Detecting internal IP as a proxy

[Nerus87]

Bungeecord version

git:BungeeCord-Bootstrap:1.20-R0.1-SNAPSHOT:b371fe6:1714

Server version

3815-Spigot-64b565e-9f64f0d (MC: 1.20.1) (Implementing API version 1.20.1-R0.1-SNAPSHOT)

Client version

1.20.1

Bungeecord plugins

N/A

The bug

When I'm trying to connect to my server I'm getting the error 'Not authenticated with Minecraft.net'
My desktop is in the same ISP but in a different part of the network as my server.
My IP is under NAT so it is visible by the server as a private/internal IP Address (class a,b,c).

With this configuration, the server detects my IP as a proxy and that's why I can't connect to the server.
So in my opinion t should check first if is internal IP then if yes skip checking the proxy if not proceed with proxy checks.
To commit the problem at this stage I need to set prevent_proxy_connections: false (but this is not the solution).

[config.yml]

enforce_secure_profile: true
online_mode: true
prevent_proxy_connections: true

Probably the problem is somewhere in here: InitialHandler.java#L484

Log output (links)

14:33:29 [INFO] [/10.132.0.12:54741] <-> InitialHandler has pinged
14:33:31 [INFO] [/10.132.0.12:54744] <-> InitialHandler has connected
14:33:50 [INFO] [Nerus87,/10.132.0.12:54766] <-> InitialHandler has connected

Checking

• I am using BungeeCord and not a fork. Issues with forks should not be reported here.
• I think this is not an issue with a bungeecord plugin.
• I have not read these checkboxes and therefore I just ticked them all.
• This is not a question or plugin creation help request.

[Janmm14]

The actual proxy check is done by mojang/microsoft by checking ip used to contact mojang servers vs ip used to join.
Bungee can only decide whether to send IP of joining player for mojang for checking or not doing so.
I do not see bungee adding code to not do this for reserved local ips.

[Outfluencer]

But why not?
We could do it, there would also be no security risk, by letting local ips bypass this check.
It could be usefull for server admins if they are connected via a local network. And have this option enabled

[Nerus87]

The actual proxy check is done by mojang/microsoft by checking ip used to contact mojang servers vs ip used to join. Bungee can only decide whether to send IP of joining player for mojang for checking or not doing so. I do not see bungee adding code to not do this for reserved local ips.

Yeah, but this can be managed by bungee.