ifconfig: T2863: only use IPv6 link-local address if interface has MAC address

With VyOS 1.2 the default WireGuard behavior is used. This means that when a
WireGuard interface is added to the system, there is no "MAC" address - also
there is no IPv6 link-local address assigned by the Kernel to this particular
interface.

With implementation of T2653 all interfaces now receive an IPv6 address - which
is also valid for WireGuard interfaces - unfortunately this logic relies on the
interface MAC address - and as there is none, the link-local address will be
always the same. The logic behind is coded here [1].

We generate an IPv6 link-local address even when there is no "MAC" address. The
behavior/functionality (as with VyOS 1.2) must be restored to not have a
link-local IPv6 address at all. Any user can add any IPv6 link-local address
manually by issuing: set interfaces wireguard wg01 address fe80::ff:1/64.

Change vyos.ifconfig.add_ipv6_eui64_address to only add the EUI64-based
link-local address if a MAC address is available.

[1] https://github.com/vyos/vyos-1x/blob/3077158391ceee4ce04c27dec33f629529727c36/python/vyos/ifconfig/interface.py#L468

1 files changed, 7 insertions, 4 deletions

diff --git a/python/vyos/ifconfig/interface.py b/python/vyos/ifconfig/interface.py
index ef2336c17..ffe69f61b 100644
--- a/python/vyos/ifconfig/interface.py
+++ b/python/vyos/ifconfig/interface.py
@@ -464,10 +464,13 @@ class Interface(Control):
         Calculate the EUI64 from the interface's MAC, then assign it
         with the given prefix to the interface.
         """
-
-        eui64 = mac2eui64(self.get_mac(), prefix)
-        prefixlen = prefix.split('/')[1]
-        self.add_addr(f'{eui64}/{prefixlen}')
+        # T2863: only add a link-local IPv6 address if the interface returns
+        # a MAC address. This is not the case on e.g. WireGuard interfaces.
+        mac = self.get_mac()
+        if mac:
+            eui64 = mac2eui64(mac, prefix)
+            prefixlen = prefix.split('/')[1]
+            self.add_addr(f'{eui64}/{prefixlen}')
 
     def del_ipv6_eui64_address(self, prefix):
         """