From: Rusty Russell <rusty@rustcorp.com.au>

Yep, culprit is obvious stupid bug.  This indicates a serious lack of
testing on my part 8(



 net/ipv4/netfilter/ip_nat_core.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletion(-)

diff -puN net/ipv4/netfilter/ip_nat_core.c~netfilter-skbuff-fix net/ipv4/netfilter/ip_nat_core.c
--- 25/net/ipv4/netfilter/ip_nat_core.c~netfilter-skbuff-fix	2003-05-07 18:42:43.000000000 -0700
+++ 25-akpm/net/ipv4/netfilter/ip_nat_core.c	2003-05-07 18:42:43.000000000 -0700
@@ -870,7 +870,8 @@ icmp_reply_translation(struct sk_buff **
 	   adjustment, so make sure the current checksum is correct. */
 	if ((*pskb)->ip_summed != CHECKSUM_UNNECESSARY
 	    && (u16)csum_fold(skb_checksum(*pskb, (*pskb)->nh.iph->ihl*4,
-					   (*pskb)->len, 0)))
+					   (*pskb)->len
+					   - (*pskb)->nh.iph->ihl*4, 0)))
 		return 0;
 
 	/* Must be RELATED */

_