[josm-dev] IPv6 problems

Greg Troxel gdt at ir.bbn.com
Wed Dec 30 22:27:04 UTC 2015

I'm not sure if I should file a ticket, or report this here, so I'll
start here.

I have been running JOSM for a long time, on a Mac, currently at OSX
10.7.  I have functional IPv6, but my tunnel is from OCCAID, and
occasionally some places are unreachable - currently
api.openstreetmap.org is one of them.

josm starts up and proclaims:

  INFO: Detected useable IPv6 network, prefering IPv6 over IPv4.

which is fine, but then when downloading data (simple pushing of
download icon, letting area be, and then pushing the download button in
the popup) normally, I get an API error.  I can ping
api.openstreetmap.org on v4, but not v6, where I get a network
unreachable in New York.  If I had a 2-minute delay and then a download,
there would be a more subtle happy eyeballs issue, but I totally failed
to download data a few hours ago.

Just now, I was able to download data.

So it seems that there is some notion of only trying one address family,
vs. trying all addresses in all familes in some sort order, and only
failing if all fail.

OSX itself has some version of Happy Eyeballs which uses RTT on v4 and
v6 to the address (prefix?) to decide which to try first, I think via
sorting getaddrinfo results.  I am totally unclear on how this interacts
with Java.

This can likely be reproduced by configuring nonworking IPv6.

Greg (osm user gdt)
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