From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?ISO-8859-1?Q?Timo_Ter=E4s?= <timo.teras@iki.fi>
Subject: ip_gre headroom allocation
Date: Thu, 11 Jun 2009 11:22:34 +0300
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Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	David Miller <davem@davemloft.net>
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I'm not entirely sure about this, but shouldn't we do something like
the below to make ip_gre allocation enough headroom for paths where
e.g. xfrm transformations take place (as a speed optimization)?

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index e62510d..eb78dd9 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -812,7 +812,7 @@ static int ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
                        tunnel->err_count = 0;
        }
 
-       max_headroom = LL_RESERVED_SPACE(tdev) + gre_hlen;
+       max_headroom = LL_RESERVED_SPACE(tdev) + gre_hlen + rt->u.dst.header_len;
 
        if (skb_headroom(skb) < max_headroom || skb_shared(skb)||
            (skb_cloned(skb) && !skb_clone_writable(skb, 0))) {