dhcpcd-discuss

Hi John

On 07/08/2019 19:19, John Roman wrote:
> im having issues with prefix delegation in dhcpcd, namely the invalid
> argument warning on my clients
>
> Aug 07 11:13:14 malt dhcpcd[1577]: enp3s0: adding address 2605:e000:130a:2fd:1079:ede8:f8aa:d026/68
> Aug 07 11:13:14 malt dhcpcd[1577]: ipv6_addaddr1: Invalid argument
> Aug 07 11:13:30 malt dhcpcd[1577]: enp3s0: adding address 2605:e000:130a:2fd:1079:ede8:f8aa:d026/68
> Aug 07 11:13:30 malt dhcpcd[1577]: ipv6_addaddr1: Invalid argument

What dhcpcd version is this please?

> My router dhcpcd.conf is set to request PD's from my provider, which
> assigns /68's to my internal router interfaces.  radvd then hands these
> out automagically with the ::/64 configuration option.

This logic is flawed. You have to hand out the prefix length assigned to 
the interface radvd is working on. In this case a /68 (but see below).

> Strangely enough, no clients on my local network can receive SLAAC from
> radvd based on the prefixes provided by dhcpcd.
>
> the route however, seems to get applied well
> Aug 07 11:12:58 malt dhcpcd[1577]: enp3s0: adding route to 2605:e000:130a:2fd:1000::/68

> router dhcpcd.conf for relevance.  prefix length specified is apparently
> always ignored by my ISP:
>
>
> noipv6rs
> denyinterfaces wlx9cefd5febaca enp2s0
> interface enp3s0
>    ipv6rs                         # enable routing solicitation get the
>    ia_na 0                        # request an IPv6 address
>    ia_pd 0 enp3s0/0 enp2s0/1 wlx9cefd5febaca/2

dhcpcd should warn about this. You can't mix a sla_id of 0 with others.

    ia_pd 0 enp3s0/1 enp2s0/2 wlx9cefd5febaca/3

Should give better results and should result in dhcpcd adding a /76 
prefix to your downstream interfaces.

Now for SLAAC to work, the prefix length needs to be /64 as you noted, 
but you cannot shrink a delegation, only grow it.
So for a 76 to work, you'll need to hand out that address scope via 
DHCP6 instead.
Or try and get a /48 or /56 from your ISP.

Roy