about ip_conntrack code

about ip_conntrack code

[zhengchuanbo]

I'm trying to read the ip_conntrack code. But it is not easy for me to 
understand the code. So I wish someone could help. Thanks in advance.
	
When an skb is received, we could call the ip_conntrack_get as following 
to get the connection info,
	 ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
and it calls,
	__ip_conntrack_get(skb->nfct, ctinfo);

What I want to ask is in the __ip_conntrack_get, how is the ip_conntrack
transformed from nfct? I can see that the code just makes a transform in
the structure as follows,
		struct ip_conntrack *ct
		= (struct ip_conntrack *)nfct->master;

I can't understand how the connection info is got by the transform. Wish I
could get some help. 

BTW, is there some more detailed documnets on netfilter code?

Thanks again.
	
regards,
	
Jack
 	
	

Re: about ip_conntrack code

[Pablo Neira]

Hi!

I just asked the same question as you not a long time ago.

See:
http://lists.netfilter.org/pipermail/netfilter-devel/2003-December/013425.html



zhengchuanbo wrote:

>I'm trying to read the ip_conntrack code. But it is not easy for me to 
>understand the code. So I wish someone could help. Thanks in advance.
>	
>When an skb is received, we could call the ip_conntrack_get as following 
>to get the connection info,
>	 ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
>and it calls,
>	__ip_conntrack_get(skb->nfct, ctinfo);
>
>What I want to ask is in the __ip_conntrack_get, how is the ip_conntrack
>transformed from nfct? I can see that the code just makes a transform in
>the structure as follows,
>		struct ip_conntrack *ct
>		= (struct ip_conntrack *)nfct->master;
>
>I can't understand how the connection info is got by the transform. Wish I
>could get some help. 
>
>BTW, is there some more detailed documnets on netfilter code?
>  
>

The netfilter hacking HOW-TO, this and a bit of patience worked for me :-).

best regards,
Pablo