commands: rotate console log file

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

src/lxc/commands.c

@@ -1064,6 +1064,10 @@ static int lxc_cmd_console_log_callback(int fd, struct lxc_cmd_req *req,
 
 	rsp.ret = 0;
 	if (log->clear) {
+		int ret;
+		size_t len;
+		char *tmp;
+
 		/* clear the ringbuffer */
 		lxc_ringbuf_clear(buf);
 
@@ -1086,6 +1090,31 @@ static int lxc_cmd_console_log_callback(int fd, struct lxc_cmd_req *req,
 				goto out;
 			}
 		}
+
+		/* rotate the console log file */
+		if (!console->log_path || console->log_rotate == 0)
+			goto out;
+
+		/* be very certain things are kosher */
+		rsp.ret = -EBADF;
+		if (console->log_fd < 0)
+			goto out;
+
+		len = strlen(console->log_path) + sizeof(".1");
+		tmp = alloca(len);
+
+		rsp.ret = -EFBIG;
+		ret = snprintf(tmp, len, "%s.1", console->log_path);
+		if (ret < 0 || (size_t)ret >= len)
+			goto out;
+
+		close(console->log_fd);
+		console->log_fd = -1;
+		rsp.ret = lxc_unpriv(rename(console->log_path, tmp));
+		if (rsp.ret < 0)
+			goto out;
+
+		rsp.ret = lxc_console_create_log_file(console);
 	} else if (rsp.datalen > 0) {
 		lxc_ringbuf_move_read_addr(buf, rsp.datalen);
 	}

src/lxc/confile.c

@@ -1803,8 +1803,11 @@ static int set_config_console_rotate(const char *key, const char *value,
 	if (lxc_safe_uint(value, &lxc_conf->console.log_rotate) < 0)
 		return -1;
 
-	if (lxc_conf->console.log_rotate > 1)
+	if (lxc_conf->console.log_rotate > 1) {
+		ERROR("The \"lxc.console.rotate\" config key can only be set "
+		      "to 0 or 1");
 		return -1;
+	}
 
 	return 0;
 }

src/lxc/console.c

@@ -674,7 +674,7 @@ static int lxc_console_create_ringbuf(struct lxc_console *console)
  * This is the console log file. Please note that the console log file is
  * (implementation wise not content wise) independent of the console ringbuffer.
  */
-static int lxc_console_create_log_file(struct lxc_console *console)
+int lxc_console_create_log_file(struct lxc_console *console)
 {
 	if (!console->log_path)
 		return 0;

src/lxc/console.h

@@ -222,5 +222,6 @@ extern int lxc_console_cb_signal_fd(int fd, uint32_t events, void *cbdata,
 extern void lxc_console_signal_fini(struct lxc_tty_state *ts);
 
 extern int lxc_console_write_ringbuffer(struct lxc_console *console);
+extern int lxc_console_create_log_file(struct lxc_console *console);
 
 #endif