Some questions about skbuff's

[PaCoRRo <pacorro@xxxxxxxxxxx>]

Hello, i'm writting to you because i sent this mail to Alan Cox and he 
gave me that email address.
My problem is that i don't know how fix the pointers skb->data and 
skb->len and why of the instructions result. 
Can you explain me how i can fix that pointers depending type of packet   
and why of the instructions that fix them?

Thank You

PD: Sorry for my poor english