Tcp sequence number calculation

Hello,
 i want know how 2.4 kernel decides which sequence no.
to be sent with next packet?
I am unable to find the location in kernel?
Also what does following statement does?
TCP_SKB_CB(__skb)= ((struct tcp_skb_cb
*)&((__skb)->cb[0]))
in tcp.h 
regards,
cranium2003.


		
_______________________________
Do you Yahoo!?
Shop for Back-to-School deals on Yahoo! Shopping.
http://shopping.yahoo.com/backtoschool