COMPSCI 356: Computer Network Architecture

Testing

We have set up several test DNS servers which you should use while developing your code: 152.3.144.151 and 152.3.144.152. You should not send queries directly to any other DNS server (e.g., Duke's DNS servers) until your code is reliably working when sending to our test machine. Otherwise, the server operators may view your packets as a security attack, with undesirable consequences for all involved. If these servers are down, please contact Prof Benson and I will reboot the server.

You can use the wireshark utility in order to diagnose problems with packets that you send out (these will likely be malformatted at the beginning). Wireshark will capture packets that you send and will let you view/explore the various fields. It will warn you about fields that are incorrect or missing, and can guide debugging your packets.

You can use the dig utility in order to help diagnose problems with interpreting responses from the DNS server that you query. To use it, see the man page, and an example of the output is shown below:

bash$ dig www.cnn.com

; <<>> DiG 9.7.3-P3 <<>> www.cnn.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43304
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.cnn.com.			IN	A

;; ANSWER SECTION:
www.cnn.com.		116	IN	A	157.166.226.25
www.cnn.com.		116	IN	A	157.166.226.26
www.cnn.com.		116	IN	A	157.166.255.18
www.cnn.com.		116	IN	A	157.166.255.19

;; Query time: 170 msec
;; SERVER: 192.168.100.1#53(192.168.100.1)
;; WHEN: Mon Mar 12 08:55:51 2012
;; MSG SIZE  rcvd: 93

You will note that the output includes a number of the DNS header fields, as well as the full contents of the question and answer sections (you can also see the output of the authority and additional sections via command-line arguments).

Additionally, we have included a basic test script to check the output of your code against our reference solution and check your code's compatibility with the grading script. If your code fails in the test script we provide, you can be assured that it will fare poorly when run under the grading script.
Note:i Verify that 'test' is executable.
To run the test script, simply type

	bash$ make test

This will compile your code and then test your DNS client on a number of inputs, comparing the results against the reference solution. If any errors are detected, the test will print out the expected and actual output. For example, you might see something like

bash$ make test
./test
  Trying with script 'www.cnn.com'                            [FAIL]
    Diff in expected output:
< www.cnn.com  157.166.226.25
> blah
bash$ 

This indicates that the test with input ./dnsclient was expected to print out the line preceded by < , but instead returned blah (the output is simply a diff between the output of your shell and the reference shell). We include a few sample tests, but these are by no means exhaustive. We expect that you will create additional test to ensure that your programs behave as expected.

Submitting your project

Grading

• 85% Program functionality
• 15% Error handling

Advice

• Remember to convert your integers, shorts, and longs to network ordering (using hton() ) and associated functions).
• Check the Piazza forum for question and clarifications. You should post project-specific questions there first, before emailing the course staff.
• Finally, get started early and come to the instructor's office hours and TA lab hours. You are welcome to come to the lab and work, and ask the TA any questions you may have.