[PATCH net] ip_gre: ipgre_tap device should keep dst

[Xin Long]

Without keeping dst, the tunnel will not update any mtu/pmtu info,
since it does not have a dst on the skb.

Reproducer:
  client(ipgre_tap1 - eth1) <-----> (eth1 - ipgre_tap1)server

After reducing eth1's mtu on client, then perforamnce became 0.

This patch is to netif_keep_dst in gre_tap_init, as ipgre does.

Reported-by: Jianlin Shi <ji...@redhat.com>
Signed-off-by: Xin Long <lucien....@gmail.com>
---
 net/ipv4/ip_gre.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 0162fb9..8b837f6 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1223,6 +1223,7 @@ static int gre_tap_init(struct net_device *dev)
 {
        __gre_tunnel_init(dev);
        dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
+       netif_keep_dst(dev);
 
        return ip_tunnel_init(dev);
 }
-- 
2.1.0