[socket][tcp_uart][uart_tcp] Reject an IPv6 host at config time (#20165)

esphome/components/socket/__init__.py

@@ -149,6 +149,21 @@ def require_wake_loop_threadsafe() -> None:
 IPV4_ALLOW_SCHEMA = cv.All(cv.ensure_list(cv.ipv4network), cv.Length(max=255))
 
 
+_HOST = cv.Any(cv.domain, cv.hostname)
+
+
+def ipv4_host(value: object) -> str:
+    """Validate an IPv4 address or a hostname; the resolver behind it is IPv4 only."""
+    value = cv.string(value)
+    try:
+        cv.ipv6address(value)
+    except cv.Invalid:
+        return _HOST(value)
+    raise cv.Invalid(
+        "IPv6 addresses are not supported, use an IPv4 address or a hostname"
+    )
+
+
 def _network_order(addr: IPv4Address) -> int:
     """The s_addr value for addr on the little endian targets."""
     return int.from_bytes(addr.packed, "little")

esphome/components/tcp_uart/__init__.py

@@ -54,7 +54,7 @@ CONFIG_SCHEMA = cv.All(
         {
             "client": BASE_SCHEMA.extend(
                 {
-                    cv.Required(CONF_HOST): cv.string,
+                    cv.Required(CONF_HOST): socket.ipv4_host,
                 }
             ),
             "server": BASE_SCHEMA.extend(

esphome/components/uart_tcp/__init__.py

@@ -44,7 +44,7 @@ BASE_SCHEMA = cv.Schema(
 CONFIG_SCHEMA = cv.All(
     cv.typed_schema(
         {
-            "client": BASE_SCHEMA.extend({cv.Required(CONF_HOST): cv.string}),
+            "client": BASE_SCHEMA.extend({cv.Required(CONF_HOST): socket.ipv4_host}),
             "server": BASE_SCHEMA.extend(
                 {cv.Optional(CONF_ALLOWED_IPS): socket.IPV4_ALLOW_SCHEMA}
             ),

tests/unit_tests/components/socket/test_socket_ipv4_host.py

@@ -0,0 +1,23 @@
+"""Tests for the socket component's IPv4 host validator."""
+
+import pytest
+
+from esphome.components import socket
+import esphome.config_validation as cv
+
+
+@pytest.mark.parametrize("value", ["192.0.2.10", "bridge.local", "bridge"])
+def test_ipv4_host_accepts_ipv4_address_and_hostname(value: str) -> None:
+    assert socket.ipv4_host(value) == value
+
+
+@pytest.mark.parametrize("value", ["2001:db8::10", "::1", "::ffff:192.0.2.10"])
+def test_ipv4_host_rejects_ipv6_address(value: str) -> None:
+    with pytest.raises(cv.Invalid, match="IPv6 addresses are not supported"):
+        socket.ipv4_host(value)
+
+
+@pytest.mark.parametrize("value", ["bridge host", ""])
+def test_ipv4_host_rejects_invalid_host(value: str) -> None:
+    with pytest.raises(cv.Invalid):
+        socket.ipv4_host(value)