[atlas] [ipv6-wg] What to do with RIPE Atlas probes that have only a ULA as IPv6 address?

On 2015/03/26 15:42 , Enno Rey wrote:
> On Thu, Mar 26, 2015 at 02:26:14PM +0100, Philip Homburg wrote:
>> I forgot that RFC-6724 (Default Address Selection for Internet
>> Protocol Version 6) now explicitly lists ULAs, so indeed they would
>> not do any harm in trying to reach a dual-stack target.
> 
> this would assume that
> 
> a) the probes are supposed to follow RFC 6724. are they?
> b) they actually _do_ this (follow RFC 6724) in practice. can this be confirmed? [keeping the wide variety of potential IPv6 node behavior in mind]

My statement was meant to reflect on whether announcing ULAs when there
is only IPv4 internet connectivity would harm a 'normal' internet user.
It was not meant to make a statement about the probes.

Probes are complicated in this aspect. For some parts of the probe
functionality the stub resolver in the c library is used. This is uClibc
except on anchors where it is glibc.

Then there are measurements where the probe has to resolve a name as
part of the measurement. In that case, the stub resolver in libevent is
used.

Finally, for most of the measurements the probe receives IP addresses
and not DNS names, so there is no issue with destination selection. For
all measurements it is up to the Linux kernel to select a suitable
source address.

Note that all measurements are explicitly directed to measure either
IPv4 or IPv6, so there can be no confusion there.

Philip