Index: sys/dev/usb/usbnet.c
===================================================================
RCS file: /cvsroot/src/sys/dev/usb/usbnet.c,v
retrieving revision 1.114
diff -p -u -r1.114 usbnet.c
--- sys/dev/usb/usbnet.c	15 Jul 2023 21:41:26 -0000	1.114
+++ sys/dev/usb/usbnet.c	8 Oct 2023 13:27:08 -0000
@@ -1011,11 +1011,12 @@ usbnet_ifflags_cb(struct ethercom *ec)
 
 	KASSERTMSG(IFNET_LOCKED(ifp), "%s", ifp->if_xname);
 
+	mutex_enter(&unp->unp_mcastlock);
 	const u_short changed = ifp->if_flags ^ unp->unp_if_flags;
-	if ((changed & ~(IFF_CANTCHANGE | IFF_DEBUG)) == 0) {
-		mutex_enter(&unp->unp_mcastlock);
-		unp->unp_if_flags = ifp->if_flags;
-		mutex_exit(&unp->unp_mcastlock);
+
+	if ((changed & ~(IFF_CANTCHANGE | IFF_DEBUG)) != 0) {
+		rv = ENETRESET;
+	} else {
 		/*
 		 * XXX Can we just do uno_mcast synchronously here
 		 * instead of resetting the whole interface?
@@ -1028,12 +1029,13 @@ usbnet_ifflags_cb(struct ethercom *ec)
 		 * Maybe the logic can be unified, but it will require
 		 * an audit and testing of all the usbnet drivers.
 		 */
-		if (changed & IFF_PROMISC)
+		if ((changed & (IFF_PROMISC|IFF_ALLMULTI)) != 0)
 			rv = ENETRESET;
-	} else {
-		rv = ENETRESET;
 	}
 
+	unp->unp_if_flags = ifp->if_flags;
+	mutex_exit(&unp->unp_mcastlock);
+
 	return rv;
 }
 
@@ -1065,23 +1067,23 @@ usbnet_if_ioctl(struct ifnet *ifp, u_lon
 
 	error = ether_ioctl(ifp, cmd, data);
 	if (error == ENETRESET) {
+		/*
+		 * If there's a hardware multicast filter, and
+		 * it has been programmed by usbnet_init_rx_tx
+		 * and is active, update it now.  Otherwise,
+		 * drop the update on the floor -- it will be
+		 * observed by usbnet_init_rx_tx next time we
+		 * bring the interface up.
+		 */
+		if (un->un_ops->uno_mcast) {
+			mutex_enter(&unp->unp_mcastlock);
+			if (unp->unp_mcastactive)
+				(*un->un_ops->uno_mcast)(ifp);
+			mutex_exit(&unp->unp_mcastlock);
+		}
 		switch (cmd) {
 		case SIOCADDMULTI:
 		case SIOCDELMULTI:
-			/*
-			 * If there's a hardware multicast filter, and
-			 * it has been programmed by usbnet_init_rx_tx
-			 * and is active, update it now.  Otherwise,
-			 * drop the update on the floor -- it will be
-			 * observed by usbnet_init_rx_tx next time we
-			 * bring the interface up.
-			 */
-			if (un->un_ops->uno_mcast) {
-				mutex_enter(&unp->unp_mcastlock);
-				if (unp->unp_mcastactive)
-					(*un->un_ops->uno_mcast)(ifp);
-				mutex_exit(&unp->unp_mcastlock);
-			}
 			error = 0;
 			break;
 		default:
@@ -1306,8 +1308,16 @@ usbnet_if_init(struct ifnet *ifp)
 	 * analysis -- and possibly some tweaking -- of sys/net to
 	 * ensure.
 	 */
-	if (ifp->if_flags & IFF_RUNNING)
+	if (ifp->if_flags & IFF_RUNNING) {
+		if (un->un_ops->uno_mcast) {
+			struct usbnet_private * const unp = un->un_pri;
+			mutex_enter(&unp->unp_mcastlock);
+			(*un->un_ops->uno_mcast)(ifp);
+			unp->unp_mcastactive = true;
+			mutex_exit(&unp->unp_mcastlock);
+		}
 		return 0;
+	}
 
 	error = uno_init(un, ifp);
 	if (error)