DNS-over-HTTP/3 (DoH3)¶

Note

This guide is about DNS over HTTP/3. For DNS over HTTP/1 and DNS over HTTP/2, please see DNS-over-HTTPS (DoH)

dnsdist supports DNS-over-HTTP/3 (DoH3) for incoming queries since 1.9.0. To see if the installation supports this, run dnsdist --version. If the output shows dns-over-http3 incoming DNS-over-HTTP/3 is supported.

Incoming¶

To make dnsdist listen for on [2001:db8:1:f00::1]:443 on UDP, using provided certificate and key to serve incoming DoH3 connections, use the following configuration:

YAML Lua

The binds key is used to create an HTTP/3 bind.

binds:
  - listen_address: "2001:db8:1:f00::1"
    protocol: "DoH3"
    tls:
      certificates:
        - certificate: "/etc/ssl/certs/example.com.pem"
          key: "/etc/ssl/private/example.com.key"

Use the addDOH3Local() function.

addDOH3Local('2001:db8:1:f00::1', '/etc/ssl/certs/example.com.pem', '/etc/ssl/private/example.com.key')

Optionally, specific options can be set on the listen socket. For instance, you can change the congestion control algorithm used:

YAML Lua

The quic subkey can be used.

binds:
  - listen_address: "2001:db8:1:f00::1"
    protocol: "DoH3"
    tls:
      certificates:
        - certificate: "/etc/ssl/certs/example.com.pem"
          key: "/etc/ssl/private/example.com.key"
    quic:
      congestion_control_algorithm: "cubic"

The fourth parameter to addDOH3Local() indicates various options.

addDOH3Local('2001:db8:1:f00::1', '/etc/ssl/certs/example.com.pem', '/etc/ssl/private/example.com.key', {congestionControlAlgo="cubic"})

A particular attention should be taken to the permissions of the certificate and key files. Many ACME clients used to get and renew certificates, like CertBot, set permissions assuming that services are started as root, which is no longer true for dnsdist as of 1.5.0. For that particular case, making a copy of the necessary files in the /etc/dnsdist directory is advised, using for example CertBot’s --deploy-hook feature to copy the files with the right permissions after a renewal.

More information about sessions management can also be found in TLS Sessions Management.

Advertising DNS over HTTP/3 support¶

If DNS over HTTP/2 is also enabled in the configuration (see DNS-over-HTTPS (DoH) for more information), it might be useful to advertise DNS over HTTP/3 support via the Alt-Svc header. An example is available in the DoH documentation.