Re: we should enable RFC7217 by default

On Tue, Jan 27, 2026 at 03:35:16AM +0330, Pouria Mousavizadeh Tehrani wrote:
> Hi everyone,
> 
> With `net.inet6.ip6.use_stableaddr` now available, I believe we should
> enable it by default in CURRENT at least.
> As you may already know, we currently use the EUI64 method for generating
> stable IPv6 addresses, which has serious privacy issues.
> 
> IMHO, trying to maintain backward compatibility defeats the purpose of a
> privacy RFC.
> 
> To be clear, we don't want to change the ip addresses of existing servers.
> However, it's reasonable for users to expect changes during a major upgrade
> (15 -> 16), a fresh install of a new major release, or living on CURRENT.
> So, for obvious reasons, changing the default value would not be MFCed.
> 
> What do you think?

I think this would be a good step for FreeBSD. In HardenedBSD, we set
net.inet6.ip6.{prefer,use}_tempaddr to 1, which creates completely
random IPv6 addresses (scoped to the prefix, of course).

The one thing I would hope is that support for completely random IPv6
addresses via SLAAC does not go the way of the dodo.

(If net.inet6.ip6.use_stableaddr becomes the default, we will likely
keep it at 0 in favor of the other aforementioned sysctl nodes.)

Thanks,

-- 
Shawn Webb
Cofounder / Security Engineer
HardenedBSD

Signal Username:  shawn_webb.74
Tor-ified Signal: +1 303-901-1600 / shawn_webb_opsec.50
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