wrenn-releases/cmd/host-agent/main.go

package main

import (
	"context"
	"crypto/tls"
	"flag"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"sync"
	"syscall"
	"time"

	"github.com/joho/godotenv"

	"git.omukk.dev/wrenn/wrenn/internal/devicemapper"
	"git.omukk.dev/wrenn/wrenn/internal/hostagent"
	"git.omukk.dev/wrenn/wrenn/internal/layout"
	"git.omukk.dev/wrenn/wrenn/internal/network"
	"git.omukk.dev/wrenn/wrenn/internal/sandbox"
	"git.omukk.dev/wrenn/wrenn/pkg/auth"
	"git.omukk.dev/wrenn/wrenn/pkg/logging"
	"git.omukk.dev/wrenn/wrenn/proto/hostagent/gen/hostagentv1connect"
)

// Set via -ldflags at build time.
var (
	version = "dev"
	commit  = "unknown"
)

func main() {
	// Best-effort load — missing .env file is fine.
	_ = godotenv.Load()

	registrationToken := flag.String("register", "", "One-time registration token from the control plane (required on first run)")
	advertiseAddr := flag.String("address", "", "Externally-reachable address (ip:port) for this host agent")
	flag.Parse()

	rootDir := envOrDefault("WRENN_DIR", "/var/lib/wrenn")
	cleanupLog := logging.Setup(filepath.Join(rootDir, "logs"), "host-agent")
	defer cleanupLog()

	if os.Geteuid() != 0 {
		slog.Error("host agent must run as root")
		os.Exit(1)
	}

	// Enable IP forwarding (required for NAT).
	if err := os.WriteFile("/proc/sys/net/ipv4/ip_forward", []byte("1"), 0644); err != nil {
		slog.Warn("failed to enable ip_forward", "error", err)
	}

	// Clean up stale resources from a previous crash.
	devicemapper.CleanupStaleDevices()
	network.CleanupStaleNamespaces()

	listenAddr := envOrDefault("WRENN_HOST_LISTEN_ADDR", ":50051")
	cpURL := os.Getenv("WRENN_CP_URL")
	credsFile := filepath.Join(rootDir, "host-credentials.json")

	if cpURL == "" {
		slog.Error("WRENN_CP_URL environment variable is required")
		os.Exit(1)
	}
	if *advertiseAddr == "" {
		slog.Error("--address flag is required (externally-reachable ip:port)")
		os.Exit(1)
	}

	// Parse default rootfs size from env (e.g. "5G", "2Gi", "1000M").
	defaultRootfsSizeMB := sandbox.DefaultDiskSizeMB
	if sizeStr := os.Getenv("WRENN_DEFAULT_ROOTFS_SIZE"); sizeStr != "" {
		parsed, err := sandbox.ParseSizeToMB(sizeStr)
		if err != nil {
			slog.Error("invalid WRENN_DEFAULT_ROOTFS_SIZE", "value", sizeStr, "error", err)
			os.Exit(1)
		}
		defaultRootfsSizeMB = parsed
		slog.Info("using custom rootfs size", "size_mb", defaultRootfsSizeMB)
	}

	// Expand base images to the configured disk size (sparse, no extra physical
	// disk). This ensures dm-snapshot sandboxes see the full size from boot.
	if err := sandbox.EnsureImageSizes(rootDir, defaultRootfsSizeMB); err != nil {
		slog.Error("failed to expand base images", "error", err)
		os.Exit(1)
	}

	// Resolve latest kernel version.
	kernelPath, kernelVersion, err := layout.LatestKernel(rootDir)
	if err != nil {
		slog.Error("failed to find kernel", "error", err)
		os.Exit(1)
	}
	slog.Info("resolved kernel", "version", kernelVersion, "path", kernelPath)

	// Detect firecracker version.
	fcBin := envOrDefault("WRENN_FIRECRACKER_BIN", "/usr/local/bin/firecracker")
	fcVersion, err := sandbox.DetectFirecrackerVersion(fcBin)
	if err != nil {
		slog.Error("failed to detect firecracker version", "error", err)
		os.Exit(1)
	}
	slog.Info("resolved firecracker", "version", fcVersion, "path", fcBin)

	cfg := sandbox.Config{
		WrennDir:            rootDir,
		DefaultRootfsSizeMB: defaultRootfsSizeMB,
		KernelPath:          kernelPath,
		KernelVersion:       kernelVersion,
		FirecrackerBin:      fcBin,
		FirecrackerVersion:  fcVersion,
		AgentVersion:        version,
	}

	mgr := sandbox.New(cfg)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	mgr.StartTTLReaper(ctx)

	// Register with the control plane and start heartbeating.
	creds, err := hostagent.Register(ctx, hostagent.RegistrationConfig{
		CPURL:             cpURL,
		RegistrationToken: *registrationToken,
		TokenFile:         credsFile,
		Address:           *advertiseAddr,
	})
	if err != nil {
		slog.Error("host registration failed", "error", err)
		os.Exit(1)
	}

	slog.Info("host registered", "host_id", creds.HostID)

	// httpServer is declared here so the shutdown func can reference it.
	httpServer := &http.Server{Addr: listenAddr}

	// mTLS is mandatory — refuse to start without a valid certificate.
	var certStore hostagent.CertStore
	if creds.CertPEM == "" || creds.KeyPEM == "" || creds.CACertPEM == "" {
		slog.Error("mTLS certificate not received from CP — ensure WRENN_CA_CERT and WRENN_CA_KEY are configured on the control plane")
		os.Exit(1)
	}
	if err := certStore.ParseAndStore(creds.CertPEM, creds.KeyPEM); err != nil {
		slog.Error("failed to load host TLS certificate", "error", err)
		os.Exit(1)
	}
	tlsCfg := auth.AgentTLSConfigFromPEM(creds.CACertPEM, certStore.GetCert)
	if tlsCfg == nil {
		slog.Error("failed to build agent TLS config: invalid CA certificate PEM")
		os.Exit(1)
	}
	httpServer.TLSConfig = tlsCfg
	slog.Info("mTLS enabled on agent server")

	// doShutdown is the single shutdown path. sync.Once ensures mgr.Shutdown
	// and httpServer.Shutdown are each called exactly once regardless of
	// whether shutdown is triggered by a signal, a heartbeat 404, or the
	// Terminate RPC.
	var shutdownOnce sync.Once
	doShutdown := func(reason string) {
		shutdownOnce.Do(func() {
			slog.Info("shutting down", "reason", reason)
			cancel()
			shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 30*time.Second)
			defer shutdownCancel()
			mgr.Shutdown(shutdownCtx)
			if err := httpServer.Shutdown(shutdownCtx); err != nil {
				slog.Error("http server shutdown error", "error", err)
			}
		})
	}

	srv := hostagent.NewServer(mgr, func() {
		doShutdown("Terminate RPC received")
	})
	path, handler := hostagentv1connect.NewHostAgentServiceHandler(srv)

	proxyHandler := hostagent.NewProxyHandler(mgr)

	mux := http.NewServeMux()
	mux.Handle(path, handler)
	mux.Handle("/proxy/", proxyHandler)
	httpServer.Handler = mux

	// Start heartbeat loop. Handler must be set before this because the
	// immediate beat can trigger doShutdown → httpServer.Shutdown synchronously.
	hostagent.StartHeartbeat(ctx, cpURL, credsFile, creds.HostID, 30*time.Second,
		// pauseAll: called on 3 consecutive network failures.
		func() {
			pauseCtx, pauseCancel := context.WithTimeout(context.Background(), 2*time.Minute)
			defer pauseCancel()
			mgr.PauseAll(pauseCtx)
		},
		// onDeleted: called when CP returns 404 (host was deleted).
		func() {
			doShutdown("host deleted from CP")
		},
		// onCredsRefreshed: hot-swap the TLS certificate after a JWT refresh.
		func(tf *hostagent.TokenFile) {
			if tf.CertPEM == "" || tf.KeyPEM == "" {
				return
			}
			if err := certStore.ParseAndStore(tf.CertPEM, tf.KeyPEM); err != nil {
				slog.Error("failed to hot-swap TLS cert after credentials refresh", "error", err)
			} else {
				slog.Info("TLS cert hot-swapped after credentials refresh")
			}
		},
	)

	// Graceful shutdown on SIGINT/SIGTERM.
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
	go func() {
		sig := <-sigCh
		doShutdown("signal: " + sig.String())
	}()

	slog.Info("host agent starting", "addr", listenAddr, "host_id", creds.HostID, "version", version, "commit", commit)
	// TLSConfig is always set (mTLS is mandatory). Create the TLS listener
	// manually because ListenAndServeTLS requires on-disk cert/key paths
	// but we use GetCertificate callback for hot-swap support.
	ln, err := tls.Listen("tcp", listenAddr, httpServer.TLSConfig)
	if err != nil {
		slog.Error("failed to start TLS listener", "error", err)
		os.Exit(1)
	}
	if err := httpServer.Serve(ln); err != nil && err != http.ErrServerClosed {
		slog.Error("https server error", "error", err)
		os.Exit(1)
	}

	slog.Info("host agent stopped")
}

func envOrDefault(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}