Domain name resolution does not handle RFC6761 special names correctly

[rzikm]

RFC 6761 Defines several DNS names to be handled specially by DNS resolution APIs and libraries:

• localhost, and *.localhost should always resolve to respective loopback address
• invalid and *.invalid should always resolve to NXDOMAIN response

Unfortunately, current OS-level resolution APIs on both Windows and Linux (I did not check MacOS, but I assume the situation is going to be identical to Linux) do not recognize subdomains of localhost or invalid as special, and forward the queries to the respective DNS server (which is against the RFC spec).

This feature would play well with dotnet/aspnetcore#62593, which introduces support for localhost subdomains was for local development.

[filipnavara]

I did not check MacOS, but I assume the situation is going to be identical to Linux

We should check. The RFC was written by Apple employees so presumably they were standardizing something present in their implementation.

UPD: macOS Sequoia doesn't seem to handle it, tested with nslookup smoke test.

[BrennanConroy]

There was a follow-up change as *.localhost doesn't really work
dotnet/aspnetcore#62668

[MHIZokuchi]

Hello, Can I pick this up?

[gbr-mendes]

Hi! I'd like to contribute a fix for this issue.

I've opened a draft PR so we can validate the approach before going further:
#120376

The idea is to handle invalid / *.invalid (always returning NXDOMAIN) and localhost / *.localhost (always resolving to loopback) before calling the OS resolver.

May I pick this up?

[rzikm]

Hello, Can I pick this up?

Hi! I'd like to contribute a fix for this issue.

Hi, thanks for the interest, both of you. I just noticed your replies. Since @gbr-mendes already has a WIP draft, I will assign it to him. Sorry @MHIZokuchi.

[laveeshb]

Hi @rzikm, the previous PR (#120376) was auto-closed twice due to inactivity (most recently last week). Is @gbr-mendes still planning to continue, or would it be okay for me to pick this up? Happy to look elsewhere if work is ongoing.