ext/sockets: Adding TCP_FUNCTION_BLK socket option for FreeBSD.

Allows to select an alternate TCP stack. For example with RACK,
a fast loss detection relying on timestamp per packet.

While it works system-wide, it can also apply in an individual socket level too.

close GH-16842

NEWS

@@ -52,6 +52,8 @@ PHP                                                                        NEWS
 - Sockets:
   . Added IPPROTO_ICMP/IPPROTO_ICMPV6 to create raw socket for ICMP usage.
     (David Carlier)
+  . Added TCP_FUNCTION_BLK to change the TCP stack algorithm on FreeBSD.
+    (David Carlier)
 
 - Standard:
   . Fixed crypt() tests on musl when using --with-external-libcrypt

UPGRADING

@@ -137,6 +137,7 @@ PHP 8.5 UPGRADE NOTES
 
 - Sockets:
   . IPPROTO_ICMP/IPPROTO_ICMPV6.
+  . TCP_FUNCTION_BLK (FreeBSD only).
 
 ========================================
 11. Changes to INI File Handling

ext/sockets/sockets.c

@@ -1703,6 +1703,25 @@ PHP_FUNCTION(socket_get_option)
 			}
 		}
 #endif
+
+#ifdef TCP_FUNCTION_BLK
+		case TCP_FUNCTION_BLK: {
+
+			struct tcp_function_set tsf = {0};
+			optlen = sizeof(tsf);
+
+			if (getsockopt(php_sock->bsd_socket, level, optname, &tsf, &optlen) != 0) {
+				PHP_SOCKET_ERROR(php_sock, "Unable to retrieve socket option", errno);
+				RETURN_FALSE;
+			}
+
+			array_init(return_value);
+
+			add_assoc_string(return_value, "function_set_name", tsf.function_set_name);
+			add_assoc_long(return_value, "pcbcnt", tsf.pcbcnt);
+			return;
+		}
+#endif
 		}
 	}
 
@@ -1915,6 +1934,27 @@ PHP_FUNCTION(socket_set_option)
 			RETURN_TRUE;
 		}
 #endif
+
+#ifdef TCP_FUNCTION_BLK
+		case TCP_FUNCTION_BLK: {
+			if (Z_TYPE_P(arg4) != IS_STRING) {
+				php_error_docref(NULL, E_WARNING, "Invalid tcp stack name argument type");
+				RETURN_FALSE;
+			}
+			struct tcp_function_set tfs = {0};
+			strlcpy(tfs.function_set_name, Z_STRVAL_P(arg4), TCP_FUNCTION_NAME_LEN_MAX);
+
+			optlen = sizeof(tfs);
+			opt_ptr = &tfs;
+			if (setsockopt(php_sock->bsd_socket, level, optname, opt_ptr, optlen) != 0) {
+				PHP_SOCKET_ERROR(php_sock, "Unable to set socket option", errno);
+				RETURN_FALSE;
+			}
+
+			RETURN_TRUE;
+		}
+#endif
+
 		}
 	}
 

ext/sockets/sockets.stub.php

@@ -640,6 +640,13 @@
  */
 const TCP_KEEPCNT = UNKNOWN;
 #endif
+#ifdef TCP_FUNCTION_BLK
+/**
+ * @var int
+ * @cvalue TCP_FUNCTION_BLK
+ */
+const TCP_FUNCTION_BLK = UNKNOWN;
+#endif
 /**
  * @var int
  * @cvalue PHP_NORMAL_READ

ext/sockets/tests/socket_set_option_tsf.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Test if socket_set_option() works, option:TCP_FUNCTION_BLK
+--EXTENSIONS--
+sockets
+--SKIPIF--
+<?php
+
+if (!defined("TCP_FUNCTION_BLK")) {
+	die('SKIP on platforms not supporting TCP_FUNCTION_BLK');
+}
+?>
+--FILE--
+<?php
+$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
+
+if (!$socket) {
+        die('Unable to create AF_INET socket [socket]');
+}
+socket_set_option( $socket, SOL_TCP, TCP_FUNCTION_BLK, "nochancetoexist");
+// TCP/RACK and other alternate stacks are not present by default, at least `freebsd` is.
+var_dump(socket_set_option( $socket, SOL_TCP, TCP_FUNCTION_BLK, "freebsd"));
+var_dump(socket_get_option( $socket, SOL_TCP, TCP_FUNCTION_BLK));
+socket_close($socket);
+?>
+--EXPECTF--
+Warning: socket_set_option(): Unable to set socket option [2]: No such file or directory in %s on line %d
+bool(true)
+array(2) {
+  ["function_set_name"]=>
+  string(7) "freebsd"
+  ["pcbcnt"]=>
+  int(%d)
+}