Index: if.c
===================================================================
RCS file: /cvs/src/sys/net/if.c,v
retrieving revision 1.464
diff -u -p -r1.464 if.c
--- if.c	2 Dec 2016 18:32:38 -0000	1.464
+++ if.c	13 Dec 2016 06:55:31 -0000
@@ -1776,20 +1776,26 @@ ifioctl(struct socket *so, u_long cmd, c
 	case SIOCSIFFLAGS:
 		if ((error = suser(p, 0)) != 0)
 			return (error);
-		if (ifp->if_flags & IFF_UP && (ifr->ifr_flags & IFF_UP) == 0) {
-			s = splnet();
-			if_down(ifp);
-			splx(s);
+
+		ifp->if_flags = (ifp->if_flags & IFF_CANTCHANGE) |
+			(ifr->ifr_flags & ~IFF_CANTCHANGE);
+
+		if (ifp->if_ioctl != NULL) {
+			error = (*ifp->if_ioctl)(ifp, cmd, data);
+			if (error != 0) {
+				ifp->if_flags = oif_flags;
+				break;
+			}
 		}
-		if (ifr->ifr_flags & IFF_UP && (ifp->if_flags & IFF_UP) == 0) {
+
+		if (ISSET(oif_flags ^ ifp->if_flags, IFF_UP)) {
 			s = splnet();
-			if_up(ifp);
+			if (ISSET(ifp->if_flags, IFF_UP))
+				if_up(ifp);
+			else
+				if_down(ifp);
 			splx(s);
 		}
-		ifp->if_flags = (ifp->if_flags & IFF_CANTCHANGE) |
-			(ifr->ifr_flags & ~IFF_CANTCHANGE);
-		if (ifp->if_ioctl)
-			(void) (*ifp->if_ioctl)(ifp, cmd, data);
 		break;
 
 	case SIOCSIFXFLAGS: