mesh-catalog/modules/netcheck/cmd/netcheck/main.go

// netcheck's Go tools bundle (novox/hq ADR 0188, ADR 0193): a process the node's runtime launches
// and speaks MCP over stdio to, through the Go SDK. It serves the two checks that are the machine's
// own sockets and resolver — a TCP connect, a DNS lookup (of the machine's resolver, or of one named),
// what listens here, and the private network's peers (hq issue 522) — and nothing that changes anything.
// Beside them it watches the tunnel and says on the bus when a peer's endpoint moves or its handshake goes
// stale or fresh again.
// The module's HTTP check is its TypeScript bundle; the runtime serves both under one module.
package main

import (
	"context"
	"fmt"
	"os"
	"strings"
	"time"

	stdio "git.novox.be/novox/mesh-sdk/go"
)

func main() {
	go watchTunnel(func(event string, body any) error { return stdio.Emit(event, body) })
	// An empty name serves as the module the runtime names (MESH_SERVED_MODULE): netcheck.
	if err := stdio.Serve("", tools()); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}

func tools() []stdio.Tool {
	return []stdio.Tool{
		{
			Name: "netcheck_tunnel",
			Description: "The private network's peers as this machine sees them (what wg show reads): each peer's machine where " +
				"the mesh's names say it, its allowed ips, the endpoint (address:port) it was last heard from, its last handshake " +
				"and that handshake's age, whether it is stale (older than three minutes, or never), and the bytes received and " +
				"sent. Never a key. On the hub it says what address and port every machine reaches it from.",
			Run: func(map[string]any) (any, error) {
				cx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
				defer cancel()
				return readTunnel(cx)
			},
		},
		{
			Name: "netcheck_listening",
			Description: "What listens on this machine: every TCP socket in the listen state and every bound UDP socket, " +
				"from the kernel's own tables (what ss -lunt reads), with the program holding it where this tool may see it. " +
				"port narrows it to one port, e.g. 53 to see on which addresses the resolver answers.",
			Input: map[string]any{
				"port": map[string]any{"type": "integer", "description": "only this port (default every port)"},
			},
			Run: func(args map[string]any) (any, error) {
				port := 0
				if _, given := args["port"]; given {
					p, err := whole(args, "port", 0)
					if err != nil {
						return nil, err
					}
					if p < 1 || p > 65535 {
						return nil, fmt.Errorf("port %d is not a port (1-65535)", p)
					}
					port = p
				}
				return Listening("/proc", port), nil
			},
		},
		{
			Name: "netcheck_tcp",
			Description: "Check whether a TCP port is reachable from this machine: opens one connection " +
				"and closes it at once, sending nothing. Answers reachable, elapsed_ms and the error when not.",
			Input: map[string]any{
				"host":       map[string]any{"type": "string", "description": "host name or IP address"},
				"port":       map[string]any{"type": "integer", "description": "TCP port, 1-65535"},
				"timeout_ms": map[string]any{"type": "integer", "description": "give up after this long (default 3000, at most 30000)"},
			},
			Run: func(args map[string]any) (any, error) {
				host, err := text(args, "host")
				if err != nil {
					return nil, err
				}
				port, err := whole(args, "port", 0)
				if err != nil {
					return nil, err
				}
				timeout, err := timeoutOf(args)
				if err != nil {
					return nil, err
				}
				return CheckTCP(host, port, timeout)
			},
		},
		{
			Name: "netcheck_dns",
			Description: "Look a name up with this machine's resolver (its /etc/resolv.conf and /etc/hosts), or — with server — ask " +
				"that one resolver alone over UDP (or TCP), answering its response code (NOERROR, NXDOMAIN, REFUSED…). " +
				"type is A, AAAA, CNAME, TXT or MX; answers the records found, or the error.",
			Input: map[string]any{
				"name":       map[string]any{"type": "string", "description": "the name to look up"},
				"type":       map[string]any{"type": "string", "enum": []string{"A", "AAAA", "CNAME", "TXT", "MX"}, "description": "record type (default A)"},
				"server":     map[string]any{"type": "string", "description": "ask this resolver alone: an address, with :port or without (53), e.g. 10.10.0.1"},
				"tcp":        map[string]any{"type": "boolean", "description": "ask the server over TCP rather than UDP (default false)"},
				"timeout_ms": map[string]any{"type": "integer", "description": "give up after this long (default 3000, at most 30000)"},
			},
			Run: func(args map[string]any) (any, error) {
				name, err := text(args, "name")
				if err != nil {
					return nil, err
				}
				kind, _ := args["type"].(string)
				timeout, err := timeoutOf(args)
				if err != nil {
					return nil, err
				}
				server, _ := args["server"].(string)
				overTCP, _ := args["tcp"].(bool)
				return AskDNS(name, kind, strings.TrimSpace(server), overTCP, timeout)
			},
		},
	}
}

func say(format string, args ...any) {
	fmt.Fprintf(os.Stderr, "[netcheck] "+format+"\n", args...)
}