[atlas] "funny" comment in pop-up display for a measurement? (v4/v6 addr mismatch)

Hi Wilfried,

On 2014/01/15 18:44 , Wilfried Woeber wrote:
> Some more digging and some more confusion?
> 
> Logged in, looking at "My measurements", selecting 1033944, a traceroutev6.
> Bringing up the Map tab, clicking on the green balloon in Bremen (Probe ID
> 13255) with the *2* (hops) in it, pop-up comes up. Nice!
> 
> But the *-comment at the bottom puzzles me, by saying:
> 
> * The last address does not match the target IP (192.153.174.196)
> 
> This is sort of obvious, as the address referred to is 2001:6f8:114e:4::1
> What's the background for this behaviour?

The target of your measurement, wsww2.cc.univie.ac.at, has, as far as I
can tell, only an IPv4 address. So an IPv6 measurement should fail. And
in fact most probes reported:

"result":[{"error":"name resolution failed: non-recoverable failure in
name resolution"}]

One question that comes up is how you were able to run this measurement
in the first place. Because the system usually doesn't allow running
measurement towards targets that don't have an address for the selected
address family.

This also why the UI complains about 192.153.174.196, because that is
the IPv4 address of wsww2.cc.univie.ac.at.

There were 3 probes where name resolution resulted in an IPv6 address. 2
of them have since changed their behavior and no longer resolve to an
IPv6 address.

One probe, 13255, is rather curious, because it resolved
wsww2.cc.univie.ac.at to 2001:6f8:114e:3::c099:aec4, which is
interesting because c099:aec4 is exactly equal to the IPv4 address of
wsww2.cc.univie.ac.at. So I suspect that this probe is behind a resolver
that does DNS64.

Philip