start: do not unconditionally dup std{in,out,err}

Starting with commit commit c5b93afb Author: Li Feng <lifeng68@huawei.com> Date: Mon Jul 10 17:19:52 2017 +0800 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> we made std{err,in,out} a duplicate of the slave file descriptor of the console if it existed. This meant we also duplicated all of them when we executed application containers in the foreground even if some std{err,in,out} file descriptor did not refer to a {p,t}ty. This blocked use cases such as: echo foo | lxc-execute -n -- cat which are very valid and common with application containers but less common with system containers where we don't have to care about this. So my suggestion is to unconditionally duplicate std{err,in,out} to the console file descriptor if we are either running daemonized - this ensures that daemonized application containers with a single bash shell keep on working - or when we are not running an application container. In other cases we only duplicate those file descriptors that actually refer to a {p,t}ty. This logic is similar to what we do for lxc-attach already. Refers to #1690. Closes #2028. Reported-by: Felix Abecassis <fabecassis@nvidia.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

start: do not unconditionally dup std{in,out,err}
1c60b12f · Christian Brauner · aa4e165d · 1c60b12f
Unverified Commit 1c60b12f authored Dec 12, 2017 by Christian Brauner
Hide whitespace changes
Inline Side-by-side

Showing with 7 additions and 2 deletions

start.c src/lxc/start.c +7 -2

No files found.
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -984,13 +984,18 @@ 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 (handler->conf->console.slave >= 0)
+	 if (handler->conf->console.slave >= 0) {
-		 if (set_stdfds(handler->conf->console.slave) < 0) {
+		 if (handler->backgrounded || handler->conf->is_execute == 0)
+			 ret = set_stdfds(handler->conf->console.slave);
+		 else
+			 ret = lxc_console_set_stdfds(handler->conf->console.slave);
+		 if (ret < 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);