From ec03728680d43c6ecf3717a47be619f0c40dee07 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mat=C4=9Bj=20Cepl?= <mcepl@cepl.eu>
Date: Mon, 27 Apr 2026 23:25:03 +0200
Subject: [PATCH] gh-149078: test_socket: verify runtime kernel support for
 UDPLite

The test suite previously only checked for the existence of the
socket.IPPROTO_UDPLITE constant. This caused test failures on systems
where the constant is defined in headers (and thus present in the
interpreter) but the protocol is not supported or enabled in the
running kernel (e.g., restricted build environments).

This change adds a _have_socket_udplite() helper that performs a
runtime check by attempting to create a UDPLite socket, aligning its
behavior with other optional protocols like RDS or AF_ALG.
---
 Lib/test/test_socket.py                       | 21 +++++++++++++++----
 ...-04-28-01-08-05.gh-issue-149078.cQNQRp.rst |  3 +++
 2 files changed, 20 insertions(+), 4 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Tests/2026-04-28-01-08-05.gh-issue-149078.cQNQRp.rst

diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index 9e03069494345b..b57b38709536d6 100644
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -170,6 +170,22 @@ def _have_socket_vsock():
     return (cid is not None)
 
 
+def _have_socket_udplite():
+    """Check whether UDPLITE sockets are supported on this host."""
+    if not hasattr(socket, "IPPROTO_UDPLITE"):
+        return False
+    # Older Android versions block UDPLITE with SELinux.
+    if support.is_android and platform.android_ver().api_level < 29:
+        return False
+    try:
+        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDPLITE)
+    except (AttributeError, OSError):
+        return False
+    else:
+        s.close()
+    return True
+
+
 def _have_socket_bluetooth():
     """Check whether AF_BLUETOOTH sockets are supported on this host."""
     try:
@@ -247,10 +263,7 @@ def downgrade_malformed_data_warning():
 
 HAVE_SOCKET_VSOCK = _have_socket_vsock()
 
-# Older Android versions block UDPLITE with SELinux.
-HAVE_SOCKET_UDPLITE = (
-    hasattr(socket, "IPPROTO_UDPLITE")
-    and not (support.is_android and platform.android_ver().api_level < 29))
+HAVE_SOCKET_UDPLITE = _have_socket_udplite()
 
 HAVE_SOCKET_BLUETOOTH = _have_socket_bluetooth()
 
diff --git a/Misc/NEWS.d/next/Tests/2026-04-28-01-08-05.gh-issue-149078.cQNQRp.rst b/Misc/NEWS.d/next/Tests/2026-04-28-01-08-05.gh-issue-149078.cQNQRp.rst
new file mode 100644
index 00000000000000..3304c7668b8fec
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2026-04-28-01-08-05.gh-issue-149078.cQNQRp.rst
@@ -0,0 +1,3 @@
+This change adds a _have_socket_udplite() helper that performs a runtime
+check by attempting to create a UDPLite socket, aligning its behavior with
+other optional protocols like RDS or AF_ALG.