Add NixOS network manager support

[jmvermeulen]

Summary

NixOS uses the Nix functional language for declarative system configuration, storing network settings in /etc/nixos/*.nix files (commonly networking.nix). None of the existing network parsers can handle this format, resulting in empty IP addresses for NixOS targets.

This adds a NixOSConfigParser to the network.py plugin that extracts:

• IPv4/IPv6 addresses with prefix length from .addresses = [...] blocks (as proper ip_interface objects)
• Default gateway from defaultGateway = "..."
• DNS nameservers from nameservers = [...]
• Interface names from interfaces = { name = { ... } } blocks and interfaces.name.ipvX patterns
• DHCP status from dhcpcd.enable / useDHCP

Detection

NixOS is detected via the /etc/NIXOS marker file or /etc/nixos/configuration.nix. On non-NixOS systems the parser yields nothing.

Example

$ target-query -f network.interfaces /path/to/nixos-image.E01

<unix/network/interface hostname='test-nixos' domain=None name='eth0' type='static' enabled=None
  cidr=[net.ipinterface('10.13.37.10/24'), net.ipinterface('2001:db8::1/64')]
  gateway=[net.ipaddress('10.13.37.0')]
  dns=[net.ipaddress('10.13.37.1'), net.ipaddress('10.13.37.2')]
  source='/etc/nixos/networking.nix' configurator='nixos'>

target-info also picks up the IPs:

Before:

Hostname       : test-nixos
Ips            :
Os family      : linux
Os version     : NixOS 25.05 (Warbler)

After:

Hostname       : test-nixos
Ips            : 10.13.37.10, 2001:db8::1
Os family      : linux
Os version     : NixOS 25.05 (Warbler)

Test fixtures

Based on a real-world networking.nix structure generated by nixos-infect, with tests for static IP, DHCP, and non-NixOS detection. All IPs in test fixtures use 10.13.37.x (consistent with existing tests) and 2001:db8:: (RFC 3849 documentation range). Test data files are stored as LFS.

Limitations

• The parser uses regex rather than a full Nix language parser, so highly dynamic configurations using Nix functions/variables for network values won't be parsed. In practice, most NixOS network configs are straightforward static declarations.

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[jmvermeulen]

@DissectBot agree

[Schamper]

Can you move this class up so that the file structure stays:

• Manager classes
• Lease classes
• Helper functions

[Schamper]

@Miauwkeru I think you use NixOS too, is there a nicer way we can parse this using the config helpers?

[Miauwkeru]

nix is a bit specific, so i think we need to make a nix specific config parser for those kind of files. The helper functions we have available will help a bit with creating the parser