ifconfig prefer_source and IPv6 privacy extensions

[Jan Behrens]

On Fri, 13 Mar 2020 23:37:52 +0100
Jan Behrens <jbe-mlist at magnetkern.de> wrote:

> On Sat, 14 Mar 2020 04:51:43 +0900 (JST)
> Hiroki Sato <hrs at FreeBSD.org> wrote:
> 
> > Jan Behrens <jbe-mlist at magnetkern.de> wrote
> >   in <20200313202833.cbbe8d1679ac0fd7a80788e1 at magnetkern.de>:
> > 
> > jb> Is it intended that "net.inet6.ip6.prefer_tempaddr" takes precedence
> > jb> over "prefer_source"? If yes, why?
> > 
> >  Yes, and the reason is that RFC 6724 specifies that behavior.
> 
> [...]
> 
> >  If prefer_source takes precedence, the tempaddr will nerver be used.
> 
> That depends on how "prefer_source" competes with other rules for
> source address selection.
> 
> [...]
> 
> Moreover, preferring temporary addresses over addresses marked with
> "prefer_source" doesn't seem to make much sense (even if the RFC would
> demand it). This is because it doesn't seem to make much sense to mark
> a temporary address as preferred.

Does anyone know a (real life) example where "prefer_source" has any
useful effect (given FreeBSD's current behavior) if privacy extensions
are enabled?

> That assumed, the current behavior of FreeBSD effectivly renders
> "prefer_source" useless if net.inet6.ip6.prefer_tempaddr=1.

I would propose to set "prefer_source"'s precedence just one level
higher than net.inet6.ip6.prefer_tempaddr.

-- Jan

> 
> > 
> > -- Hiroki
> 
> Regards,
> Jan Behrens