Implement a clean way to open /dev/null and use it to close stdin/out/err in the needed places (#624)

- as stderr gets redirected to /dev/null before exec in childs, we cannot
   write to the log afterwards, so disabled that log messages too.


git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.4.x@2163 152afb58-edef-0310-8abb-c4023f1b3aa9

NEWS

@@ -24,6 +24,7 @@ NEWS
   * Remove lighttpd.spec* from source, fixing all problems with it ;-)
   * Do not rely on PATH_MAX (POSIX does not require it) (#580)
   * Disable logging to access.log if filename is an empty string
+  * Implement a clean way to open /dev/null and use it to close stdin/out/err in the needed places (#624)
 
 - 1.4.19 - 2008-03-10
 

src/log.c

@@ -31,6 +31,29 @@
 # define O_LARGEFILE 0
 #endif
 
+/* Close fd and _try_ to get a /dev/null for it instead.
+ * close() alone may trigger some bugs when a
+ * process opens another file and gets fd = STDOUT_FILENO or STDERR_FILENO
+ * and later tries to just print on stdout/stderr
+ *
+ * Returns 0 on success and -1 on failure (fd gets closed in all cases)
+ */
+int openDevNull(int fd) {
+	int tmpfd;
+	close(fd);
+#if defined(__WIN32)
+	/* Cygwin should work with /dev/null */
+	tmpfd = open("nul", O_RDWR);
+#else
+	tmpfd = open("/dev/null", O_RDWR);
+#endif
+	if (tmpfd != -1 && tmpfd != fd) {
+		dup2(tmpfd, fd);
+		close(tmpfd);
+	}
+	return (tmpfd != -1) ? 0 : -1;
+}
+
 /**
  * open the errorlog
  *
@@ -44,7 +67,6 @@
  */
 
 int log_error_open(server *srv) {
-	int fd;
 	int close_stderr = 1;
 
 #ifdef HAVE_SYSLOG_H
@@ -78,15 +100,16 @@ int log_error_open(server *srv) {
 	/* don't close stderr for debugging purposes if run in valgrind */
 	if (RUNNING_ON_VALGRIND) close_stderr = 0;
 #endif
-	if (srv->errorlog_mode == ERRORLOG_STDERR) close_stderr = 0;
 
-	/* move stderr to /dev/null */
-	if (close_stderr &&
-	    -1 != (fd = open("/dev/null", O_WRONLY))) {
-		close(STDERR_FILENO);
-		dup2(fd, STDERR_FILENO);
-		close(fd);
+	if (srv->errorlog_mode == ERRORLOG_STDERR && srv->srvconf.dont_daemonize) {
+		/* We can only log to stderr in dont-daemonize mode;
+		 * if we do daemonize and no errorlog file is specified, we log into /dev/null
+		 */
+		close_stderr = 0;
 	}
+
+	/* move stderr to /dev/null */
+	if (close_stderr) openDevNull(STDERR_FILENO);
 	return 0;
 }
 

src/log.h

@@ -3,6 +3,11 @@
 
 #include "server.h"
 
+/* Close fd and _try_ to get a /dev/null for it instead.
+ * Returns 0 on success and -1 on failure (fd gets closed in all cases)
+ */
+int openDevNull(int fd);
+
 #define WP() log_error_write(srv, __FILE__, __LINE__, "");
 
 int log_error_open(server *srv);

src/mod_accesslog.c

@@ -498,6 +498,8 @@ SETDEFAULTS_FUNC(log_access_open) {
 				/* not needed */
 				close(to_log_fds[1]);
 
+				openDevNull(STDERR_FILENO);
+
 				/* we don't need the client socket */
 				for (i = 3; i < 256; i++) {
 					close(i);

src/mod_cgi.c

@@ -987,6 +987,8 @@ static int cgi_create_env(server *srv, connection *con, plugin_data *p, buffer *
 			*c = '/';
 		}
 
+		openDevNull(STDERR_FILENO);
+
 		/* we don't need the client socket */
 		for (i = 3; i < 256; i++) {
 			if (i != srv->errorlog_fd) close(i);
@@ -995,7 +997,7 @@ static int cgi_create_env(server *srv, connection *con, plugin_data *p, buffer *
 		/* exec the cgi */
 		execve(args[0], args, env.ptr);
 
-		log_error_write(srv, __FILE__, __LINE__, "sss", "CGI failed:", strerror(errno), args[0]);
+		/* log_error_write(srv, __FILE__, __LINE__, "sss", "CGI failed:", strerror(errno), args[0]); */
 
 		/* */
 		SEGFAULT();

src/mod_fastcgi.c

@@ -937,6 +937,8 @@ static int fcgi_spawn_connection(server *srv,
 				close(fcgi_fd);
 			}
 
+			openDevNull(STDERR_FILENO);
+
 			/* we don't need the client socket */
 			for (i = 3; i < 256; i++) {
 				close(i);
@@ -1000,8 +1002,8 @@ static int fcgi_spawn_connection(server *srv,
 			/* exec the cgi */
 			execve(arg.ptr[0], arg.ptr, env.ptr);
 
-			log_error_write(srv, __FILE__, __LINE__, "sbs",
-					"execve failed for:", host->bin_path, strerror(errno));
+			/* log_error_write(srv, __FILE__, __LINE__, "sbs",
+					"execve failed for:", host->bin_path, strerror(errno)); */
 
 			exit(errno);
 

src/mod_rrdtool.c

@@ -148,6 +148,8 @@ int mod_rrd_create_pipe(server *srv, plugin_data *p) {
 		args[i++] = dash;
 		args[i++] = NULL;
 
+		openDevNull(STDERR_FILENO);
+	
 		/* we don't need the client socket */
 		for (i = 3; i < 256; i++) {
 			close(i);
@@ -156,7 +158,7 @@ int mod_rrd_create_pipe(server *srv, plugin_data *p) {
 		/* exec the cgi */
 		execv(args[0], args);
 
-		log_error_write(srv, __FILE__, __LINE__, "sss", "spawing rrdtool failed: ", strerror(errno), args[0]);
+		/* log_error_write(srv, __FILE__, __LINE__, "sss", "spawing rrdtool failed: ", strerror(errno), args[0]); */
 
 		/* */
 		SEGFAULT();

src/server.c

@@ -573,19 +573,8 @@ int main (int argc, char **argv) {
 	}
 
 	/* close stdin and stdout, as they are not needed */
-	/* move stdin to /dev/null */
-	if (-1 != (fd = open("/dev/null", O_RDONLY))) {
-		close(STDIN_FILENO);
-		dup2(fd, STDIN_FILENO);
-		close(fd);
-	}
-
-	/* move stdout to /dev/null */
-	if (-1 != (fd = open("/dev/null", O_WRONLY))) {
-		close(STDOUT_FILENO);
-		dup2(fd, STDOUT_FILENO);
-		close(fd);
-	}
+	openDevNull(STDIN_FILENO);
+	openDevNull(STDOUT_FILENO);
 
 	if (0 != config_set_defaults(srv)) {
 		log_error_write(srv, __FILE__, __LINE__, "s",