addons: vxlan: attr vxlan-port: add DRYRUN check

-n sets DRYRUN flags, when DRYRUN is set many functions return True
(like link_exists), in this case vxlanattrs is set to False because
not cached. But since link_exists=True we still try to access it like
a dictionary.

Signed-off-by: Julien Fortin <julien@cumulusnetworks.com>

ifupdown2/addons/vxlan.py

@@ -10,6 +10,7 @@ from ipaddr import IPNetwork, IPv4Address, IPv4Network, AddressValueError
 
 try:
     import ifupdown2.ifupdown.policymanager as policymanager
+    import ifupdown2.ifupdown.ifupdownflags as ifupdownflags
 
     from ifupdown2.nlmanager.nlmanager import Link
 
@@ -21,6 +22,7 @@ try:
     from ifupdown2.ifupdownaddons.modulebase import moduleBase
 except ImportError:
     import ifupdown.policymanager as policymanager
+    import ifupdown.ifupdownflags as ifupdownflags
 
     from nlmanager.nlmanager import Link
 
@@ -290,7 +292,7 @@ class vxlan(moduleBase):
                 self.logger.warning('%s: vxlan-port: using default %s: invalid configured value %s' % (ifname, netlink.VXLAN_UDP_PORT, str(e)))
                 vxlan_port = netlink.VXLAN_UDP_PORT
 
-            if link_exists:
+            if link_exists and not ifupdownflags.flags.DRYRUN:
                 cache_port = vxlanattrs.get(Link.IFLA_VXLAN_PORT)
                 if vxlan_port != cache_port:
                     self.logger.warning('%s: vxlan-port (%s) cannot be changed - to apply the desired change please run: ifdown %s && ifup %s'