Re: High latency for IPv6 on netbsd-8

[Roy Marples <roy%marples.name@localhost>]

On 29/07/2018 18:38, Robert Elz wrote:
>      Date:        Sun, 29 Jul 2018 23:05:01 +0700
>      From:        Gua Chung Lim <gua.chunglim%gmail.com@localhost>
>      Message-ID:  <20180729160500.GA3458%gmail.com@localhost>
>
>
>    | I don't suspect my router,
>    | I don't suspect dhcpcd
>    | I don't suspect name resolution
>    |
>    | Any ideas?
>
> NetBSD 7 would have ignored the DHCP part, as there was no DHCPv6
> client there

That's not true.
NetBSD 7 shipped with dhcpcd-6.4.3 which did have a functional DHCPv6 
client. Now an awful lot of RA and DHCP6 issues have since been fixed, 
and -8 (and the next non teeny -7 release) ship with dhcpcd-7.0 which 
has currently zero reported issues as yet. While I wont rule out this 
problem could be a dhcpcd issue, currently nothing points to that being 
the case.

> Is the DHCP server in the router?
>
> If so, one possibility is that when it assigns an address to a client host, it
> expects the client to use that address, and not something else.   Your NetBSD-8
> host is using its autoconfigured address, and ignoring (though configuring)
> the DHCP assigned one.   The router might be dropping packets either from,
> or to, the autoconfigured address.

So one of the changes in dhcpcd-7 was the default location of some 
files, including the secret file which generates the SLAAC stable 
private address. If you didn't change the location using postinstall(8) 
before running dhcpcd it will have generated a new secret (and duid) 
file which would result in different addresses being defined on the 
interface. This could be an issue as well.

> In any case, there is lots more that can be done.     And perhaps Roy
> can suggest some options for dhcpcd which would make it ignore the
> "use DHCP" in the RA or ignore the "autoconfigure using this prefix"
> so you could try each of those (if it can be done) and see if one helps.

You can add `nodhcp6` to dhcpcd.conf to disable DHCP6 entirely.
This should ignore both the RA O and M flags and probably any static 
DHCP6 setup you might have installed as well, unless a following dhcp6 
option re-enables it.

Roy