MFC r260913,266895:

Add a new flag to /etc/ttys: onifconsole. This is equivalent to "on" if the
device is an active kernel console and "off" otherwise. This is designed to
allow serial-booting x86 systems to provide a login prompt on the serial line
by default without providing one on all systems by default. Set this flag
on x86 systems for ttyu0.

Comments and suggestions by:	grehan, dteske, jilles

UPDATING

@@ -16,6 +16,13 @@ from older versions of FreeBSD, try WITHOUT_CLANG to bootstrap to the tip of
 stable/10, and then rebuild without this option. The bootstrap process from
 older version of current is a bit fragile.
 
+20140608:
+	On i386 and amd64 systems, the onifconsole flag is now set by default
+	in /etc/ttys for ttyu0. This causes ttyu0 to be automatically enabled
+	as a login TTY if it is set in the bootloader as an active kernel
+	console. No changes in behavior should result otherwise. To revert to
+	the previous behavior, set ttyu0 to "off" in /etc/ttys.
+
 20140512:
 	Clang and llvm have been upgraded to 3.4.1 release.
 

etc/etc.amd64/ttys

@@ -41,7 +41,7 @@ ttyv7	"/usr/libexec/getty Pc"		xterm	on  secure
 ttyv8	"/usr/local/bin/xdm -nodaemon"	xterm	off secure
 # Serial terminals
 # The 'dialup' keyword identifies dialin lines to login, fingerd etc.
-ttyu0	"/usr/libexec/getty std.9600"	dialup	off secure
+ttyu0	"/usr/libexec/getty std.9600"	vt100	onifconsole secure
 ttyu1	"/usr/libexec/getty std.9600"	dialup	off secure
 ttyu2	"/usr/libexec/getty std.9600"	dialup	off secure
 ttyu3	"/usr/libexec/getty std.9600"	dialup	off secure

etc/etc.i386/ttys

@@ -41,7 +41,7 @@ ttyv7	"/usr/libexec/getty Pc"		xterm	on  secure
 ttyv8	"/usr/local/bin/xdm -nodaemon"	xterm	off secure
 # Serial terminals
 # The 'dialup' keyword identifies dialin lines to login, fingerd etc.
-ttyu0	"/usr/libexec/getty std.9600"	dialup	off secure
+ttyu0	"/usr/libexec/getty std.9600"	vt100	onifconsole secure
 ttyu1	"/usr/libexec/getty std.9600"	dialup	off secure
 ttyu2	"/usr/libexec/getty std.9600"	dialup	off secure
 ttyu3	"/usr/libexec/getty std.9600"	dialup	off secure

include/ttyent.h

@@ -37,6 +37,7 @@
 
 #define	_TTYS_OFF	"off"
 #define	_TTYS_ON	"on"
+#define	_TTYS_ONIFCONSOLE "onifconsole"
 #define	_TTYS_SECURE	"secure"
 #define	_TTYS_INSECURE	"insecure"
 #define	_TTYS_WINDOW	"window"

lib/libc/gen/getttyent.c

@@ -39,6 +39,9 @@ __FBSDID("$FreeBSD$");
 #include <ctype.h>
 #include <string.h>
 
+#include <sys/types.h>
+#include <sys/sysctl.h>
+
 static char zapchar;
 static FILE *tf;
 static size_t lbsize;
@@ -64,6 +67,36 @@ getttynam(const char *tty)
 	return (t);
 }
 
+static int
+auto_tty_status(const char *ty_name)
+{
+	size_t len;
+	char *buf, *cons, *nextcons;
+
+	/* Check if this is an enabled kernel console line */
+	buf = NULL;
+	if (sysctlbyname("kern.console", NULL, &len, NULL, 0) == -1)
+		return (0); /* Errors mean don't enable */
+	buf = malloc(len);
+	if (sysctlbyname("kern.console", buf, &len, NULL, 0) == -1)
+		goto done;
+
+	if ((cons = strchr(buf, '/')) == NULL)
+		goto done;
+	*cons = '\0';
+	nextcons = buf;
+	while ((cons = strsep(&nextcons, ",")) != NULL && strlen(cons) != 0) {
+		if (strcmp(cons, ty_name) == 0) {
+			free(buf);
+			return (TTY_ON);
+		}
+	}
+
+done:
+	free(buf);
+	return (0);
+}
+
 struct ttyent *
 getttyent(void)
 {
@@ -126,6 +159,8 @@ getttyent(void)
 			tty.ty_status &= ~TTY_ON;
 		else if (scmp(_TTYS_ON))
 			tty.ty_status |= TTY_ON;
+		else if (scmp(_TTYS_ONIFCONSOLE))
+			tty.ty_status |= auto_tty_status(tty.ty_name);
 		else if (scmp(_TTYS_SECURE))
 			tty.ty_status |= TTY_SECURE;
 		else if (scmp(_TTYS_INSECURE))

libexec/getty/ttys.5

@@ -98,8 +98,11 @@ ttys as a group.
 .Pp
 As flag values, the strings ``on'' and ``off'' specify that
 .Xr init 8
-should (should not) execute the command given in the second field,
-while ``secure'' (if ``on'' is also specified) allows users with a
+should (should not) execute the command given in the second field.
+``onifconsole'' will cause this line to be enabled if and only if it is
+an active kernel console device (it is equivalent to ``on'' in this
+case).
+The flag ``secure'' (if the console is enabled) allows users with a
 uid of 0 to login on
 this line.
 The flag ``dialin'' indicates that a tty entry describes a dialin