netns exec $ns1 ./pm_nl_ctl limits 0 1