cmd/containerboot: PID1 for running tailscaled in a container.

This implements the same functionality as the former run.sh, but in Go and with a little better awareness of tailscaled's lifecycle. Also adds TS_AUTH_ONCE, which fixes the unfortunate behavior run.sh had where it would unconditionally try to reauth every time if you gave it an authkey, rather than try to use it only if auth is actually needed. This makes it a bit nicer to deploy these containers in automation, since you don't have to run the container once, then go and edit its definition to remove authkeys. Signed-off-by: David Anderson <danderson@tailscale.com>
2024-11-25 11:05:45 +00:00 · 2022-10-25 13:12:54 -07:00 · 2022-10-25 13:12:54 -07:00 · 76904b82e7
commit 76904b82e7
parent 0759d78f12
8 changed files with 641 additions and 107 deletions
--- a/6
+++ b/6
@ -66,10 +66,12 @@ RUN GOARCH=$TARGETARCH go install -ldflags="\
      -X tailscale.com/version.Long=$VERSION_LONG \
      -X tailscale.com/version.Short=$VERSION_SHORT \
      -X tailscale.com/version.GitCommit=$VERSION_GIT_HASH" \
-      -v ./cmd/tailscale ./cmd/tailscaled
+      -v ./cmd/tailscale ./cmd/tailscaled ./cmd/containerboot

 FROM alpine:3.16
 RUN apk add --no-cache ca-certificates iptables iproute2 ip6tables

 COPY --from=build-env /go/bin/* /usr/local/bin/
-COPY --from=build-env /go/src/tailscale/docs/k8s/run.sh /usr/local/bin/
+# For compat with the previous run.sh, although ideally you should be
+# using build_docker.sh which sets an entrypoint for the image.
+RUN ln -s /usr/local/bin/containerboot /tailscale/run.sh
--- a/build_docker.sh
+++ b/build_docker.sh
@ -35,14 +35,14 @@ BASE="${BASE:-${DEFAULT_BASE}}"
 go run github.com/tailscale/mkctr \
  --gopaths="\
    tailscale.com/cmd/tailscale:/usr/local/bin/tailscale, \
-    tailscale.com/cmd/tailscaled:/usr/local/bin/tailscaled" \
+    tailscale.com/cmd/tailscaled:/usr/local/bin/tailscaled, \
+    tailscale.com/cmd/containerboot:/usr/local/bin/containerboot" \
  --ldflags="\
    -X tailscale.com/version.Long=${VERSION_LONG} \
    -X tailscale.com/version.Short=${VERSION_SHORT} \
    -X tailscale.com/version.GitCommit=${VERSION_GIT_HASH}" \
-  --files="docs/k8s/run.sh:/tailscale/run.sh" \
  --base="${BASE}" \
  --tags="${TAGS}" \
  --repos="${REPOS}" \
  --push="${PUSH}" \
-  /bin/sh /tailscale/run.sh
+  /usr/local/bin/containerboot
--- a/cmd/containerboot/kube.go
+++ b/cmd/containerboot/kube.go
@ -0,0 +1,190 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux
+// +build linux
+
+package main
+
+import (
+	"bytes"
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+	"sync"
+	"time"
+)
+
+// findKeyInKubeSecret inspects the kube secret secretName for a data
+// field called "authkey", and returns its value if present.
+func findKeyInKubeSecret(ctx context.Context, secretName string) (string, error) {
+	kubeOnce.Do(initKube)
+	req, err := http.NewRequest("GET", fmt.Sprintf("/api/v1/namespaces/%s/secrets/%s", kubeNamespace, secretName), nil)
+	if err != nil {
+		return "", err
+	}
+	resp, err := doKubeRequest(ctx, req)
+	if err != nil {
+		if resp != nil && resp.StatusCode == http.StatusNotFound {
+			// Kube secret doesn't exist yet, can't have an authkey.
+			return "", nil
+		}
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	bs, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	// We use a map[string]any here rather than import corev1.Secret,
+	// because we only do very limited things to the secret, and
+	// importing corev1 adds 12MiB to the compiled binary.
+	var s map[string]any
+	if err := json.Unmarshal(bs, &s); err != nil {
+		return "", err
+	}
+	if d, ok := s["data"].(map[string]any); ok {
+		if v, ok := d["authkey"].(string); ok {
+			bs, err := base64.StdEncoding.DecodeString(v)
+			if err != nil {
+				return "", err
+			}
+			return string(bs), nil
+		}
+	}
+	return "", nil
+}
+
+// storeDeviceID writes deviceID into the "device_id" data field of
+// the kube secret secretName.
+func storeDeviceID(ctx context.Context, secretName, deviceID string) error {
+	kubeOnce.Do(initKube)
+	m := map[string]map[string]string{
+		"stringData": map[string]string{
+			"device_id": deviceID,
+		},
+	}
+	var b bytes.Buffer
+	if err := json.NewEncoder(&b).Encode(m); err != nil {
+		return err
+	}
+	req, err := http.NewRequest("PATCH", fmt.Sprintf("/api/v1/namespaces/%s/secrets/%s?fieldManager=tailscale-container", kubeNamespace, secretName), &b)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/strategic-merge-patch+json")
+	if _, err := doKubeRequest(ctx, req); err != nil {
+		return err
+	}
+	return nil
+}
+
+// deleteAuthKey deletes the 'authkey' field of the given kube
+// secret. No-op if there is no authkey in the secret.
+func deleteAuthKey(ctx context.Context, secretName string) error {
+	kubeOnce.Do(initKube)
+	// m is a JSON Patch data structure, see https://jsonpatch.com/ or RFC 6902.
+	m := []struct {
+		Op   string `json:"op"`
+		Path string `json:"path"`
+	}{
+		{
+			Op:   "remove",
+			Path: "/data/authkey",
+		},
+	}
+	var b bytes.Buffer
+	if err := json.NewEncoder(&b).Encode(m); err != nil {
+		return err
+	}
+	req, err := http.NewRequest("PATCH", fmt.Sprintf("/api/v1/namespaces/%s/secrets/%s?fieldManager=tailscale-container", kubeNamespace, secretName), &b)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json-patch+json")
+	if resp, err := doKubeRequest(ctx, req); err != nil {
+		if resp != nil && resp.StatusCode == http.StatusUnprocessableEntity {
+			// This is kubernetes-ese for "the field you asked to
+			// delete already doesn't exist", aka no-op.
+			return nil
+		}
+		return err
+	}
+	return nil
+}
+
+var (
+	kubeOnce      sync.Once
+	kubeHost      string
+	kubeNamespace string
+	kubeToken     string
+	kubeHTTP      *http.Transport
+)
+
+func initKube() {
+	// If running in Kubernetes, set things up so that doKubeRequest
+	// can talk successfully to the kube apiserver.
+	if os.Getenv("KUBERNETES_SERVICE_HOST") == "" {
+		return
+	}
+
+	kubeHost = os.Getenv("KUBERNETES_SERVICE_HOST") + ":" + os.Getenv("KUBERNETES_SERVICE_PORT_HTTPS")
+
+	bs, err := os.ReadFile("/var/run/secrets/kubernetes.io/serviceaccount/namespace")
+	if err != nil {
+		log.Fatalf("Error reading kube namespace: %v", err)
+	}
+	kubeNamespace = strings.TrimSpace(string(bs))
+
+	bs, err = os.ReadFile("/var/run/secrets/kubernetes.io/serviceaccount/token")
+	if err != nil {
+		log.Fatalf("Error reading kube token: %v", err)
+	}
+	kubeToken = strings.TrimSpace(string(bs))
+
+	bs, err = os.ReadFile("/var/run/secrets/kubernetes.io/serviceaccount/ca.crt")
+	if err != nil {
+		log.Fatalf("Error reading kube CA cert: %v", err)
+	}
+	cp := x509.NewCertPool()
+	cp.AppendCertsFromPEM(bs)
+	kubeHTTP = &http.Transport{
+		TLSClientConfig: &tls.Config{
+			RootCAs: cp,
+		},
+		IdleConnTimeout: time.Second,
+	}
+}
+
+// doKubeRequest sends r to the kube apiserver.
+func doKubeRequest(ctx context.Context, r *http.Request) (*http.Response, error) {
+	kubeOnce.Do(initKube)
+	if kubeHTTP == nil {
+		panic("not in kubernetes")
+	}
+
+	r.URL.Scheme = "https"
+	r.URL.Host = kubeHost
+	r.Header.Set("Authorization", "Bearer "+kubeToken)
+	r.Header.Set("Accept", "application/json")
+
+	resp, err := kubeHTTP.RoundTrip(r)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return resp, fmt.Errorf("got non-200 status code %d", resp.StatusCode)
+	}
+	return resp, nil
+}
--- a/cmd/containerboot/main.go
+++ b/cmd/containerboot/main.go
@ -0,0 +1,424 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux
+// +build linux
+
+// The containerboot binary is a wrapper for starting tailscaled in a
+// container. It handles reading the desired mode of operation out of
+// environment variables, bringing up and authenticating Tailscale,
+// and any other kubernetes-specific side jobs.
+//
+// As with most container things, configuration is passed through
+// environment variables. All configuration is optional.
+//
+//  - TS_AUTH_KEY: the authkey to use for login.
+//  - TS_ROUTES: subnet routes to advertise.
+//  - TS_DEST_IP: proxy all incoming Tailscale traffic to the given
+//                destination.
+//  - TS_TAILSCALED_EXTRA_ARGS: extra arguments to 'tailscaled'.
+//  - TS_EXTRA_ARGS: extra arguments to 'tailscale up'.
+//  - TS_USERSPACE: run with userspace networking (the default)
+//                  instead of kernel networking.
+//  - TS_STATE_DIR: the directory in which to store tailscaled
+//                  state. The data should persist across container
+//                  restarts.
+//  - TS_ACCEPT_DNS: whether to use the tailnet's DNS configuration.
+//  - TS_KUBE_SECRET: the name of the Kubernetes secret in which to
+//                    store tailscaled state.
+//  - TS_SOCKS5_SERVER: the address on which to listen for SOCKS5
+//                      proxying into the tailnet.
+//  - TS_OUTBOUND_HTTP_PROXY_LISTEN: the address on which to listen
+//                                   for HTTP proxying into the tailnet.
+//  - TS_SOCKET: the path where the tailscaled local API socket should
+//               be created.
+//  - TS_AUTH_ONCE: if true, only attempt to log in if not already
+//                  logged in. If false (the default, for backwards
+//                  compatibility), forcibly log in every time the
+//                  container starts.
+//
+// When running on Kubernetes, TS_KUBE_SECRET takes precedence over
+// TS_STATE_DIR. Additionally, if TS_AUTH_KEY is not provided and the
+// TS_KUBE_SECRET contains an "authkey" field, that key is used.
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"log"
+	"net/netip"
+	"os"
+	"os/exec"
+	"os/signal"
+	"strconv"
+	"strings"
+	"syscall"
+	"time"
+
+	"golang.org/x/sys/unix"
+	"tailscale.com/client/tailscale"
+	"tailscale.com/ipn/ipnstate"
+)
+
+func main() {
+	log.SetPrefix("boot: ")
+	tailscale.I_Acknowledge_This_API_Is_Unstable = true
+
+	cfg := &settings{
+		AuthKey:         defaultEnv("TS_AUTH_KEY", ""),
+		Routes:          defaultEnv("TS_ROUTES", ""),
+		ProxyTo:         defaultEnv("TS_DEST_IP", ""),
+		DaemonExtraArgs: defaultEnv("TS_TAILSCALED_EXTRA_ARGS", ""),
+		ExtraArgs:       defaultEnv("TS_EXTRA_ARGS", ""),
+		InKubernetes:    os.Getenv("KUBERNETES_SERVICE_HOST") != "",
+		UserspaceMode:   defaultBool("TS_USERSPACE", true),
+		StateDir:        defaultEnv("TS_STATE_DIR", ""),
+		AcceptDNS:       defaultBool("TS_ACCEPT_DNS", false),
+		KubeSecret:      defaultEnv("TS_KUBE_SECRET", "tailscale"),
+		SOCKSProxyAddr:  defaultEnv("TS_SOCKS5_SERVER", ""),
+		HTTPProxyAddr:   defaultEnv("TS_OUTBOUND_HTTP_PROXY_LISTEN", ""),
+		Socket:          defaultEnv("TS_SOCKET", "/tmp/tailscaled.sock"),
+		AuthOnce:        defaultBool("TS_AUTH_ONCE", false),
+	}
+
+	if cfg.ProxyTo != "" && cfg.UserspaceMode {
+		log.Fatal("TS_DEST_IP is not supported with TS_USERSPACE")
+	}
+
+	if !cfg.UserspaceMode {
+		if err := ensureTunFile(); err != nil {
+			log.Fatalf("Unable to create tuntap device file: %v", err)
+		}
+	}
+	if cfg.ProxyTo != "" || cfg.Routes != "" {
+		if err := ensureIPForwarding(); err != nil {
+			log.Printf("Failed to enable IP forwarding: %v", err)
+			log.Printf("To run tailscale as a proxy or router container, IP forwarding must be enabled.")
+			if cfg.InKubernetes {
+				log.Fatalf("You can either set the sysctls as a privileged initContainer, or run the tailscale container with privileged=true.")
+			} else {
+				log.Fatalf("You can fix this by running the container with privileged=true, or the equivalent in your container runtime that permits access to sysctls.")
+			}
+		}
+	}
+
+	// Context is used for all setup stuff until we're in steady
+	// state, so that if something is hanging we eventually time out
+	// and crashloop the container.
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+
+	if cfg.InKubernetes && cfg.KubeSecret != "" && cfg.AuthKey == "" {
+		key, err := findKeyInKubeSecret(ctx, cfg.KubeSecret)
+		if err != nil {
+			log.Fatalf("Getting authkey from kube secret: %v", err)
+		}
+		if key != "" {
+			log.Print("Using authkey found in kube secret")
+			cfg.AuthKey = key
+		} else {
+			log.Print("No authkey found in kube secret and TS_AUTHKEY not provided, login will be interactive if needed.")
+		}
+	}
+
+	st, daemonPid, err := startAndAuthTailscaled(ctx, cfg)
+	if err != nil {
+		log.Fatalf("failed to bring up tailscale: %v", err)
+	}
+
+	if cfg.ProxyTo != "" {
+		if err := installIPTablesRule(ctx, cfg.ProxyTo, st.TailscaleIPs); err != nil {
+			log.Fatalf("installing proxy rules: %v", err)
+		}
+	}
+	if cfg.KubeSecret != "" {
+		if err := storeDeviceID(ctx, cfg.KubeSecret, string(st.Self.ID)); err != nil {
+			log.Fatalf("storing device ID in kube secret: %v", err)
+		}
+		if cfg.AuthOnce {
+			// We were told to only auth once, so any secret-bound
+			// authkey is no longer needed. We don't strictly need to
+			// wipe it, but it's good hygiene.
+			log.Printf("Deleting authkey from kube secret")
+			if err := deleteAuthKey(ctx, cfg.KubeSecret); err != nil {
+				log.Fatalf("deleting authkey from kube secret: %v", err)
+			}
+		}
+	}
+
+	log.Println("Startup complete, waiting for shutdown signal")
+	// Reap all processes, since we are PID1 and need to collect
+	// zombies.
+	for {
+		var status unix.WaitStatus
+		pid, err := unix.Wait4(-1, &status, 0, nil)
+		if errors.Is(err, unix.EINTR) {
+			continue
+		}
+		if err != nil {
+			log.Fatalf("Waiting for exited processes: %v", err)
+		}
+		if pid == daemonPid {
+			log.Printf("Tailscaled exited")
+			os.Exit(0)
+		}
+	}
+}
+
+// startAndAuthTailscaled starts the tailscale daemon and attempts to
+// auth it, according to the settings in cfg. If successful, returns
+// tailscaled's Status and pid.
+func startAndAuthTailscaled(ctx context.Context, cfg *settings) (*ipnstate.Status, int, error) {
+	args := tailscaledArgs(cfg)
+	sigCh := make(chan os.Signal, 1)
+	signal.Notify(sigCh, unix.SIGTERM, unix.SIGINT)
+	// tailscaled runs without context, since it needs to persist
+	// beyond the startup timeout in ctx.
+	cmd := exec.Command("tailscaled", args...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Setpgid: true,
+	}
+	log.Printf("Starting tailscaled")
+	if err := cmd.Start(); err != nil {
+		return nil, 0, fmt.Errorf("starting tailscaled failed: %v", err)
+	}
+	go func() {
+		<-sigCh
+		log.Printf("Received SIGTERM from container runtime, shutting down tailscaled")
+		cmd.Process.Signal(unix.SIGTERM)
+	}()
+
+	// Wait for the socket file to appear, otherwise 'tailscale up'
+	// can fail.
+	log.Printf("Waiting for tailscaled socket")
+	for {
+		if ctx.Err() != nil {
+			log.Fatalf("Timed out waiting for tailscaled socket")
+		}
+		_, err := os.Stat(cfg.Socket)
+		if errors.Is(err, fs.ErrNotExist) {
+			time.Sleep(100 * time.Millisecond)
+			continue
+		} else if err != nil {
+			log.Fatalf("Waiting for tailscaled socket: %v", err)
+		}
+		break
+	}
+
+	if !cfg.AuthOnce {
+		if err := tailscaleUp(ctx, cfg); err != nil {
+			return nil, 0, fmt.Errorf("couldn't log in: %v", err)
+		}
+	}
+
+	tsClient := tailscale.LocalClient{
+		Socket:        cfg.Socket,
+		UseSocketOnly: true,
+	}
+
+	// Poll for daemon state until it goes to either Running or
+	// NeedsLogin. The latter only happens if cfg.AuthOnce is true,
+	// because in that case we only try to auth when it's necessary to
+	// reach the running state.
+	for {
+		if ctx.Err() != nil {
+			return nil, 0, ctx.Err()
+		}
+
+		loopCtx, cancel := context.WithTimeout(ctx, time.Second)
+		st, err := tsClient.Status(loopCtx)
+		cancel()
+		if err != nil {
+			return nil, 0, fmt.Errorf("Getting tailscaled state: %w", err)
+		}
+
+		switch st.BackendState {
+		case "Running":
+			if len(st.TailscaleIPs) > 0 {
+				return st, cmd.Process.Pid, nil
+			}
+			log.Printf("No Tailscale IPs assigned yet")
+		case "NeedsLogin":
+			// Alas, we cannot currently trigger an authkey login from
+			// LocalAPI, so we still have to shell out to the
+			// tailscale CLI for this bit.
+			if err := tailscaleUp(ctx, cfg); err != nil {
+				return nil, 0, fmt.Errorf("couldn't log in: %v", err)
+			}
+		default:
+			log.Printf("tailscaled in state %q, waiting", st.BackendState)
+		}
+
+		time.Sleep(500 * time.Millisecond)
+	}
+}
+
+// tailscaledArgs uses cfg to construct the argv for tailscaled.
+func tailscaledArgs(cfg *settings) []string {
+	args := []string{"--socket=" + cfg.Socket}
+	switch {
+	case cfg.InKubernetes && cfg.KubeSecret != "":
+		args = append(args, "--state=kube:"+cfg.KubeSecret, "--statedir=/tmp")
+	case cfg.StateDir != "":
+		args = append(args, "--state="+cfg.StateDir)
+	default:
+		args = append(args, "--state=mem:", "--statedir=/tmp")
+	}
+
+	if cfg.UserspaceMode {
+		args = append(args, "--tun=userspace-networking")
+	} else if err := ensureTunFile(); err != nil {
+		log.Fatalf("ensuring that /dev/net/tun exists: %v", err)
+	}
+
+	if cfg.SOCKSProxyAddr != "" {
+		args = append(args, "--socks5-server="+cfg.SOCKSProxyAddr)
+	}
+	if cfg.HTTPProxyAddr != "" {
+		args = append(args, "--outbound-http-proxy-listen="+cfg.HTTPProxyAddr)
+	}
+	if cfg.DaemonExtraArgs != "" {
+		args = append(args, strings.Fields(cfg.DaemonExtraArgs)...)
+	}
+	return args
+}
+
+// tailscaleUp uses cfg to run 'tailscale up'.
+func tailscaleUp(ctx context.Context, cfg *settings) error {
+	args := []string{"--socket=" + cfg.Socket, "up"}
+	if cfg.AcceptDNS {
+		args = append(args, "--accept-dns=true")
+	} else {
+		args = append(args, "--accept-dns=false")
+	}
+	if cfg.AuthKey != "" {
+		args = append(args, "--authkey="+cfg.AuthKey)
+	}
+	if cfg.Routes != "" {
+		args = append(args, "--advertise-routes="+cfg.Routes)
+	}
+	if cfg.ExtraArgs != "" {
+		args = append(args, strings.Fields(cfg.ExtraArgs)...)
+	}
+	log.Printf("Running 'tailscale up'")
+	cmd := exec.CommandContext(ctx, "tailscale", args...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("tailscale up failed: %v", err)
+	}
+	return nil
+}
+
+// ensureTunFile checks that /dev/net/tun exists, creating it if
+// missing.
+func ensureTunFile() error {
+	// Verify that /dev/net/tun exists, in some container envs it
+	// needs to be mknod-ed.
+	if _, err := os.Stat("/dev/net"); errors.Is(err, fs.ErrNotExist) {
+		if err := os.MkdirAll("/dev/net", 0755); err != nil {
+			return err
+		}
+	}
+	if _, err := os.Stat("/dev/net/tun"); errors.Is(err, fs.ErrNotExist) {
+		dev := unix.Mkdev(10, 200) // tuntap major and minor
+		if err := unix.Mknod("/dev/net/tun", 0600|unix.S_IFCHR, int(dev)); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// ensureIPForwarding enables IPv4/IPv6 forwarding for the container.
+func ensureIPForwarding() error {
+	// In some common configurations (e.g. default docker,
+	// kubernetes), the container environment denies write access to
+	// most sysctls, including IP forwarding controls. Check the
+	// sysctl values before trying to change them, so that we
+	// gracefully do nothing if the container's already been set up
+	// properly by e.g. a k8s initContainer.
+	for _, path := range []string{"/proc/sys/net/ipv4/ip_forward", "/proc/sys/net/ipv6/conf/all/forwarding"} {
+		bs, err := os.ReadFile(path)
+		if err != nil {
+			return fmt.Errorf("reading %q: %w", path, err)
+		}
+		if v := strings.TrimSpace(string(bs)); v != "1" {
+			if err := os.WriteFile(path, []byte("1"), 0644); err != nil {
+				return fmt.Errorf("enabling %q: %w", path, err)
+			}
+		}
+	}
+	return nil
+}
+
+func installIPTablesRule(ctx context.Context, dstStr string, tsIPs []netip.Addr) error {
+	dst, err := netip.ParseAddr(dstStr)
+	if err != nil {
+		return err
+	}
+	argv0 := "iptables"
+	if dst.Is6() {
+		argv0 = "ip6tables"
+	}
+	var local string
+	for _, ip := range tsIPs {
+		if ip.Is4() != dst.Is4() {
+			continue
+		}
+		local = ip.String()
+		break
+	}
+	if local == "" {
+		return fmt.Errorf("no tailscale IP matching family of %s found in %v", dstStr, tsIPs)
+	}
+	cmd := exec.CommandContext(ctx, argv0, "-t", "nat", "-I", "PREROUTING", "1", "-d", local, "-j", "DNAT", "--to-destination", dstStr)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("executing iptables failed: %w", err)
+	}
+	return nil
+}
+
+// settings is all the configuration for containerboot.
+type settings struct {
+	AuthKey         string
+	Routes          string
+	ProxyTo         string
+	DaemonExtraArgs string
+	ExtraArgs       string
+	InKubernetes    bool
+	UserspaceMode   bool
+	StateDir        string
+	AcceptDNS       bool
+	KubeSecret      string
+	SOCKSProxyAddr  string
+	HTTPProxyAddr   string
+	Socket          string
+	AuthOnce        bool
+}
+
+// defaultEnv returns the value of the given envvar name, or defVal if
+// unset.
+func defaultEnv(name, defVal string) string {
+	if v := os.Getenv(name); v != "" {
+		return v
+	}
+	return defVal
+}
+
+// defaultBool returns the boolean value of the given envvar name, or
+// defVal if unset or not a bool.
+func defaultBool(name string, defVal bool) bool {
+	v := os.Getenv(name)
+	ret, err := strconv.ParseBool(v)
+	if err != nil {
+		return defVal
+	}
+	return ret
+}
--- a/docs/k8s/proxy.yaml
+++ b/docs/k8s/proxy.yaml
@ -41,6 +41,8 @@ spec:
          optional: true
    - name: TS_DEST_IP
      value: "{{TS_DEST_IP}}"
+    - name: TS_AUTH_ONCE
+      value: "true"
    securityContext:
      capabilities:
        add:
--- a/docs/k8s/run.sh
+++ b/docs/k8s/run.sh
@ -1,93 +0,0 @@
-# Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
-# Use of this source code is governed by a BSD-style
-# license that can be found in the LICENSE file.
-
-#! /bin/sh
-
-export PATH=$PATH:/tailscale/bin
-
-TS_AUTH_KEY="${TS_AUTH_KEY:-}"
-TS_ROUTES="${TS_ROUTES:-}"
-TS_DEST_IP="${TS_DEST_IP:-}"
-TS_EXTRA_ARGS="${TS_EXTRA_ARGS:-}"
-TS_USERSPACE="${TS_USERSPACE:-true}"
-TS_STATE_DIR="${TS_STATE_DIR:-}"
-TS_ACCEPT_DNS="${TS_ACCEPT_DNS:-false}"
-TS_KUBE_SECRET="${TS_KUBE_SECRET:-tailscale}"
-TS_SOCKS5_SERVER="${TS_SOCKS5_SERVER:-}"
-TS_OUTBOUND_HTTP_PROXY_LISTEN="${TS_OUTBOUND_HTTP_PROXY_LISTEN:-}"
-TS_TAILSCALED_EXTRA_ARGS="${TS_TAILSCALED_EXTRA_ARGS:-}"
-TS_SOCKET="${TS_SOCKET:-/tmp/tailscaled.sock}"
-
-set -e
-
-TAILSCALED_ARGS="--socket=${TS_SOCKET}"
-
-if [[ ! -z "${KUBERNETES_SERVICE_HOST}" ]]; then
-  TAILSCALED_ARGS="${TAILSCALED_ARGS} --state=kube:${TS_KUBE_SECRET} --statedir=${TS_STATE_DIR:-/tmp}"
-elif [[ ! -z "${TS_STATE_DIR}" ]]; then
-  TAILSCALED_ARGS="${TAILSCALED_ARGS} --statedir=${TS_STATE_DIR}"
-else
-  TAILSCALED_ARGS="${TAILSCALED_ARGS} --state=mem: --statedir=/tmp"
-fi
-
-if [[ "${TS_USERSPACE}" == "true" ]]; then
-  if [[ ! -z "${TS_DEST_IP}" ]]; then
-    echo "IP forwarding is not supported in userspace mode"
-    exit 1
-  fi
-  TAILSCALED_ARGS="${TAILSCALED_ARGS} --tun=userspace-networking"
-else
-  if [[ ! -d /dev/net ]]; then
-    mkdir -p /dev/net
-  fi
-
-  if [[ ! -c /dev/net/tun ]]; then
-    mknod /dev/net/tun c 10 200
-  fi
-fi
-
-if [[ ! -z "${TS_SOCKS5_SERVER}" ]]; then
-  TAILSCALED_ARGS="${TAILSCALED_ARGS} --socks5-server ${TS_SOCKS5_SERVER}"
-fi
-
-if [[ ! -z "${TS_OUTBOUND_HTTP_PROXY_LISTEN}" ]]; then
-  TAILSCALED_ARGS="${TAILSCALED_ARGS} --outbound-http-proxy-listen ${TS_OUTBOUND_HTTP_PROXY_LISTEN}"
-fi
-
-if [[ ! -z "${TS_TAILSCALED_EXTRA_ARGS}" ]]; then
-  TAILSCALED_ARGS="${TAILSCALED_ARGS} ${TS_TAILSCALED_EXTRA_ARGS}"
-fi
-
-handler() {
-  echo "Caught SIGINT/SIGTERM, shutting down tailscaled"
-  kill -s SIGINT $PID
-  wait ${PID}
-}
-
-echo "Starting tailscaled"
-tailscaled ${TAILSCALED_ARGS} &
-PID=$!
-trap handler SIGINT SIGTERM
-
-UP_ARGS="--accept-dns=${TS_ACCEPT_DNS}"
-if [[ ! -z "${TS_ROUTES}" ]]; then
-  UP_ARGS="--advertise-routes=${TS_ROUTES} ${UP_ARGS}"
-fi
-if [[ ! -z "${TS_AUTH_KEY}" ]]; then
-  UP_ARGS="--authkey=${TS_AUTH_KEY} ${UP_ARGS}"
-fi
-if [[ ! -z "${TS_EXTRA_ARGS}" ]]; then
-  UP_ARGS="${UP_ARGS} ${TS_EXTRA_ARGS:-}"
-fi
-
-echo "Running tailscale up"
-tailscale --socket="${TS_SOCKET}" up ${UP_ARGS}
-
-if [[ ! -z "${TS_DEST_IP}" ]]; then
-  echo "Adding iptables rule for DNAT"
-  iptables -t nat -I PREROUTING -d "$(tailscale --socket=${TS_SOCKET} ip -4)" -j DNAT --to-destination "${TS_DEST_IP}"
-fi
-
-echo "Waiting for tailscaled to exit"
-wait ${PID}
--- a/go.mod
+++ b/go.mod
@ -180,6 +180,7 @@ require (
 	github.com/jirfag/go-printf-func-name v0.0.0-20200119135958-7558a9eaa5af // indirect
 	github.com/jmespath/go-jmespath v0.4.0 // indirect
 	github.com/josharian/native v1.0.0 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/julz/importas v0.0.0-20210922140945-27e0a5d4dee2 // indirect
 	github.com/kevinburke/ssh_config v1.1.0 // indirect
 	github.com/kisielk/errcheck v1.6.0 // indirect
@ -213,6 +214,7 @@ require (
 	github.com/nishanths/exhaustive v0.7.11 // indirect
 	github.com/nishanths/predeclared v0.2.1 // indirect
 	github.com/olekukonko/tablewriter v0.0.5 // indirect
+	github.com/onsi/gomega v1.20.1 // indirect
 	github.com/opencontainers/go-digest v1.0.0 // indirect
 	github.com/opencontainers/image-spec v1.0.3-0.20220114050600-8b9d41f48198 // indirect
 	github.com/pelletier/go-toml v1.9.4 // indirect
@ -246,8 +248,8 @@ require (
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/spf13/viper v1.9.0 // indirect
 	github.com/ssgreg/nlreturn/v2 v2.2.1 // indirect
-	github.com/stretchr/objx v0.3.0 // indirect
-	github.com/stretchr/testify v1.7.0 // indirect
+	github.com/stretchr/objx v0.4.0 // indirect
+	github.com/stretchr/testify v1.8.0 // indirect
 	github.com/subosito/gotenv v1.2.0 // indirect
 	github.com/sylvia7788/contextcheck v1.0.4 // indirect
 	github.com/tdakkota/asciicheck v0.1.1 // indirect
@ -273,7 +275,7 @@ require (
 	gopkg.in/ini.v1 v1.66.2 // indirect
 	gopkg.in/warnings.v0 v0.1.2 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
-	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 	howett.net/plist v1.0.0 // indirect
 	mvdan.cc/gofumpt v0.2.0 // indirect
 	mvdan.cc/interfacer v0.0.0-20180901003855-c20040233aed // indirect
--- a/go.sum
+++ b/go.sum
@ -661,8 +661,9 @@ github.com/json-iterator/go v1.1.6/go.mod h1:+SdeFBvtyEkXs7REEP0seUULqWtbJapLOCV
 github.com/json-iterator/go v1.1.7/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
 github.com/json-iterator/go v1.1.9/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
 github.com/json-iterator/go v1.1.10/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
-github.com/json-iterator/go v1.1.11 h1:uVUAXhF2To8cbw/3xN3pxj6kk7TYKs98NIrTqPlMWAQ=
 github.com/json-iterator/go v1.1.11/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
+github.com/json-iterator/go v1.1.12 h1:PV8peI4a0ysnczrg+LtxykD8LfKY9ML6u2jnxaEnrnM=
+github.com/json-iterator/go v1.1.12/go.mod h1:e30LSqwooZae/UwlEbR2852Gd8hjQvJoHmT4TnhNGBo=
 github.com/jstemmer/go-junit-report v0.0.0-20190106144839-af01ea7f8024/go.mod h1:6v2b51hI/fHJwM22ozAgKL4VKDeJcHhJFhtBdhmNjmU=
 github.com/jstemmer/go-junit-report v0.9.1/go.mod h1:Brl9GWCQeLvo8nXZwPNNblvFj/XSXhF0NWZEnDohbsk=
 github.com/jtolds/gls v4.20.0+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
@ -832,8 +833,9 @@ github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421/go.mod h1:6dJ
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd h1:TRLaZ9cD/w8PVh93nsPXa1VrQ6jlwL5oN8l14QlcNfg=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/reflect2 v0.0.0-20180701023420-4b7aa43c6742/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
-github.com/modern-go/reflect2 v1.0.1 h1:9f412s+6RmYXLWZSEzVVgPGK7C2PphHj5RJrvfx9AWI=
 github.com/modern-go/reflect2 v1.0.1/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
+github.com/modern-go/reflect2 v1.0.2 h1:xBagoLtFs94CBntxluKeaWgTMpvLxC4ur3nMaC9Gz0M=
+github.com/modern-go/reflect2 v1.0.2/go.mod h1:yWuevngMOJpCy52FWWMvUC8ws7m/LJsjYzDa0/r8luk=
 github.com/mohae/deepcopy v0.0.0-20170929034955-c48cc78d4826/go.mod h1:TaXosZuwdSHYgviHp1DAtfrULt5eUgsSMsZf+YrPgl8=
 github.com/moricho/tparallel v0.2.1 h1:95FytivzT6rYzdJLdtfn6m1bfFJylOJK41+lgv/EHf4=
 github.com/moricho/tparallel v0.2.1/go.mod h1:fXEIZxG2vdfl0ZF8b42f5a78EhjjD5mX8qUplsoSU4k=
@ -878,8 +880,9 @@ github.com/onsi/gomega v1.7.1/go.mod h1:XdKZgCCFLUoM/7CFJVPcG8C1xQ1AJ0vpAezJrB7J
 github.com/onsi/gomega v1.10.1/go.mod h1:iN09h71vgCQne3DLsj+A5owkum+a2tYe+TOCB1ybHNo=
 github.com/onsi/gomega v1.10.2/go.mod h1:iN09h71vgCQne3DLsj+A5owkum+a2tYe+TOCB1ybHNo=
 github.com/onsi/gomega v1.16.0/go.mod h1:HnhC7FXeEQY45zxNK3PPoIUhzk/80Xly9PcubAlGdZY=
-github.com/onsi/gomega v1.17.0 h1:9Luw4uT5HTjHTN8+aNcSThgH1vdXnmdJ8xIfZ4wyTRE=
 github.com/onsi/gomega v1.17.0/go.mod h1:HnhC7FXeEQY45zxNK3PPoIUhzk/80Xly9PcubAlGdZY=
+github.com/onsi/gomega v1.20.1 h1:PA/3qinGoukvymdIDV8pii6tiZgC8kbmJO6Z5+b002Q=
+github.com/onsi/gomega v1.20.1/go.mod h1:DtrZpjmvpn2mPm4YWQa0/ALMDj9v4YxLgojwPeREyVo=
 github.com/op/go-logging v0.0.0-20160315200505-970db520ece7/go.mod h1:HzydrMdWErDVzsI23lYNej1Htcns9BCg93Dk0bBINWk=
 github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8Oi/yOhh5U=
 github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=
@ -1065,8 +1068,9 @@ github.com/ssgreg/nlreturn/v2 v2.2.1 h1:X4XDI7jstt3ySqGU86YGAURbxw3oTDPK9sPEi6YE
 github.com/ssgreg/nlreturn/v2 v2.2.1/go.mod h1:E/iiPB78hV7Szg2YfRgyIrk1AD6JVMTRkkxBiELzh2I=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.3.0 h1:NGXK3lHquSN08v5vWalVI/L8XU9hdzE/G6xsrze47As=
 github.com/stretchr/objx v0.3.0/go.mod h1:qt09Ya8vawLte6SNmTgCsAVtYtaKzEcn8ATUoHMkEqE=
+github.com/stretchr/objx v0.4.0 h1:M2gUjqZET1qApGOWNSnZ49BAIMX4F/1plDv3+l31EJ4=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/testify v0.0.0-20170130113145-4d4bfba8f1d1/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.1.4/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
@ -1074,8 +1078,10 @@ github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UV
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/subosito/gotenv v1.2.0 h1:Slr1R9HxAlEKefgq5jn9U+DnETlIUa6HfgEzj0g5d7s=
 github.com/subosito/gotenv v1.2.0/go.mod h1:N0PQaV/YGNqwC0u51sEeR/aUtSLEXKX9iv69rRypqCw=
 github.com/sylvia7788/contextcheck v1.0.4 h1:MsiVqROAdr0efZc/fOCt0c235qm9XJqHtWwM+2h2B04=
@ -1819,8 +1825,9 @@ gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
 gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gotest.tools/v3 v3.0.3 h1:4AuOwCGf4lLR9u3YOe2awrHygurzhO/HeQ6laiA6Sx0=
 gvisor.dev/gvisor v0.0.0-20220817001344-846276b3dbc5 h1:cv/zaNV0nr1mJzaeo4S5mHIm5va1W0/9J3/5prlsuRM=
 gvisor.dev/gvisor v0.0.0-20220817001344-846276b3dbc5/go.mod h1:TIvkJD0sxe8pIob3p6T8IzxXunlp6yfgktvTNp+DGNM=