Re: IPv6 and Android auto conf

[Hugo Slabbert <hugo () slabnet com>]

On Mon 2015-Sep-28 21:15:02 +0530, Anurag Bhatia <me () anuragbhatia com> wrote:

> Hi Hugo
>
>
> (My reply in line)
>
> On Mon, Sep 28, 2015 at 8:50 PM, Hugo Slabbert <hugo () slabnet com> wrote:
>
> > On Mon 2015-Sep-28 17:33:46 +0530, Anurag Bhatia <me () anuragbhatia com>
> > wrote:
> >
> > Hello everyone
> > > I recently got IPv6 working at home LAN. My Android device (Google Nexus
> > > 5)
> > > is connected via wifi to LAN and LAN's core router is Map2N
> > > <http://routerboard.com/RBmAP2n>. I have a /64 on the LAN with
> > > "advertise"
> > > enabled to make ND to work and have autoconfig working on all devices.
> > > There are bunch of other layer 2 devices in LAN but all just acting as
> > > layer 2 transparently and core L3 remains on Map2N.
> > >
> > >
> > > All works well for most part but only trouble I am getting is on Nexus 5
> > > where after around 24hrs IPv6 stops working.
> >
> > How, specifically, does it "stop working" on the Nexus 5?
> > - temp addresses expired and does not generate new, valid, slaac addresses?
> > - RA entry ages out and doesn't get refreshed?
> > - cannot reach v6 gateway (ND fails somehow)?
>
> The last one - everything appears normal (with 4 IPv6 addresses on the
> device) but I cannot point any neighbor in same VLAN. Nor I can ping from
> them.

That sounds either like NDP is busted on the phone or the AP is eating the 
Android device's ND traffic.

When this happens, does the Android device show up in the ND cache of the 
other devices on the network that you are trying to reach/ping?

Does it show up in the ND cache of the segment's router?

If the Android device isn't showing up in other hosts ND caches when you 
try to ping them, can you do a pcap on one of those hosts when you try to 
initiate pings from the Android device to confirm if NS packets are being 
received?

Have you tried doing captures on the Android device directly [1][2][3] to 
see if it still receives RAs when this happens?

The symptoms seem to possibly line up with Android issue #32662[4].  
Possible you're being hit by that?

> The visible impact I see of it is slightly slow behavior of IPv6 enabled
> apps/websites which take a few seconds, timeout and fallback to IPv4.
>
>
>
>
> Thanks.
>
> > Only unusual thing I notice at that time is that phone 4 IPv6 as opposed
> > > to 2 (autoconf and temporary randomised address). Seems like some kind of
> > > issue in way NDP works either on Microtik or phone. The fix I am doing from
> > > few days is to restart wifi and phone interface gets fresh (two) IPv6
> > > addresses and all works well
> > > again.
> > >
> > >
> > >
> > > Anyone facing similar issue? (Note: No issues on OS X or iOS which are in
> > > same LAN)
> > >
> > >
> > > I can try DHCPv6 but I guess most of devices do not support it yet. (I see
> > > support for that in routerboard though).
> > Unless something's changed, DHCPv6 IA_NA isn't an option for getting an
> > IPv6 address assigned to an Android device[1][2]
> >
> >
> >
> > > Thanks.
> > >
> > >
> > > --
> > >
> > >
> > > Anurag Bhatia
> > > anuragbhatia.com
> > >
> > >
> > > PGP Key Fingerprint: 3115 677D 2E94 B696 651B 870C C06D D524 245E 58E2
> >
> >
> > --
> > Hugo
> >
> > hugo () slabnet com: email, xmpp/jabber
> > PGP fingerprint (B178313E):
> > CF18 15FA 9FE4 0CD1 2319
> > 1D77 9AB1 0FFD B178 313E
> >
> > [1] https://code.google.com/p/android/issues/detail?id=32621
> > [2] http://mailman.nanog.org/pipermail/nanog/2015-June/075915.html
>
>
>
> --
>
>
> Anurag Bhatia
> anuragbhatia.com
>
>
> PGP Key Fingerprint: 3115 677D 2E94 B696 651B 870C C06D D524 245E 58E2

--
Hugo

hugo () slabnet com: email, xmpp/jabber
PGP fingerprint (B178313E):
CF18 15FA 9FE4 0CD1 2319
1D77 9AB1 0FFD B178 313E

(also on textsecure & redphone)

[1] https://sites.google.com/site/androidarts/packet-sniffer (needs root)
[2] https://www.kismetwireless.net/android-pcap/ (some limitations, but 
shouldn't need root)
[3] https://play.google.com/store/apps/details?id=lv.n3o.shark (needs root)
[4] https://code.google.com/p/android/issues/detail?id=32662

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