dhcpcd-discuss

On 07/06/2016 20:41, Neal P. Murphy wrote:
>> As far as I can see we are in agreement about the prefix length and
>> dhcpcd does this already. So now I'm confused as to where any
>> problem lies?
> 
> The problem lies in the fact that dhcpcd solicited a /60, Comcrash
> advertised a /64, and dhcpcd requested that /64 and tried to use it.
> This happened a number of times. It may not be dhcpcd's fault, but it
> shouldn't accept a /64 when it solicited a /60. It sure seems that
> this is what happened over and over.

Ah, ok.
So what happens is this, with no lease.
dhcpcd solicits an ia_pd with the desired address/prefix.
server replies with it's own idea of what this should be.
dhcpcd knows it HAS to work with what the server offers, so it then
requests it - THIS IS WHAT YOU SEE.
server replies OK - dhcpcd then tries to apply it's config to the end
result and at this point if it doesn't fit then it displays an error and
refuses to continue.

It works like so because the requested prefix and length is just a hint
and the config could be adjusted to match the server, which is commonly
the case.

> Unless I had a God-awful mess of a configuration where my callback
> script saved xxx/64 as the DP, my .conf writer picked up that /64 and
> put it in the IA_PD line with the three SLAs. And then Comcrash
> became confused and would not advertise a /60 in response to a /60
> solicit for many hours.

I can't explain that.

> Mayhap dhcpcd should perform a quick sanity check on the IA_PD params
> to ensure that the request is large enough for the configured
> delegations before proceeding. E.g., if it sees three /64s requested
> and it sees that a /64 is requested (explicitly or by default), it
> should grouse about the misconfiguration and refuse to proceed.

It does this, but after the DHCP handshakes, not during.

> If dhcpcd already performs these checks, then I am at a complete loss
> to explain what I saw, time and again, other than that something,
> somewhere, is fragile and my noob blundering about triggered the
> fragility.

Heh, don't call yourself a noob.
Why won't we start over, post your config and dhcpcd debug output and
work out what's going wrong because I know a few dhcpcd users are using
PD with Comcast just fine.

Roy