I tried deleting the rule and it drops the traffic completely. So DNS resolution stops working and I am unsure why. It's not like default drop or anything. I can edit the rule and whatever active port 53 related rule is there works. But I want case of no such rule at all. :-) 


I setup pihole on Intel NUC little while ago and all Pihole gets is 100% of wifi client traffic behind Asus wifi management IP. :-\


Plus no matter what DNS I put, queries goes via whatever router gave up when Asus booted up. 


Here's how creepy it gets: 

On Rasberry Pi (which is not behind Asus AP but a different switch)

anurag@raspberrypi:~ $ dig whoami.akamai.com @1.1.1.1 a +short
whoami.akamai.net.
162.158.226.218
anurag@raspberrypi:~ $ dig whoami.akamai.com @8.8.8.8 a +short
whoami.akamai.net.
172.253.244.3
anurag@raspberrypi:~ $ dig whoami.akamai.com @9.9.9.9 a +short
whoami.akamai.net.
103.224.242.10
anurag@raspberrypi:~ $

All normal and good. 



Now, from the device (which is behind Asus AP): 

 ~> dig whoami.akamai.net @1.1.1.1 a +short
172.217.34.65

~> dig whoami.akamai.net @8.8.8.8 a +short
172.217.34.65

~> dig whoami.akamai.net @9.9.9.9 a +short
172.217.34.65

dig whoami.akamai.net @1.2.3.4 a +short
172.217.34.65

dig whoami.akamai.net @5.6.7.8 a +short
172.217.34.65


Essentially Asus picked 8.8.8.8 because I put that during the test and rebooted the AP. I will stick with 8.8.8.8 until DHCP lease expires and the new server is provided. 


On Thu, Oct 29, 2020 at 2:01 AM Neil Hanlon <neil@shrug.pw> wrote:
And if so, can you set up your own service to remove their iptables rule after it's been added or otherwise counteract it.

At least temporarily, anyways.

-Neil

On Wed, Oct 28, 2020 at 4:26 PM Ryan Hamel <ryan@rkhtech.org> wrote:
I'm curious to know why they would add such a thing, and how you got the iptables rules from the device. Do these Asus routers provide SSH directly into the shell?

Ryan
On Oct 28 2020, at 11:33 am, Anurag Bhatia <me@anuragbhatia.com> wrote:
Hello, 

Wondering anyone from Asus here or anyone who could connect me to the developers there? 

Using Asus RT-AC58U in Access Point(AP) mode and expect it to simply bridge wired with wireless but seems like it's re-writing DNS packets source as well as the destination. 

  1. DNS port 53 traffic going out, the source is re-written with the management IP of the AP on the LAN. So virtually all DNS traffic hits the router from the (management) IP of the Asus AP instead of real clients. 

  2. If I define DNS as x.x.x.x on DHCP, the Asus AP picks that up and re-writes destination to x.x.x.x and hence even if any client uses y.y.y.y, the packets are simply re-written. 

I see the rule in iptables on Asus AP. All these issues give an idea that someone created AP mode (besides regular routing mode) and missed to disable the DNS related NATing features in the AP mode. So far my discussions with their support have been going quite slow and would greatly appreciate if someone could connect me to right folks in there so they can release a firmware fix for it. 



Thanks. 

--
Anurag Bhatia


--
Anurag Bhatia