From e3626da307d66c34e4ce12c7c38cdb8fa5da9889 Mon Sep 17 00:00:00 2001
From: Christian Poessinger <christian@poessinger.com>
Date: Wed, 30 Mar 2022 19:18:09 +0200
Subject: vyos.util: T4319: add is_ipv6_enabled() helper function

(cherry picked from commit df0fbfeedce0f163e9d10be21d58ad4dc797a28a)
---
 python/vyos/ifconfig/interface.py |  4 ++--
 python/vyos/ifconfig/loopback.py  | 13 +++++--------
 python/vyos/util.py               |  4 ++++
 src/tests/test_util.py            | 14 +++++++++++++-
 4 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/python/vyos/ifconfig/interface.py b/python/vyos/ifconfig/interface.py
index a2fa96d82..99a06b1dd 100644
--- a/python/vyos/ifconfig/interface.py
+++ b/python/vyos/ifconfig/interface.py
@@ -38,7 +38,7 @@ from vyos.util import dict_search
 from vyos.util import read_file
 from vyos.util import get_interface_config
 from vyos.util import is_systemd_service_active
-from vyos.util import sysctl_read
+from vyos.util import is_ipv6_enabled
 from vyos.template import is_ipv4
 from vyos.template import is_ipv6
 from vyos.validate import is_intf_addr_assigned
@@ -1359,7 +1359,7 @@ class Interface(Control):
         self.set_ipv4_source_validation(value)
 
         # Only change IPv6 parameters if IPv6 was not explicitly disabled
-        if sysctl_read('net.ipv6.conf.all.disable_ipv6') == '0':
+        if is_ipv6_enabled():
             # IPv6 forwarding
             tmp = dict_search('ipv6.disable_forwarding', config)
             value = '0' if (tmp != None) else '1'
diff --git a/python/vyos/ifconfig/loopback.py b/python/vyos/ifconfig/loopback.py
index de554ef44..30c890fdf 100644
--- a/python/vyos/ifconfig/loopback.py
+++ b/python/vyos/ifconfig/loopback.py
@@ -13,9 +13,8 @@
 # You should have received a copy of the GNU Lesser General Public
 # License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 
-import vyos.util
-
 from vyos.ifconfig.interface import Interface
+from vyos.util import is_ipv6_enabled
 
 @Interface.register
 class LoopbackIf(Interface):
@@ -34,8 +33,6 @@ class LoopbackIf(Interface):
         }
     }
 
-    name = 'loopback'
-
     def remove(self):
         """
         Loopback interface can not be deleted from operating system. We can
@@ -62,11 +59,11 @@ class LoopbackIf(Interface):
         on any interface. """
 
         addr = config.get('address', [])
-        # We must ensure that the loopback addresses are never deleted from the system
-        addr += ['127.0.0.1/8']
 
-        if (vyos.util.sysctl_read('net.ipv6.conf.all.disable_ipv6') == '0'):
-            addr += ['::1/128']
+        # We must ensure that the loopback addresses are never deleted from the system
+        addr.append('127.0.0.1/8')
+        if is_ipv6_enabled():
+            addr.append('::1/128')
 
         # Update IP address entry in our dictionary
         config.update({'address' : addr})
diff --git a/python/vyos/util.py b/python/vyos/util.py
index b5d81fba5..4283e604c 100644
--- a/python/vyos/util.py
+++ b/python/vyos/util.py
@@ -827,3 +827,7 @@ def sysctl_write(name, value):
         call(f'sysctl -wq {name}={value}')
         return True
     return False
+
+def is_ipv6_enabled() -> bool:
+    """ Check if IPv6 support on the system is enabled or not """
+    return (sysctl_read('net.ipv6.conf.all.disable_ipv6') == '0')
diff --git a/src/tests/test_util.py b/src/tests/test_util.py
index 22bc085c5..8afa531d0 100644
--- a/src/tests/test_util.py
+++ b/src/tests/test_util.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (C) 2020 VyOS maintainers and contributors
+# Copyright (C) 2020-2022 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
@@ -24,3 +24,15 @@ class TestVyOSUtil(TestCase):
         new_data = mangle_dict_keys(data, '-', '_')
         self.assertEqual(new_data, expected_data)
 
+    def test_sysctl_read(self):
+        self.assertEqual(sysctl_read('net.ipv4.conf.lo.forwarding'), '1')
+
+    def test_ipv6_enabled(self):
+        tmp = sysctl_read('net.ipv6.conf.all.disable_ipv6')
+        # We need to test for both variants as this depends on how the
+        # Docker container is started (with or without IPv6 support) - so we
+        # will simply check both cases to not make the users life miserable.
+        if tmp == '0':
+            self.assertTrue(is_ipv6_enabled())
+        else:
+            self.assertFalse(is_ipv6_enabled())
-- 
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