From bf6627087b996e27497f191a75c785e664dcccfc Mon Sep 17 00:00:00 2001
From: William Tu <u9012063@gmail.com>
Date: Thu, 10 May 2018 20:03:31 -0700
Subject: [PATCH] ip6erspan: make sure enough headroom at xmit.

Upstream commit:
    commit e41c7c68ea771683cae5a7f81c268f38d7912ecb
    Author: William Tu <u9012063@gmail.com>
    Date:   Fri Mar 9 07:34:42 2018 -0800

    ip6erspan: make sure enough headroom at xmit.

    The patch adds skb_cow_header() to ensure enough headroom
    at ip6erspan_tunnel_xmit before pushing the erspan header
    to the skb.

    Signed-off-by: William Tu <u9012063@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Cc: William Tu <u9012063@gmail.com>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: William Tu <u9012063@gmail.com>
---
 datapath/linux/compat/ip6_gre.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/datapath/linux/compat/ip6_gre.c b/datapath/linux/compat/ip6_gre.c
index 25f24e39016..c9bd80dac69 100644
--- a/datapath/linux/compat/ip6_gre.c
+++ b/datapath/linux/compat/ip6_gre.c
@@ -1094,6 +1094,9 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
 	    (ntohs(ip_hdr(skb)->tot_len) > skb->len - nhoff))
 		truncate = true;
 
+	if (skb_cow_head(skb, dev->needed_headroom))
+		goto tx_err;
+
 	t->parms.o_flags &= ~TUNNEL_KEY;
 	IPCB(skb)->flags = 0;