dhcpcd-discuss

Hi Roy,

Thanks for the quick response.

You wrote:

> DHCPv6 requires a IPv6RA to work - nothing else will set the IPv6
> default route other than say a native IPv6 connection over PPP.
> And certainly nothing else will set any prefix (subnet like route).

Right, understood. This is why the accept_ra kernel parameter would 
normally need to be turned on (on GNU/Linux systems) for this to work.

> The RA itself contains two mutually exclusive flags, Other and Managed.
> If Other is set, DHCPv6 is used just to get extra information like IPv6
> DNS.
> If Managed is set, DHCPv6 is used to get IPv6 addresses as well.

Agree.

> If neither of these flags are set, DHCPv6 is not started.

Right.

> Now, the RA message *can* also contain a prefix, like 2002:1:2::/64.
> The prefix can also contain some flags (not mutually exclusive)
> OnLink - the prefix is directly associated with the interface and a
> subnet like route will be created
> Auto - generate a SLAAC address for the prefix.
>
> The kicker is the all the above is *optional*.
> So to now answer your question, simply ensure that all advertised
> prefixes don't have the Auto flag set and that the RA message itself has
> the Managed flag set and you're golden!

This is an answer only if one wanted to disable autonomous 
auto-configuration globally as a policy for the subnet, but this wasn't 
my question. Sorry, I should have made this clear.

The question is about client-side configuration. On a subnet where the 
router allows both autonomous and managed address configuration we want 
to configure a host such that it only configures the address assigned by 
DHCP, but not generate addresses autonomously based on the hardware 
address or randomized (privacy extension).

Although I haven't confirmed this, I'm guessing that ISC's dhclient does 
this when the autoconf kernel setting is off, but accept_ra turned on. 
Unfortunately, dhcpcd currently seems to treat this as an error and 
won't start the DHCP negotiation.

Thanks,

Joachim


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