EDNS support help

[agneevX]

I'm trying to use Google DNS remotely hosted in a VPS with EDNS as I've discovered it returns CDN IPs that my ISP publicly hosts, something Cloudflare or other public resolvers do not return.

I've set up blocky there with a basic config:

logLevel: warn
upstream:
  default:
    - https://8.8.8.8/dns-query
    - https://8.8.4.4/dns-query
caching:
  minTime: 5
  maxTime: 30
  prefetching: true
  prefetchExpires: 360
  prefetchThreshold: 2

compose.yml

version: '3.8'
services:
  blocky:
    image: spx01/blocky
    container_name: blocky
    restart: unless-stopped
    ports:
      - 2800:53/udp
      - 32070:53/tcp
    environment:
      - TZ=
    volumes:
      - type: bind
        source: /opt/appdata/blocky/blocky.yml
        target: /app/config.yml

It still seems to use the VPS' subnet:

❯ dig TXT o-o.myaddr.l.google.com +short @152.67.x.x -p 32070 +tcp +subnet="116.x.x.0/24"
"2404:6800:4000:1003::102"
"edns0-client-subnet 152.67.x.0/24"
# Should return my ISP's subnet

[agneevX]

I queried AdGuard Home over DoT and used blocky as an upstream and it seems to work!

[adrianmace]

I came here looking for clarification on this too. I’m running the same setup - blocky running on a public cloud instance with Quad9 w/ ECS upstream 9.9.9.11.

Adguardhome has a feature to send the ECS data of the client making the query through to the upstream resolver.

Does blocky?

[agneevX]

In my testing, it did not. I put AdGuard between blocky and my local resolver.

[0xERR0R]

Hey,

I'm not so aware about EDNS features. I tried the setup with google upstream servers and my dig returns:

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
; CLIENT-SUBNET: 116.0.0.0/32/21

Maybe you could describe, what is a valid test for this feature?

Current implementation of blocky sends client't request to the upstream (if not cached) and returns response as is. The used lib supports all DNS protocols.

[agneevX]

Maybe you could describe, what is a valid test for this feature?

EDNS takes a /24 usually.

With and without EDNS:

❯ kdig +short +tls @8.8.8.8 TXT o-o.myaddr.l.google.com +subnet="xxx.193.128.0/24"
"2404:6800:4000:1006::102"
"edns0-client-subnet xxx.193.128.0/24"

❯ kdig +short +tls @8.8.8.8 TXT o-o.myaddr.l.google.com
"74.125.178.197"
"edns0-client-subnet xxx.67.182.0/24"