hello, Thanks for ur reply that relaxes me that i can do that. Actually what i want i told u that to add 2 four bytes fields of my own of each packet. So as per ur suggestion i can use it in cb varialble. Now what i want to know Whether kernel passes whole skb or only packet with data and headers. cause as part of my project i want those fields at next host to recalculate the checksum of my own on data only. so those fields should be accessible to me at next host. can it be possible? Parag.