Wednesday, April 29, 2015
Alien packets from outer space
To help test “Project: Sippy-Cup,”
I wrote a mock component to return precanned data releated to our test data.
The mock component is basically a specialized DNS server that only expects a certain type of query.
I wrote it so it would be easier to configure and run than a full blown
But for the past few weeks it was crashing and pretty much the only report I would get back is “it crashed.” Sigh. I did find the error path in the mock component to be a bit spotty, but this was never intended to be a full blown product but rather something that would work just well enough to get the testing done. I never tested it with bogus queries because I never expected it to get bogus queries. We had control over all the data. The mock component would only talk to programs we were testing.
Even after fixing some “how did I not see that error?” type problems, the mock component was still crashing, and the only way that could happen is if the queries being sent were too large (over 512 bytes), the query was corrupted or malformed and could not be decoded, or if the query wasn't the single query type supported by the mock component. And there was no way any of that could happen. We controlled all the data!
Or so I thought.
It turns out the mock component was receiving God knows what from random computers on the Internet, which is incredible when the computer the mock component is running on doesn't have a public IP address!
Well, okay, it does have a public address, but it's a public IPv6 address, but the queries causing the crashes were all coming from IPv4 addresses.
About the only thing I got to explain that behavior is the IPv6 address is routed via a tunnel, and perhaps there's some routing leakage that lets public IPv4 packets through. Other than that, I got nothing.
At the very least, I did fix the dodgy error handling so the mock component doesn't crash from data that it shouldn't get.
A trip to the hospital
Bunny was in the process of cutting up an old computer desk on the back porch with a sawzall when a chunk fell off in such a way not to break her big toe, but rip the nail off of it (ugh).
She managed to bandage it up and off we headed to the non-emergency emergency room at the local hospital. Bunny said it was more of a clinic than an emergency room but that it happens to be located in the emergency room.
I drop her off, then spent the next ten minutes trying to locate the parking lot. Turns out that at the Boca Raton Regional Hospital, the emergency room parking lot (as well as the non-emergency emergency room parking lot) was across the street, marked by a few tiny signs with a low albedo.
Oddly enough, the emergency room wasn't crowded, and thus non-emergency emerency room wasn't crowded. By the time I had arrived in person, Bunny was already in the bowels of the hospital being treated.
And I'm stuck in the waiting room watching “Jurassic Park III.”
Limping, but at home
A bunch of people got eaten. Sam Neil managed to escape being eaten. The dinosaurs still roam that Central American Island like they own the place or something. And Bunny finally limped out of the non-emergency emergency room.
One clunky foot brace, some good medicine, dinner from Denny's (slogan: “You never start out for us, but you'll always end up here”) and all is, mostly, right with the world.