fix: Prioritize find link info by permanent MAC address, with fallbac…

…k to current address

Updated the link_info_find method to prioritize matching links by
perm-address when it is valid and available. If the perm-address is
unavailable (None or "00:00:00:00:00:00"), the method falls back to
matching by address. Additionally, if ifname is provided, it takes
precedence and returns the corresponding linkinfo immediately.

The change resolves scenarios where multiple network interfaces might
share the same current MAC address (address), leading to potential
ambiguity in link matching. By prioritizing the permanent MAC address
(perm-address), the method provides a more precise and consistent match.
This is particularly crucial in environments with:

- MAC address spoofing or dynamic changes, where the current MAC
  address may not reliably identify the interface.
- Virtual interfaces or VLANs, which often lack a valid perm-address
  and rely on the parent interface's address.
- Ambiguity when multiple interfaces share the same address.

This change improves the robustness of MAC address matching by ensuring
that permanent addresses are prioritized while maintaining a reliable
fallback mechanism for interfaces with no permanent address.

Signed-off-by: Wen Liang <[email protected]>

library/network_connections.py

@@ -226,14 +226,26 @@ def link_info_find(cls, refresh=False, mac=None, ifname=None):
         if mac is not None:
             mac = Util.mac_norm(mac)
         for linkinfo in cls.link_infos(refresh).values():
-            if mac is not None and mac not in [
-                linkinfo.get("perm-address", None),
-                linkinfo.get("address", None),
-            ]:
-                continue
-            if ifname is not None and ifname != linkinfo.get("ifname", None):
-                continue
-            return linkinfo
+            perm_address = linkinfo.get("perm-address", None)
+            current_address = linkinfo.get("address", None)
+
+            # Match by perm-address (prioritized)
+            if mac is not None and perm_address not in [None, "00:00:00:00:00:00"]:
+                if mac == perm_address:
+                    return linkinfo
+
+            # Fallback to match by address
+            if mac is not None and (perm_address in [None, "00:00:00:00:00:00"]):
+                if mac == current_address:
+                    matched_by_address = linkinfo  # Save for potential fallback
+
+            if ifname is not None and ifname == linkinfo.get("ifname", None):
+                return linkinfo
+
+        # Return fallback match by address if no perm-address match found
+        if "matched_by_address" in locals():
+            return matched_by_address
+
         return None