T5941: Migration policy delete orphaned interface policy

We can get orphaned interface policy when the policy name was
removed from the interface but the node `policy` still attached
to the interface

For exmaple we have orphaned node policy on interface:
```
set interfaces bonding bond0 vif 995 policy
```

This causes of incorrect migration and we do not see VLANs on
the bonding interface after update.

Delete policy from all interfaces if policy does not exist

(cherry picked from commit 53670e1fb201cf1d27b01b4bc796ff097f82552d)

1 files changed, 47 insertions, 1 deletions

diff --git a/src/migration-scripts/policy/4-to-5 b/src/migration-scripts/policy/4-to-5
index f6f889c35..5b8fee17e 100755
--- a/src/migration-scripts/policy/4-to-5
+++ b/src/migration-scripts/policy/4-to-5
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (C) 2022 VyOS maintainers and contributors
+# Copyright (C) 2022-2024 VyOS maintainers and contributors
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 or later as
@@ -37,7 +37,53 @@ base4 = ['policy', 'route']
 base6 = ['policy', 'route6']
 config = ConfigTree(config_file)
 
+
+def delete_orphaned_interface_policy(config, iftype, ifname, vif=None, vifs=None, vifc=None):
+    """Delete unexpected policy on interfaces in cases when
+       policy does not exist but inreface has a policy configuration
+       Example T5941:
+         set interfaces bonding bond0 vif 995 policy
+    """
+    if_path = ['interfaces', iftype, ifname]
+
+    if vif:
+        if_path += ['vif', vif]
+    elif vifs:
+        if_path += ['vif-s', vifs]
+        if vifc:
+            if_path += ['vif-c', vifc]
+
+    if not config.exists(if_path + ['policy']):
+        return
+
+    config.delete(if_path + ['policy'])
+
+
 if not config.exists(base4) and not config.exists(base6):
+    # Delete orphaned nodes on interfaces T5941
+    for iftype in config.list_nodes(['interfaces']):
+        for ifname in config.list_nodes(['interfaces', iftype]):
+            delete_orphaned_interface_policy(config, iftype, ifname)
+
+            if config.exists(['interfaces', iftype, ifname, 'vif']):
+                for vif in config.list_nodes(['interfaces', iftype, ifname, 'vif']):
+                    delete_orphaned_interface_policy(config, iftype, ifname, vif=vif)
+
+            if config.exists(['interfaces', iftype, ifname, 'vif-s']):
+                for vifs in config.list_nodes(['interfaces', iftype, ifname, 'vif-s']):
+                    delete_orphaned_interface_policy(config, iftype, ifname, vifs=vifs)
+
+                    if config.exists(['interfaces', iftype, ifname, 'vif-s', vifs, 'vif-c']):
+                        for vifc in config.list_nodes(['interfaces', iftype, ifname, 'vif-s', vifs, 'vif-c']):
+                            delete_orphaned_interface_policy(config, iftype, ifname, vifs=vifs, vifc=vifc)
+
+    try:
+        with open(file_name, 'w') as f:
+            f.write(config.to_string())
+    except OSError as e:
+        print("Failed to save the modified config: {}".format(e))
+        exit(1)
+
     # Nothing to do
     exit(0)