--- zzzz-none-000/linux-4.1.52/net/ipv4/ip_forward.c	2018-05-28 02:26:45.000000000 +0000
+++ bcm63-7530ax-731/linux-4.1.52/net/ipv4/ip_forward.c	2022-03-02 11:37:13.000000000 +0000
@@ -139,6 +139,15 @@
 
 	skb->priority = rt_tos2priority(iph->tos);
 
+#if defined(CONFIG_BCM_KF_WANDEV)
+#if !defined(CONFIG_BCM_WAN_2_WAN_FWD_ENABLED)
+	/* Never forward a packet from a WAN intf to the other WAN intf */
+	if( (skb->dev) && (rt->dst.dev) && 
+		((skb->dev->priv_flags & rt->dst.dev->priv_flags) & IFF_WANDEV) )
+		goto drop;
+#endif
+#endif
+
 	return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, NULL, skb,
 		       skb->dev, rt->dst.dev, ip_forward_finish);