1. January 9, 2001 Router Plugins (Crossbow) 1 Washington WASHINGTON UNIVERSITY IN ST LOUIS Router Plugins (Formerly Crossbow) A Software Architecture for Next Generation Routers John DeHart jdd@arl.wustl.edu

2. January 9, 2001 Router Plugins (Crossbow) 2 Washington WASHINGTON UNIVERSITY IN ST LOUIS Agenda 9:00 - 9:20 Introduction (John) 9:20 -10:00 NetBSD Kernel Topics (John) 10:00 -10:30Kernel Programming Guidelines (Fred) 10:30 - 10:45Break 10:45 -11:15Router Plugins System Architecture (John) 11:15 -11:45 The Anatomy of a Plugin (John) 11:45 -12:00 Utilities (John) 12:00 -12:15 Exercises (John) Distribution and Your Plans for Usage 12:15 - 1:15Lunch (Brought in) 1:15 - 6:00Exercises

3. January 9, 2001 Router Plugins (Crossbow) 3 Washington WASHINGTON UNIVERSITY IN ST LOUIS Overview Introduction NetBSD Kernel Topics –IP Processing –mbuf –Loadable Kernel Modules –Interrupts –Miscellaneous –Kernel Programming Guidelines: Fred The Router Plugins system architecture The architecture of a plugin Utilities –System Utilities (modstat, moduload, modload) –Crossbow Manager utility

4. January 9, 2001 Router Plugins (Crossbow) 4 Washington WASHINGTON UNIVERSITY IN ST LOUIS Overview (continued) Exercises –Load an existing plugin and test »For each packet received, prints “I got a packet” –Modify plugin to print out UDP/IP info from select packets »do using plugin code »do using filter manipulations –Have plugin perform manipulation of packet payload »print out packet payload information »perform a payload operation dependent on whats there –Use plugin as two instances with different filters »one instance for each of two different destination addresses

5. January 9, 2001 Router Plugins (Crossbow) 5 Washington WASHINGTON UNIVERSITY IN ST LOUIS Acknowledgements

6. January 9, 2001 Router Plugins (Crossbow) 6 Washington WASHINGTON UNIVERSITY IN ST LOUIS Cast of Thousands? Dan Decasper Ralph Keller Hari Adiseshu Fred Kuhns Ken Wong Sumi Choi Tilman Wolf Anshul Kantawala Ed Spitznagel John DeHart Guru Parulkar Bernie Plattner Jon Turner others I’m sure... Special Thanks to: Ken Wong Fred Kuhns Anshul Kantawala Tilman Wolf Sumi Choi Jyoti Parwatikar Samphel Norden Ed Spitznagel

7. January 9, 2001 Router Plugins (Crossbow) 7 Washington WASHINGTON UNIVERSITY IN ST LOUIS Introduction

8. January 9, 2001 Router Plugins (Crossbow) 8 Washington WASHINGTON UNIVERSITY IN ST LOUIS Socket Layer Example: Normal IP Processing IP Queue IP InputIP Forward IP Output TCP Processing IP VersHLenTOS IDFragment Offset Source Address Destination Address Total length Flags TTL Protocol Header Checksum Source Port... Destination Port Packet Payload IP Is this packet for this Host? YES NO User Kernel IP Packet coming in on the wire Device Driver processing packet IP Device Driver puts packet in IP Input Queue

9. January 9, 2001 Router Plugins (Crossbow) 9 Washington WASHINGTON UNIVERSITY IN ST LOUIS Socket Layer User Kernel TCP Processing Example: IP Processing with a Plugin IP IP Queue IP Input IP Output IP IP Forward IP Does this packet Match the Filter? VersHLenTOS IDFragment Offset Source Address Destination Address Total length Flags TTL Protocol Header Checksum Source Port... Destination Port Packet Payload Interface IP YES NO Gate Filter (Intf,P,SA,DA,SP,DP) Plugin Code IP

10. January 9, 2001 Router Plugins (Crossbow) 10 Washington WASHINGTON UNIVERSITY IN ST LOUIS Router Plugins Router Plugins = = Crossbow –Same thing, different name. This is NOT Commercial Softare –Expect some bugs Router Plugins is Kernel level programming –You will need root access Currently works with NetBSD 1.4.1 –Moving to a new version of NetBSD takes about 2 weeks for us »Right now, no plans to move –Linux Port »Attempted once »About 50% done »Person working on it has left. »Right now, no plans to continue the port ANN: Active Network Node –Not to be discussed in this Tutorial

11. January 9, 2001 Router Plugins (Crossbow) 11 Washington WASHINGTON UNIVERSITY IN ST LOUIS Do Not Be Afraid Read and Understand the kernel source code –Not all of it, but some of it. Especially: »the structure of the IP processing loop »mbuf data structure and processing Buy a book –Stevens is a good set of books for TCP/IP Try things!!! EXPERIMENT!! –If the kernel doesn’t crash or hang at least once, you aren’t trying hard enough The Kernel is just another piece of software –Yes, there are some special things about it but its just ‘C’ code –… and some assembly code … but you won’t need to touch that. Programming at the kernel level takes a commitment –Be ready to spend some time in the code

12. January 9, 2001 Router Plugins (Crossbow) 12 Washington WASHINGTON UNIVERSITY IN ST LOUIS … But, Be Cautious... Be able to get back to the original kernel code Remember, plugins are not compiled in to the kernel –a reboot will always remove them –modunload will remove them Fred will present some other warnings and suggestions

13. January 9, 2001 Router Plugins (Crossbow) 13 Washington WASHINGTON UNIVERSITY IN ST LOUIS Installing Router Plugins New Kernel –Router Plugins kernel source tree –Router Plugins (Crossbow) kernel configuration file System Utilities that need to be rebuilt: –source tree; make build –cm (crossbow manager)