SLAAC IPV6 addressing associated with Private reverse DNS servers not kept private when No hostname available.

[jumpsmm7]

Issue Details

AdguardHome is using WHOIS by contacting the ISP to resolve client IPV6 Hostnames instead of using RDNS and relying on the local reverse lookup for ipv6 to discover client hostnames.

• Version of AdGuard Home server:
  • Lastest Bleeding Edge (basically Master)
• How did you install AdGuard Home:
  • Using AdguardHome provided Binaries directly
• How did you setup DNS configuration:
  • AdguardHome is providing DNS directly on port 53, while DNSMASQ listens on a different upstream dns port while still providing DHCP service to clients. AdguardHome forwards Hostname lookup request to upstream DNSMASQ.
• If it's a router or IoT, please write device model:
  • Asus RT-AX88U running Asuswrt-Merlin
• CPU architecture:
  • aarch64
• Operating system and version:
  • linux kernal 4.1.51 (busy box)

    Expected Behavior

    I expected Adguard Home would be able to resolve hostnames for clients for both ipv4 and ipv6.

    Actual Behavior

    AdguardHome does not resolve hostnames for ipv6 properly. It appears to be using WHOIS to obtain the ISP hostname from the upstream instead of honoring the reverse lookup option specified as a Private reverse DNS server reverse lookup options. If the Hostname for a SLAAC IPV6 address associated with a defined Private Reverse DNS Network cannot be found in the corresponding Private Reverse DNS server lookup, then the device hostname look up should not be passed off to WHOIS. here is another place this is mentioned https://github.com/AdguardTeam/AdGuardHome/discussions/2912#discussioncomment-1609475

[EugeneOne1]

@jumpsmm7, hello and sorry for a long response. AdGuard Home tries to obtain the WHOIS information for all the clients whose IP address isn't a special one. RDNS clients resolving used not instead WHOIS but in combination with it having a higher priority. Thus if the client appears to be resolved via WHOIS, it means that AGH can't resolve client's IP via RDNS.

Note also that RDNS uses private upstream resolvers (the local_ptr_upstreams setting) for the clients with IP addresses from locally-served networks.

If your router (or any other machine in the network) responds to PTR requests for addresses of these clients?

[jumpsmm7]

The biggest issue faced that the client should be easier to identify given if EDNS0 information is available, for example if it can be identified through EDNS0 that the client shares common information such as a mac-address for example, then host name for one can correspond to the other. This may have to be a feature request. The biggest challenge is that even with ipv6 slaac addressing matching the same PTR data as a stateful addressing, the hostname assingnment should not be queried with whois to the upstream ISP or DNS service provider. Instead it should be treated locally and assumed no hostname unless defined in /etc/hosts or derivable from local ptr lookup. BTW, I love the work the adguardhometeam has done so far.

[EugeneOne1]

@jumpsmm7, unfortunately, we still can't quite figure out what you're asking for. Can you please show us the kind of request that currently fails or returns invalid information using nslookup or dig? Thanks.

[jumpsmm7]

@jumpsmm7, unfortunately, we still can't quite figure out what you're asking for. Can you please show us the kind of request that currently fails or returns invalid information using nslookup or dig? Thanks.

The Issue I am having is that if I define a [/Some-IPV6-Address.ip6.arpa/]Some-IPV6-Address for a Private reverse DNS servers If I have a slaac address assignment associated with this network and that same slaac address has no retrievable hostname, WHOIS should not be attempting to retrieve a host name from the upstream because this network is defined as "private". Otherwise this could potentially be seen as leaking client information to the upstream.

[jumpsmm7]

I adjusted the title to reflect the actual problem.