[Bug] IPv6 DNS advertising

[src386]

Hi everyone,
I have IPv6 enabled on my Asus RT-AC66U and I have specified a custom DNS in the IPv6 tab.
However, all computers are still advertised with the "default" DNS (the router itself).
That problem occurrs even with stock firmware but I have found a workarround by editing /etc/radvd.conf and setting my DNS. But in merlin, radvd.conf is missing, I assume it has been replaced by dnsmasq.
Regards
Xavier

 

[PabloAbonia]

I believe this will work:

Under LAN->DHCP Server, choose Advertise router IP in addition to user-specified DNS, and set to no.

 

[src386]

Just tried this, it's not working, the only advertised DNS is still the router itself.

 

[Puppa]

Do you mean your computers are seen as having the ip address of the router? Or are they simply missing? How are you checking the DNS advertisement? On the Web UI tools of the router, or from a different device?

Sent from my SM-N910V using Tapatalk

 

[RMerlin]

Post the content of your dnsmasq config file.

IPv6 RA is indeed handled by dnsmasq now.

 

[src386]

Do you mean your computers are seen as having the ip address of the router? Or are they simply missing? How are you checking the DNS advertisement? On the Web UI tools of the router, or from a different device?

No, I mean my computers have a bad primary DNS address. Instead of the real DNS address, it's the router address.
I can see this in local /etc/resolv.conf or in network-manager.

Post the content of your dnsmasq config file.
IPv6 RA is indeed handled by dnsmasq now.

pid-file=/var/run/dnsmasq.pid
user=nobody
bind-dynamic
interface=br0
interface=ppp1*
no-dhcp-interface=ppp1*
resolv-file=/tmp/resolv.conf
servers-file=/tmp/resolv.dnsmasq
no-poll
no-negcache
cache-size=1500
min-port=4096
dhcp-range=lan,192.168.0.100,192.168.0.200,255.255.255.0,86400s
dhcp-option=lan,3,192.168.0.254
dhcp-option=lan,6,192.168.0.31,0.0.0.0
dhcp-option=lan,252,"\n"
ra-param=br0,10,600
enable-ra
quiet-ra
dhcp-range=lan,::,constructor:br0,ra-stateless,64,600
dhcp-option=lan,option6:23,[::]
dhcp-authoritative

As you can see, I have set a custom primary DNS address for advertisement, but dnsmasq.conf ignores it.

 

[john9527]

As you can see, I have set a custom primary DNS address for advertisement, but dnsmasq.conf ignores it.

It's not ignored.....it gets added to the /tmp/resolv.dnsmasq file as one of the DNS servers that dnsmasq can use. dnsmasq will then act as the caching server.

 

[src386]

It's not ignored.....it gets added to the /tmp/resolv.dnsmasq file as one of the DNS servers that dnsmasq can use. dnsmasq will then act as the caching server.

Okay, but in my case, it uses my ISP DNS, not my custom DNS.
I know that because thepiratebay.se resolves to 127.0.0.1 ("blocked" in france in all ISP' dns)...

 

[microchip]

Okay, but in my case, it uses my ISP DNS, not my custom DNS.
I know that because thepiratebay.se resolves to 127.0.0.1 ("blocked" in france in all ISP' dns)...

TPB doesn't even have an IPv6 address

 

[src386]

TPB doesn't even have an IPv6 address

And ? I can query my DNS using ipv6 and get ipv4 address.
dig thepiratebay.se @mydns is ok.
dig thepiratebay.se @myrouter returns 127.0.0.1.

 

[john9527]

Okay, but in my case, it uses my ISP DNS, not my custom DNS.
I know that because thepiratebay.se resolves to 127.0.0.1 ("blocked" in france in all ISP' dns)...

That's because it's just one of the DNS servers available. dnsmasq will randomly (or round robin, I forget which) select a DNS server to use.

You should be able to do what you want by using a dnsmasq.postconf script to change this line

dhcp-option=lan,option6:23,[::]

to specify your IPv6 DNS server (change the :: to your server address). Then, if you are using Windows, it will always go to this server first...you essentially won't have any router caching.

EDIT: Windows is very stubborn about changing it's IPv6 config. You should reboot your PC afterwards to pick up the change.

 

[src386]

I will try this, thanks.
But I think this is a bug.

 

[john9527]

Well, you have one other option. My fork based on the older 374 code has this as an option. But you have to be careful using it. If you are also using a VPN Client it can lead to DNS leaks.

 

[kvic]

In case none of the above work/available, you can try the last resort... add the following line to /jffs/configs/dnsmasq.conf.add

dhcp-option=option6:dns-server,[1234::77],[1234::88]

Replace the ipv6 addresses with your DNS. Depends how well it works in your version of firmware, you may also want to add your router's ipv6 addr to the list...

EDIT:

oops..realised I essentially repeating what John said in #11