Computer Science 686

1. Computer Science 686 SPECIAL TOPIC: Programming Gigabit Ethernet Spring 2008 Professor Allan Cruse

2. Some important prerequisites • You are a computer science grad student • You are acquainted with x86 architecture • You can execute Linux/UNIX commands • You know how to use a text-editing tool • You can write programs in the C language • You can print out a program’s source-file

3. Instructor Contact Information • Office: Harney Science Center – 212 • Hours: Mon-Wed-Fri 1:30pm-2:20pm Tues-Thurs 6:15pm-7:15pm • Phone: (415) 422-6562 • Email: cruse@usfca.edu • Webpage: http://cs.usfca.edu/~cruse/

4. The class website • URL: http://cs.usfca.edu/~cruse/cs686/ • General description of the course • Links to some useful online resources • Lecture-slides and demo-programs • System software for use with this course • Class announcements (e.g., exam dates) • A link to our CS686 discussion-list • Our schedule of textbook readings

5. Recommended texts Mark Norris, Gigabit Ethernet Technology and Applications Artech House (2002), ISBN 1-580-53504-4 Corbet, Rubini, and Kroah-Hartman, Linux Device Drivers (3rd Ed), O’Reilly (2005), ISBN 0-596-00590-3

6. Course’s continuing theme is… “Using the computer to study the computer”

7. Normal C/C++ programming We would write most of this source-code “app.cpp” but we would call some library-functions e.g., open(), read(), write(), malloc(), … then our code would get ‘linked’ with standard runtime libraries written usually by other programmers and ‘shared’ among many applications (So this is an example of “code reuse”) application call ret standard “runtime” libraries

8. Normal C/C++ programming Many standard library functions perform services that require executing privileged instructions (which only the kernel can do) application call Operating System kernel ret syscall standard “runtime” libraries sysret user space kernel space

9. Linux Kernel Modules Linux allows us to write our own installable kernel modules and add them to a running system application module call ret call Operating System kernel ret syscall standard “runtime” libraries sysret user space kernel space

10. Requirements/Benefits • An LKM has to be written using “C” -- but can include “inline” assembly language • An LKM runs in kernel-space – so it can do anything that the CPU supports • Therefore, an LKM can – • directly control any peripheral devices • modify the kernel’s scheduling algorithms • examine the kernel’s hidden data-structures

11. Network Interface Controllers • One of the most interesting peripherals in every modern PC is its Network Interface Controller (NIC), allowing communication among computers (and other equipment)

12. Thanks, Intel!☻ • Intel Corporation has kindly posted details online for programming its family of gigabit Ethernet controllers – our course’s focus

13. Thanks, Linus! ☻ • Linus Torvalds initiated the collaboration among programmers that has resulted in our free “open source” operating system • The Linux OS continues to evolve – new version is posted almost every week, at: http://www.kernel.org • For example, late last August we started our semester with version 2.6.22.1 – then, by mid-December version 2.6.22.15 had been released

14. Thanks, Richard! ☻ • Richard Stallman (who spoke at USF last semester) established the Free Software Foundation, which produces the systems software (e.g., editors, compilers, linkers, libraries, debuggers) that will allow us to write Linux application-programs – and Loadable Kernel Modules – that explore the capabilities of Intel’s 82573L NIC • Website: http://www.fsf.org

15. Thanks, Alex! ☻ • Alex Fedosov (USF ’01) is SysAdmin for our department’s ‘anchor’ server-cluster • We can connect to those servers from our classroom’s workstations or the CS Labs • They have Intel’s gigabit Ethernet NICs • Alex has connected them via a switched hub, thereby creating a private Local Area Network for doing course-experiments

16. Thanks, Alfred! ☻ • Alfred Chuang (USF, ’82) is a founder of BEA Systems, Inc. (located in San Jose) • As a computer science undergraduate at USF, he was inspired by his teacher and Faculty Advisor, Dr. Michael D. Kudlick • To express his gratitude in a way that would benefit future USF students, Alfred made the generous gift of this classroom

17. Course acknowledgements Paul Otellini Linus Torvalds Richard Stallman Alex Fedosov Alfred Chuang Interactive learning classroom ‘anchor’ cluster servers Linux operating system GNU software tools Intel NIC documents This ‘special topics’ course would not be possible without these contributions

18. Why use a private LAN? • For our class exercises and experiments we’ll be able to use the CS department’s ‘anchor’ cluster (which currently consists of 8 server stations, but soon will be 16) • These stations have Intel’s 82573L NIC and they all connect to a ‘switched hub’ • We can control the network-traffic volume and not worry about causing others trouble

19. Our ‘anchor’ servers D-Link Gigabit Switched Hub anchor00 anchor07 anchor01 anchor06 anchor02 anchor05 anchor03 anchor04 computer science department’s student network (138.202.171.0)

20. Demo program: ‘netsniff.cpp’ • This privileged application can monitor a Linux station’s network-traffic, showing all the data-packets that are being processed by between the station’s network interface • We can demonstrate this tool on stations in our classroom or on the ‘anchor’ cluster • It will give you a chance to see how those ‘anchor’ machines can be accessed

21. Berkeley ‘sockets’ API • The BSD sockets application programming interface provides a standardized library of functions for writing network programs in C • These functions make it straightforward to create programs following a ‘client/server’ programming paradigm request ‘client’ program ‘server’ program reply

22. Simple ‘echo’ server • A former USF grad student presented a very simple example in his M.S. Thesis, based on the User Datagram Protocol • We’ve adapted his UNIX code for Linux: • ‘udpserver.cpp’ • ‘udpclient.cpp’ • We can run this demo in our classroom, but it’s also instructive to run it on ‘anchor’

23. A few socket-API functions // create a new socket (i.e., an endpoint for network communication) int socket( int domain, int type, int protocol ); // bind an ‘address’ to a socket int bind( int sockfd, struct sockaddr *addr, socklen_t alen ); // receive a datagram from a client-process int recvfrom( int sock, char *buf, int len, int flags, struct sockaddr *from, socklen_t *fromlen ); // transmit a datagram to another process int sendto( int sock, const char *msg, size_t msglen, int flags, struct sockaddr *to, socklen_t tolen );

24. Our course’s context • This course is NOT about writing network application programs – but instead about programming ethernet interface hardware • Nevertheless, we believe it is helpful for understanding why we consider various system programming issues if we know what uses will be made by application-programs of our hardware’s capabilities

25. For some exercises… • We will need to use a few standard UNIX tools for performing our experiments: • The ‘ping’ command is useful for testing if a pair of network-stations can communicate • The ‘ifconfig’ program will allow us to assign an internet-address to a specific interface, so that standard network programs can be used • The ‘sudo’ command will allow classmembers to execute certain ‘privileged’ system tools

26. Classroom’s stations # Kudlick classroom hosts 138.202.171.61 hrn23501.usfca.edu hrn23501 138.202.171.62 hrn23502.usfca.edu hrn23502 … 138.202.171.90 hrn23530.usfca.edu hrn23530 # Fifth-Floor CS-Lab hosts 138.202.171.21 hrn53501.usfca.edu hrn53501 … 138.202.171.32 hrn53512.usfca,edu hrn53512 # ‘anchor’ server-cluster hosts 138.202.171.200 anchor00.usfca.edu anchor00 … 138.202.171.207 anchor07.usfca.edu anchor07

27. Kudlick Classroom 08 09 10 15 16 17 18 19 20 28 29 30 04 05 06 07 11 12 13 14 24 25 26 27 01 02 03 21 22 23 lectern

28. In-class exercises • Use ‘ping’ to check that you can reach at least three other stations: • Another station in our Kudlick classroom • One of the stations in the 5th-Floor CS Lab • One of the stations on our ‘anchor’ cluster • Try using our ‘netsniff.cpp’ application to capture some network-packets (by using I/O-redirection): $ netsniff > netsniff.out