New experiment request: DDR queries

[frcroth]

DDR is a protocol that allows client to get information about encrypted DNS resolvers.

This probe would perform a DNS lookup for "_dns.resolver.arpa." in the SVCB record. Interesting would be whether DDR is implemented and which designated resolvers are listed.

Scans using zmap have shown some regional differences, e.g. China having very few servers with DDR available, while Latin America and Africa have the DDR support among DNS servers.