netdev - Problem with the first ICMP

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Date:	Wed, 30 Nov 2011 11:10:54 +0800
From:	Li Wei <lw@...fujitsu.com>
To:	netdev <netdev@...r.kernel.org>
Subject: Problem with the first ICMP_REDIRECT message

Hi all, 

I am doing some tests on ICMP_REDIRECT messages and found that I never receive
the first ICMP_REDIRECT message, but the following REDIRECT messages was normal.

My test environment as follow:
three pc:
PC A:
	IP: 192.168.0.1 MAC: HW:0A
PC B:
	IP: 192.168.0.2 MAC: HW:0B
	module nf_nat loaded and at least one rule in nat table(rule content not concern)
PC C:
	IP: 192.168.0.3 MAC: HW:0C

enable ip forwarding on PC B:
# echo 1 > /proc/sys/net/ipv4/ip_forward

add a static arp on PC A:
# arp -s 192.168.0.3 HW:0B

ping 192.168.0.3 on PC A:
# ping -c1 192.168.0.3

I expect that PC A will receive a ICMP_REDIRECT message from PC B, but nothing
received.

ping three times 192.168.0.3 on PC A:
# ping -c3 192.168.0.3 

PC A got two ICMP_REDIRECT messages from PC B, the first one missing.

After some code search, I found in function nf_nat_icmp_reply_translation() the first
ICMP_REDIRECT message was droped because the ct->status is not IPS_NAT_DONE_MASK.

Does anyone has some suggestion?

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