vyos.ifconfig: T1579: do not remove IPv6 link-local address on reconfiguration

3 files changed, 12 insertions, 5 deletions

diff --git a/python/vyos/ifconfig/interface.py b/python/vyos/ifconfig/interface.py
index 6837e2d6a..d695f05e3 100644
--- a/python/vyos/ifconfig/interface.py
+++ b/python/vyos/ifconfig/interface.py
@@ -40,6 +40,7 @@ from vyos.util import read_file
 from vyos.template import is_ipv4
 from vyos.template import is_ipv6
 from vyos.validate import is_intf_addr_assigned
+from vyos.validate import is_ipv6_link_local
 from vyos.validate import assert_boolean
 from vyos.validate import assert_list
 from vyos.validate import assert_mac
@@ -1042,7 +1043,10 @@ class Interface(Control):
         # 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):
-            self.del_addr(addr)
+            # do not clean out link-local IPv6 addresses - it makes no sense
+            # as they will be readded so this prevents any flapping links
+            if not is_ipv6_link_local(addr):
+                self.del_addr(addr)
 
         for addr in new_addr:
             self.add_addr(addr)
diff --git a/python/vyos/validate.py b/python/vyos/validate.py
index 84a7bc2de..98bd40f74 100644
--- a/python/vyos/validate.py
+++ b/python/vyos/validate.py
@@ -27,11 +27,11 @@ from vyos.util import cmd
 
 def is_ipv6_link_local(addr):
     """ Check if addrsss is an IPv6 link-local address. Returns True/False """
-    from ipaddress import IPv6Address
+    from ipaddress import ip_interface
     from vyos.template import is_ipv6
     addr = addr.split('%')[0]
     if is_ipv6(addr):
-        if IPv6Address(addr).is_link_local:
+        if ip_interface(addr).is_link_local:
             return True
 
     return False
diff --git a/src/tests/test_validate.py b/src/tests/test_validate.py
index 226e856a3..4348e2ef8 100644
--- a/src/tests/test_validate.py
+++ b/src/tests/test_validate.py
@@ -22,13 +22,16 @@ class TestVyOSValidate(TestCase):
         pass
 
     def test_is_ipv6_link_local(self):
-        self.assertFalse(vyos.validate.is_ipv6_link_local('169.254.0.1'))
         self.assertTrue(vyos.validate.is_ipv6_link_local('fe80::'))
         self.assertTrue(vyos.validate.is_ipv6_link_local('fe80::affe:1'))
+        self.assertTrue(vyos.validate.is_ipv6_link_local('fe80::250:56ff:febf:efaa/64'))
+
+        self.assertFalse(vyos.validate.is_ipv6_link_local('169.254.0.1'))
         self.assertFalse(vyos.validate.is_ipv6_link_local('2001:db8::'))
+        self.assertFalse(vyos.validate.is_ipv6_link_local('2001:db8::1/64'))
         self.assertFalse(vyos.validate.is_ipv6_link_local('VyOS'))
 
-    def test_is_ipv6_link_local(self):
+    def test_is_loopback(self):
         self.assertTrue(vyos.validate.is_loopback_addr('127.0.0.1'))
         self.assertTrue(vyos.validate.is_loopback_addr('127.0.1.1'))
         self.assertTrue(vyos.validate.is_loopback_addr('127.1.1.1'))