tailscale/logpolicy/logpolicy.go

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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package logpolicy manages the creation or reuse of logtail loggers,
// caching collection instance state on disk for use on future runs of
// programs on the same machine.
package logpolicy
import (
"bufio"
"bytes"
"context"
"crypto/tls"
"encoding/json"
"errors"
"fmt"
"io"
"log"
"net"
"net/http"
"net/url"
"os"
"os/exec"
"path/filepath"
"runtime"
"strings"
"sync"
"time"
"golang.org/x/term"
"tailscale.com/atomicfile"
"tailscale.com/envknob"
"tailscale.com/log/filelogger"
"tailscale.com/logtail"
"tailscale.com/logtail/filch"
"tailscale.com/net/dnscache"
"tailscale.com/net/dnsfallback"
"tailscale.com/net/netknob"
"tailscale.com/net/netns"
"tailscale.com/net/tlsdial"
"tailscale.com/net/tshttpproxy"
"tailscale.com/paths"
"tailscale.com/safesocket"
"tailscale.com/smallzstd"
"tailscale.com/types/logger"
"tailscale.com/types/logid"
"tailscale.com/util/clientmetric"
"tailscale.com/util/must"
"tailscale.com/util/racebuild"
"tailscale.com/util/winutil"
"tailscale.com/version"
"tailscale.com/version/distro"
)
var getLogTargetOnce struct {
sync.Once
v string // URL of logs server, or empty for default
}
func getLogTarget() string {
getLogTargetOnce.Do(func() {
if val, ok := os.LookupEnv("TS_LOG_TARGET"); ok {
getLogTargetOnce.v = val
} else {
if runtime.GOOS == "windows" {
getLogTargetOnce.v = winutil.GetRegString("LogTarget", "")
}
}
})
return getLogTargetOnce.v
}
// LogURL is the base URL for the configured logtail server, or the default.
// It is guaranteed to not terminate with any forward slashes.
func LogURL() string {
if v := getLogTarget(); v != "" {
return strings.TrimRight(v, "/")
}
return "https://" + logtail.DefaultHost
}
// LogHost returns the hostname only (without port) of the configured
// logtail server, or the default.
//
// Deprecated: Use LogURL instead.
func LogHost() string {
if v := getLogTarget(); v != "" {
if u, err := url.Parse(v); err == nil {
return u.Hostname()
}
}
return logtail.DefaultHost
}
// Config represents an instance of logs in a collection.
type Config struct {
Collection string
PrivateID logid.PrivateID
PublicID logid.PublicID
}
// Policy is a logger and its public ID.
type Policy struct {
// Logtail is the logger.
Logtail *logtail.Logger
// PublicID is the logger's instance identifier.
PublicID logid.PublicID
}
// NewConfig creates a Config with collection and a newly generated PrivateID.
func NewConfig(collection string) *Config {
id := must.Get(logid.NewPrivateID())
return &Config{
Collection: collection,
PrivateID: id,
PublicID: id.Public(),
}
}
// Validate verifies that the Config matches the collection,
// and that the PrivateID and PublicID pair are sensible.
func (c *Config) Validate(collection string) error {
switch {
case c == nil:
return errors.New("config is nil")
case c.Collection != collection:
return fmt.Errorf("config collection %q does not match %q", c.Collection, collection)
case c.PrivateID.IsZero():
return errors.New("config has zero PrivateID")
case c.PrivateID.Public() != c.PublicID:
return errors.New("config PrivateID does not match PublicID")
}
return nil
}
// ToBytes returns the JSON representation of c.
func (c *Config) ToBytes() []byte {
data, err := json.MarshalIndent(c, "", "\t")
if err != nil {
log.Fatalf("logpolicy.Config marshal: %v", err)
}
return data
}
// Save writes the JSON representation of c to stateFile.
func (c *Config) Save(stateFile string) error {
c.PublicID = c.PrivateID.Public()
if err := os.MkdirAll(filepath.Dir(stateFile), 0750); err != nil {
return err
}
data := c.ToBytes()
if err := atomicfile.WriteFile(stateFile, data, 0600); err != nil {
return err
}
return nil
}
// ConfigFromFile reads a Config from a JSON file.
func ConfigFromFile(statefile string) (*Config, error) {
b, err := os.ReadFile(statefile)
if err != nil {
return nil, err
}
return ConfigFromBytes(b)
}
// ConfigFromBytes parses a Config from its JSON encoding.
func ConfigFromBytes(jsonEnc []byte) (*Config, error) {
c := &Config{}
if err := json.Unmarshal(jsonEnc, c); err != nil {
return nil, err
}
return c, nil
}
// stderrWriter is an io.Writer that always writes to the latest
// os.Stderr, even if os.Stderr changes during the lifetime of the
// stderrWriter value.
type stderrWriter struct{}
func (stderrWriter) Write(buf []byte) (int, error) {
return os.Stderr.Write(buf)
}
type logWriter struct {
logger *log.Logger
}
func (l logWriter) Write(buf []byte) (int, error) {
l.logger.Printf("%s", buf)
return len(buf), nil
}
// LogsDir returns the directory to use for log configuration and
// buffer storage.
func LogsDir(logf logger.Logf) string {
if d := os.Getenv("TS_LOGS_DIR"); d != "" {
fi, err := os.Stat(d)
if err == nil && fi.IsDir() {
return d
}
}
switch runtime.GOOS {
case "windows":
if version.CmdName() == "tailscaled" {
// In the common case, when tailscaled is run as the Local System (as a service),
// we want to use %ProgramData% (C:\ProgramData\Tailscale), aside the
// system state config with the machine key, etc. But if that directory's
// not accessible, then it's probably because the user is running tailscaled
// as a regular user (perhaps in userspace-networking/SOCK5 mode) and we should
// just use the %LocalAppData% instead. In a user context, %LocalAppData% isn't
// subject to random deletions from Windows system updates.
dir := filepath.Join(os.Getenv("ProgramData"), "Tailscale")
if winProgramDataAccessible(dir) {
logf("logpolicy: using dir %v", dir)
return dir
}
}
dir := filepath.Join(os.Getenv("LocalAppData"), "Tailscale")
logf("logpolicy: using LocalAppData dir %v", dir)
return dir
case "linux":
// STATE_DIRECTORY is set by systemd 240+ but we support older
// systems-d. For example, Ubuntu 18.04 (Bionic Beaver) is 237.
systemdStateDir := os.Getenv("STATE_DIRECTORY")
if systemdStateDir != "" {
logf("logpolicy: using $STATE_DIRECTORY, %q", systemdStateDir)
return systemdStateDir
}
}
// Default to e.g. /var/lib/tailscale or /var/db/tailscale on Unix.
if d := paths.DefaultTailscaledStateFile(); d != "" {
d = filepath.Dir(d) // directory of e.g. "/var/lib/tailscale/tailscaled.state"
if err := os.MkdirAll(d, 0700); err == nil {
logf("logpolicy: using system state directory %q", d)
return d
}
}
cacheDir, err := os.UserCacheDir()
if err == nil {
d := filepath.Join(cacheDir, "Tailscale")
logf("logpolicy: using UserCacheDir, %q", d)
return d
}
// Use the current working directory, unless we're being run by a
// service manager that sets it to /.
wd, err := os.Getwd()
if err == nil && wd != "/" {
logf("logpolicy: using current directory, %q", wd)
return wd
}
// No idea where to put stuff. Try to create a temp dir. It'll
// mean we might lose some logs and rotate through log IDs, but
// it's something.
tmp, err := os.MkdirTemp("", "tailscaled-log-*")
if err != nil {
panic("no safe place found to store log state")
}
logf("logpolicy: using temp directory, %q", tmp)
return tmp
}
// runningUnderSystemd reports whether we're running under systemd.
func runningUnderSystemd() bool {
if runtime.GOOS == "linux" && os.Getppid() == 1 {
slurp, _ := os.ReadFile("/proc/1/stat")
return bytes.HasPrefix(slurp, []byte("1 (systemd) "))
}
return false
}
func redirectStderrToLogPanics() bool {
return runningUnderSystemd() || envknob.Bool("TS_PLEASE_PANIC")
}
// winProgramDataAccessible reports whether the directory (assumed to
// be a Windows %ProgramData% directory) is accessible to the current
// process. It's created if needed.
func winProgramDataAccessible(dir string) bool {
if err := os.MkdirAll(dir, 0700); err != nil {
// TODO: windows ACLs
return false
}
// The C:\ProgramData\Tailscale directory should be locked down
// by with ACLs to only be readable by the local system so a
// regular user shouldn't be able to do this operation:
if _, err := os.ReadDir(dir); err != nil {
return false
}
return true
}
// tryFixLogStateLocation is a temporary fixup for
// https://github.com/tailscale/tailscale/issues/247 . We accidentally
// wrote logging state files to /, and then later to $CACHE_DIRECTORY
// (which is incorrect because the log ID is not reconstructible if
// deleted - it's state, not cache data).
//
// If log state for cmdname exists in / or $CACHE_DIRECTORY, and no
// log state for that command exists in dir, then the log state is
// moved from wherever it does exist, into dir. Leftover logs state
// in / and $CACHE_DIRECTORY is deleted.
func tryFixLogStateLocation(dir, cmdname string) {
switch runtime.GOOS {
case "linux", "freebsd", "openbsd":
// These are the OSes where we might have written stuff into
// root. Others use different logic to find the logs storage
// dir.
default:
return
}
if cmdname == "" {
log.Printf("[unexpected] no cmdname given to tryFixLogStateLocation, please file a bug at https://github.com/tailscale/tailscale")
return
}
if dir == "/" {
// Trying to store things in / still. That's a bug, but don't
// abort hard.
log.Printf("[unexpected] storing logging config in /, please file a bug at https://github.com/tailscale/tailscale")
return
}
if os.Getuid() != 0 {
// Only root could have written log configs to weird places.
return
}
// We stored logs in 2 incorrect places: either /, or CACHE_DIR
// (aka /var/cache/tailscale). We want to move files into the
// provided dir, preferring those in CACHE_DIR over those in / if
// both exist. If files already exist in dir, don't
// overwrite. Finally, once we've maybe moved files around, we
// want to delete leftovers in / and CACHE_DIR, to clean up after
// our past selves.
files := []string{
fmt.Sprintf("%s.log.conf", cmdname),
fmt.Sprintf("%s.log1.txt", cmdname),
fmt.Sprintf("%s.log2.txt", cmdname),
}
// checks if any of the files above exist in d.
checkExists := func(d string) (bool, error) {
for _, file := range files {
p := filepath.Join(d, file)
_, err := os.Stat(p)
if os.IsNotExist(err) {
continue
} else if err != nil {
return false, fmt.Errorf("stat %q: %w", p, err)
}
return true, nil
}
return false, nil
}
// move files from d into dir, if they exist.
moveFiles := func(d string) error {
for _, file := range files {
src := filepath.Join(d, file)
_, err := os.Stat(src)
if os.IsNotExist(err) {
continue
} else if err != nil {
return fmt.Errorf("stat %q: %v", src, err)
}
dst := filepath.Join(dir, file)
bs, err := exec.Command("mv", src, dst).CombinedOutput()
if err != nil {
return fmt.Errorf("mv %q %q: %v (%s)", src, dst, err, bs)
}
}
return nil
}
existsInRoot, err := checkExists("/")
if err != nil {
log.Printf("checking for configs in /: %v", err)
return
}
existsInCache := false
cacheDir := os.Getenv("CACHE_DIRECTORY")
if cacheDir != "" {
existsInCache, err = checkExists("/var/cache/tailscale")
if err != nil {
log.Printf("checking for configs in %s: %v", cacheDir, err)
}
}
existsInDest, err := checkExists(dir)
if err != nil {
log.Printf("checking for configs in %s: %v", dir, err)
return
}
switch {
case !existsInRoot && !existsInCache:
// No leftover files, nothing to do.
return
case existsInDest:
// Already have "canonical" configs, just delete any remnants
// (below).
case existsInCache:
// CACHE_DIRECTORY takes precedence over /, move files from
// there.
if err := moveFiles(cacheDir); err != nil {
log.Print(err)
return
}
case existsInRoot:
// Files from root is better than nothing.
if err := moveFiles("/"); err != nil {
log.Print(err)
return
}
}
// If moving succeeded, or we didn't need to move files, try to
// delete any leftover files, but it's okay if we can't delete
// them for some reason.
dirs := []string{}
if existsInCache {
dirs = append(dirs, cacheDir)
}
if existsInRoot {
dirs = append(dirs, "/")
}
for _, d := range dirs {
for _, file := range files {
p := filepath.Join(d, file)
_, err := os.Stat(p)
if os.IsNotExist(err) {
continue
} else if err != nil {
log.Printf("stat %q: %v", p, err)
return
}
if err := os.Remove(p); err != nil {
log.Printf("rm %q: %v", p, err)
}
}
}
}
// New returns a new log policy (a logger and its instance ID) for a
// given collection name.
func New(collection string) *Policy {
return NewWithConfigPath(collection, "", "")
}
// NewWithConfigPath is identical to New,
// but uses the specified directory and command name.
// If either is empty, it derives them automatically.
func NewWithConfigPath(collection, dir, cmdName string) *Policy {
var lflags int
if term.IsTerminal(2) || runtime.GOOS == "windows" {
lflags = 0
} else {
lflags = log.LstdFlags
}
if envknob.Bool("TS_DEBUG_LOG_TIME") {
lflags = log.LstdFlags | log.Lmicroseconds
}
if runningUnderSystemd() {
// If journalctl is going to prepend its own timestamp
// anyway, no need to add one.
lflags = 0
}
console := log.New(stderrWriter{}, "", lflags)
var earlyErrBuf bytes.Buffer
earlyLogf := func(format string, a ...any) {
fmt.Fprintf(&earlyErrBuf, format, a...)
earlyErrBuf.WriteByte('\n')
}
if dir == "" {
dir = LogsDir(earlyLogf)
}
if cmdName == "" {
cmdName = version.CmdName()
}
tryFixLogStateLocation(dir, cmdName)
cfgPath := filepath.Join(dir, fmt.Sprintf("%s.log.conf", cmdName))
if runtime.GOOS == "windows" {
switch cmdName {
case "tailscaled":
// Tailscale 1.14 and before stored state under %LocalAppData%
// (usually "C:\WINDOWS\system32\config\systemprofile\AppData\Local"
// when tailscaled.exe is running as a non-user system service).
// However it is frequently cleared for almost any reason: Windows
// updates, System Restore, even various System Cleaner utilities.
//
// The Windows service previously ran as tailscale-ipn.exe, so
// machines which ran very old versions might still have their
// log conf named %LocalAppData%\tailscale-ipn.log.conf
//
// Machines which started using Tailscale more recently will have
// %LocalAppData%\tailscaled.log.conf
//
// Attempt to migrate the log conf to C:\ProgramData\Tailscale
oldDir := filepath.Join(os.Getenv("LocalAppData"), "Tailscale")
oldPath := filepath.Join(oldDir, "tailscaled.log.conf")
if fi, err := os.Stat(oldPath); err != nil || !fi.Mode().IsRegular() {
// *Only* if tailscaled.log.conf does not exist,
// check for tailscale-ipn.log.conf
oldPathOldCmd := filepath.Join(oldDir, "tailscale-ipn.log.conf")
if fi, err := os.Stat(oldPathOldCmd); err == nil && fi.Mode().IsRegular() {
oldPath = oldPathOldCmd
}
}
cfgPath = paths.TryConfigFileMigration(earlyLogf, oldPath, cfgPath)
case "tailscale-ipn":
for _, oldBase := range []string{"wg64.log.conf", "wg32.log.conf"} {
oldConf := filepath.Join(dir, oldBase)
if fi, err := os.Stat(oldConf); err == nil && fi.Mode().IsRegular() {
cfgPath = paths.TryConfigFileMigration(earlyLogf, oldConf, cfgPath)
break
}
}
}
}
newc, err := ConfigFromFile(cfgPath)
if err != nil {
earlyLogf("logpolicy.ConfigFromFile %v: %v", cfgPath, err)
}
if err := newc.Validate(collection); err != nil {
earlyLogf("logpolicy.Config.Validate for %v: %v", cfgPath, err)
newc = NewConfig(collection)
if err := newc.Save(cfgPath); err != nil {
earlyLogf("logpolicy.Config.Save for %v: %v", cfgPath, err)
}
}
conf := logtail.Config{
Collection: newc.Collection,
PrivateID: newc.PrivateID,
Stderr: logWriter{console},
NewZstdEncoder: func() logtail.Encoder {
w, err := smallzstd.NewEncoder(nil)
if err != nil {
panic(err)
}
return w
},
HTTPC: &http.Client{Transport: NewLogtailTransport(logtail.DefaultHost)},
}
if collection == logtail.CollectionNode {
conf.MetricsDelta = clientmetric.EncodeLogTailMetricsDelta
conf.IncludeProcID = true
conf.IncludeProcSequence = true
}
if envknob.NoLogsNoSupport() {
log.Println("You have disabled logging. Tailscale will not be able to provide support.")
conf.HTTPC = &http.Client{Transport: noopPretendSuccessTransport{}}
} else if val := getLogTarget(); val != "" {
log.Println("You have enabled a non-default log target. Doing without being told to by Tailscale staff or your network administrator will make getting support difficult.")
conf.BaseURL = val
u, _ := url.Parse(val)
conf.HTTPC = &http.Client{Transport: NewLogtailTransport(u.Host)}
}
filchOptions := filch.Options{
ReplaceStderr: redirectStderrToLogPanics(),
}
filchPrefix := filepath.Join(dir, cmdName)
// NAS disks cannot hibernate if we're writing logs to them all the time.
// https://github.com/tailscale/tailscale/issues/3551
if runtime.GOOS == "linux" && (distro.Get() == distro.Synology || distro.Get() == distro.QNAP) {
tmpfsLogs := "/tmp/tailscale-logs"
if err := os.MkdirAll(tmpfsLogs, 0755); err == nil {
filchPrefix = filepath.Join(tmpfsLogs, cmdName)
filchOptions.MaxFileSize = 1 << 20
} else {
// not a fatal error, we can leave the log files on the spinning disk
log.Printf("Unable to create /tmp directory for log storage: %v\n", err)
}
}
filchBuf, filchErr := filch.New(filchPrefix, filchOptions)
if filchBuf != nil {
conf.Buffer = filchBuf
if filchBuf.OrigStderr != nil {
conf.Stderr = filchBuf.OrigStderr
}
}
lw := logtail.NewLogger(conf, log.Printf)
var logOutput io.Writer = lw
if runtime.GOOS == "windows" && conf.Collection == logtail.CollectionNode {
logID := newc.PublicID.String()
exe, _ := os.Executable()
if strings.EqualFold(filepath.Base(exe), "tailscaled.exe") {
diskLogf := filelogger.New("tailscale-service", logID, lw.Logf)
logOutput = logger.FuncWriter(diskLogf)
}
}
log.SetFlags(0) // other log flags are set on console, not here
log.SetOutput(logOutput)
log.Printf("Program starting: v%v, Go %v: %#v",
version.Long(),
goVersion(),
os.Args)
log.Printf("LogID: %v", newc.PublicID)
if filchErr != nil {
log.Printf("filch failed: %v", filchErr)
}
if earlyErrBuf.Len() != 0 {
log.Printf("%s", earlyErrBuf.Bytes())
}
return &Policy{
Logtail: lw,
PublicID: newc.PublicID,
}
}
// dialLog is used by NewLogtailTransport to log the happy path of its
// own dialing.
//
// By default it goes nowhere and is only enabled when
// tailscaled's in verbose mode.
//
// log.Printf isn't used so its own logs don't loop back into logtail
// in the happy path, thus generating more logs.
var dialLog = log.New(io.Discard, "logtail: ", log.LstdFlags|log.Lmsgprefix)
// SetVerbosityLevel controls the verbosity level that should be
// written to stderr. 0 is the default (not verbose). Levels 1 or higher
// are increasingly verbose.
//
// It should not be changed concurrently with log writes.
func (p *Policy) SetVerbosityLevel(level int) {
p.Logtail.SetVerbosityLevel(level)
if level > 0 {
dialLog.SetOutput(os.Stderr)
}
}
// Close immediately shuts down the logger.
func (p *Policy) Close() {
ctx, cancel := context.WithCancel(context.Background())
cancel()
p.Shutdown(ctx)
}
// Shutdown gracefully shuts down the logger, finishing any current
// log upload if it can be done before ctx is canceled.
func (p *Policy) Shutdown(ctx context.Context) error {
if p.Logtail != nil {
log.Printf("flushing log.")
return p.Logtail.Shutdown(ctx)
}
return nil
}
// NewLogtailTransport returns an HTTP Transport particularly suited to uploading
// logs to the given host name. This includes:
// - If DNS lookup fails, consult the bootstrap DNS list of Tailscale hostnames.
// - If TLS connection fails, try again using LetsEncrypt's built-in root certificate,
// for the benefit of older OS platforms which might not include it.
func NewLogtailTransport(host string) *http.Transport {
// Start with a copy of http.DefaultTransport and tweak it a bit.
tr := http.DefaultTransport.(*http.Transport).Clone()
tr.Proxy = tshttpproxy.ProxyFromEnvironment
tshttpproxy.SetTransportGetProxyConnectHeader(tr)
// We do our own zstd compression on uploads, and responses never contain any payload,
// so don't send "Accept-Encoding: gzip" to save a few bytes on the wire, since there
// will never be any body to decompress:
tr.DisableCompression = true
// Log whenever we dial:
tr.DialContext = func(ctx context.Context, netw, addr string) (net.Conn, error) {
nd := netns.FromDialer(log.Printf, &net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: netknob.PlatformTCPKeepAlive(),
})
t0 := time.Now()
c, err := nd.DialContext(ctx, netw, addr)
d := time.Since(t0).Round(time.Millisecond)
if err == nil {
dialLog.Printf("dialed %q in %v", addr, d)
return c, nil
}
if version.IsWindowsGUI() && strings.HasPrefix(netw, "tcp") {
if c, err := safesocket.Connect(safesocket.DefaultConnectionStrategy("")); err == nil {
fmt.Fprintf(c, "CONNECT %s HTTP/1.0\r\n\r\n", addr)
br := bufio.NewReader(c)
res, err := http.ReadResponse(br, nil)
if err == nil && res.StatusCode != 200 {
err = errors.New(res.Status)
}
if err != nil {
log.Printf("logtail: CONNECT response error from tailscaled: %v", err)
c.Close()
} else {
dialLog.Printf("connected via tailscaled")
return c, nil
}
}
}
// If we failed to dial, try again with bootstrap DNS.
log.Printf("logtail: dial %q failed: %v (in %v), trying bootstrap...", addr, err, d)
dnsCache := &dnscache.Resolver{
Forward: dnscache.Get().Forward, // use default cache's forwarder
UseLastGood: true,
LookupIPFallback: dnsfallback.Lookup,
}
dialer := dnscache.Dialer(nd.DialContext, dnsCache)
c, err = dialer(ctx, netw, addr)
if err == nil {
log.Printf("logtail: bootstrap dial succeeded")
}
return c, err
}
// We're contacting exactly 1 hostname, so the default's 100
// max idle conns is very high for our needs. Even 2 is
// probably double what we need:
tr.MaxIdleConns = 2
// Provide knob to force HTTP/1 for log uploads.
// TODO(bradfitz): remove this debug knob once we've decided
// to upload via HTTP/1 or HTTP/2 (probably HTTP/1). Or we might just enforce
// it server-side.
if envknob.Bool("TS_DEBUG_FORCE_H1_LOGS") {
tr.TLSClientConfig = nil // DefaultTransport's was already initialized w/ h2
tr.ForceAttemptHTTP2 = false
tr.TLSNextProto = map[string]func(authority string, c *tls.Conn) http.RoundTripper{}
}
tr.TLSClientConfig = tlsdial.Config(host, tr.TLSClientConfig)
return tr
}
func goVersion() string {
v := strings.TrimPrefix(runtime.Version(), "go")
if racebuild.On {
return v + "-race"
}
return v
}
type noopPretendSuccessTransport struct{}
func (noopPretendSuccessTransport) RoundTrip(req *http.Request) (*http.Response, error) {
io.ReadAll(req.Body)
req.Body.Close()
return &http.Response{
StatusCode: 200,
Status: "200 OK",
}, nil
}