Re: [v6ops] When Android might disconnect because lack of DHCPv6 (was: Implementation Status of PREF64)

Alexandre Petrescu <alexandre.petrescu@gmail.com> Sat, 16 October 2021 19:51 UTC

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From: Alexandre Petrescu <alexandre.petrescu@gmail.com>
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Subject: Re: [v6ops] When Android might disconnect because lack of DHCPv6 (was: Implementation Status of PREF64)
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Le 12/10/2021 à 19:05, Philip Homburg a écrit :
>> The data necessary for SLAAC is in the RA that includes the M bit 
>> to tell the host to go ask the DHCPv6 server for an address, so
>> how would your CPE prevent the android from doing SLAAC without 
>> authorization?
> 
> I didn't verify it. But I assume clearing that 'A' bit in the PIO 
> should prevent android from doing SLAAC. It is not as if rogue 
> android devices are creating address from every prefix they see.

The ISP CPE I use has the A bit reset in the PIO, and the M bit set in
RA header, when the user selects 'DHCPv6' in the GUI of the ISP CPE.

Also, when checking that DHCPv6 option in the GUI, there is a warning:
in French: "Attention si vous activez le serveur DHCPv6, certains
périphériques Android risquent de ne plus avoir de connectivité IPv6".
In English it means: "Warning, if you activate the DHCPv6 server, then
certain Android devices are at risk of no longer having IPv6 connectivity".

The day I switch off completely IPv4 in my setting and continue with
DHCPv6 the Android will be fully disconnected from the Internet.  It is
not easy to completely turn off IPv4 in my setting, but it is not
impossible.

Alex

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