Merge pull request #2305 from brauner/2018-05-04/fix_execute_logging

fix logic for execute log file

src/lxc/execute.c

@@ -21,11 +21,13 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#define _GNU_SOURCE
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <errno.h>
 #include <unistd.h>
 #include <stdlib.h>
+#include <stdio.h>
 
 #include "conf.h"
 #include "log.h"
@@ -36,19 +38,22 @@ lxc_log_define(lxc_execute, lxc_start);
 
 static int execute_start(struct lxc_handler *handler, void* data)
 {
-	int j, i = 0;
-	struct execute_args *my_args = data;
+	int argc_add, j;
 	char **argv;
-	int argc = 0, argc_add;
+	int argc = 0, i = 0, logfd = -1;
+	struct execute_args *my_args = data;
+	char logfile[LXC_PROC_PID_FD_LEN];
 
 	while (my_args->argv[argc++]);
 
 	/* lxc-init -n name -- [argc] NULL -> 5 */
 	argc_add = 5;
 	if (my_args->quiet)
 		argc_add++;
+
 	if (!handler->conf->rootfs.path)
 		argc_add += 2;
+
 	if (lxc_log_has_valid_level())
 		argc_add += 2;
 
@@ -69,9 +74,25 @@ static int execute_start(struct lxc_handler *handler, void* data)
 		argv[i++] = (char *)lxc_log_priority_to_string(lxc_log_get_level());
 	}
 
-	if (handler->conf->logfile) {
+	if (current_config->logfd != -1 || lxc_log_fd != -1) {
+		int ret;
+		int to_dup = current_config->logfd;
+
+		if (current_config->logfd == -1)
+			to_dup = lxc_log_fd;
+
+		logfd = dup(to_dup);
+		if (logfd < 0) {
+			SYSERROR("Failed to duplicate log file descriptor");
+			goto out2;
+		}
+
+		ret = snprintf(logfile, sizeof(logfile), "/proc/1/fd/%d", logfd);
+		if (ret < 0 || (size_t)ret >= sizeof(logfile))
+			goto out3;
+
 		argv[i++] = "-o";
-		argv[i++] = (char *)handler->conf->logfile;
+		argv[i++] = logfile;
 	}
 
 	if (my_args->quiet)
@@ -92,6 +113,8 @@ static int execute_start(struct lxc_handler *handler, void* data)
 	execvp(argv[0], argv);
 	SYSERROR("Failed to exec %s", argv[0]);
 
+out3:
+	close(logfd);
 out2:
 	free(argv);
 out1:

src/lxc/utils.h

@@ -101,6 +101,17 @@
 #define LXC_LINELEN 4096
 #define LXC_IDMAPLEN 4096
 #define LXC_MAX_BUFFER 4096
+/* /proc/       =    6
+ *                +
+ * <pid-as-str> =   LXC_NUMSTRLEN64
+ *                +
+ * /fd/         =    4
+ *                +
+ * <fd-as-str>  =   LXC_NUMSTRLEN64
+ *                +
+ * \0           =    1
+ */
+#define LXC_PROC_PID_FD_LEN (6 + LXC_NUMSTRLEN64 + 4 + LXC_NUMSTRLEN64 + 1)
 
 /* returns 1 on success, 0 if there were any failures */
 extern int lxc_rmdir_onedev(const char *path, const char *exclude);