net: fix interface matching support (#1552)

- broken in bf94945fb855c40c5188cef5fb
- factor out a reusable helper function
- stylistic change for Python's new match keyword

LP: #1979877

2 files changed, 18 insertions, 5 deletions

diff --git a/cloudinit/net/__init__.py b/cloudinit/net/__init__.py
index f5545fc1..4bc48676 100644
--- a/cloudinit/net/__init__.py
+++ b/cloudinit/net/__init__.py
@@ -928,6 +928,13 @@ def get_interfaces_by_mac(blacklist_drivers=None) -> dict:
         )
 
 
+def find_interface_name_from_mac(mac: str) -> Optional[str]:
+    for interface_mac, interface_name in get_interfaces_by_mac().items():
+        if mac.lower() == interface_mac.lower():
+            return interface_name
+    return None
+
+
 def get_interfaces_by_mac_on_freebsd(blacklist_drivers=None) -> dict:
     (out, _) = subp.subp(["ifconfig", "-a", "ether"])
 
diff --git a/cloudinit/net/network_state.py b/cloudinit/net/network_state.py
index 2c64e492..80f2b108 100644
--- a/cloudinit/net/network_state.py
+++ b/cloudinit/net/network_state.py
@@ -11,6 +11,7 @@ from typing import Any, Dict
 
 from cloudinit import safeyaml, util
 from cloudinit.net import (
+    find_interface_name_from_mac,
     get_interfaces_by_mac,
     ipv4_mask_to_net_prefix,
     ipv6_mask_to_net_prefix,
@@ -700,15 +701,14 @@ class NetworkStateInterpreter(metaclass=CommandHandlerMeta):
             #   * interface name looked up by mac
             #   * value of "eth" key from this loop
             name = eth
-            set_name = cfg.get("set-name", None)
+            set_name = cfg.get("set-name")
             if set_name:
                 name = set_name
             elif mac_address and ifaces_by_mac:
                 lcase_mac_address = mac_address.lower()
-                for iface_mac, iface_name in ifaces_by_mac.items():
-                    if lcase_mac_address == iface_mac.lower():
-                        name = iface_name
-                        break
+                mac = find_interface_name_from_mac(lcase_mac_address)
+                if mac:
+                    name = mac
             phy_cmd["name"] = name
 
             driver = match.get("driver", None)
@@ -780,6 +780,12 @@ class NetworkStateInterpreter(metaclass=CommandHandlerMeta):
                 if len(dns) > 0:
                     name_cmd.update({"address": dns})
                 self.handle_nameserver(name_cmd)
+
+                mac_address = dev_cfg.get("match", {}).get("macaddress")
+                real_if_name = find_interface_name_from_mac(mac_address)
+                if real_if_name:
+                    iface = real_if_name
+
                 self._handle_individual_nameserver(name_cmd, iface)
 
     def _handle_bond_bridge(self, command, cmd_type=None):