Sort resolved IP addresses for dashboard (#8536)

Co-authored-by: J. Nick Koston <nick+github@koston.org>

esphome/dashboard/web_server.py

@@ -38,7 +38,7 @@ import yaml
 from yaml.nodes import Node
 
 from esphome import const, platformio_api, yaml_util
-from esphome.helpers import get_bool_env, mkdir_p
+from esphome.helpers import get_bool_env, mkdir_p, sort_ip_addresses
 from esphome.storage_json import (
     StorageJSON,
     archive_storage_path,
@@ -336,7 +336,7 @@ class EsphomePortCommandWebSocket(EsphomeCommandWebSocket):
                 # Use the IP address if available but only
                 # if the API is loaded and the device is online
                 # since MQTT logging will not work otherwise
-                port = address_list[0]
+                port = sort_ip_addresses(address_list)[0]
             elif (
                 entry.address
                 and (
@@ -347,7 +347,7 @@ class EsphomePortCommandWebSocket(EsphomeCommandWebSocket):
                 and not isinstance(address_list, Exception)
             ):
                 # If mdns is not available, try to use the DNS cache
-                port = address_list[0]
+                port = sort_ip_addresses(address_list)[0]
 
         return [
             *DASHBOARD_COMMAND,

esphome/helpers.py

@@ -200,6 +200,45 @@ def resolve_ip_address(host, port):
     return res
 
 
+def sort_ip_addresses(address_list: list[str]) -> list[str]:
+    """Takes a list of IP addresses in string form, e.g. from mDNS or MQTT,
+    and sorts them into the best order to actually try connecting to them.
+
+    This is roughly based on RFC6724 but a lot simpler: First we choose
+    IPv6 addresses, then Legacy IP addresses, and lowest priority is
+    link-local IPv6 addresses that don't have a link specified (which
+    are useless, but mDNS does provide them in that form). Addresses
+    which cannot be parsed are silently dropped.
+    """
+    import socket
+
+    # First "resolve" all the IP addresses to getaddrinfo() tuples of the form
+    # (family, type, proto, canonname, sockaddr)
+    res: list[
+        tuple[
+            int,
+            int,
+            int,
+            Union[str, None],
+            Union[tuple[str, int], tuple[str, int, int, int]],
+        ]
+    ] = []
+    for addr in address_list:
+        # This should always work as these are supposed to be IP addresses
+        try:
+            res += socket.getaddrinfo(
+                addr, 0, proto=socket.IPPROTO_TCP, flags=socket.AI_NUMERICHOST
+            )
+        except OSError:
+            _LOGGER.info("Failed to parse IP address '%s'", addr)
+
+    # Now use that information to sort them.
+    res.sort(key=addr_preference_)
+
+    # Finally, turn the getaddrinfo() tuples back into plain hostnames.
+    return [socket.getnameinfo(r[4], socket.NI_NUMERICHOST)[0] for r in res]
+
+
 def get_bool_env(var, default=False):
     value = os.getenv(var, default)
     if isinstance(value, str):

tests/unit_tests/test_helpers.py

@@ -267,3 +267,13 @@ def test_sanitize(text, expected):
     actual = helpers.sanitize(text)
 
     assert actual == expected
+
+
+@pytest.mark.parametrize(
+    "text, expected",
+    ((["127.0.0.1", "fe80::1", "2001::2"], ["2001::2", "127.0.0.1", "fe80::1"]),),
+)
+def test_sort_ip_addresses(text: list[str], expected: list[str]) -> None:
+    actual = helpers.sort_ip_addresses(text)
+
+    assert actual == expected