T3357: Fix invoking TunnelIf() from op-mode

As we can also use the TunnelIf() class from op-mode we must ensure that read-only
access to the class works even if required configuration keys as "encapsulation"
are not passed to the class on invokation.

This fixes an isse where "show interfaces tunnel" returned:

Traceback (most recent call last):
  File "/usr/libexec/vyos/op_mode/show_interfaces.py", line 313, in <module>
    args.vrrp
  File "/usr/libexec/vyos/op_mode/show_interfaces.py", line 48, in handled_function
    function(*args, **kwargs)
  File "/usr/libexec/vyos/op_mode/show_interfaces.py", line 222, in run_show_intf_brief
    for interface in filtered_interfaces(ifnames, iftypes, vif, vrrp):
  File "/usr/libexec/vyos/op_mode/show_interfaces.py", line 77, in filtered_interfaces
    interface = klass(ifname, create=False, debug=False)
  File "/usr/lib/python3/dist-packages/vyos/ifconfig/tunnel.py", line 99, in __init__
    if self.iftype in ['gretap', 'ip6gretap']:
AttributeError: 'TunnelIf' object has no attribute 'iftype'

1 files changed, 14 insertions, 12 deletions

diff --git a/python/vyos/ifconfig/tunnel.py b/python/vyos/ifconfig/tunnel.py
index 439d88dbc..e5e1300b2 100644
--- a/python/vyos/ifconfig/tunnel.py
+++ b/python/vyos/ifconfig/tunnel.py
@@ -90,19 +90,21 @@ class TunnelIf(Interface):
     }
 
     def __init__(self, ifname, **kargs):
-        self.iftype = kargs['encapsulation']
-        super().__init__(ifname, **kargs)
-
-        # The gretap interface has the possibility to act as L2 bridge
-        if self.iftype in ['gretap', 'ip6gretap']:
-            # no multicast, ttl or tos for gretap
-            self.definition = {
-                **TunnelIf.definition,
-                **{
-                    'bridgeable': True,
-                },
-            }
+        # T3357: we do not have the 'encapsulation' in kargs when calling this
+        # class from op-mode like "show interfaces tunnel"
+        if 'encapsulation' in kargs:
+            self.iftype = kargs['encapsulation']
+            # The gretap interface has the possibility to act as L2 bridge
+            if self.iftype in ['gretap', 'ip6gretap']:
+                # no multicast, ttl or tos for gretap
+                self.definition = {
+                    **TunnelIf.definition,
+                    **{
+                        'bridgeable': True,
+                    },
+                }
 
+        super().__init__(ifname, **kargs)
 
     def _create(self):
         if self.config['encapsulation'] in ['ipip6', 'ip6ip6', 'ip6gre']: