iutf8.patch

diff --git a/bin/stty/modes.c b/bin/stty/modes.c
index 0fe4e5168d2c..30990c578637 100644
--- a/bin/stty/modes.c
+++ b/bin/stty/modes.c
@@ -129,6 +129,8 @@ static const struct modes imodes[] = {
 	{ "-decctlq",	IXANY, 0 },
 	{ "imaxbel",	IMAXBEL, 0 },
 	{ "-imaxbel",	0, IMAXBEL },
+	{ "iutf8",	IUTF8, 0 },
+	{ "-iutf8",	0, IUTF8 },
 	{ NULL,		0, 0 },
 };
 
diff --git a/bin/stty/stty.1 b/bin/stty/stty.1
index 1863c2286176..0b4efbf802b6 100644
--- a/bin/stty/stty.1
+++ b/bin/stty/stty.1
@@ -211,6 +211,8 @@ empty/full.
 Allow any character (allow only
 .Dv START )
 to restart output.
+.It Cm iutf8 Pq Fl iutf8
+Erase multibyte UTF-8 letters.
 .It Cm imaxbel Pq Fl imaxbel
 The system imposes a limit of
 .Dv MAX_INPUT
diff --git a/share/man/man4/termios.4 b/share/man/man4/termios.4
index 9478c87c158f..7f32f586345e 100644
--- a/share/man/man4/termios.4
+++ b/share/man/man4/termios.4
@@ -876,6 +876,8 @@ following masks:
 /* enable input flow control */
 .It Dv IXANY
 /* any char will restart after stop */
+.It Dv IUTF8
+/* make ERASE character remove UTF-8 multibyte letters */
 .It Dv IMAXBEL
 /* ring bell on input queue full */
 .El
@@ -1052,6 +1054,15 @@ and
 characters are transmitted are implementation defined.
 .Pp
 If
+.Dv IUTF8
+and
+.Dv ICANON
+are set,
+every letter would be removed as a UTF-8 multibyte letter upon receipt of the
+.Dv ERASE
+character.
+.Pp
+If
 .Dv IMAXBEL
 is set and the input queue is full, subsequent input shall cause an
 .Tn ASCII
diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index 4c11ff56000b..1f75214cbf42 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -86,7 +86,7 @@ static const char	*dev_console_filename;
  * Flags that are supported and stored by this implementation.
  */
 #define TTYSUP_IFLAG	(IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK|ISTRIP|\
-			INLCR|IGNCR|ICRNL|IXON|IXOFF|IXANY|IMAXBEL)
+			INLCR|IGNCR|ICRNL|IXON|IXOFF|IXANY|IMAXBEL|IUTF8)
 #define TTYSUP_OFLAG	(OPOST|ONLCR|TAB3|ONOEOT|OCRNL|ONOCR|ONLRET)
 #define TTYSUP_LFLAG	(ECHOKE|ECHOE|ECHOK|ECHO|ECHONL|ECHOPRT|\
 			ECHOCTL|ISIG|ICANON|ALTWERASE|IEXTEN|TOSTOP|\
diff --git a/sys/kern/tty_ttydisc.c b/sys/kern/tty_ttydisc.c
index 0e3c785545a1..adb7db4da0a8 100644
--- a/sys/kern/tty_ttydisc.c
+++ b/sys/kern/tty_ttydisc.c
@@ -737,9 +737,16 @@ ttydisc_rubchar(struct tty *tp)
 	int quote;
 	unsigned int prevpos, tablen;
 
-	if (ttyinq_peekchar(&tp->t_inq, &c, &quote) != 0)
-		return (-1);
-	ttyinq_unputchar(&tp->t_inq);
+#define MULTIBYTE(u) (((u) & 0x80) == 0x80)
+#define FIRST_OCTET(u) (((u) & 0xC0) == 0xC0)
+	bool utf8 = CMP_FLAG(i, IUTF8);
+	do {
+		if (ttyinq_peekchar(&tp->t_inq, &c, &quote) != 0)
+			return (-1);
+		ttyinq_unputchar(&tp->t_inq);
+	} while(utf8 && MULTIBYTE(c) && !FIRST_OCTET(c));
+#undef MULTIBYTE
+#undef FIRST_OCTET
 
 	if (CMP_FLAG(l, ECHO)) {
 		/*
diff --git a/sys/sys/_termios.h b/sys/sys/_termios.h
index fab12cfa4064..b1970430d289 100644
--- a/sys/sys/_termios.h
+++ b/sys/sys/_termios.h
@@ -98,6 +98,7 @@
 #endif
 #if __BSD_VISIBLE
 #define	IMAXBEL		0x00002000	/* ring bell on input queue full */
+#define	IUTF8		0x00004000	/* support UTF-8 encoding */
 #endif
 
 /*