Re: sending ICMP messages in kernel module

["J. Scott Kasten" <jscottkasten@yahoo.com>]

rajat swarup wrote:

> Hi,
> I have placed a netfilter hook in which I grab the packets in the
> pre-routing stage.
> I need to send ICMP messages in response to certain messages in this hook.
> I looked at alloc_skb(), skb_reserve() and skb_put() functions but it
> is still not clear to me as to how to construct the packets using
> these methods.
> Since I am getting the packets in the Pre-routing stage should I
> explicitly construct the MAC header, IP header & data & ICMP message?
> Also, I'll need to calculate the checksum to be transmitted in the
> ICMP packet...which method could I use to do that?
>  
Hello,

I had a similar problem once.  In the icmp.c file, look at how the ping 
echo reply works.  That is as close to a tutorial as you will find in 
the code.  I think you might find it strait forward from there.

-Scott-

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