[josm-dev] IPv6 problems

[Dirk Stöcker]

On Fri, 1 Jan 2016, Florian Lohoff wrote:

>> There are too few users with that specific issue to care for them
>> right now with an automatic approach.
>
> Germany - Bigges Community - Largest ISP Telekom is switching all
> DSL contracts to Dualstack. Kabel Deutschland is already handing
> out IPv6 be default with DS Light. So within a very short timeframe
> you'll see a lot more people complaining.

No. Because only a minority will walk between IPv6-enabled and IPv4-only 
networks.

>> Java does not support on-the-fly detection, but this setting must be
>> done before first network usage and cannot be changed later. We
>> can't change that behaviour. Feel free to submit a Java bug report.
>
> There is no such thing as a on-the-fly detection. You as the application
> author need to write the detection. You need robust "connect" logic
> which tries ipv6 and falls back to ipv4 when the connect does not
> work. The latest RFCs gives even more advice on how to work around
> long delays induced by servers advertising ipv6 and not responding
> to it or intermitted ipv6 problems e.g. packet loss in the v6 path. This
> is the daily business for an ISP - You path are different for v4 than
> for v6 so you have different latencys, paths, packet loss probabilities
> etc.

As said: We don't provide Happy Eyeballs. WHY should JOSM try to resolve 
the issues of the ISP? Loss on the path, delays, ... are all ISP issues 
and have to be solved by the ISP. Happy eyeballs only hides them.

The only valid argument ATM is that JOSM needs one additional start when 
you switch from an IPv6 enabled network to a non-enabled network. That's a 
known bug. And as said the reason is that Java does not allow us to change 
behaviour after we did a first network connection. I'll check if we can at 
least auto-restart it in this case.

> My user setup is continously broken and i work around it. YOU refuse
> to even implement 20 year old Best Common Practices written in RFCs
> for a good reason.

It's not my problem that you have a constantly broken setup. I have not. 
I use IPv6 for years now at home and in my company and all our internal 
traffic goes over IPv6 and I have no reasons for workarounds.

When I had IPv6 trouble then I contacted the ISP and they fixed it which 
in the end resulted in better monitoring on their side and less trouble.

> http://comments.gmane.org/gmane.comp.gis.openstreetmap.region.de/110207

Also this is a typical setup error. If someone accesses "localhost", then 
the tool also must listen on localhost which nowadays means IPv4 and IPv6 
otherwise the address must be 127.0.0.1 which is the IPv4 address for 
localhost.

> Sorry - NO - I have a perfectly working ipv6 setup with German Telekom
> at home. Even there i need workarounds with josm not falling back
> to ipv4 with the tracer plugin.

Then contact the tracer author and tell him to fix his software and not 
to try to access illegal address. Either the tracer plugin must use 
127.0.0.1 only or the tracer tool itself must listen also on ::1.

> EVERY single connection needs the fallback logic for itself without
> cached prior knowledge of the environment.

No. It does not need this. No software does this for IPv4. Why should we 
do this for IPv6? To make IPv4/IPv6 transition smoother some people 
thought that IPv6 errors should be silently ignored. And what's the result 
- people like you assume that having errors is ok. IT IS NOT OK.

> With mobility my ipv4 only connection can change to dualstack to dslight
> to a pure ipv6 with 6to4 NAT back to ipv4. If my services are reachable
> Dualstack there should be service everywhere. With JOSM the first
> change in network environment needs an application restart.

As told multiple times this has technical reasons. Java does not allow to 
switch the handling of IPv6 after I did a single network access. I would 
be happy to have it like for all other tools which follow the OS 
preference, but that's not possible ATM. If you can't live with it, 
disable it. I don't rewrite the whole Java network stack only to satisfy 
your need for perfection.

Ciao
-- 
http://www.dstoecker.eu/ (PGP key available)