[Dnsmasq-discuss] override DNS server for particular hosts on IPv6

[Petr Menšík]

Hi Hamish,

I don't see any set:adblock on any host. How are selected hosts, which
should receive adblock server?

--log-dhcp might help to log also tags obtained for each requests. It
should help you checking selected hosts got assigned adblock tag to
whatever rule you have used. And then just set common options for the tag.

On 3/25/21 9:50 AM, Hamish Moffatt wrote:
> I'm attempting to override the DNS server for a few hosts on both IPv4
> and IPv6. I've tagged the hosts and applied dhcp-option to that tag and
> it's working correctly for IPv4, but I'm not having much luck with IPv6.
> 
> I'll admit right now that I don't fully understand the use of DHCPv6 and
> how DNS servers are discovered, so it might be that this is just not
> possible, at least for all types of clients.
> 
> My dnsmasq is at ::1, and I want to use the DNS server at ::18 on the
> same prefix. What I have is:
> 
> dhcp-option=tag:adblock,6,192.168.42.18
> dhcp-option=tag:adblock,option6:dns-server,[<MY ULA>::18],[<MY GLA>::18]
> 
> dhcp-range=set:lan,192.168.42.20,192.168.42.239,255.255.255.0,12h
> ra-param=br-lan,0,7200
> dhcp-range=set:lan,::1000,::ffff,constructor:br-lan,slaac,ra-names,12h
> dhcp-option=lan,option6:dns-server,[::]
> 
> enable-ra
> quiet-ra
> 
> 
> What I see is that Android just has the <MY GLA>::1 address as its DNS
> server. A Linux client using NetworkManager has <MY GLA>::1 as well as
> the two override servers. Even when I set <MY GLA>::18 as the server in
> the dhcp-option clause for the whole network, the devices still learned
> the <MY GLA>::1 address.
> 
> If I remove the dhcp-option clause for the whole network then Android
> shows it's using the link local address for ::1 instead.
> 
> How is Android always learning of the dnsmasq server itself as the DNS
> server, and can I fix it?
> 
> 
> 
> Thanks
> 
> Hamish
> 
> 
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> 

-- 
Petr Menšík
Software Engineer
Red Hat, http://www.redhat.com/
email: pemensik at redhat.com
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB

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