From 223a7c9ce0979d5886dea0b64df56655665fff6a Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Fri, 18 Nov 2011 20:39:00 +0100
Subject: agetty: support silent re-open of the tty

Instead of complaining loudly that a TTY could not be opened and
preventing it from working for 5 minutes, now we silently try in slow
loops. This allows machines to work normally with pre-configured serial
ports even if these ports are not present (eg: USB).
---
 term-utils/agetty.c | 74 ++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 50 insertions(+), 24 deletions(-)

diff --git a/term-utils/agetty.c b/term-utils/agetty.c
index 4c1ed04..a3497c0 100644
--- a/term-utils/agetty.c.old
+++ b/term-utils/agetty.c
@@ -1013,34 +1013,61 @@ static void open_tty(char *tty, struct t
 		if (len < 0 || (size_t)len >= sizeof(buf))
 			log_err(_("/dev/%s: cannot open as standard input: %m"), tty);
 
-		/* Open the tty as standard input. */
-		if ((fd = open(buf, O_RDWR|O_NOCTTY|O_NONBLOCK, 0)) < 0)
-			log_err(_("/dev/%s: cannot open as standard input: %m"), tty);
-
-		/*
-		 * There is always a race between this reset and the call to
-		 * vhangup() that s.o. can use to get access to your tty.
-		 * Linux login(1) will change tty permissions. Use root owner and group
-		 * with permission -rw------- for the period between getty and login.
+		/* We loop forever trying to open the device every 5 seconds in case it
+		 * spontaneously appears (eg: USB device).
 		 */
-		if (fchown(fd, 0, gid) || fchmod(fd, (gid ? 0620 : 0600))) {
-			if (errno == EROFS)
-				log_warn("%s: %m", buf);
-			else
-				log_err("%s: %m", buf);
-		}
+		for (;; sleep(5)) {
+			/* Open the tty as standard input. */
+			if ((fd = open(buf, O_RDWR|O_NOCTTY|O_NONBLOCK, 0)) < 0) {
+				//log_err(_("/dev/%s: cannot open as standard input: %m"), tty);
+				continue;
+			}
+
+			/*
+			 * There is always a race between this reset and the call to
+			 * vhangup() that s.o. can use to get access to your tty.
+			 * Linux login(1) will change tty permissions. Use root owner and group
+			 * with permission -rw------- for the period between getty and login.
+			 */
+			if (fchown(fd, 0, gid) || fchmod(fd, (gid ? 0620 : 0600))) {
+				if (errno == EROFS) {
+					//log_warn("%s: %m", buf);
+				}
+				else {
+					close(fd);
+					continue;
+					// log_err("%s: %m", buf);
+				}
+			}
+
+			/* Sanity checks... */
+			if (fstat(fd, &st) < 0) {
+				close(fd);
+				continue;
+				// log_err("%s: %m", buf);
+			}
+
+			if ((st.st_mode & S_IFMT) != S_IFCHR) {
+				close(fd);
+				continue;
+				// log_err(_("/dev/%s: not a character device"), tty);
+			}
+
+			if (!isatty(fd)) {
+				close(fd);
+				continue;
+				// log_err(_("/dev/%s: not a tty"), tty);
+			}
 
-		/* Sanity checks... */
-		if (fstat(fd, &st) < 0)
-			log_err("%s: %m", buf);
-		if ((st.st_mode & S_IFMT) != S_IFCHR)
-			log_err(_("/dev/%s: not a character device"), tty);
-		if (!isatty(fd))
-			log_err(_("/dev/%s: not a tty"), tty);
-
-		if (((tid = tcgetsid(fd)) < 0) || (pid != tid)) {
-			if (ioctl(fd, TIOCSCTTY, 1) == -1)
-				log_warn(_("/dev/%s: cannot get controlling tty: %m"), tty);
+			if (((tid = tcgetsid(fd)) < 0) || (pid != tid)) {
+				if (ioctl(fd, TIOCSCTTY, 1) == -1) {
+					close(fd);
+					continue;
+					// log_warn(_("/dev/%s: cannot get controlling tty: %m"), tty);
+				}
+			}
+			/* Excellent, our new terminal is open and ready */
+			break;
 		}
 
 		close(STDIN_FILENO);