struct page *page = virt_to_page(skb->data);
int offset =?(unsigned long) skb->data - (unsigned long) page_address(page);
skb_add_rx_frag(master_skb,?skb_shinfo(master_skb)->nr_frags, page, offset,
skb->len)
.
.
is this the right way to do ?

This will work if skb->len < PAGE_SIZE, otherwise it means it spans
more than a page and you need to do skb_add_rx_frag for each PAGE_SIZE
data present. Refer to Understanding Linux network internals By
Christian Benvenuti p 488/489.

-syed