op-mode: T3619: bugfix "show interfaces" for VLANs

Commit 31169fa8a7 ("vyos.ifconfig: T3619: only set offloading options if
supported by NIC") always instantiated an object of the Ethtool class for an
ethernet object - this is right as a real ethernet interface is managed by
Ethtool.

Unfortunately the script used for "show interface" determindes the "base class"
for an interface by its name, so eth0 -> Ethernet, eth0.10 -> Ethernet. This
assumption is incorrect as a VLAN interface can not have the physical parameters
changed of its underlaying interface. This can only be done for eth0.

There is no need for the op-mode script to determine the implementation class
for an interface at this level, as we are only interested in the state of the
interface and it's IP addresses - which is a common operation valid for every
interface on VyOS.

1 files changed, 3 insertions, 4 deletions

diff --git a/src/op_mode/show_interfaces.py b/src/op_mode/show_interfaces.py
index 2eaaa34f8..1707d8669 100755
--- a/src/op_mode/show_interfaces.py
+++ b/src/op_mode/show_interfaces.py
@@ -69,10 +69,9 @@ def filtered_interfaces(ifnames, iftypes, vif, vrrp):
         if ifnames and ifname not in ifnames:
             continue
 
-        # return the class which can handle this interface name
-        klass = Section.klass(ifname)
-        # connect to the interface
-        interface = klass(ifname, create=False, debug=False)
+        # As we are only "reading" from the interface - we must use the
+        # generic base class which exposes all the data via a common API
+        interface = Interface(ifname, create=False, debug=False)
 
         if iftypes and interface.definition['section'] not in iftypes:
             continue