Re: [v6ops] out-of-focus: why DHCPv6 breaks Android computers?

"STARK, BARBARA H" <> Tue, 29 October 2019 14:42 UTC

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To: "'Ted Lemon'" <>, "'Alexandre Petrescu'" <>
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Thread-Topic: [v6ops] out-of-focus: why DHCPv6 breaks Android computers?
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Date: Tue, 29 Oct 2019 14:42:37 +0000
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Subject: Re: [v6ops] out-of-focus: why DHCPv6 breaks Android computers?
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> From: Ted Lemon
>> On Oct 29, 2019, at 6:37 AM, Alexandre Petrescu <> wrote:
>> Well no.  After  activating DHCPv6 on CPE the CPE sent three RAs
>> changing the Lifetime and flipping the M(anaged) and A(utonomous) flags.
>> Packet dumps available upon request.

> That’s the problem.   It should turn on the managed bit but not turn off the autonomous bit.  The two can validly be on at the same time.

> Of course, since their meanings are deprecated, it’s not too surprising that implementations get this wrong.

Deprecated? Their meanings aren't deprecated at all, AFAIK. Specifically, the Autonomous bit continues to mean "this prefix can be used to generate SLAAC addresses". If there is no prefix with A set, then there is no prefix to use to generate SLAAC addresses. If there is a prefix with A set, hosts are free to create SLAAC addresses from it to their hearts' content. Or not. I agree that based on Alex's description of the A bit being flipped, it suggests there are no prefixes being advertised with A set -- which means SLAAC is being disabled.

And I'm not going to get started with debating the "M" hint. M's meaning is very clear. Problems arise when people try to attribute or (think they can) demand more meaning than it has. It's a beautiful little bit, and I like it very much. It doesn't deserve to be maligned like this. It has served me very well.