gh-149776: Skip UDP Lite tests if it's not supported (#149777)

Fix test_socket on Linux kernel 7.1 and newer: skip UDP Lite tests if
it's not supported.

Author: vstinner

Lib/test/test_socket.py

@@ -205,6 +205,25 @@ def _have_socket_hyperv():
     return True
 
 
+def _have_udp_lite():
+    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:
+        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDPLITE)
+    except OSError as exc:
+        # Linux 7.1 removed UDP Lite support
+        if exc.errno == errno.EPROTONOSUPPORT:
+            return False
+        raise
+    sock.close()
+
+    return True
+
+
 @contextlib.contextmanager
 def socket_setdefaulttimeout(timeout):
     old_timeout = socket.getdefaulttimeout()
@@ -247,10 +266,7 @@ 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_udp_lite()
 
 HAVE_SOCKET_BLUETOOTH = _have_socket_bluetooth()
 

Misc/NEWS.d/next/Tests/2026-05-13-14-53-23.gh-issue-149776.orqgsn.rst

@@ -0,0 +1,2 @@
+Fix test_socket on Linux kernel 7.1 and newer: skip UDP Lite tests if it's
+not supported. Patch by Victor Stinner.