MAC header size from skbuff

[rajat swarup <rajats@xxxxxxxxx>]

Hi,
I am capturing packets in the Kernel using Netfilter hooks. So I get
access to the packets as sk_buff structs.
I want to access the IP data field. Could anyone please tell me what
is exactly wrong with this math:

ptr = sb->data+sb->nh.iph->ihl*4 

Andif I want to find the length of the IP data field (when I've just
captured packets thru the netfilter PRE_ROUTING hook ) what could be
the length of this?
For what fields should ntohs() be used to convert from NB to Host order?
Now does ptr point to IP data (i.e. just past the IP header)?

Any help will be appreciated!

Thanks!
-Rajat
http://rajatswarup.blogspot.com/

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