Man page 9 : skb_copy_datagram_iovec

skb_copy_datagram_iovec - Copy a datagram to an iovec.

int skb_copy_datagram_iovec(const struct sk_buff *  skb , int  offset , struct iovec *  to , int  len );

skb
    buffer to copy

offset
    offset in the buffer to start copying from

to
    io vector to copy to

len
    amount of data to copy from buffer to iovec

the iovec is modified during the copy.