about headroom in sk_buff

Hi,
My kernel module should expand received IP packets with new IP header and UDP header and other private data in head( some like IP in IP encapsuled), all expand data will more than than 16, so I will have to use skb_realloc_headroom to expand the sk_buff, but I don't want to do this for performance,is it possible to allocate sk_buff reserve more than 16 in headroom and how to do this?

hope you can understande my problem:)!

Thanks!

Hi,
You have to re-allocate the buffer with sufficient head room or you will have to make the driver allocate extra bytes during buffer allocation and then reserve the required headroom for you.

First one will impact your performance as skb_cow or skb_expand_headroom will allocate and copy the complete buffer.

Regards
Narender

I got it

Thanks!
Ian