Index: if_tun.c
===================================================================
RCS file: /cvs/src/sys/net/if_tun.c,v
retrieving revision 1.189
diff -u -p -r1.189 if_tun.c
--- if_tun.c	12 Sep 2019 01:28:29 -0000	1.189
+++ if_tun.c	12 Sep 2019 01:37:36 -0000
@@ -1008,9 +1008,6 @@ tun_dev_poll(struct tun_softc *tp, int e
  *
  * The tun driver uses an array of tun_softc's based on the minor number
  * of the device.  kn->kn_hook gets set to the specific tun_softc.
- *
- * filt_tunread() sets kn->kn_data to the iface qsize
- * filt_tunwrite() sets kn->kn_data to the MTU size
  */
 int
 tunkqfilter(dev_t dev, struct knote *kn)
@@ -1082,7 +1079,6 @@ filt_tunread(struct knote *kn, long hint
 {
 	struct tun_softc	*tp;
 	struct ifnet		*ifp;
-	unsigned int		 len;
 
 	if (kn->kn_status & KN_DETACHED) {
 		kn->kn_data = 0;
@@ -1092,16 +1088,9 @@ filt_tunread(struct knote *kn, long hint
 	tp = (struct tun_softc *)kn->kn_hook;
 	ifp = &tp->tun_if;
 
-	len = IFQ_LEN(&ifp->if_snd);
-	if (len > 0) {
-		kn->kn_data = len;
+	kn->kn_data = ifq_hdatalen(&ifp->if_snd);
 
-		TUNDEBUG(("%s: tunkqread q=%d\n", ifp->if_xname,
-		    IFQ_LEN(&ifp->if_snd)));
-		return (1);
-	}
-	TUNDEBUG(("%s: tunkqread waiting\n", ifp->if_xname));
-	return (0);
+	return (kn->kn_data > 0);
 }
 
 void
@@ -1131,7 +1120,7 @@ filt_tunwrite(struct knote *kn, long hin
 	tp = (struct tun_softc *)kn->kn_hook;
 	ifp = &tp->tun_if;
 
-	kn->kn_data = ifp->if_mtu;
+	kn->kn_data = ifp->if_hdrlen + ifp->if_hardmtu;
 
 	return (1);
 }