DoH not working for Quad9 when system DNS is set to the dnscrypt

[alexyangjie]

I recently encountered an issue when using DoH for Quad9 server on Asus-Merlin (ASUS-AC68U).

DNSCrypt-proxy version: v2.0.18
Server: ['quad9-doh-ip4-filter-pri','quad9-doh-ip4-filter-alt']

When using the dnscrypt version ('quad9-dnscrypt-ip4-filter-pri'), it worked without any issue. When I switch the config to the doh version and restart the client manually, it also worked and could resolve domains with no issue.

However, once I restart the router and let the service start itself, it no longer works.

Logs:
[2018-05-05 05:05:35] [NOTICE] Source [public-resolvers.md] loaded
[2018-05-05 05:05:37] [NOTICE] dnscrypt-proxy 2.0.18
[2018-05-05 05:05:37] [NOTICE] Loading the set of cloaking rules from [/opt/etc/cloaking-rules.txt]
[2018-05-05 05:05:37] [NOTICE] Now listening to 0.0.0.0:60053 [UDP]
[2018-05-05 05:05:37] [NOTICE] Now listening to 0.0.0.0:60053 [TCP]
[2018-05-05 05:05:47] [ERROR] Get https://dns9.quad9.net:443/dns-query?ct=&dns=yv4BAAABAAAAAAABAAACAAEAACkQAAAAgAAAAA&random_padding=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
[2018-05-05 05:05:47] [NOTICE] dnscrypt-proxy is waiting for at least one server to be reachable

[alexyangjie]

The same issue happens on the Macos as well for the dnscrypt-proxy package. When system DNS is set to 127.0.0.1, the DoH will not work.

I think the reason is that dnscrypt-proxy cannot resolve the ip address of dns9.quad9.net during the initialization. It always looks for system dns to resolve that domain, even when the 'ignore_system_dns' is set to true. I tried to add an entry into the hosts file, and it worked fine.

However, I can't use this method in the Asus router, as the hosts file are system generated.

Is there any way to let dnscrypt-proxy to follow the 'ignore_system_dns' directive, and resolve the ip of the dns servers using the fallback resolver?

Thanks.

[alexyangjie]

I've got a workaround by using the ip address as the hostname and calculate a new stamp. Hope this helps others with the same issue.

  [static.'quad9-pri']
  stamp = 'sdns://AgcAAAAAAAAABzkuOS45LjkACzkuOS45Ljk6NDQzCi9kbnMtcXVlcnk'

  [static.'quad9-alt']
  stamp = 'sdns://AgcAAAAAAAAADTE0OS4xMTIuMTEyLjkAETE0OS4xMTIuMTEyLjk6NDQzCi9kbnMtcXVlcnk'