Re: IPv6 default routes / NM vs. kernel autoconfig vs DHCP6

[Pavel Simerda <psimerda redhat com>]

> From: "Stuart D Gathman" <stuart gathman org>
> One situation that ought to work IMHO (although ~1/2 of IPv6 experts
> disagree) is that DHCP6 should work in concert with routes that are
> not /64.

DHCPv6 should not care about *any* routes.

> For instance, RA provides a 2001:db8:1:2:3::1/80 default route,

Default route is technically always /0 and in case of RA-based default
route it points to a link-local IPv6 address.

> sets the M bit, and DHCP6 provides the address
> 2001:db8:1:2:3::1000.  NM should be able to set the default route
> *and*
> apply the /80 prefix length to the DHCP6 address.  This could get
> non-trivial when there are multiple routes provided by RA.  NM must
> then
> find the route that matches the DHCP6 address to determine the
> correct
> prefix.

With the above information in mind, this is not really the case.

> Note: the experts that disagree feel that all LANs should be /64
> always forever,

This is also stated by IPv6 addressing architecture RFC. But for
non-SLAAC cases, linux won't prevent you from doing that AFAIK
and NM doesn't have any reason to do that either.

So, even though your use case is against RFC, allowing it doesn't
cause any harm.

> and prefixes should only be used in routers.

I don't understand this.

> I find it quite
> handy to be able to subnet the /64 provided by the ISP, and while I
> agree that ISPs should always forever allocate a minimum of /64 to
> end
> users, nevertheless endusers should be able to subnet that and still
> have workstations and devices work without manual configuration.

This is ideology. I won't comment on this as this is purely philosophical
but apparently there is no reason linux or NM should prevent you from
doing that.

Cheers,

Pavel