tc-testing: don't hardcode 'ip' in nsPlugin.py

the following tdc test fails on Fedora:

 # ./tdc.py -e 2638
  -- ns/SubPlugin.__init__
 Test 2638: Add matchall and try to get it
 -----> prepare stage *** Could not execute: "$TC qdisc add dev $DEV1 clsact"
 -----> prepare stage *** Error message: "/bin/sh: ip: command not found"
 returncode 127; expected [0]
 -----> prepare stage *** Aborting test run.

Let nsPlugin.py use the 'IP' variable introduced with commit 92c1a19
("tc-tests: added path to ip command in tdc"), so that the path to 'ip' is
correctly resolved to the value we have in tdc_config.py.

 # ./tdc.py -e 2638
  -- ns/SubPlugin.__init__
 Test 2638: Add matchall and try to get it
 All test results:
 1..1
 ok 1 2638 - Add matchall and try to get it

Fixes: 489ce2f ("tc-testing: Restore original behaviour for namespaces in tdc")
Reported-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/tc-testing/plugin-lib/nsPlugin.py

@@ -64,7 +64,7 @@ def adjust_command(self, stage, command):
             cmdlist.insert(0, self.args.NAMES['NS'])
             cmdlist.insert(0, 'exec')
             cmdlist.insert(0, 'netns')
-            cmdlist.insert(0, 'ip')
+            cmdlist.insert(0, self.args.NAMES['IP'])
         else:
             pass
 
@@ -78,16 +78,16 @@ def adjust_command(self, stage, command):
         return command
 
     def _ports_create(self):
-        cmd = 'ip link add $DEV0 type veth peer name $DEV1'
+        cmd = '$IP link add $DEV0 type veth peer name $DEV1'
         self._exec_cmd('pre', cmd)
-        cmd = 'ip link set $DEV0 up'
+        cmd = '$IP link set $DEV0 up'
         self._exec_cmd('pre', cmd)
         if not self.args.namespace:
-            cmd = 'ip link set $DEV1 up'
+            cmd = '$IP link set $DEV1 up'
             self._exec_cmd('pre', cmd)
 
     def _ports_destroy(self):
-        cmd = 'ip link del $DEV0'
+        cmd = '$IP link del $DEV0'
         self._exec_cmd('post', cmd)
 
     def _ns_create(self):
@@ -97,16 +97,16 @@ def _ns_create(self):
         '''
         self._ports_create()
         if self.args.namespace:
-            cmd = 'ip netns add {}'.format(self.args.NAMES['NS'])
+            cmd = '$IP netns add {}'.format(self.args.NAMES['NS'])
             self._exec_cmd('pre', cmd)
-            cmd = 'ip link set $DEV1 netns {}'.format(self.args.NAMES['NS'])
+            cmd = '$IP link set $DEV1 netns {}'.format(self.args.NAMES['NS'])
             self._exec_cmd('pre', cmd)
-            cmd = 'ip -n {} link set $DEV1 up'.format(self.args.NAMES['NS'])
+            cmd = '$IP -n {} link set $DEV1 up'.format(self.args.NAMES['NS'])
             self._exec_cmd('pre', cmd)
             if self.args.device:
-                cmd = 'ip link set $DEV2 netns {}'.format(self.args.NAMES['NS'])
+                cmd = '$IP link set $DEV2 netns {}'.format(self.args.NAMES['NS'])
                 self._exec_cmd('pre', cmd)
-                cmd = 'ip -n {} link set $DEV2 up'.format(self.args.NAMES['NS'])
+                cmd = '$IP -n {} link set $DEV2 up'.format(self.args.NAMES['NS'])
                 self._exec_cmd('pre', cmd)
 
     def _ns_destroy(self):
@@ -115,7 +115,7 @@ def _ns_destroy(self):
         devices as well)
         '''
         if self.args.namespace:
-            cmd = 'ip netns delete {}'.format(self.args.NAMES['NS'])
+            cmd = '$IP netns delete {}'.format(self.args.NAMES['NS'])
             self._exec_cmd('post', cmd)
 
     def _exec_cmd(self, stage, command):