[PATCH pve-network] sdn: controller: prevent invalid router-id generation from zero mac

[Hannes Laimer <h.laimer@proxmox.com>]

When a standard loopback interface is used, the retrieved MAC is
typically 00:00:00:00:00:00. This causes the router-id generation logic
to produce "0.0.0.0", which is an invalid BGP ID.

Explicitly check for a zero MAC address and fail with a descriptive
error.

Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
---
 src/PVE/Network/SDN/Controllers/Plugin.pm | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/PVE/Network/SDN/Controllers/Plugin.pm b/src/PVE/Network/SDN/Controllers/Plugin.pm
index d70e518..54d6402 100644
--- a/src/PVE/Network/SDN/Controllers/Plugin.pm
+++ b/src/PVE/Network/SDN/Controllers/Plugin.pm
@@ -118,6 +118,11 @@ sub get_router_id {
 
     die "can't autofind a router-id value from ip or mac" if !$mac;
 
+    if ($mac eq '00:00:00:00:00:00') {
+        die "Interface $iface has a zero MAC address. Cannot derive a BGP router-id. "
+            . "Please use a dummy interface or assign an IPv4 address to $iface.\n";
+    }
+
     my @mac_bytes = split(':', $mac);
     return
         hex($mac_bytes[2]) . "."
-- 
2.47.3