push apps failing in Android until you disable IPv6

[Tore Anderson]

* Erik Kline <ek at google.com>

> If this router were to send out an RA advertising itself as a default
> router in this configuration that would probably cause the symptoms
> you're seeing.  That's why I asked for a sample of any RAs seen on
> such a network.  (Such a configuration would of course be broken,
> effectively requiring Happy Eyeballs to function at all.)

Assuming the source address selection is implemented in a sane way,
just having a an IPv6 default router doesn't on its own explain the
symptoms described. IPv4 should be preferred due to the Android device's
link-local address not having the same scope as the IPv6 address of the
web site or whatever. See RFC6724 sections 5 and 6, rule 2.

The RA would have to additionally contain a PIO with global scope, as I
understand it. Then you'd certainly get in trouble (disregarding Happy
Eyeballs). Even a ULA PIO could be problematic if Android's source
address selection algorithm isn't updated to RFC6724 defaults. RFC3484
predates ULAs, so it treats them the same as other globally scoped
addresses.

Tore