[core] lighttpd -tt performs preflight startup checks (fixes #411)

lighttpd -t loads config file and performs syntax check
lighttpd -tt (new) performs preflight startup checks,
  including loading and initializing modules, but skipping any
  potentially destructive actions which might affect an already
  running server (separate instance).  These currently include:
  - skipping pidfile modification
  - skipping bind() to network sockets
  - skipping open of error and access logs

From: Glenn Strauss <gstrauss@gluelogic.com>

git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.4.x@3130 152afb58-edef-0310-8abb-c4023f1b3aa9

NEWS

@@ -54,6 +54,7 @@ NEWS
   * [core] wait for grandchild to be ready when daemonizing (fixes #2712, thx pasdVn)
   * [core] respond 411 Length Required if request has Transfer-Encoding: chunked (fixes #631)
   * [core] fixed the loading for default modules if they are specified explicitly
+  * [core] lighttpd -tt performs preflight startup checks (fixes #411)
 
 - 1.4.39 - 2016-01-02
   * [core] fix memset_s call (fixes #2698)

src/base.h

@@ -510,6 +510,7 @@ typedef struct {
 	buffer *breakagelog_file;
 
 	unsigned short dont_daemonize;
+	unsigned short preflight_check;
 	buffer *changeroot;
 	buffer *username;
 	buffer *groupname;

src/mod_accesslog.c

@@ -584,6 +584,8 @@ SETDEFAULTS_FUNC(log_access_open) {
 
 		if (buffer_string_is_empty(s->access_logfile)) continue;
 
+		if (srv->srvconf.preflight_check) continue;
+
 		if (-1 == (s->log_access_fd = open_logfile_or_pipe(srv, s->access_logfile->ptr)))
 			return HANDLER_ERROR;
 

src/network.c

@@ -170,11 +170,11 @@ static int network_server_init(server *srv, buffer *host_token, specific_config
 	buffer *b;
 	int is_unix_domain_socket = 0;
 	int fd;
+	int err;
 
 #ifdef __WIN32
 	WORD wVersionRequested;
 	WSADATA wsaData;
-	int err;
 
 	wVersionRequested = MAKEWORD( 2, 2 );
 
@@ -185,6 +185,7 @@ static int network_server_init(server *srv, buffer *host_token, specific_config
 		    return -1;
 	}
 #endif
+	err = -1;
 
 	srv_socket = calloc(1, sizeof(*srv_socket));
 	force_assert(NULL != srv_socket);
@@ -380,6 +381,8 @@ static int network_server_init(server *srv, buffer *host_token, specific_config
 #endif
 		}
 
+		if (srv->srvconf.preflight_check) break;
+
 		/* check if the socket exists and try to connect to it. */
 		if (-1 != (fd = connect(srv_socket->fd, (struct sockaddr *) &(srv_socket->addr), addr_len))) {
 			close(fd);
@@ -412,6 +415,11 @@ static int network_server_init(server *srv, buffer *host_token, specific_config
 		goto error_free_socket;
 	}
 
+	if (srv->srvconf.preflight_check) {
+		err = 0;
+		goto error_free_socket;
+	}
+
 	if (0 != bind(srv_socket->fd, (struct sockaddr *) &(srv_socket->addr), addr_len)) {
 		switch(srv_socket->addr.plain.sa_family) {
 		case AF_UNIX:
@@ -501,7 +509,7 @@ error_free_socket:
 
 	buffer_free(b);
 
-	return -1;
+	return err; /* -1 if error; 0 if srv->srvconf.preflight_check successful */
 }
 
 int network_close(server *srv) {

src/server.c

@@ -649,6 +649,7 @@ int main (int argc, char **argv) {
 	i_am_root = 0;
 #endif
 	srv->srvconf.dont_daemonize = 0;
+	srv->srvconf.preflight_check = 0;
 
 	while(-1 != (o = getopt(argc, argv, "f:m:hvVDpt"))) {
 		switch(o) {
@@ -669,7 +670,7 @@ int main (int argc, char **argv) {
 			buffer_copy_string(srv->srvconf.modules_dir, optarg);
 			break;
 		case 'p': print_config = 1; break;
-		case 't': test_config = 1; break;
+		case 't': ++test_config; break;
 		case 'D': srv->srvconf.dont_daemonize = 1; break;
 		case 'v': show_version(); return 0;
 		case 'V': show_features(); return 0;
@@ -701,7 +702,14 @@ int main (int argc, char **argv) {
 	}
 
 	if (test_config) {
-		printf("Syntax OK\n");
+		if (1 == test_config) {
+			printf("Syntax OK\n");
+		} else { /*(test_config > 1)*/
+			test_config = 0;
+			srv->srvconf.preflight_check = 1;
+			srv->srvconf.dont_daemonize = 1;
+			buffer_reset(srv->srvconf.pid_file);
+		}
 	}
 
 	if (test_config || print_config) {
@@ -1084,7 +1092,7 @@ int main (int argc, char **argv) {
 
 	/* Close stderr ASAP in the child process to make sure that nothing
 	 * is being written to that fd which may not be valid anymore. */
-	if (-1 == log_error_open(srv)) {
+	if (!srv->srvconf.preflight_check && -1 == log_error_open(srv)) {
 		log_error_write(srv, __FILE__, __LINE__, "s", "Opening errorlog failed. Going down.");
 
 		plugins_free(srv);
@@ -1143,6 +1151,15 @@ int main (int argc, char **argv) {
 		return -1;
 	}
 
+	if (srv->srvconf.preflight_check) {
+		/*printf("Preflight OK");*//*(stdout reopened to /dev/null)*/
+		plugins_free(srv);
+		network_close(srv);
+		server_free(srv);
+
+		exit(0);
+	}
+
 
 #ifdef HAVE_FORK
 	/**