selftests: mptcp: add set_flags tests in pm_netlink.sh

This patch added the setting flags test cases, using both addr-based and
id-based lookups for the setting address.

The output looks like this:

 set flags (backup)                                 [ OK ]
           (nobackup)                               [ OK ]
           (fullmesh)                               [ OK ]
           (nofullmesh)                             [ OK ]
           (backup,fullmesh)                        [ OK ]
Signed-off-by: Geliang Tang <geliang.tang@suse.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/pm_netlink.sh

@@ -164,4 +164,22 @@ id 253 flags  10.0.0.5
 id 254 flags  10.0.0.2
 id 255 flags  10.0.0.3" "wrap-around ids"
 
+ip netns exec $ns1 ./pm_nl_ctl flush
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.1 flags subflow
+ip netns exec $ns1 ./pm_nl_ctl set 10.0.1.1 flags backup
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags \
+subflow,backup 10.0.1.1" "set flags (backup)"
+ip netns exec $ns1 ./pm_nl_ctl set 10.0.1.1 flags nobackup
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags \
+subflow 10.0.1.1" "          (nobackup)"
+ip netns exec $ns1 ./pm_nl_ctl set id 1 flags fullmesh
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags \
+subflow,fullmesh 10.0.1.1" "          (fullmesh)"
+ip netns exec $ns1 ./pm_nl_ctl set id 1 flags nofullmesh
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags \
+subflow 10.0.1.1" "          (nofullmesh)"
+ip netns exec $ns1 ./pm_nl_ctl set id 1 flags backup,fullmesh
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags \
+subflow,backup,fullmesh 10.0.1.1" "          (backup,fullmesh)"
+
 exit $ret