how to construct the sk_buff structure by myself?

Hi,everyone!
I want to ask for help about the sk_buff.
How can I construct an packet by myself?use sk_buff structure.

If as the following?
sk = alloc_skb(sizeof(struct sk_buff),GFP_ATOMIC);
sk->data=mydata;//mydata is data what we know

but I don't know if I should fill in other part of sk.

besides ,I found document about sk_buff is too little, so can you give
me some faq or document about it?

thank you very much!!