[yjftsjthsd-h]

I think this would allow that, yes.

However, I personally would just do it in userspace, especially for that simple of a use. I'm doing the opposite; I have a webapp that somehow doesn't handle IPv6, so to access it over a pure-v6 network I just run this on the same host:

  socat TCP6-LISTEN:8002,fork TCP4:127.0.0.1:8000

I believe you could trivially reverse this;

  socat TCP4-LISTEN:8002,fork TCP6:[::1]:8000

should serve [::1]:8000 as 0.0.0.0:8002 (I don't remember if changing ports was strictly required; that may be a quirk of my exact setup).

[anotherpaul]

I did that with forwarding to another host but it's super slow (10 Mbit) on a cheap hetzner box. So I am looking for this functionality but faster

[rnhmjoj]

The point of Jool and similar tools (there is also one called Tayga that runs in userspace, if you want) is to translate network traffic between multiple hosts, where some only have IPv6 and others only IPv4 addresses.

If your machine has both IPv6 and IPv4 addresses you don't need to any translation.

[yjftsjthsd-h]

Sure, but if your goal is

> I got some services with only ipv6 addresses and want clients with only ipv4 (sadly still exists) to at least be able to reach them.

then that seems like overkill. Although it depends on your network, of course.

[rnhmjoj]

I interpreted "services with only IPv6 addresses" as IPv6-only servers, in which case some sort of translation is needed, but if these are just processes in a dual stack server, then yes.