ip_tunnel: Make none-tunnel-dst tunnel port work with lwtunnel

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@ucloud.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 1 deletions

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index c4f5602308ed..054d01c16dc6 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);
                 }