Android (lack of) support for DHCPv6

Wed Jun 10 07:14:12 UTC 2015

From: Lorenzo Colitti [mailto:lorenzo at colitti.com] 
Sent: Tuesday, June 09, 2015 11:47 PM
To: Tony Hain
Cc: Mikael Abrahamsson; Chris Adams; NANOG
Subject: Re: Android (lack of) support for DHCPv6

On Wed, Jun 10, 2015 at 3:38 PM, Tony Hain <alh-ietf at tndh.net> wrote: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.

This is not how current Android works. Each network can run IPv4, IPv6 or both independently of any other network. If you can reproduce this on a device running current Android (preferably a Nexus device), please file a bug.

There is indeed an issue with OEMs dropping RAs when the screen is off. Because it is the OEM that provides the wifi firmware and not Android, it's not really fair to say it's an Android bug. FWIW, recent Nexus devices do not have that bug.

My Nexus tablet does not have a Cell interface, and T-Mobile has stopped releasing updates for my phone, so I can't test that. For the issue I saw in the past, there was no screen-off event. All I had to do was enable the IPv6 APN, and given that I live on the edge of the service area the link would drop at some point shortly after. At that point the expected behavior is that IPv6 would still work via wifi, but no. While it still has an address, and can talk to anything on the wire, it has no router because that was removed and the RA is being ignored. 

I agree the OEM's are likely the problem here, but the platform should not allow them to create an invalid network state. Doing so only insures that they will pick the wrong options and break the network unnecessarily.

Tony