--- zzzz-none-000/linux-4.4.60/net/ipv4/ip_gre.c	2017-04-08 07:53:53.000000000 +0000
+++ scorpion-7490-727/linux-4.4.60/net/ipv4/ip_gre.c	2021-02-04 17:41:59.000000000 +0000
@@ -633,6 +633,8 @@
 	if (IS_ERR(skb))
 		goto out;
 
+	skb->skb_iif = dev->ifindex;
+
 	__gre_xmit(skb, dev, tnl_params, skb->protocol);
 	return NETDEV_TX_OK;
 
@@ -660,6 +662,8 @@
 	if (skb_cow_head(skb, dev->needed_headroom))
 		goto free_skb;
 
+	skb->skb_iif = dev->ifindex;
+
 	__gre_xmit(skb, dev, &tunnel->parms.iph, htons(ETH_P_TEB));
 	return NETDEV_TX_OK;
 
@@ -703,7 +707,6 @@
    It allows to construct virtual multiprotocol broadcast "LAN"
    over the Internet, provided multicast routing is tuned.
 
-
    I have no idea was this bicycle invented before me,
    so that I had to set ARPHRD_IPGRE to a random value.
    I have an impression, that Cisco could make something similar,
@@ -1062,7 +1065,7 @@
 {
 	ether_setup(dev);
 	dev->netdev_ops		= &gre_tap_netdev_ops;
-	dev->priv_flags 	|= IFF_LIVE_ADDR_CHANGE;
+	dev->priv_flags		|= IFF_LIVE_ADDR_CHANGE | IFF_GRE_V4_TAP;
 	ip_tunnel_setup(dev, gre_tap_net_id);
 }