[PATCH AUTOSEL 4.19 178/219] ip_tunnel: Make none-tunnel-dst tunnel port work with lwtunnel

[Sasha Levin]

From: wenxu <wenxu@xxxxxxxxx>

[ Upstream commit d71b57532d70c03f4671dd04e84157ac6bf021b0 ]

ip l add dev tun type gretap key 1000
ip a a dev tun 10.0.0.1/24

Packets with tun-id 1000 can be recived by tun dev. But packet can't
be sent through dev tun for non-tunnel-dst

With this patch: tunnel-dst can be get through lwtunnel like beflow:
ip r a 10.0.0.7 encap ip dst 172.168.0.11 dev tun

Signed-off-by: wenxu <wenxu@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/ipv4/ip_tunnel.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index c4f5602308edc..054d01c16dc6a 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -644,13 +644,19 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
 	dst = tnl_params->daddr;
 	if (dst == 0) {
 		/* NBMA tunnel */
+		struct ip_tunnel_info *tun_info;
 
 		if (!skb_dst(skb)) {
 			dev->stats.tx_fifo_errors++;
 			goto tx_error;
 		}
 
-		if (skb->protocol == htons(ETH_P_IP)) {
+		tun_info = skb_tunnel_info(skb);
+		if (tun_info && (tun_info->mode & IP_TUNNEL_INFO_TX) &&
+		    ip_tunnel_info_af(tun_info) == AF_INET &&
+		    tun_info->key.u.ipv4.dst)
+			dst = tun_info->key.u.ipv4.dst;
+		else if (skb->protocol == htons(ETH_P_IP)) {
 			rt = skb_rtable(skb);
 			dst = rt_nexthop(rt, inner_iph->daddr);
 		}
-- 
2.20.1