tailscale/tsnet/tsnet.go

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// Copyright (c) 2021 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 tsnet provides Tailscale as a library.
//
// It is an experimental work in progress.
package tsnet
import (
"context"
"errors"
"fmt"
"log"
"net"
"net/http"
"os"
"path/filepath"
"strings"
"sync"
"time"
"inet.af/netaddr"
"tailscale.com/client/tailscale"
"tailscale.com/control/controlclient"
"tailscale.com/envknob"
"tailscale.com/ipn"
"tailscale.com/ipn/ipnlocal"
"tailscale.com/ipn/localapi"
"tailscale.com/net/nettest"
"tailscale.com/net/tsdial"
"tailscale.com/smallzstd"
"tailscale.com/types/logger"
"tailscale.com/wgengine"
"tailscale.com/wgengine/monitor"
"tailscale.com/wgengine/netstack"
)
// Server is an embedded Tailscale server.
//
// Its exported fields may be changed until the first call to Listen.
type Server struct {
// Dir specifies the name of the directory to use for
// state. If empty, a directory is selected automatically
// under os.UserConfigDir (https://golang.org/pkg/os/#UserConfigDir).
// based on the name of the binary.
Dir string
// Hostname is the hostname to present to the control server.
// If empty, the binary name is used.
Hostname string
// Logf, if non-nil, specifies the logger to use. By default,
// log.Printf is used.
Logf logger.Logf
// Ephemeral, if true, specifies that the instance should register
// as an Ephemeral node (https://tailscale.com/kb/1111/ephemeral-nodes/).
Ephemeral bool
initOnce sync.Once
initErr error
lb *ipnlocal.LocalBackend
// the state directory
dir string
hostname string
mu sync.Mutex
listeners map[listenKey]*listener
dialer *tsdial.Dialer
}
// Dial connects to the address on the tailnet.
// It will start the server if it has not been started yet.
func (s *Server) Dial(ctx context.Context, network, address string) (net.Conn, error) {
if err := s.Start(); err != nil {
return nil, err
}
return s.dialer.UserDial(ctx, network, address)
}
func (s *Server) doInit() {
if err := s.start(); err != nil {
s.initErr = fmt.Errorf("tsnet: %w", err)
}
}
// Start connects the server to the tailnet.
// Optional: any calls to Dial/Listen will also call Start.
func (s *Server) Start() error {
s.initOnce.Do(s.doInit)
return s.initErr
}
func (s *Server) start() error {
if !envknob.UseWIPCode() {
return errors.New("code disabled without environment variable TAILSCALE_USE_WIP_CODE set true")
}
exe, err := os.Executable()
if err != nil {
return err
}
prog := strings.TrimSuffix(strings.ToLower(filepath.Base(exe)), ".exe")
s.hostname = s.Hostname
if s.hostname == "" {
s.hostname = prog
}
s.dir = s.Dir
if s.dir == "" {
confDir, err := os.UserConfigDir()
if err != nil {
return err
}
s.dir = filepath.Join(confDir, "tslib-"+prog)
if err := os.MkdirAll(s.dir, 0700); err != nil {
return err
}
}
if fi, err := os.Stat(s.dir); err != nil {
return err
} else if !fi.IsDir() {
return fmt.Errorf("%v is not a directory", s.dir)
}
logf := s.Logf
if logf == nil {
logf = log.Printf
}
// TODO(bradfitz): start logtail? don't use filch, perhaps?
// only upload plumbed Logf?
linkMon, err := monitor.New(logf)
if err != nil {
return err
}
s.dialer = new(tsdial.Dialer) // mutated below (before used)
eng, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
ListenPort: 0,
LinkMonitor: linkMon,
Dialer: s.dialer,
})
if err != nil {
return err
}
tunDev, magicConn, ok := eng.(wgengine.InternalsGetter).GetInternals()
if !ok {
return fmt.Errorf("%T is not a wgengine.InternalsGetter", eng)
}
ns, err := netstack.Create(logf, tunDev, eng, magicConn, s.dialer)
if err != nil {
return fmt.Errorf("netstack.Create: %w", err)
}
ns.ProcessLocalIPs = true
ns.ForwardTCPIn = s.forwardTCP
if err := ns.Start(); err != nil {
return fmt.Errorf("failed to start netstack: %w", err)
}
s.dialer.UseNetstackForIP = func(ip netaddr.IP) bool {
_, ok := eng.PeerForIP(ip)
return ok
}
s.dialer.NetstackDialTCP = func(ctx context.Context, dst netaddr.IPPort) (net.Conn, error) {
return ns.DialContextTCP(ctx, dst)
}
statePath := filepath.Join(s.dir, "tailscaled.state")
store, err := ipn.NewFileStore(statePath)
if err != nil {
return err
}
logid := "tslib-TODO"
loginFlags := controlclient.LoginDefault
if s.Ephemeral {
loginFlags = controlclient.LoginEphemeral
}
lb, err := ipnlocal.NewLocalBackend(logf, logid, store, s.dialer, eng, loginFlags)
if err != nil {
return fmt.Errorf("NewLocalBackend: %v", err)
}
lb.SetVarRoot(s.dir)
s.lb = lb
lb.SetDecompressor(func() (controlclient.Decompressor, error) {
return smallzstd.NewDecoder(nil)
})
prefs := ipn.NewPrefs()
prefs.Hostname = s.hostname
prefs.WantRunning = true
err = lb.Start(ipn.Options{
StateKey: ipn.GlobalDaemonStateKey,
UpdatePrefs: prefs,
AuthKey: os.Getenv("TS_AUTHKEY"),
})
if err != nil {
return fmt.Errorf("starting backend: %w", err)
}
if os.Getenv("TS_LOGIN") == "1" || os.Getenv("TS_AUTHKEY") != "" {
s.lb.StartLoginInteractive()
}
// Run the localapi handler, to allow fetching LetsEncrypt certs.
lah := localapi.NewHandler(lb, logf, logid)
lah.PermitWrite = true
lah.PermitRead = true
// Create an in-process listener.
// nettest.Listen provides a in-memory pipe based implementation for net.Conn.
// TODO(maisem): Rename nettest package to remove "test".
lal := nettest.Listen("local-tailscaled.sock:80")
// Override the Tailscale client to use the in-process listener.
tailscale.TailscaledDialer = lal.Dial
go func() {
if err := http.Serve(lal, lah); err != nil {
logf("localapi serve error: %v", err)
}
}()
return nil
}
func (s *Server) forwardTCP(c net.Conn, port uint16) {
s.mu.Lock()
ln, ok := s.listeners[listenKey{"tcp", "", fmt.Sprint(port)}]
s.mu.Unlock()
if !ok {
c.Close()
return
}
t := time.NewTimer(time.Second)
defer t.Stop()
select {
case ln.conn <- c:
case <-t.C:
c.Close()
}
}
// Listen announces only on the Tailscale network.
// It will start the server if it has not been started yet.
func (s *Server) Listen(network, addr string) (net.Listener, error) {
host, port, err := net.SplitHostPort(addr)
if err != nil {
return nil, fmt.Errorf("tsnet: %w", err)
}
if err := s.Start(); err != nil {
return nil, err
}
key := listenKey{network, host, port}
ln := &listener{
s: s,
key: key,
addr: addr,
conn: make(chan net.Conn),
}
s.mu.Lock()
if s.listeners == nil {
s.listeners = map[listenKey]*listener{}
}
if _, ok := s.listeners[key]; ok {
s.mu.Unlock()
return nil, fmt.Errorf("tsnet: listener already open for %s, %s", network, addr)
}
s.listeners[key] = ln
s.mu.Unlock()
return ln, nil
}
type listenKey struct {
network string
host string
port string
}
type listener struct {
s *Server
key listenKey
addr string
conn chan net.Conn
}
func (ln *listener) Accept() (net.Conn, error) {
c, ok := <-ln.conn
if !ok {
return nil, fmt.Errorf("tsnet: %w", net.ErrClosed)
}
return c, nil
}
func (ln *listener) Addr() net.Addr { return addr{ln} }
func (ln *listener) Close() error {
ln.s.mu.Lock()
defer ln.s.mu.Unlock()
if v, ok := ln.s.listeners[ln.key]; ok && v == ln {
delete(ln.s.listeners, ln.key)
close(ln.conn)
}
return nil
}
type addr struct{ ln *listener }
func (a addr) Network() string { return a.ln.key.network }
func (a addr) String() string { return a.ln.addr }