From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Thu, 15 Jul 2021 16:37:22 +0000 (+0200)
Subject: terminal: log TIOCGPTPEER failure less alarmingly
X-Git-Tag: lxc-5.0.0~137^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f382bcc6d820c46a54ec928ea7cbfaa3847adc66;p=thirdparty%2Flxc.git

terminal: log TIOCGPTPEER failure less alarmingly

This is not a fatal error and the fallback codepath is equally safe.
When we use TIOCGPTPEER we're using a stashed fd to the container's
devpts mount's ptmx device and allocating a new fd non-path based
through this ioctl. If this ioctl can't be used we're falling back to
allocating a pts device from the host's devpts mount's ptmx device which
is path-based but is not under control of the container and so that's
safe. The difference is just that the first method gets you a nice
native terminal with all the pleasantries of having tty and friends
working whereas the latter method does not.

Fixes: #3625
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---

diff --git a/src/lxc/terminal.c b/src/lxc/terminal.c
index 029e36bbb..6e1a2c288 100644
--- a/src/lxc/terminal.c
+++ b/src/lxc/terminal.c
@@ -931,7 +931,17 @@ static int lxc_terminal_create_native(const char *name, const char *lxcpath, str
 
 	terminal->pty = ioctl(terminal->ptx, TIOCGPTPEER, O_RDWR | O_NOCTTY | O_CLOEXEC);
 	if (terminal->pty < 0) {
-		SYSWARN("Failed to allocate new pty device");
+		switch (errno) {
+		case ENOTTY:
+			SYSTRACE("Pure fd-based terminal allocation not possible");
+			break;
+		case ENOSPC:
+			SYSTRACE("Exceeding number of allocatable terminals");
+			break;
+		default:
+			SYSWARN("Failed to allocate new pty device");
+			break;
+		}
 		goto err;
 	}