push apps failing in Android until you disable IPv6

[Mikael Abrahamsson]

On Mon, 9 May 2016, JORDI PALET MARTINEZ wrote:

> Just got a “screen” capture from one of those situations (rdisc6).
>
> Hopefully is useful ! They made it from a virtual machine in the same network as the Androids have the problema, having the VMware interfaces in bridge mode.

So that looks like something is sending an RA, announcing itself as a 
router but there are no addresses to be used on the link (there is no 
on-link prefix thus implicitly A=0, and M=0).

My guess is that any device which sees this, will install default IPv6 
route but will only have link local addresses on the interface, thus there 
is no source address to use to send packets to the world outside the link.

According to standards, this shouldn't be a problem. IPv6 would not be 
used to communicate with the outside world.

Looking at https://tools.ietf.org/html/rfc6724 2.1 and the table there. 
Why is there nothing there matching fe80::/10 ? I guess it just implicitly 
takes for granted that anything in fe80::/10 can't be used without also 
specifying the interface? If someone did something "smart" and thought 
they'd help the user by not requiring them to specify interface, then this 
might cause problems unless the application immediately gets an error 
back? And if it gets an error back, how do we know it tries the next 
option, for instance IPv4? Could this be the problem here, the 
applications only try one address family and if that doesn't work, it 
won't establish the notification channel?

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se