Add UNIX domain FastCGI support

Resolves a long-standing todo comment and has made wiki.synchro.net page
rendering even faster.

PHP-FPM defaults to creating/listening on UNIX domain sockets.

This resolves gitlab issue #507

src/sbbs3/websrvr.c

@@ -30,8 +30,6 @@
  *
  * Add support for multipart/form-data
  *
- * Add support for UNIX-domain sockets for FastCGI
- *
  * Improved Win32 support for POST data... currently will read past Content-Length
  *
  */
@@ -3926,19 +3924,38 @@ static SOCKET fastcgi_connect(const char *orig_path, SOCKET client_sock)
 {
 	int result;
 	char *path = strdup(orig_path);
-	char *port = split_port_part(path);
 	ulong val;
 	SOCKET sock;
-	struct addrinfo	hints,*res,*cur;
 
-	// TODO: UNIX-domain sockets...
 	if (strncmp(path, "unix:", 5) == 0) {
-		lprintf(LOG_ERR, "%04d UNIX-domain FastCGI sockets not supported (yet)", client_sock);
+		// UNIX-domain socket
+		struct sockaddr_un addr;
+		socklen_t addr_len;
+		sock = socket(AF_UNIX, SOCK_STREAM, 0);
+		if (sock == INVALID_SOCKET) {
+			lprintf(LOG_ERR, "%04d ERROR creating UNIX domain FastCGI socket", client_sock);
 			free(path);
-		return INVALID_SOCKET;
+			return sock;
 		}
 
+		addr.sun_family = AF_UNIX;
+		SAFECOPY(addr.sun_path, path + 5);
+#ifdef SUN_LEN
+		addr_len = SUN_LEN(&addr);
+#else
+		addr_len = sizeof(addr);
+#endif
+		if(connect(sock, (struct sockaddr*)&addr, addr_len) != 0) {
+			lprintf(LOG_ERR, "%04d ERROR %d connecting to UNIX domain FastCGI socket: %s"
+				,client_sock, ERROR_VALUE, addr.sun_path);
+			closesocket(sock);
+			sock = INVALID_SOCKET;
+		}
+	} else {
 		// TCP Socket
+		char *port = split_port_part(path);
+		struct addrinfo	hints,*res,*cur;
+
 		memset(&hints, 0, sizeof(hints));
 		hints.ai_socktype = SOCK_STREAM;
 		hints.ai_flags = AI_ADDRCONFIG;
@@ -3971,6 +3988,7 @@ static SOCKET fastcgi_connect(const char *orig_path, SOCKET client_sock)
 		}
 
 		freeaddrinfo(res);
+	}
 	if(sock == INVALID_SOCKET) {
 		lprintf(LOG_ERR, "%04d ERROR unable to make FastCGI connection to %s", client_sock, orig_path);
 		free(path);