[ixp1200] Packet processing in the IXP board.

Hi, I am new to IXP programming. I am looking at the Vera software to learn about programming in IXP. I am planning to do some operations at the router on the packets flowing through the IXP router (simple read oprations such as reading the source and destination IP addresses and keeping a table of last "k" such addresses, and possibly altering some fields of interest in the IP packet). Can someone tell me how to go about doing the same ? Thank you very much for your time. Jagan.