X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=libustcomm%2Fustcomm.c;h=cb72db65733eb5353c7d10a74018ff856874c648;hb=69c37f741b8bd8aea95019e1debf5e3bfa9d7fff;hp=0a5ab6aaaf1110d8e66a44b123f81f4d9829c878;hpb=69ba01560f9193dbf4ad2fc8361efb725704807c;p=ust.git

diff --git a/libustcomm/ustcomm.c b/libustcomm/ustcomm.c
index 0a5ab6a..cb72db6 100644
--- a/libustcomm/ustcomm.c
+++ b/libustcomm/ustcomm.c
@@ -23,6 +23,7 @@
 #include <sys/un.h>
 #include <unistd.h>
 #include <poll.h>
+#include <sys/stat.h>
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -30,13 +31,12 @@
 #include <execinfo.h>
 
 #include "ustcomm.h"
-#include "localerr.h"
+#include "usterr.h"
+#include "share.h"
 
 #define UNIX_PATH_MAX 108
-#define SOCK_DIR "/tmp/socks"
-#define UST_SIGNAL SIGIO
 
-#define MSG_MAX 1000
+#define MSG_MAX 10000
 
 /* FIXME: ustcomm blocks on message sending, which might be problematic in
  * some cases. Fix the poll() usage so sends are buffered until they don't
@@ -52,6 +52,55 @@
 //	backtrace_symbols_fd(buffer, result, STDERR_FILENO);
 //}
 
+static int mkdir_p(const char *path, mode_t mode)
+{
+	const char *path_p;
+	char *tmp;
+
+	int retval = 0;
+	int result;
+
+	tmp = malloc(strlen(path) + 1);
+	if (tmp == NULL)
+		return -1;
+
+	/* skip first / */
+	path_p = path+1;
+
+	for(;;) {
+		while (*path_p != '/') {
+			if(*path_p == 0)
+				break;
+			++path_p;
+		}
+		if (*path_p == '/') {
+			strncpy(tmp, path, path_p - path);
+			tmp[path_p-path] = '\0';
+			if (tmp[path_p - path - 1] != '/') {
+				result = mkdir(tmp, mode);
+				if(result == -1) {
+					if (!(errno == EEXIST || errno == EACCES || errno == EROFS)) {
+						/* Then this is a real error */
+						retval = -1;
+						break;
+					}
+				}
+			}
+			/* pass / */
+			path_p++;
+		} else {
+			/* last component */
+			result = mkdir(path, mode);
+			if (result == -1)
+				retval = -1;
+			break;
+		}
+	}
+
+	free(tmp);
+	return retval;
+}
+
 char *strdup_malloc(const char *s)
 {
 	char *retval;
@@ -68,156 +117,186 @@ char *strdup_malloc(const char *s)
 
 static int signal_process(pid_t pid)
 {
-	int result;
-
-	result = kill(pid, UST_SIGNAL);
-	if(result == -1) {
-		PERROR("kill");
-		return -1;
-	}
+	return 0;
+}
 
-	/* FIXME: should wait in a better way */
-	//sleep(1);
+void ustcomm_init_connection(struct ustcomm_connection *conn)
+{
+	conn->recv_buf = NULL;
+	conn->recv_buf_size = 0;
+	conn->recv_buf_alloc = 0;
+}
 
-	return 0;
+int pid_is_online(pid_t pid) {
+	return 1;
 }
 
+/* Send a message
+ *
+ * @fd: file descriptor to send to
+ * @msg: a null-terminated string containing the message to send
+ *
+ * Return value:
+ * -1: error
+ * 0: connection closed
+ * 1: success
+ */
+
 static int send_message_fd(int fd, const char *msg)
 {
 	int result;
 
-	result = send(fd, msg, strlen(msg), 0);
+	/* Send including the final \0 */
+	result = patient_send(fd, msg, strlen(msg)+1, MSG_NOSIGNAL);
 	if(result == -1) {
-		PERROR("send");
+		if(errno != EPIPE)
+			PERROR("send");
 		return -1;
 	}
 	else if(result == 0) {
 		return 0;
 	}
 
+	DBG("sent message \"%s\"", msg);
 	return 1;
-
-//	*reply = (char *) malloc(MSG_MAX+1);
-//	result = recv(fd, *reply, MSG_MAX, 0);
-//	if(result == -1) {
-//		PERROR("recv");
-//		return -1;
-//	}
-//	else if(result == 0) {
-//		return 0;
-//	}
-//	
-//	(*reply)[result] = '\0';
-//
-//	return 1;
 }
 
-static int send_message_path(const char *path, const char *msg, int signalpid)
+/* Called by an app to ask the consumer daemon to connect to it. */
+
+int ustcomm_request_consumer(pid_t pid, const char *channel)
 {
-	int fd;
+	char path[UNIX_PATH_MAX];
 	int result;
-	struct sockaddr_un addr;
+	char *msg=NULL;
+	int retval = 0;
+	struct ustcomm_connection conn;
+	char *explicit_daemon_socket_path;
 
-	result = fd = socket(PF_UNIX, SOCK_STREAM, 0);
-	if(result == -1) {
-		PERROR("socket");
-		return -1;
+	explicit_daemon_socket_path = getenv("UST_DAEMON_SOCKET");
+	if(explicit_daemon_socket_path) {
+		/* user specified explicitly a socket path */
+		result = snprintf(path, UNIX_PATH_MAX, "%s", explicit_daemon_socket_path);
+	}
+	else {
+		/* just use the default path */
+		result = snprintf(path, UNIX_PATH_MAX, "%s/ustd", SOCK_DIR);
 	}
 
-	addr.sun_family = AF_UNIX;
-
-	result = snprintf(addr.sun_path, UNIX_PATH_MAX, "%s", path);
 	if(result >= UNIX_PATH_MAX) {
 		ERR("string overflow allocating socket name");
 		return -1;
 	}
 
-	if(signalpid >= 0) {
-		result = signal_process(signalpid);
-		if(result == -1) {
-			ERR("could not signal process");
-			return -1;
-		}
+	asprintf(&msg, "collect %d %s", pid, channel); 
+
+	/* don't signal it because it's the daemon */
+	result = ustcomm_connect_path(path, &conn, -1);
+	if(result == -1) {
+		WARN("ustcomm_connect_path failed");
+		retval = -1;
+		goto del_string;
 	}
 
-	result = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
+	result = ustcomm_send_request(&conn, msg, NULL);
 	if(result == -1) {
-		PERROR("connect");
-		return -1;
+		WARN("ustcomm_send_request failed");
+		retval = -1;
+		goto disconnect;
 	}
 
-	return send_message_fd(fd, msg);
+	disconnect:
+	ustcomm_disconnect(&conn);
+	del_string:
+	free(msg);
+
+	return retval;
 }
 
-///* pid: the pid of the trace process that must receive the msg
-//   msg: pointer to a null-terminated message to send
-//   reply: location where to put the null-terminated string of the reply;
-//	  it must be free'd after usage
-// */
-//
-//int send_message_pid(pid_t pid, const char *msg, char **reply)
-//{
-//	int result;
-//	char path[UNIX_PATH_MAX];
-//
-//	result = snprintf(path, UNIX_PATH_MAX, "%s/%d", SOCK_DIR, pid);
-//	if(result >= UNIX_PATH_MAX) {
-//		fprintf(stderr, "string overflow allocating socket name");
-//		return -1;
-//	}
-//
-//	send_message_path(path, msg, reply, pid);
-//
-//	return 0;
-//}
+/* returns 1 to indicate a message was received
+ * returns 0 to indicate no message was received (end of stream)
+ * returns -1 to indicate an error
+ */
 
-/* Called by an app to ask the consumer daemon to connect to it. */
+#define RECV_INCREMENT 1000
+#define RECV_INITIAL_BUF_SIZE 10
 
-int ustcomm_request_consumer(pid_t pid, const char *channel)
+static int recv_message_fd(int fd, char **recv_buf, int *recv_buf_size, int *recv_buf_alloc, char **msg)
 {
-	char path[UNIX_PATH_MAX];
 	int result;
-	char *msg;
 
-	result = snprintf(path, UNIX_PATH_MAX, "%s/ustd", SOCK_DIR);
-	if(result >= UNIX_PATH_MAX) {
-		fprintf(stderr, "string overflow allocating socket name");
-		return -1;
-	}
+	/* 1. Check if there is a message in the buf */
+	/* 2. If not, do:
+           2.1 receive chunk and put it in buffer
+	   2.2 process full message if there is one
+	   -- while no message arrived
+	*/
 
-	asprintf(&msg, "collect %d %s", pid, channel); 
+	for(;;) {
+		int i;
+		int nulfound = 0;
+
+		/* Search for full message in buffer */
+		for(i=0; i<*recv_buf_size; i++) {
+			if((*recv_buf)[i] == '\0') {
+				nulfound = 1;
+				break;
+			}
+		}
 
-	send_message_path(path, msg, -1);
-	free(msg);
+		/* Process found message */
+		if(nulfound == 1) {
+			char *newbuf;
 
-	return 0;
-}
+			if(i == 0) {
+				/* problem */
+				WARN("received empty message");
+			}
+			*msg = strndup(*recv_buf, i);
 
-/* returns 1 to indicate a message was received
- * returns 0 to indicate no message was received (cannot happen)
- * returns -1 to indicate an error
- */
+			/* Remove processed message from buffer */
+			newbuf = (char *) malloc(*recv_buf_size - (i+1));
+			memcpy(newbuf, *recv_buf + (i+1), *recv_buf_size - (i+1));
+			free(*recv_buf);
+			*recv_buf = newbuf;
+			*recv_buf_size -= (i+1);
+			*recv_buf_alloc -= (i+1);
 
-static int recv_message_fd(int fd, char **msg, struct ustcomm_source *src)
-{
-	int result;
+			return 1;
+		}
 
-	*msg = (char *) malloc(MSG_MAX+1);
+		/* Receive a chunk from the fd */
+		if(*recv_buf_alloc - *recv_buf_size < RECV_INCREMENT) {
+			*recv_buf_alloc += RECV_INCREMENT - (*recv_buf_alloc - *recv_buf_size);
+			*recv_buf = (char *) realloc(*recv_buf, *recv_buf_alloc);
+		}
 
-	result = recv(fd, *msg, MSG_MAX, 0);
-	if(result == -1) {
-		PERROR("recv");
-		return -1;
-	}
+		result = recv(fd, *recv_buf+*recv_buf_size, RECV_INCREMENT, 0);
+		if(result == -1) {
+			if(errno == ECONNRESET) {
+				*recv_buf_size = 0;
+				return 0;
+			}
+			/* real error */
+			PERROR("recv");
+			return -1;
+		}
+		if(result == 0) {
+			return 0;
+		}
+		*recv_buf_size += result;
 
-	(*msg)[result] = '\0';
-	
-	DBG("ustcomm_app_recv_message: result is %d, message is %s", result, (*msg));
+		/* Go back to the beginning to check if there is a full message in the buffer */
+	}
 
-	if(src)
-		src->fd = fd;
+	DBG("received message \"%s\"", *recv_buf);
 
 	return 1;
+
+}
+
+static int recv_message_conn(struct ustcomm_connection *conn, char **msg)
+{
+	return recv_message_fd(conn->fd, &conn->recv_buf, &conn->recv_buf_size, &conn->recv_buf_alloc, msg);
 }
 
 int ustcomm_send_reply(struct ustcomm_server *server, char *msg, struct ustcomm_source *src)
@@ -233,6 +312,23 @@ int ustcomm_send_reply(struct ustcomm_server *server, char *msg, struct ustcomm_
 	return 0;
 } 
 
+/* Called after a fork. */
+
+int ustcomm_close_all_connections(struct ustcomm_server *server)
+{
+	struct ustcomm_connection *conn;
+	struct ustcomm_connection *deletable_conn = NULL;
+
+	list_for_each_entry(conn, &server->connections, list) {
+		free(deletable_conn);
+		deletable_conn = conn;
+		ustcomm_close_app(conn);
+		list_del(&conn->list);
+	}
+
+	return 0;
+}
+
 /* @timeout: max blocking time in milliseconds, -1 means infinity
  *
  * returns 1 to indicate a message was received
@@ -243,6 +339,7 @@ int ustcomm_send_reply(struct ustcomm_server *server, char *msg, struct ustcomm_
 int ustcomm_recv_message(struct ustcomm_server *server, char **msg, struct ustcomm_source *src, int timeout)
 {
 	struct pollfd *fds;
+	struct ustcomm_connection **conn_table;
 	struct ustcomm_connection *conn;
 	int result;
 	int retval;
@@ -261,6 +358,13 @@ int ustcomm_recv_message(struct ustcomm_server *server, char **msg, struct ustco
 			return -1;
 		}
 
+		conn_table = (struct ustcomm_connection **) malloc(n_fds * sizeof(struct ustcomm_connection *));
+		if(conn_table == NULL) {
+			ERR("malloc returned NULL");
+			retval = -1;
+			goto free_fds_return;
+		}
+
 		/* special idx 0 is for listening socket */
 		fds[idx].fd = server->listen_fd;
 		fds[idx].events = POLLIN;
@@ -269,6 +373,7 @@ int ustcomm_recv_message(struct ustcomm_server *server, char **msg, struct ustco
 		list_for_each_entry(conn, &server->connections, list) {
 			fds[idx].fd = conn->fd;
 			fds[idx].events = POLLIN;
+			conn_table[idx] = conn;
 			idx++;
 		}
 
@@ -276,11 +381,14 @@ int ustcomm_recv_message(struct ustcomm_server *server, char **msg, struct ustco
 			/* nothing */;
 		if(result == -1) {
 			PERROR("poll");
-			return -1;
+			retval = -1;
+			goto free_conn_table_return;
 		}
 
-		if(result == 0)
-			return 0;
+		if(result == 0) {
+			retval = 0;
+			goto free_conn_table_return;
+		}
 
 		if(fds[0].revents) {
 			struct ustcomm_connection *newconn;
@@ -289,7 +397,8 @@ int ustcomm_recv_message(struct ustcomm_server *server, char **msg, struct ustco
 			result = newfd = accept(server->listen_fd, NULL, NULL);
 			if(result == -1) {
 				PERROR("accept");
-				return -1;
+				retval = -1;
+				goto free_conn_table_return;
 			}
 
 			newconn = (struct ustcomm_connection *) malloc(sizeof(struct ustcomm_connection));
@@ -298,6 +407,7 @@ int ustcomm_recv_message(struct ustcomm_server *server, char **msg, struct ustco
 				return -1;
 			}
 
+			ustcomm_init_connection(newconn);
 			newconn->fd = newfd;
 
 			list_add(&newconn->list, &server->connections);
@@ -305,27 +415,33 @@ int ustcomm_recv_message(struct ustcomm_server *server, char **msg, struct ustco
 
 		for(idx=1; idx<n_fds; idx++) {
 			if(fds[idx].revents) {
-				retval = recv_message_fd(fds[idx].fd, msg, src);
-				if(**msg == 0) {
-					/* connection finished */
-					close(fds[idx].fd);
+				retval = recv_message_conn(conn_table[idx], msg);
+				if(src)
+					src->fd = fds[idx].fd;
 
+				if(retval == 0) {
+					/* connection finished */
 					list_for_each_entry(conn, &server->connections, list) {
 						if(conn->fd == fds[idx].fd) {
+							ustcomm_close_app(conn);
 							list_del(&conn->list);
+							free(conn);
 							break;
 						}
 					}
 				}
 				else {
-					goto free_fds_return;
+					goto free_conn_table_return;
 				}
 			}
 		}
 
 		free(fds);
+		free(conn_table);
 	}
 
+free_conn_table_return:
+	free(conn_table);
 free_fds_return:
 	free(fds);
 	return retval;
@@ -361,7 +477,7 @@ found:
 	return src->fd;
 }
 
-static int init_named_socket(char *name, char **path_out)
+static int init_named_socket(const char *name, char **path_out)
 {
 	int result;
 	int fd;
@@ -387,7 +503,7 @@ static int init_named_socket(char *name, char **path_out)
 			PERROR("unlink of socket file");
 			goto close_sock;
 		}
-		WARN("socket already exists; overwriting");
+		DBG("socket already exists; overwriting");
 	}
 
 	result = bind(fd, (struct sockaddr *)&addr, sizeof(addr));
@@ -403,8 +519,7 @@ static int init_named_socket(char *name, char **path_out)
 	}
 
 	if(path_out) {
-		*path_out = "";
-		*path_out = strdupa(addr.sun_path);
+		*path_out = strdup(addr.sun_path);
 	}
 
 	return fd;
@@ -415,40 +530,52 @@ static int init_named_socket(char *name, char **path_out)
 	return -1;
 }
 
-int ustcomm_send_request(struct ustcomm_connection *conn, char *req, char **reply)
+/*
+ * Return value:
+ *   0: Success, but no reply because recv() returned 0
+ *   1: Success
+ *   -1: Error
+ *
+ * On error, the error message is printed, except on
+ * ECONNRESET, which is normal when the application dies.
+ */
+
+int ustcomm_send_request(struct ustcomm_connection *conn, const char *req, char **reply)
 {
 	int result;
 
-	result = send(conn->fd, req, strlen(req), 0);
-	if(result == -1) {
-		PERROR("send");
-		return -1;
-	}
+	/* Send including the final \0 */
+	result = send_message_fd(conn->fd, req);
+	if(result != 1)
+		return result;
 
 	if(!reply)
 		return 1;
 
-	*reply = (char *) malloc(MSG_MAX+1);
-	result = recv(conn->fd, *reply, MSG_MAX, 0);
+	result = recv_message_conn(conn, reply);
 	if(result == -1) {
-		PERROR("recv");
 		return -1;
 	}
 	else if(result == 0) {
 		return 0;
 	}
 	
-	(*reply)[result] = '\0';
-
 	return 1;
 }
 
-int ustcomm_connect_path(char *path, struct ustcomm_connection *conn, pid_t signalpid)
+/* Return value:
+ *  0: success
+ * -1: error
+ */
+
+int ustcomm_connect_path(const char *path, struct ustcomm_connection *conn, pid_t signalpid)
 {
 	int fd;
 	int result;
 	struct sockaddr_un addr;
 
+	ustcomm_init_connection(conn);
+
 	result = fd = socket(PF_UNIX, SOCK_STREAM, 0);
 	if(result == -1) {
 		PERROR("socket");
@@ -473,7 +600,7 @@ int ustcomm_connect_path(char *path, struct ustcomm_connection *conn, pid_t sign
 
 	result = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
 	if(result == -1) {
-		PERROR("connect");
+		PERROR("connect (path=%s)", path);
 		return -1;
 	}
 
@@ -487,6 +614,13 @@ int ustcomm_disconnect(struct ustcomm_connection *conn)
 	return close(conn->fd);
 }
 
+/* Open a connection to a traceable app.
+ *
+ * Return value:
+ *  0: success
+ * -1: error
+ */
+
 int ustcomm_connect_app(pid_t pid, struct ustcomm_connection *conn)
 {
 	int result;
@@ -495,19 +629,56 @@ int ustcomm_connect_app(pid_t pid, struct ustcomm_connection *conn)
 
 	result = snprintf(path, UNIX_PATH_MAX, "%s/%d", SOCK_DIR, pid);
 	if(result >= UNIX_PATH_MAX) {
-		fprintf(stderr, "string overflow allocating socket name");
+		ERR("string overflow allocating socket name");
 		return -1;
 	}
 
 	return ustcomm_connect_path(path, conn, pid);
 }
 
-int ustcomm_disconnect_app(struct ustcomm_connection *conn)
+/* Close a connection to a traceable app. It frees the
+ * resources. It however does not free the
+ * ustcomm_connection itself.
+ */
+
+int ustcomm_close_app(struct ustcomm_connection *conn)
 {
 	close(conn->fd);
+	free(conn->recv_buf);
+
 	return 0;
 }
 
+static int ensure_dir_exists(const char *dir)
+{
+	struct stat st;
+	int result;
+
+	if(!strcmp(dir, ""))
+		return -1;
+
+	result = stat(dir, &st);
+	if(result == -1 && errno != ENOENT) {
+		return -1;
+	}
+	else if(result == -1) {
+		/* ENOENT */
+		int result;
+
+		result = mkdir_p(dir, 0777);
+		if(result != 0) {
+			ERR("executing in recursive creation of directory %s", dir);
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+/* Called by an application to initialize its server so daemons can
+ * connect to it.
+ */
+
 int ustcomm_init_app(pid_t pid, struct ustcomm_app *handle)
 {
 	int result;
@@ -519,9 +690,15 @@ int ustcomm_init_app(pid_t pid, struct ustcomm_app *handle)
 		return -1;
 	}
 
+	result = ensure_dir_exists(SOCK_DIR);
+	if(result == -1) {
+		ERR("Unable to create socket directory %s", SOCK_DIR);
+		return -1;
+	}
+
 	handle->server.listen_fd = init_named_socket(name, &(handle->server.socketpath));
 	if(handle->server.listen_fd < 0) {
-		ERR("error initializing named socket");
+		ERR("Error initializing named socket (%s). Check that directory exists and that it is writable.", name);
 		goto free_name;
 	}
 	free(name);
@@ -535,34 +712,96 @@ free_name:
 	return -1;
 }
 
-int ustcomm_init_ustd(struct ustcomm_ustd *handle)
+/* Used by the daemon to initialize its server so applications
+ * can connect to it.
+ */
+
+int ustcomm_init_ustd(struct ustcomm_ustd *handle, const char *sock_path)
 {
-	int result;
 	char *name;
+	int retval = 0;
 
-	result = asprintf(&name, "%s/%s", SOCK_DIR, "ustd");
-	if(result >= UNIX_PATH_MAX) {
-		ERR("string overflow allocating socket name");
-		return -1;
+	if(sock_path) {
+		asprintf(&name, "%s", sock_path);
+	}
+	else {
+		int result;
+
+		/* Only check if socket dir exists if we are using the default directory */
+		result = ensure_dir_exists(SOCK_DIR);
+		if(result == -1) {
+			ERR("Unable to create socket directory %s", SOCK_DIR);
+			return -1;
+		}
+
+		asprintf(&name, "%s/%s", SOCK_DIR, "ustd");
 	}
 
 	handle->server.listen_fd = init_named_socket(name, &handle->server.socketpath);
 	if(handle->server.listen_fd < 0) {
 		ERR("error initializing named socket at %s", name);
+		retval = -1;
 		goto free_name;
 	}
-	free(name);
 
 	INIT_LIST_HEAD(&handle->server.connections);
 
-	return 0;
-
 free_name:
 	free(name);
-	return -1;
+
+	return retval;
+}
+
+static void ustcomm_fini_server(struct ustcomm_server *server, int keep_socket_file)
+{
+	int result;
+	struct stat st;
+
+	if(!keep_socket_file) {
+		/* Destroy socket */
+		result = stat(server->socketpath, &st);
+		if(result == -1) {
+			PERROR("stat (%s)", server->socketpath);
+			return;
+		}
+
+		/* Paranoid check before deleting. */
+		result = S_ISSOCK(st.st_mode);
+		if(!result) {
+			ERR("The socket we are about to delete is not a socket.");
+			return;
+		}
+
+		result = unlink(server->socketpath);
+		if(result == -1) {
+			PERROR("unlink");
+		}
+	}
+
+	free(server->socketpath);
+
+	result = close(server->listen_fd);
+	if(result == -1) {
+		PERROR("close");
+		return;
+	}
+}
+
+/* Free a traceable application server */
+
+void ustcomm_fini_app(struct ustcomm_app *handle, int keep_socket_file)
+{
+	ustcomm_fini_server(&handle->server, keep_socket_file);
+}
+
+/* Free a ustd server */
+
+void ustcomm_fini_ustd(struct ustcomm_ustd *handle)
+{
+	ustcomm_fini_server(&handle->server, 0);
 }
 
-static char *find_tok(char *str)
+static const char *find_tok(const char *str)
 {
 	while(*str == ' ') {
 		str++;
@@ -574,7 +813,7 @@ static char *find_tok(char *str)
 	return str;
 }
 
-static char *find_sep(char *str)
+static const char *find_sep(const char *str)
 {
 	while(*str != ' ') {
 		str++;
@@ -586,11 +825,11 @@ static char *find_sep(char *str)
 	return str;
 }
 
-int nth_token_is(char *str, char *token, int tok_no)
+int nth_token_is(const char *str, const char *token, int tok_no)
 {
 	int i;
-	char *start;
-	char *end;
+	const char *start;
+	const char *end;
 
 	for(i=0; i<=tok_no; i++) {
 		str = find_tok(str);
@@ -615,12 +854,12 @@ int nth_token_is(char *str, char *token, int tok_no)
 	return 1;
 }
 
-char *nth_token(char *str, int tok_no)
+char *nth_token(const char *str, int tok_no)
 {
 	static char *retval = NULL;
 	int i;
-	char *start;
-	char *end;
+	const char *start;
+	const char *end;
 
 	for(i=0; i<=tok_no; i++) {
 		str = find_tok(str);