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tailscale/envknob/envknob.go

447 lines
12 KiB
Go

// 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.
// Package envknob provides access to environment-variable tweakable
// debug settings.
//
// These are primarily knobs used by Tailscale developers during
// development or by users when instructed to by Tailscale developers
// when debugging something. They are not a stable interface and may
// be removed or any time.
//
// A related package, control/controlknobs, are knobs that can be
// changed at runtime by the control plane. Sometimes both are used:
// an envknob for the default/explicit value, else falling back
// to the controlknob value.
package envknob
import (
"bufio"
"fmt"
"io"
"log"
"os"
"path/filepath"
"runtime"
"sort"
"strconv"
"strings"
"sync"
"sync/atomic"
"tailscale.com/types/opt"
"tailscale.com/version"
"tailscale.com/version/distro"
)
var (
mu sync.Mutex
set = map[string]string{}
regStr = map[string]*string{}
regBool = map[string]*bool{}
regOptBool = map[string]*opt.Bool{}
)
func noteEnv(k, v string) {
mu.Lock()
defer mu.Unlock()
noteEnvLocked(k, v)
}
func noteEnvLocked(k, v string) {
if v != "" {
set[k] = v
} else {
delete(set, k)
}
}
// logf is logger.Logf, but logger depends on envknob, so for circular
// dependency reasons, make a type alias (so it's still assignable,
// but has nice docs here).
type logf = func(format string, args ...any)
// LogCurrent logs the currently set environment knobs.
func LogCurrent(logf logf) {
mu.Lock()
defer mu.Unlock()
list := make([]string, 0, len(set))
for k := range set {
list = append(list, k)
}
sort.Strings(list)
for _, k := range list {
logf("envknob: %s=%q", k, set[k])
}
}
// Setenv changes an environment variable.
//
// It is not safe for concurrent reading of environment variables via the
// Register functions. All Setenv calls are meant to happen early in main before
// any goroutines are started.
func Setenv(envVar, val string) {
mu.Lock()
defer mu.Unlock()
os.Setenv(envVar, val)
noteEnvLocked(envVar, val)
if p := regStr[envVar]; p != nil {
*p = val
}
if p := regBool[envVar]; p != nil {
setBoolLocked(p, envVar, val)
}
if p := regOptBool[envVar]; p != nil {
setOptBoolLocked(p, envVar, val)
}
}
// String returns the named environment variable, using os.Getenv.
//
// If the variable is non-empty, it's also tracked & logged as being
// an in-use knob.
func String(envVar string) string {
v := os.Getenv(envVar)
noteEnv(envVar, v)
return v
}
// RegisterString returns a func that gets the named environment variable,
// without a map lookup per call. It assumes that mutations happen via
// envknob.Setenv.
func RegisterString(envVar string) func() string {
mu.Lock()
defer mu.Unlock()
p, ok := regStr[envVar]
if !ok {
val := os.Getenv(envVar)
if val != "" {
noteEnvLocked(envVar, val)
}
p = &val
regStr[envVar] = p
}
return func() string { return *p }
}
// RegisterBool returns a func that gets the named environment variable,
// without a map lookup per call. It assumes that mutations happen via
// envknob.Setenv.
func RegisterBool(envVar string) func() bool {
mu.Lock()
defer mu.Unlock()
p, ok := regBool[envVar]
if !ok {
var b bool
p = &b
setBoolLocked(p, envVar, os.Getenv(envVar))
regBool[envVar] = p
}
return func() bool { return *p }
}
// RegisterOptBool returns a func that gets the named environment variable,
// without a map lookup per call. It assumes that mutations happen via
// envknob.Setenv.
func RegisterOptBool(envVar string) func() opt.Bool {
mu.Lock()
defer mu.Unlock()
p, ok := regOptBool[envVar]
if !ok {
var b opt.Bool
p = &b
setOptBoolLocked(p, envVar, os.Getenv(envVar))
regOptBool[envVar] = p
}
return func() opt.Bool { return *p }
}
func setBoolLocked(p *bool, envVar, val string) {
noteEnvLocked(envVar, val)
if val == "" {
*p = false
return
}
var err error
*p, err = strconv.ParseBool(val)
if err != nil {
log.Fatalf("invalid boolean environment variable %s value %q", envVar, val)
}
}
func setOptBoolLocked(p *opt.Bool, envVar, val string) {
noteEnvLocked(envVar, val)
if val == "" {
*p = ""
return
}
b, err := strconv.ParseBool(val)
if err != nil {
log.Fatalf("invalid boolean environment variable %s value %q", envVar, val)
}
p.Set(b)
}
// Bool returns the boolean value of the named environment variable.
// If the variable is not set, it returns false.
// An invalid value exits the binary with a failure.
func Bool(envVar string) bool {
return boolOr(envVar, false)
}
// BoolDefaultTrue is like Bool, but returns true by default if the
// environment variable isn't present.
func BoolDefaultTrue(envVar string) bool {
return boolOr(envVar, true)
}
func boolOr(envVar string, implicitValue bool) bool {
assertNotInInit()
val := os.Getenv(envVar)
if val == "" {
return implicitValue
}
b, err := strconv.ParseBool(val)
if err == nil {
noteEnv(envVar, strconv.FormatBool(b)) // canonicalize
return b
}
log.Fatalf("invalid boolean environment variable %s value %q", envVar, val)
panic("unreachable")
}
// LookupBool returns the boolean value of the named environment value.
// The ok result is whether a value was set.
// If the value isn't a valid int, it exits the program with a failure.
func LookupBool(envVar string) (v bool, ok bool) {
assertNotInInit()
val := os.Getenv(envVar)
if val == "" {
return false, false
}
b, err := strconv.ParseBool(val)
if err == nil {
return b, true
}
log.Fatalf("invalid boolean environment variable %s value %q", envVar, val)
panic("unreachable")
}
// OptBool is like Bool, but returns an opt.Bool, so the caller can
// distinguish between implicitly and explicitly false.
func OptBool(envVar string) opt.Bool {
assertNotInInit()
b, ok := LookupBool(envVar)
if !ok {
return ""
}
var ret opt.Bool
ret.Set(b)
return ret
}
// LookupInt returns the integer value of the named environment value.
// The ok result is whether a value was set.
// If the value isn't a valid int, it exits the program with a failure.
func LookupInt(envVar string) (v int, ok bool) {
assertNotInInit()
val := os.Getenv(envVar)
if val == "" {
return 0, false
}
v, err := strconv.Atoi(val)
if err == nil {
noteEnv(envVar, val)
return v, true
}
log.Fatalf("invalid integer environment variable %s: %v", envVar, val)
panic("unreachable")
}
// UseWIPCode is whether TAILSCALE_USE_WIP_CODE is set to permit use
// of Work-In-Progress code.
func UseWIPCode() bool { return Bool("TAILSCALE_USE_WIP_CODE") }
// CanSSHD reports whether the Tailscale SSH server is allowed to run.
//
// If disabled (when this reports false), the SSH server won't start (won't
// intercept port 22) if previously configured to do so and any attempt to
// re-enable it will result in an error.
func CanSSHD() bool { return !Bool("TS_DISABLE_SSH_SERVER") }
// CanTaildrop reports whether the Taildrop feature is allowed to function.
//
// If disabled, Taildrop won't receive files regardless of user & server config.
func CanTaildrop() bool { return !Bool("TS_DISABLE_TAILDROP") }
// SSHPolicyFile returns the path, if any, to the SSHPolicy JSON file for development.
func SSHPolicyFile() string { return String("TS_DEBUG_SSH_POLICY_FILE") }
// SSHIgnoreTailnetPolicy is whether to ignore the Tailnet SSH policy for development.
func SSHIgnoreTailnetPolicy() bool { return Bool("TS_DEBUG_SSH_IGNORE_TAILNET_POLICY") }
// TKASkipSignatureCheck is whether to skip node-key signature checking for development.
func TKASkipSignatureCheck() bool { return Bool("TS_UNSAFE_SKIP_NKS_VERIFICATION") }
// NoLogsNoSupport reports whether the client's opted out of log uploads and
// technical support.
func NoLogsNoSupport() bool {
return Bool("TS_NO_LOGS_NO_SUPPORT")
}
// SetNoLogsNoSupport enables no-logs-no-support mode.
func SetNoLogsNoSupport() {
Setenv("TS_NO_LOGS_NO_SUPPORT", "true")
}
// notInInit is set true the first time we've seen a non-init stack trace.
var notInInit atomic.Bool
func assertNotInInit() {
if notInInit.Load() {
return
}
skip := 0
for {
pc, _, _, ok := runtime.Caller(skip)
if !ok {
notInInit.Store(true)
return
}
fu := runtime.FuncForPC(pc)
if fu == nil {
return
}
name := fu.Name()
name = strings.TrimRightFunc(name, func(r rune) bool { return r >= '0' && r <= '9' })
if strings.HasSuffix(name, ".init") || strings.HasSuffix(name, ".init.") {
stack := make([]byte, 1<<10)
stack = stack[:runtime.Stack(stack, false)]
envCheckedInInitStack = stack
}
skip++
}
}
var envCheckedInInitStack []byte
// PanicIfAnyEnvCheckedInInit panics if environment variables were read during
// init.
func PanicIfAnyEnvCheckedInInit() {
if envCheckedInInitStack != nil {
panic("envknob check of called from init function: " + string(envCheckedInInitStack))
}
}
var applyDiskConfigErr error
// ApplyDiskConfigError returns the most recent result of ApplyDiskConfig.
func ApplyDiskConfigError() error { return applyDiskConfigErr }
// ApplyDiskConfig returns a platform-specific config file of environment keys/values and
// applies them. On Linux and Unix operating systems, it's a no-op and always returns nil.
// If no platform-specific config file is found, it also returns nil.
//
// It exists primarily for Windows to make it easy to apply environment variables to
// a running service in a way similar to modifying /etc/default/tailscaled on Linux.
// On Windows, you use %ProgramData%\Tailscale\tailscaled-env.txt instead.
func ApplyDiskConfig() (err error) {
var f *os.File
defer func() {
if err != nil {
// Stash away our return error for the healthcheck package to use.
applyDiskConfigErr = fmt.Errorf("error parsing %s: %w", f.Name(), err)
}
}()
// First try the explicitly-provided value for development testing. Not
// useful for users to use on their own. (if they can set this, they can set
// any environment variable anyway)
if name := os.Getenv("TS_DEBUG_ENV_FILE"); name != "" {
f, err = os.Open(name)
if err != nil {
return fmt.Errorf("error opening explicitly configured TS_DEBUG_ENV_FILE: %w", err)
}
defer f.Close()
return applyKeyValueEnv(f)
}
name := getPlatformEnvFile()
if name == "" {
return nil
}
f, err = os.Open(name)
if os.IsNotExist(err) {
return nil
}
if err != nil {
return err
}
defer f.Close()
return applyKeyValueEnv(f)
}
// getPlatformEnvFile returns the current platform's path to an optional
// tailscaled-env.txt file. It returns an empty string if none is defined
// for the platform.
func getPlatformEnvFile() string {
switch runtime.GOOS {
case "windows":
return filepath.Join(os.Getenv("ProgramData"), "Tailscale", "tailscaled-env.txt")
case "linux":
if distro.Get() == distro.Synology {
return "/etc/tailscale/tailscaled-env.txt"
}
case "darwin":
// TODO(bradfitz): figure this out. There are three ways to run
// Tailscale on macOS (tailscaled, GUI App Store, GUI System Extension)
// and we should deal with all three.
}
return ""
}
// applyKeyValueEnv reads key=value lines r and calls Setenv for each.
//
// Empty lines and lines beginning with '#' are skipped.
//
// Values can be double quoted, in which case they're unquoted using
// strconv.Unquote.
func applyKeyValueEnv(r io.Reader) error {
bs := bufio.NewScanner(r)
for bs.Scan() {
line := strings.TrimSpace(bs.Text())
if line == "" || line[0] == '#' {
continue
}
k, v, ok := strings.Cut(line, "=")
k = strings.TrimSpace(k)
if !ok || k == "" {
continue
}
v = strings.TrimSpace(v)
if strings.HasPrefix(v, `"`) {
var err error
v, err = strconv.Unquote(v)
if err != nil {
return fmt.Errorf("invalid value in line %q: %v", line, err)
}
}
Setenv(k, v)
}
return bs.Err()
}
// IPCVersion returns version.Long usually, unless TS_DEBUG_FAKE_IPC_VERSION is
// set, in which it contains that value. This is only used for weird development
// cases when testing mismatched versions and you want the client to act like it's
// compatible with the server.
func IPCVersion() string {
if v := String("TS_DEBUG_FAKE_IPC_VERSION"); v != "" {
return v
}
return version.Long
}