RackPeek/Shared.Rcl/Commands/Discovery/DiscoverNetworkCommand.cs

using System.ComponentModel;
using RackPeek.Domain.Discovery;
using RackPeek.Domain.Resources;
using RackPeek.Domain.Resources.Services.Networking;
using Spectre.Console;
using Spectre.Console.Cli;
using NetworkCidr = RackPeek.Domain.Resources.Services.Networking.Cidr;

namespace Shared.Rcl.Commands.Discovery;

public sealed class DiscoverNetworkSettings : DiscoverSettings {
    private IReadOnlyList<int>? _resolvedPorts;

    [CommandOption("--cidr <CIDR>")]
    [Description("Subnet to sweep, e.g. 192.168.1.0/24. Defaults to this machine's own subnet.")]
    public string? Cidr { get; init; }

    [CommandOption("--ports <LIST>")]
    [Description("TCP ports probed to catch hosts that ignore ping, e.g. 22,80,443. " +
                 "Defaults to a curated homelab list.")]
    public string? Ports { get; init; }

    [CommandOption("--timeout <MS>")]
    [Description("Milliseconds to wait on each port probe.")]
    public int Timeout { get; init; } = 500;

    [CommandOption("--parallel <N>")]
    [Description("How many hosts to probe at once.")]
    public int Parallel { get; init; } = 128;

    /// <summary>The parsed --cidr, or null when it was omitted or does not parse.</summary>
    public NetworkCidr? ParsedCidr =>
        NetworkCidr.TryParse(Cidr, out NetworkCidr parsed) ? parsed : null;

    public IReadOnlyList<int> ResolvedPorts =>
        _resolvedPorts ??= string.IsNullOrWhiteSpace(Ports)
            ? WellKnownPorts.Defaults
            : ParsePorts(Ports) ?? WellKnownPorts.Defaults;

    public override ValidationResult Validate() {
        if (Cidr != null) {
            if (ParsedCidr is not { } parsed)
                return ValidationResult.Error(
                    $"'{Cidr}' is not a usable CIDR block. Use e.g. --cidr 192.168.1.0/24");

            if (parsed.Prefix < NetworkScanner.MinPrefix)
                return ValidationResult.Error(
                    $"/{parsed.Prefix} is more than 65,534 hosts. Narrow the sweep to /{NetworkScanner.MinPrefix} or smaller.");
        }

        if (Ports != null && ParsePorts(Ports) == null)
            return ValidationResult.Error(
                $"'{Ports}' is not a usable port list. Use e.g. --ports 22,80,443");

        if (Timeout is < 1 or > 60_000)
            return ValidationResult.Error("--timeout must be between 1 and 60000 milliseconds.");

        if (Parallel is < 1 or > 1024)
            return ValidationResult.Error("--parallel must be between 1 and 1024.");

        return base.Validate();
    }

    private static IReadOnlyList<int>? ParsePorts(string list) {
        var ports = new List<int>();

        foreach (var part in list.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)) {
            if (!int.TryParse(part, out var port) || port is < 1 or > 65_535)
                return null;

            ports.Add(port);
        }

        return ports.Count == 0 ? null : ports;
    }
}

/// <summary>
///     Sweeps a subnet and emits every answering host as a System resource — the
///     collector for machines nothing else can describe: no agent, no API, just an
///     address that answers.
/// </summary>
public sealed class DiscoverNetworkCommand(INetworkProbe probe)
    : AsyncCommand<DiscoverNetworkSettings> {
    protected override async Task<int> ExecuteAsync(
        CommandContext context,
        DiscoverNetworkSettings settings,
        CancellationToken cancellationToken) {
        if (!probe.IsSupported) {
            // Without this, the browser console's sandboxed sockets would swallow every
            // probe and the command would report an empty network as if it were true.
            AnsiConsole.MarkupLine(
                "[red]Network scanning is not supported on this platform.[/] " +
                "Run rpk on a machine attached to the network instead.");

            return 1;
        }

        Cidr cidr;

        if (settings.ParsedCidr is { } requested) {
            cidr = requested;
        }
        else {
            Cidr? detected = probe.LocalSubnet();

            if (detected == null) {
                AnsiConsole.MarkupLine(
                    "[red]Could not detect this machine's subnet.[/] Pass --cidr, e.g. --cidr 192.168.1.0/24");

                return 1;
            }

            // The same cap --cidr gets: a VPN or CGNAT interface can carry a /10, and
            // auto-detection must never be the way around the sweep limit.
            if (detected.Value.Prefix < NetworkScanner.MinPrefix) {
                AnsiConsole.MarkupLine(
                    $"[red]This machine's subnet is {Markup.Escape(detected.Value.ToString())} — more than " +
                    $"65,534 hosts.[/] Pass --cidr with a narrower block, e.g. --cidr 192.168.1.0/24");

                return 1;
            }

            cidr = detected.Value;
        }

        var options = new NetworkScanOptions {
            Cidr = cidr,
            Ports = settings.ResolvedPorts,
            PortTimeout = TimeSpan.FromMilliseconds(settings.Timeout),
            Concurrency = settings.Parallel
        };

        var targets = NetworkScanner.EnumerateTargets(cidr).Count();

        AnsiConsole.MarkupLine(
            $"[grey]Sweeping {Markup.Escape(cidr.ToString())} — {targets} address(es), " +
            $"ping + {options.Ports.Count} TCP port(s)…[/]");

        IReadOnlyList<NetworkHostFact> hosts = await NetworkScanner.ScanAsync(probe, options, cancellationToken);

        var withoutMac = hosts.Count(h => h.Mac == null);

        if (withoutMac > 0)
            AnsiConsole.MarkupLine(
                $"[grey]{withoutMac} host(s) had no ARP entry, so their identity is seeded on the IP " +
                "address — a DHCP re-lease will make them look like new machines.[/]");

        List<Resource> resources = NetworkScanMapper.ToResources(hosts);

        return await DiscoveryOutput.EmitAsync(resources, settings, cancellationToken);
    }
}