Fix GH-24173: Sockets left in non-blocking mode on Windows

NEWS

@@ -18,6 +18,10 @@ PHP                                                                        NEWS
   . Fixed chown() and lchown() failing to resolve user names in ZTS builds
     when getpwnam_r() needs a larger buffer. (Ilia Alshanetsky)
 
+- Streams:
+  . Fixed bug GH-24173 (Sockets from synchronous stream_socket_client() are
+    left in non-blocking mode on Windows). (vibbow)
+
 22 Oct 2026, PHP 8.4.27
 
 - BCMath:

ext/standard/tests/streams/gh24173.phpt

@@ -0,0 +1,25 @@
+--TEST--
+GH-24173 (Sockets from synchronous stream_socket_client() are left in non-blocking mode on Windows)
+--EXTENSIONS--
+sockets
+--SKIPIF--
+<?php
+if (PHP_OS_FAMILY !== 'Windows') die('skip Windows only');
+?>
+--FILE--
+<?php
+$srv = stream_socket_server('tcp://127.0.0.1:0', $errno, $errstr);
+$client = stream_socket_client('tcp://' . stream_socket_get_name($srv, false), $errno, $errstr, 5);
+$conn = stream_socket_accept($srv);
+
+$sock = socket_import_stream($client);
+socket_set_option($sock, SOL_SOCKET, SO_RCVTIMEO, ['sec' => 0, 'usec' => 100000]);
+
+// No data is sent: a blocking socket waits and times out, while a
+// non-blocking one fails at once with WSAEWOULDBLOCK.
+var_dump(@socket_read($sock, 10));
+var_dump(socket_last_error($sock) === SOCKET_ETIMEDOUT);
+?>
+--EXPECT--
+bool(false)
+bool(true)

main/network.c

@@ -286,8 +286,10 @@ PHPAPI int php_network_getaddresses(const char *host, int socktype, struct socka
 typedef u_long php_non_blocking_flags_t;
 #  define SET_SOCKET_BLOCKING_MODE(sock, save) \
 	save = TRUE; ioctlsocket(sock, FIONBIO, &save)
+/* Winsock cannot query the current mode; callers pass freshly created
+ * (blocking) sockets, so restore to blocking. */
 #  define RESTORE_SOCKET_BLOCKING_MODE(sock, save) \
-	ioctlsocket(sock, FIONBIO, &save)
+	save = FALSE; ioctlsocket(sock, FIONBIO, &save)
 #else
 typedef int php_non_blocking_flags_t;
 #  define SET_SOCKET_BLOCKING_MODE(sock, save) \