Re: tor server thinks IP address changed twice when it did not change

[Roger Dingledine <arma@xxxxxxx>]

On Wed, Nov 21, 2007 at 09:11:36AM -0600, Scott Bennett wrote:
>      However, a while later and completely unnecessarily, tor did this:
> 
> Nov 21 07:56:52.311 [notice] Your IP address seems to have changed. Updating.
> Nov 21 07:56:53.403 [notice] Self-testing indicates your ORPort is reachable from the outside. Excellent. Publishing server descriptor.
> Nov 21 07:57:55.025 [notice] Your IP address seems to have changed. Updating.
> Nov 21 07:57:59.599 [notice] Self-testing indicates your ORPort is reachable from the outside. Excellent. Publishing server descriptor.
> Nov 21 07:58:02.279 [notice] Self-testing indicates your DirPort is reachable from the outside. Excellent.

Interesting. Looks like it changed, then changed back. I just made
the "seems to have changed" log entry more informative:
http://archives.seul.org/or/cvs/Nov-2007/msg00246.html

> Nov 21 07:58:16.929 [notice] Have tried resolving or connecting to address '[scrubbed]' at 3 different places. Giving up.
> Nov 21 07:58:16.965 [warn] We just marked ourself as down. Are your external addresses reachable?

And these two are from the dirport reachability test launched at
07:56:52.

>      Meanwhile, the connection was good the whole time, tor traffic was being
> relayed, and the IP address remained unchanged since the previously noted
> event.  In the slightly more than an hour that has passed since the weirdness
> occurred between 07:56 and 07:59, tor has continued to run, answering directory
> requests and passing traffic.

Right. That's because Tor clients were using the IP address advertised
in the descriptor you published before this hiccup.

>      So it looks like there is a bug involved here, and it apparently does
> not depend upon starting up with no cached-descriptors* files.

Right, there's no reason to think it has to do with your cached files.
Tor doesn't look at your old cached descriptors to decide your current
IP address -- that would just be too fragile.

>  Does anyone
> working on tor development recognize these symptoms?  Or is this something new?

My first thought is that in fact your "thruhere.net" address resolved
to the old IP address briefly. This might happen because thruhere.net
has a big pile of dns servers, if one of them had an old answer cached
for a little while.

How repeatable is this? If you could get an info-level log, that would
give some more hints. (A debug-level log would provide even more hints,
but it would be really loud, so let's first see if info is enough.)

Thanks!
--Roger