DNAT & SNAT delay

[Martin Bangiev]

Thanks guys
I'm using 2.6 kernel and I did
echo "0" > /proc/sys/net/ipv4/netfilter/ip_conntrack_udp_timeout
everything works perfectly now:)

Ferry Huberts wrote:

>You can also use a hack I sometimes use:
>- reconfigure rules
>- set the connection tracking timeout for your connection type to zero in
>/proc
>- wait 1 second
>- restore the connection tracking timeout for your connection type in /proc
>
>Or use connection tracking flushing; I had a short discussion with Pablo
>Neira a while ago on this on the list but continued it privately because his
>solution was for 2.6 only and I use 2.4
>
>I have a 2.4 kernel patch for connection tracking entry flushing and Pablo
>can point you to a 2.6 solution (but first check the list for our
>discussion...)
>
>Good luck!
>
>________________________________
>
>Ferry Huberts
>
> Linux Rocks!  
>________________________________
>
>Brady's First Law of Problem Solving: 
>
>When confronted by a difficult problem, you can solve it more easily by
>reducing it to the question: "How would the Lone Ranger have handled this?" 
>
> 
>
>  
>
>>-----Original Message-----
>>From: netfilter-devel-bounces at lists.netfilter.org 
>>[mailto:netfilter-devel-bounces at lists.netfilter.org] On 
>>Behalf Of Jan Engelhardt
>>Sent: Tuesday, June 14, 2005 15:17
>>To: Martin Bangiev
>>Cc: netfilter-devel at lists.netfilter.org
>>Subject: Re: DNAT & SNAT delay
>>
>>
>>    
>>
>>>Just before the communication starts I add rules to DNAT 
>>>      
>>>
>>udp packets 
>>    
>>
>>>from
>>>Client1 to Client2, and to SNAT packets to Client2 to be from 
>>>Firewall:IP2. I do it for the Client2 respective (of course 
>>>      
>>>
>>I set up the ports too).
>>    
>>
>>>The problem is that the NAT starts with about 30 seconds delay. 
>>>tcpdump shows
>>>      
>>>
>>>Can you please tell me where this delay can be coming from?
>>>Thanks in advance:)
>>>      
>>>
>>Exactly 30? Then this:
>>
>>the default conntrack time-to-live for udp "connections" is 
>>30 seconds so you need to wait 30 seconds until the 
>>old-and-stale udp conn (the one "without" 
>>DNAT/SNAT) expires.
>>
>>Well, that's a guess.
>>
>>
>>
>>Jan Engelhardt                                                
>>               
>>--                                                            
>>                
>>| Gesellschaft fuer Wissenschaftliche Datenverarbeitung 
>>Goettingen, Am 
>>| Fassberg, 37077 Goettingen, www.gwdg.de
>>
>>    
>>
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