Re: [v6ops] M/O flags and PD

[Brian E Carpenter <[e-mail]>]

On 31/10/2015 04:24, Sander Steffann wrote:
> Hi Tore,
> 
> Op 30 okt. 2015, om 09:10 heeft Tore Anderson <[e-mail]> het volgende geschreven:
>> * Gert Doering <[e-mail]>
>>
>>> I do not have RFCs to counter that, but my interpretation is a bit
>>> different.  I see that section of 4861 as traditionally applied to 
>>> *hosts*, while IA_PD traditionally is a *router* function, so out of 
>>> scope for the "host part" of 4861.
>>
>> Section 4.2 of RFC 4861 simply describes the RA message format, it's
>> not in a "host part" of the RFC as far as I can tell. Keep in mind that
>> RAs are typically multicast to all IPv6 nodes, so the originating router
>> does not know whether it is a host or a router (or both, or none) that
>> will be receiving the RA.
> 
> I always understood this bit from RFC 3633 to mean that any host configuration flags (such as M/O) are not relevant to DHCPv6-PD: "Note that this use of DHCP is not bound to the assignment of IP addresses or other configuration information to hosts".

The phrase "is not bound to" is rather unclear, don't you think? It neither says
nor implies that routers are thereby exempt from issuing correct RAs.

However, being realistic, note that
On 30/10/2015 21:55, Tore Anderson wrote:

> It boils down to this: If you are about to originate an RA to a link, and
> know that there is information available in DHCPv6 on said link, you
> should set set the M or O flag.

Even if you accept that, in the case that you *don't* know that such information
is available, you physically cannot set the M or O flag. So in the real world,
a node that is interested in IA_PD had better go fishing for it, whatever the
MO bits say. So I retract all the if statements in the pseudocode that I sent.
The only robust implementation is one that always looks for DHCPv6 information.

    Brian