From b9fb91699b9af7a8ea375d4662a50363004eacfd Mon Sep 17 00:00:00 2001
From: Christian Breunig <christian@breunig.cc>
Date: Wed, 26 Jun 2024 15:35:10 +0200
Subject: [PATCH] interfaces: T6519: harden config migration if ethernet
 interface is missing

During a corner case where the configuration is migrated to a different system
with fewer ethernet interfaces, migration will fail during an image upgrade.

vyos.ethtool.Ethtool() is instantiated with an invalid interface leading to an
exception that kills the migrator

(cherry picked from commit e47d4fd385631236da6882233b09f6364cbb077b)
---
 python/vyos/ethtool.py                    | 4 ++++
 src/migration-scripts/interfaces/20-to-21 | 7 ++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/python/vyos/ethtool.py b/python/vyos/ethtool.py
index d45c9c2722..80bb56fa2b 100644
--- a/python/vyos/ethtool.py
+++ b/python/vyos/ethtool.py
@@ -16,6 +16,7 @@
 import re
 
 from json import loads
+from vyos.utils.network import interface_exists
 from vyos.utils.process import popen
 
 # These drivers do not support using ethtool to change the speed, duplex, or
@@ -64,6 +65,9 @@ class Ethtool:
 
     def __init__(self, ifname):
         # Get driver used for interface
+        if not interface_exists(ifname):
+            raise ValueError(f'Interface "{ifname}" does not exist!')
+
         out, _ = popen(f'ethtool --driver {ifname}')
         driver = re.search(r'driver:\s(\w+)', out)
         if driver:
diff --git a/src/migration-scripts/interfaces/20-to-21 b/src/migration-scripts/interfaces/20-to-21
index 14ad0fe4db..05a0c72373 100755
--- a/src/migration-scripts/interfaces/20-to-21
+++ b/src/migration-scripts/interfaces/20-to-21
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (C) 2021 VyOS maintainers and contributors
+# Copyright (C) 2021-2024 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
@@ -22,6 +22,7 @@ from sys import argv
 
 from vyos.ethtool import Ethtool
 from vyos.configtree import ConfigTree
+from vyos.utils.network import interface_exists
 
 if len(argv) < 2:
     print("Must specify file name!")
@@ -38,6 +39,10 @@ if not config.exists(base):
     exit(0)
 
 for ifname in config.list_nodes(base):
+    # Bail out early if interface vanished from system
+    if not interface_exists(ifname):
+        continue
+
     eth = Ethtool(ifname)
 
     # If GRO is enabled by the Kernel - we reflect this on the CLI. If GRO is