Mystery
Today at work, I came across what’s gotta be the strangest bug (software wise, not real life!) that I’ve ever seen.
It started innocently enough - the ICAP server I wrote dies under heavy request modification stress. I realized that one of the required headers called Encapsulated was not being sent properly. Since Encapsulated tells the server the location of boundaries of different data sent over in a single request, it’s pretty important. 
So, I start sniffing packets… Packet captures on client side showed that right data is being sent over… Packet captures on the server side (on the networking layer) showed that right data is being sent over… but once it got to my program, the Encapsulated header would mysteriously change to another syntactically valid but nevertheless wrong value. And I wasn’t using any libraries to connect either! It was all low level socket programming (you know, select() and stuff) so nothing should’ve gotten in anywhere…
Anyhoo, I figured out the pattern that caused the server to crash thereby sort of jumping over the sections that caused the crash (at a slight Performance hit… it’s a QA tool, so compliance is more important than performance anyway)… but I still don’t understand why it worked the way it did. Not a slightest clue. Bah!
L Said,
December 12, 2003 @ 2:46 am
“It was all low level socket programming (you know, select() and stuff)”
Well no, I DON’T know! Help! I’m not learning anything!
T Said,
December 12, 2003 @ 9:46 am
*Takes out voodoo stick and starts shaking it*
Devils and bugs begone from Daniel’s program..
hahahaha
SO what is a ICAP server?
Daniel Said,
December 12, 2003 @ 2:03 pm
ICAP is HTTP like protocol that lets caching boxes do virus scanning, content filtering, and other security stuff… Companies like Symantec and TrendMicro makes ICAP servers which does the virus scanning, so all caching box has to do is ship the data over to ICAP server and see what it says about it.
I’ve *just* commited all the changes into the source tree…
It’s out of my hands now… hehe