Subject: [PATCH BUG-FIX] ipv6: udp: fix the wrong headroom check

From: Shan Wei <[email-masked]>
Date: Wed, 20 Apr 2011 16:52:49 +0800

At this point, skb->data points to skb_transport_header.
So, headroom check is wrong. 

For some case:bridge(UFO is on) + eth device(UFO is off),
there is no enough headroom for IPv6 frag head.
But headroom check is always false.

This will bring about data be moved to there prior to skb->head,
when adding IPv6 frag header to skb.

Signed-off-by: Shan Wei <[email-masked]>
---
 net/ipv6/udp.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 15c3774..9e305d7 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1335,7 +1335,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb, u32 features)
 	skb->ip_summed = CHECKSUM_NONE;
 
 	/* Check if there is enough headroom to insert fragment header. */
-	if ((skb_headroom(skb) < frag_hdr_sz) &&
+	if ((skb_mac_header(skb) < skb->head + frag_hdr_sz) &&
 	    pskb_expand_head(skb, frag_hdr_sz, 0, GFP_ATOMIC))
 		goto out;
 
-- 
1.6.3.3