Android (lack of) support for DHCPv6

[swmike at swm.pp.se (Mikael Abrahamsson)]

On Tue, 9 Jun 2015, Tony Hain wrote:

> I filed a platform bug on this back in the ICS timeframe, and it still
> persists. As I recall, there are 2 flags provided by the OS related to RA
> handling. Rather than using the one that sets a preference between the Cell
> vs. Wifi interface, at least Samsung (possibly others) have chosen to use
> the other flag that says to completely ignore the WiFi RA if an RA on the
> Cell interface has ever occurred. This means devices that have no IPv6 on
> their Cell interface will appear to work fine on WiFi.

I just re-verified (same Nexus4 using 5.1.1 on swedish mobile provider 
Tele2):

I disable wifi.
I have dual stack on my mobile bearer (PDP context). Verified with 10/10 
for both ipv4 and ipv6 on test-ipv4.com (no 464xlat though, this is 
NAT44:ed IPv4 and native IPv6 on the mobile side).
I enable wifi.
After a few seconds the Nexus4 connects to my home wifi and starts using 
it, I get 10/10 for IPv4 on test-ipv4.com and 9/10 for IPv6 because my 
provider DNS resolver doesn't support native IPv6 lookups.

> I claim that there is a platform bug, because there is never a reason to 
> ignore the WiFi RA. Use the other flag to set a preference if that is 
> needed, but ignoring the RA just breaks things in unexpected ways. LC 
> has did a hand-wave that the "ignore RA" flag is needed for battery 
> life, but beyond that we appear to be stuck in a world where Clueless 
> OEMs believe in breaking one network when another might exist.

Well, it's not present on my Google device anyhow.

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