nixos/create_ap: add module

[onny]

Description of changes

Working on a module for the new package linux-wifi-hotspot. I would like to be able to create a wifi hotspot with this NixOS service like this:

services.create_ap = {
  enable = true;
  settings = {
    INTERNET_IFACE = "eth0";
    WIFI_IFACE = "wlan0";
    SSID = "onnys hotspot";
    PASSPHRASE = "12345678";
  };
};

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.05 Release Notes (or backporting 21.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[onny]

create_ap --config test.conf works well for creating a access point, unfortunately it doesn't work inside the systemd service. In there, it couldn't find the wireless network device.
I'm using the upstream systemd unit and overwrite the ExecStart section. Maybe it is missing some important environment settings which are needed on NixOS?

[cheriimoya]

so the module does not work at the moment?

[cheriimoya]

didn't test the service so far, will try that next

[onny]

Okay tested the service and it works now :) Ready to merge if it is okay for you

[cheriimoya]

if this is still a draft, please mark it as such

[onny]

Thank you for this explanation, I guess that makes sense.

I added the changes and it looks fine for me :)

[cheriimoya]

After this change I think I'm happy:)

[cheriimoya]

I tested basic functionality and it seems to work. My phone is connecting (dhcp isn't working but i didn't configure it anyway) and i can ping it from my laptop.

I might use this in the future 👍

[cheriimoya]

cc @Lassulus

[ajs124]

This might be a stupid question, but what does this do that services.hostapd doesn't?

[onny]

This script also uses hostapd as a dependency. I guess it is even simpler than using hostapd directly since it also setups dhcp and routing

[happysalada]

Looks good to me, thanks to everyone involved!