vyos.ifconfig: T2738: do not remove OS assigned IP addresses from interface

When using VRRP on any given interface and performing an action against that
interface - be it even only changing the alias - will trigger a removal of the
VRRP IP address.

The issue is caused by:

  # determine IP addresses which are assigned to the interface and build a
  # list of addresses which are no longer in the dict so they can be removed
  cur_addr = self.get_addr()
  for addr in list_diff(cur_addr, new_addr):

When the script calls into the library - we will drop all IP addresses set on
the adapter but not available in the config dict.

We should only remove the IP addresses marked by the CLI to be deleted!

2 files changed, 14 insertions, 9 deletions

diff --git a/python/vyos/configdict.py b/python/vyos/configdict.py
index 8d7142049..5c6836e97 100644
--- a/python/vyos/configdict.py
+++ b/python/vyos/configdict.py
@@ -375,6 +375,9 @@ def get_interface_dict(config, base, ifname=''):
     # XXX: T2665: blend in proper DHCPv6-PD default values
     dict = T2665_set_dhcpv6pd_defaults(dict)
 
+    address = leaf_node_changed(config, ['address'])
+    if address: dict.update({'address_old' : address})
+
     # Check if we are a member of a bridge device
     bridge = is_member(config, ifname, 'bridge')
     if bridge: dict.update({'is_bridge_member' : bridge})
diff --git a/python/vyos/ifconfig/interface.py b/python/vyos/ifconfig/interface.py
index 14b782db4..963f47c89 100755
--- a/python/vyos/ifconfig/interface.py
+++ b/python/vyos/ifconfig/interface.py
@@ -1085,6 +1085,8 @@ class Interface(Control):
         >>> j.get_addr()
         ['2001:db8::ffff/64']
         """
+        if not addr:
+            raise ValueError()
 
         # remove from interface
         if addr == 'dhcp':
@@ -1364,16 +1366,16 @@ class Interface(Control):
 
         # determine IP addresses which are assigned to the interface and build a
         # list of addresses which are no longer in the dict so they can be removed
-        cur_addr = self.get_addr()
-        for addr in list_diff(cur_addr, new_addr):
-            # we will delete all interface specific IP addresses if they are not
-            # explicitly configured on the CLI
-            if is_ipv6_link_local(addr):
-                eui64 = mac2eui64(self.get_mac(), 'fe80::/64')
-                if addr != f'{eui64}/64':
+        if 'address_old' in config:
+            for addr in list_diff(config['address_old'], new_addr):
+                # we will delete all interface specific IP addresses if they are not
+                # explicitly configured on the CLI
+                if is_ipv6_link_local(addr):
+                    eui64 = mac2eui64(self.get_mac(), 'fe80::/64')
+                    if addr != f'{eui64}/64':
+                        self.del_addr(addr)
+                else:
                     self.del_addr(addr)
-            else:
-                self.del_addr(addr)
 
         for addr in new_addr:
             self.add_addr(addr)