--- zzzz-none-000/linux-5.4.213/net/ipv4/ip_tunnel_core.c	2022-09-15 10:04:56.000000000 +0000
+++ miami-7690-761/linux-5.4.213/net/ipv4/ip_tunnel_core.c	2024-05-29 11:20:02.000000000 +0000
@@ -34,6 +34,7 @@
 #include <net/netns/generic.h>
 #include <net/rtnetlink.h>
 #include <net/dst_metadata.h>
+#include <net/vxlan.h>
 
 const struct ip_tunnel_encap_ops __rcu *
 		iptun_encaps[MAX_IPTUN_ENCAP_OPS] __read_mostly;
@@ -51,7 +52,12 @@
 	struct net *net = dev_net(rt->dst.dev);
 	struct net_device *dev = skb->dev;
 	struct iphdr *iph;
+	struct net_device *in_dev = NULL;
 	int err;
+	int skb_iif;
+
+	/* Save input interface index */
+	skb_iif = skb->skb_iif;
 
 	skb_scrub_packet(skb, xnet);
 
@@ -75,6 +81,15 @@
 	iph->ttl	=	ttl;
 	__ip_select_ident(net, iph, skb_shinfo(skb)->gso_segs ?: 1);
 
+	/* Get input interface */
+	if (skb_iif) {
+		in_dev = __dev_get_by_index(&init_net, skb_iif);
+	}
+
+	if (proto == IPPROTO_IPV6 || proto == IPPROTO_GRE || (in_dev && netif_is_vxlan(in_dev))) {
+		skb->skb_iif = skb_iif;
+	}
+
 	err = ip_local_out(net, sk, skb);
 
 	if (dev) {