The patch 'ip_gre: ipgre_tap device should keep dst' fixed
the issue ipgre_tap dev mtu couldn't be updated in tx path.
The same fix is needed for erspan as well.
Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
        dev->features           |= GRE_FEATURES;
        dev->hw_features        |= GRE_FEATURES;
        dev->priv_flags         |= IFF_LIVE_ADDR_CHANGE;
+       netif_keep_dst(dev);
 
        return ip_tunnel_init(dev);
 }