Re: Enabling SLAAC for IPv6 by default

[Roy Marples <roy%marples.name@localhost>]

On 25/09/2018 20:56, Greg Troxel wrote:
> Roy Marples <roy%marples.name@localhost> writes:
>
> > dhcpcd generates stable private addresses - not temporary addresses.
> > These are a different beast and a better solution than temporary addresses.
> > See RFC 7217.
>
> It would be nice to have a reference in dhcpcd(8) about this; I found it
> in the dhcpcd.conf(5) page.
>
> It is hard for me to tell from the dhcpcd.conf man page, but it seems
> like the default for slaac is hwaddr (since it's listed first), but the
> config file installed with the OS says "private".

This is correct.
It's so that new installs get the privacy address and legacy installs 
before dhcpcd grew the option keep their current hwaddr based one.

> I'm generally a fan of being able to operate with defaults with no
> config file at all, so it would be nice to clarify in the man page which
> options are effective in the absence of a config file.  (Admittedly this
> is a nit; the documentation now that I'm reading answers almost all of
> my questions.)

I'm generally a fan of this as well.
However to keep dhcpcd compatible over the years vs new features added I 
try and do this via dhcpcd.conf.
Sometimes it's a fine balancing act.

> So perhaps the kernel code should be modified to support, and prefer by
> default over the original SLAAC, the RFC7217 mechanism, to address the
> concern Pierre raises for the case when someone uses the in-kernel
> SLAAC client?   Or perhaps the situation we have, where it is disabled
> by default, is ok?

I think it's OK.
The kernel doesn't need to know about RFC7217 when dhcpcd is used.

Roy