sending ICMP messages in kernel module

[rajat swarup]

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?

Any help will be really appreciated!

Thanks and regards,
Rajat.
http://rajatswarup.blogspot.com/
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