test-network: add tests for flags of tun or tap devices

test/test-network/conf/25-tap.netdev

@@ -5,3 +5,4 @@ Kind=tap
 [Tap]
 MultiQueue=true
 PacketInfo=true
+VNetHeader=true

test/test-network/conf/25-tun.netdev

@@ -5,3 +5,4 @@ Kind=tun
 [Tun]
 MultiQueue=true
 PacketInfo=true
+VNetHeader=true

test/test-network/systemd-networkd-tests.py

@@ -602,12 +602,22 @@ class NetworkdNetDevTests(unittest.TestCase, Utilities):
 
         self.wait_online(['tun99:off'])
 
+        output = subprocess.check_output(['ip', '-d', 'link', 'show', 'tun99'], universal_newlines=True).rstrip()
+        print(output)
+        # Old ip command does not support IFF_ flags
+        self.assertRegex(output, 'tun (?:type tun pi on vnet_hdr on multi_queue|addrgenmode) ')
+
     def test_tap(self):
         self.copy_unit_to_networkd_unit_path('25-tap.netdev')
         self.start_networkd(0)
 
         self.wait_online(['tap99:off'])
 
+        output = subprocess.check_output(['ip', '-d', 'link', 'show', 'tap99'], universal_newlines=True).rstrip()
+        print(output)
+        # Old ip command does not support IFF_ flags
+        self.assertRegex(output, 'tun (?:type tap pi on vnet_hdr on multi_queue|addrgenmode) ')
+
     @expectedFailureIfModuleIsNotAvailable('vrf')
     def test_vrf(self):
         self.copy_unit_to_networkd_unit_path('25-vrf.netdev')