start: dup std{in,out,err} to pty slave

In the case the container has a console with a valid slave pty file descriptor we duplicate std{in,out,err} to the slave file descriptor so console logging works correctly. When the container does not have a valid slave pty file descriptor for its console and is started daemonized we should dup to /dev/null. Closes #1646. Signed-off-by: Li Feng <lifeng68@huawei.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

start: dup std{in,out,err} to pty slave
b4700e2c · Li Feng · Stéphane Graber · bad62acb · b4700e2c
Unverified Commit b4700e2c authored Jul 10, 2017 by Li Feng Committed by Stéphane Graber Jul 17, 2017
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Showing with 13 additions and 4 deletions

start.c src/lxc/start.c +13 -4

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--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -1036,8 +1036,13 @@ static int do_start(void *data)
 	 * setup on its console ie. the pty allocated in lxc_console_create() so
 	 * make sure that that pty is stdin,stdout,stderr.
 	 */
-	if (lxc_console_set_stdfds(handler->conf->console.slave) < 0)
+	 if (handler->conf->console.slave >= 0)
-		goto out_warn_father;
+		 if (set_stdfds(handler->conf->console.slave) < 0) {
+			ERROR("Failed to redirect std{in,out,err} to pty file "
+			      "descriptor %d",
+			      handler->conf->console.slave);
+			goto out_warn_father;
+		 }
 	/* If we mounted a temporary proc, then unmount it now. */
 	tmp_proc_unmount(handler->conf);
@@ -1115,8 +1120,12 @@ static int do_start(void *data)
 			goto out_warn_father;
 	}
-	if (handler->backgrounded && set_stdfds(devnull_fd))
+	if (handler->conf->console.slave < 0 && handler->backgrounded)
-		goto out_warn_father;
+		if (set_stdfds(devnull_fd) < 0) {
+			ERROR("Failed to redirect std{in,out,err} to "
+			      "\"/dev/null\"");
+			goto out_warn_father;
+		}
 	if (devnull_fd >= 0) {
 		close(devnull_fd);