fix: avoid loading adapter list twice

agners · agners · commit d236934153ae · 2025-04-11T00:13:33.000+02:00
Load adapter list only once if operating in dual-stack mode. Also
fix typing around adapater list to match what ifaddr defines.
diff --git a/src/zeroconf/_utils/net.py b/src/zeroconf/_utils/net.py
@@ -28,7 +28,7 @@
 import socket
 import struct
 import sys
-from collections.abc import Sequence
+from collections.abc import Iterable, Sequence
 from typing import Any, Union, cast
 
 import ifaddr
@@ -73,19 +73,27 @@ def _encode_address(address: str) -> bytes:
     return socket.inet_pton(address_family, address)
 
 
-def get_all_addresses() -> list[str]:
-    return list({addr.ip for iface in ifaddr.get_adapters() for addr in iface.ips if addr.is_IPv4})  # type: ignore[misc]
+def get_all_addresses_ipv4(adapters: Iterable[ifaddr.Adapter]) -> list[str]:
+    return list({addr.ip for iface in adapters for addr in iface.ips if addr.is_IPv4})  # type: ignore[misc]
 
 
-def get_all_addresses_v6() -> list[tuple[tuple[str, int, int], int]]:
+def get_all_addresses_ipv6(adapters: Iterable[ifaddr.Adapter]) -> list[tuple[tuple[str, int, int], int]]:
     # IPv6 multicast uses positive indexes for interfaces
     # TODO: What about multi-address interfaces?
     return list(
-        {(addr.ip, iface.index) for iface in ifaddr.get_adapters() for addr in iface.ips if addr.is_IPv6}  # type: ignore[misc]
+        {(addr.ip, iface.index) for iface in adapters for addr in iface.ips if addr.is_IPv6}  # type: ignore[misc]
     )
 
 
-def ip6_to_address_and_index(adapters: list[ifaddr.Adapter], ip: str) -> tuple[tuple[str, int, int], int]:
+def get_all_addresses() -> list[str]:  # required for backwards compat
+    return get_all_addresses_ipv4(ifaddr.get_adapters())
+
+
+def get_all_addresses_v6() -> list[tuple[tuple[str, int, int], int]]:  # required for backwards compat
+    return get_all_addresses_ipv6(ifaddr.get_adapters())
+
+
+def ip6_to_address_and_index(adapters: Iterable[ifaddr.Adapter], ip: str) -> tuple[tuple[str, int, int], int]:
     if "%" in ip:
         ip = ip[: ip.index("%")]  # Strip scope_id.
     ipaddr = ipaddress.ip_address(ip)
@@ -102,7 +110,7 @@ def ip6_to_address_and_index(adapters: list[ifaddr.Adapter], ip: str) -> tuple[t
     raise RuntimeError(f"No adapter found for IP address {ip}")
 
 
-def interface_index_to_ip6_address(adapters: list[ifaddr.Adapter], index: int) -> tuple[str, int, int]:
+def interface_index_to_ip6_address(adapters: Iterable[ifaddr.Adapter], index: int) -> tuple[str, int, int]:
     for adapter in adapters:
         if adapter.index == index:
             for adapter_ip in adapter.ips:
@@ -152,10 +160,11 @@ def normalize_interface_choice(
         if ip_version != IPVersion.V6Only:
             result.append("0.0.0.0")
     elif choice is InterfaceChoice.All:
+        adapters = ifaddr.get_adapters()
         if ip_version != IPVersion.V4Only:
-            result.extend(get_all_addresses_v6())
+            result.extend(get_all_addresses_ipv6(adapters))
         if ip_version != IPVersion.V6Only:
-            result.extend(get_all_addresses())
+            result.extend(get_all_addresses_ipv4(adapters))
         if not result:
             raise RuntimeError(
                 f"No interfaces to listen on, check that any interfaces have IP version {ip_version}"
diff --git a/tests/utils/test_net.py b/tests/utils/test_net.py
@@ -84,8 +84,8 @@ def test_ip6_addresses_to_indexes():
 def test_normalize_interface_choice_errors():
     """Test we generate exception on invalid input."""
     with (
-        patch("zeroconf._utils.net.get_all_addresses", return_value=[]),
-        patch("zeroconf._utils.net.get_all_addresses_v6", return_value=[]),
+        patch("zeroconf._utils.net.get_all_addresses_ipv4", return_value=[]),
+        patch("zeroconf._utils.net.get_all_addresses_ipv6", return_value=[]),
         pytest.raises(RuntimeError),
     ):
         netutils.normalize_interface_choice(r.InterfaceChoice.All)
