Re: Understanding IPv6-PD over PPPoE

[Andrei Borzenkov <arvidjaar gmail com>]

On Wed, Jun 16, 2021 at 11:39 AM Beniamino Galvani via
networkmanager-list <networkmanager-list gnome org> wrote:
> > It feels as though NetworkManager should always be making both IA_NA and
> > IA_PD requests and, if it didn't receive an IA_NA response from the ISP, it
> > should assign an address from the delegated prefix to the PPP interface.
> > This would prevent the situation where a machine with no
> > "ipv6.method=shared" NICs ends up with no public v6 address at all.
> >
> >
> > Any insight would be appreciated - many thanks. :)
>
> Hi,
>
> as you have seen, currently NM only requests a prefix delegation when
> there is an other interface in IPv6 shared mode. The IPv6 address on
> the PPP interface itself can only be obtained via SLAAC or
> DHCPv6(IA_NA), not via DHCPv6(IA_PD).
>
> I'm not sure how the latter is common; to support it, NM would need to
> always request a prefix delegation (even without another interface in
> shared mode) or, better, to have a new option to make this behavior
> configurable (for example, "ipv6.dhcp-request-pd=yes|no|auto").

It is explicitly prohibited to assign any IA_PD prefix to the same
interface via which this was obtained.

                                              the requesting router MUST
   NOT assign any delegated prefixes or subnets from the delegated
   prefix(es) to the link through which it received the DHCP message
   from the delegating router.