Re: Disabling temporary addresses by default?

[Fred Baker <[e-mail]>]

+1 on this. We can discuss whether a temporary address should have a limited lifetime or whether a given interface might have at most some number of temporary addresses at any given time, but to say that in the default (e.g., usual) case each system has zero seems like a bad idea.

> On Jan 28, 2020, at 6:59 AM, Lorenzo Colitti <lorenzo=[e-mail]> wrote:
> 
> Changing subject because many participants are likely to just ignore yet another "SLAAC vs DHCPv6" thread. :-)
> 
> On Tue, Jan 28, 2020 at 11:27 PM <[e-mail]> wrote:
> In the context of 4941bis last call, it might be prudent of us to revisit this change:
> 
> https://tools.ietf.org/html/draft-ietf-6man-rfc4941bis-05#section-8
> 6.  Temporary addresses are *not* disabled by default.
> 
> Saying that temporary addresses should be disabled by default (assuming hosts actually do that) seems like a terrible privacy problem. It means that by default, a host that doesn't change prefix will use the same IPv6 address to communicate with *everyone* on the internet until the end of time. That provides lots of opportunities for cross-site tracking, and the user can do very little to protect themselves because they don't have control over IP addressing like they do over higher-layer identifiers (e.g., users can clear cookies, or use different browser profiles or different browsers/apps for different sites).
> 
> I don't think 4191bis should advance if it says that privacy addresses are disabled by default. It would be a strong statement by the IETF that we don't care about privacy of IP addresses and would be a terrible signal to send.
> 
> Instead of disabling, why not change the default of the number of addresses maintained? For example, instead of maintaining 1 permanent + 1 valid + 7 deprecated, why not just default to maintaining 1 permanent + 1 valid + 1 deprecated. That means that applications would have to re-establish their connections once a day instead of once every 7 days. But if they use privacy addresses, they already need to re-establish connections after 7 days. And they can always use not to use privacy addresses via the appropriate socket option.
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