Tinc crashes when node with identical configuration is present twice

[Guus Sliepen]

On Fri, Jun 04, 2010 at 01:44:15PM +0200, Jörg Weske wrote:

> Today we observed an interesting scenario. By mistake, one node with
> identical configuration was present twice inside our tinc network, logged in
> from a different dialup connection. (This happened after a migration from an
> old PC to a new one, as the tinc-directory was simply copied to the new PC.)
> 
> This led to an almost immediate crash of the tinc daemons on both supernodes
> within a few dozen seconds of the second PC with the identical configuration
> coming online. Any attempt to restart the daemons would lead to another crash
> within a few minutes.
> 
> The following log entry appears before the crash:
> 
> 1275643910 tinc[31243]: Ready
> 1275644063 tinc[31243]: Error while translating addresses: ai_family not supported
> 1275644063 tinc[31243]: Got unexpected signal 8 (Floating point exception)

That is definitely not supposed to happen. It would help if you could run tinc
with a higher debug level (-d5) and try to reproduce it, and send me the log.

> I found the following message in the tinc list archives mentioning
> the same error and crash, though apparently for a different reason:
> http://www.mail-archive.com/tinc@tinc-vpn.org/msg00538.html

Yes. The crash is forced by the code, when it is unable to parse an address. I
could let tinc continue, but it would probably not work properly anymore
anyway. I do not know yet why it has a problem parsing an address when you have
two identical nodes...  it is probably because of an unrelated bug somewhere
else in the code.

> Although I understand having the same node twice inside the network
> is clearly a hefty configuration error, maybe there is a way to make
> tinc a bit more robust against such a situation? After all, our
> mistake may accidentially occur in other setups as well.
> 
> We were only get our tinc network back online after identifying the
> culprit and disabling one of the two nodes causing the trouble.

I'll see if I can make tinc detect such a situation.

-- 
Met vriendelijke groet / with kind regards,
     Guus Sliepen <guus at tinc-vpn.org>
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