tunnels: harmonize cleanup done on skb on xmit path

The goal of this patch is to harmonize cleanup done on a skbuff on xmit path.
Before this patch, behaviors were different depending of the tunnel type.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index f2d0a42..f179ff1 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -694,6 +694,8 @@
 			tunnel->err_count = 0;
 	}
 
+	skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(dev)));
+
 	max_headroom = LL_RESERVED_SPACE(tdev) + gre_hlen + dst->header_len;
 
 	if (skb_headroom(skb) < max_headroom || skb_shared(skb) ||
@@ -710,8 +712,6 @@
 		skb = new_skb;
 	}
 
-	skb_dst_drop(skb);
-
 	if (fl6->flowi6_mark) {
 		skb_dst_set(skb, dst);
 		ndst = NULL;