Index: sys/kern/tty.c
===================================================================
--- sys/kern/tty.c
+++ sys/kern/tty.c
@@ -1930,6 +1930,7 @@
 		return (0);
 	case TIOCSTART:
 		tp->t_flags &= ~TF_STOPPED;
+		tp->t_termios.c_lflag &= ~FLUSHO;
 		ttydevsw_outwakeup(tp);
 		ttydevsw_pktnotify(tp, TIOCPKT_START);
 		return (0);
Index: sys/kern/tty_ttydisc.c
===================================================================
--- sys/kern/tty_ttydisc.c
+++ sys/kern/tty_ttydisc.c
@@ -474,6 +474,11 @@
 
 		MPASS(oblen == 0);
 
+		if (CMP_FLAG(l, FLUSHO)) {
+			uio->uio_resid = 0;
+			return (0);
+		}
+
 		/* Step 1: read data. */
 		obstart = ob;
 		nlen = MIN(uio->uio_resid, sizeof ob);
@@ -495,6 +500,11 @@
 		do {
 			unsigned int plen, wlen;
 
+			if (CMP_FLAG(l, FLUSHO)) {
+				uio->uio_resid = 0;
+				return (0);
+			}
+
 			/* Search for special characters for post processing. */
 			if (CMP_FLAG(o, OPOST)) {
 				plen = ttydisc_findchar(obstart, oblen);
@@ -629,6 +639,9 @@
 ttydisc_echo_force(struct tty *tp, char c, int quote)
 {
 
+	if (CMP_FLAG(l, FLUSHO))
+		return 0;
+
 	if (CMP_FLAG(o, OPOST) && CTL_ECHO(c, quote)) {
 		/*
 		 * Only perform postprocessing when OPOST is turned on
@@ -906,6 +919,17 @@
 			tp->t_flags |= TF_LITERAL;
 			return (0);
 		}
+		/* Discard processing */
+		if (CMP_CC(VDISCARD, c)) {
+			if (CMP_FLAG(l, FLUSHO)) {
+				tp->t_termios.c_lflag &= ~FLUSHO;
+			} else {
+				tty_flush(tp, FWRITE);
+				ttydisc_echo(tp, c, 0);
+				// XXX netbsd does retype, should we? XXX
+				tp->t_termios.c_lflag |= FLUSHO;
+			}
+		}
 	}
 
 	/*