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273 lines
6.8 KiB
Go
273 lines
6.8 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// The derper binary is a simple DERP server.
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package main // import "tailscale.com/cmd/derper"
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import (
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"context"
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"encoding/json"
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"errors"
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"expvar"
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"flag"
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"fmt"
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"io"
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"io/ioutil"
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"log"
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"net"
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"net/http"
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"os"
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"path/filepath"
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"regexp"
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"time"
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"github.com/tailscale/wireguard-go/wgcfg"
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"golang.org/x/crypto/acme/autocert"
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"tailscale.com/atomicfile"
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"tailscale.com/derp"
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"tailscale.com/derp/derphttp"
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"tailscale.com/logpolicy"
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"tailscale.com/stun"
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"tailscale.com/tsweb"
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"tailscale.com/types/key"
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)
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var (
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dev = flag.Bool("dev", false, "run in localhost development mode")
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addr = flag.String("a", ":443", "server address")
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configPath = flag.String("c", "", "config file path")
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certDir = flag.String("certdir", tsweb.DefaultCertDir("derper-certs"), "directory to store LetsEncrypt certs, if addr's port is :443")
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hostname = flag.String("hostname", "derp.tailscale.com", "LetsEncrypt host name, if addr's port is :443")
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mbps = flag.Int("mbps", 5, "Mbps (mebibit/s) per-client rate limit; 0 means unlimited")
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logCollection = flag.String("logcollection", "", "If non-empty, logtail collection to log to")
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runSTUN = flag.Bool("stun", false, "also run a STUN server")
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)
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type config struct {
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PrivateKey wgcfg.PrivateKey
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}
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func loadConfig() config {
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if *dev {
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return config{PrivateKey: mustNewKey()}
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}
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if *configPath == "" {
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log.Fatalf("derper: -c <config path> not specified")
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}
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b, err := ioutil.ReadFile(*configPath)
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switch {
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case os.IsNotExist(err):
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return writeNewConfig()
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case err != nil:
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log.Fatal(err)
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panic("unreachable")
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default:
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var cfg config
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if err := json.Unmarshal(b, &cfg); err != nil {
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log.Fatalf("derper: config: %v", err)
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}
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return cfg
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}
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}
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func mustNewKey() wgcfg.PrivateKey {
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key, err := wgcfg.NewPrivateKey()
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if err != nil {
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log.Fatal(err)
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}
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return key
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}
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func writeNewConfig() config {
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key := mustNewKey()
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if err := os.MkdirAll(filepath.Dir(*configPath), 0777); err != nil {
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log.Fatal(err)
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}
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cfg := config{
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PrivateKey: key,
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}
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b, err := json.MarshalIndent(cfg, "", "\t")
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if err != nil {
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log.Fatal(err)
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}
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if err := atomicfile.WriteFile(*configPath, b, 0666); err != nil {
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log.Fatal(err)
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}
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return cfg
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}
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func main() {
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flag.Parse()
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if *dev {
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*logCollection = ""
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*addr = ":3340" // above the keys DERP
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log.Printf("Running in dev mode.")
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tsweb.DevMode = true
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}
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var logPol *logpolicy.Policy
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if *logCollection != "" {
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logPol = logpolicy.New(*logCollection)
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log.SetOutput(logPol.Logtail)
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}
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cfg := loadConfig()
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letsEncrypt := tsweb.IsProd443(*addr)
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s := derp.NewServer(key.Private(cfg.PrivateKey), log.Printf)
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if *mbps != 0 {
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s.BytesPerSecond = (*mbps << 20) / 8
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}
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expvar.Publish("derp", s.ExpVar())
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// Create our own mux so we don't expose /debug/ stuff to the world.
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mux := tsweb.NewMux(debugHandler(s))
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mux.Handle("/derp", derphttp.Handler(s))
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mux.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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w.Header().Set("Content-Type", "text/html; charset=utf-8")
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w.WriteHeader(200)
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io.WriteString(w, `<html><body>
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<h1>DERP</h1>
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<p>
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This is a
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<a href="https://tailscale.com/">Tailscale</a>
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<a href="https://godoc.org/tailscale.com/derp">DERP</a>
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server.
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</p>
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`)
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if tsweb.AllowDebugAccess(r) {
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io.WriteString(w, "<p>Debug info at <a href='/debug/'>/debug/</a>.</p>\n")
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}
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}))
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if *runSTUN {
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go serveSTUN()
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}
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httpsrv := &http.Server{
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Addr: *addr,
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Handler: mux,
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}
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var err error
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if letsEncrypt {
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if *certDir == "" {
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log.Fatalf("missing required --certdir flag")
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}
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log.Printf("derper: serving on %s with TLS", *addr)
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certManager := &autocert.Manager{
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Prompt: autocert.AcceptTOS,
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HostPolicy: autocert.HostWhitelist(*hostname),
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Cache: autocert.DirCache(*certDir),
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}
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if *hostname == "derp.tailscale.com" {
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certManager.HostPolicy = prodAutocertHostPolicy
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certManager.Email = "security@tailscale.com"
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}
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httpsrv.TLSConfig = certManager.TLSConfig()
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go func() {
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err := http.ListenAndServe(":80", certManager.HTTPHandler(tsweb.Port80Handler{mux}))
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if err != nil {
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if err != http.ErrServerClosed {
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log.Fatal(err)
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}
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}
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}()
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err = httpsrv.ListenAndServeTLS("", "")
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} else {
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log.Printf("derper: serving on %s", *addr)
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err = httpsrv.ListenAndServe()
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}
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if err != nil && err != http.ErrServerClosed {
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log.Fatalf("derper: %v", err)
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}
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}
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func debugHandler(s *derp.Server) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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f := func(format string, args ...interface{}) { fmt.Fprintf(w, format, args...) }
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f(`<html><body>
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<h1>DERP debug</h1>
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<ul>
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`)
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f("<li><b>Hostname:</b> %v</li>\n", *hostname)
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f("<li><b>Rate Limit:</b> %v Mbps</li>\n", *mbps)
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f("<li><b>Uptime:</b> %v</li>\n", tsweb.Uptime())
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f(`<li><a href="/debug/vars">/debug/vars</a></li>
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<li><a href="/debug/pprof/">/debug/pprof/</a></li>
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<li><a href="/debug/pprof/goroutine?debug=1">/debug/pprof/goroutine</a> (collapsed)</li>
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<li><a href="/debug/pprof/goroutine?debug=2">/debug/pprof/goroutine</a> (full)</li>
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<ul>
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</html>
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`)
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})
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}
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func serveSTUN() {
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pc, err := net.ListenPacket("udp", ":3478")
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if err != nil {
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log.Fatalf("failed to open STUN listener: %v", err)
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}
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log.Printf("running STUN server on %v", pc.LocalAddr())
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var (
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stunReadErrors = expvar.NewInt("stun_read_error")
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stunWriteErrors = expvar.NewInt("stun_write_error")
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stunReadNotSTUN = expvar.NewInt("stun_read_not_stun")
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stunReadNotSTUNValid = expvar.NewInt("stun_read_not_stun_valid")
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stunReadIPv4 = expvar.NewInt("stun_read_ipv4")
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stunReadIPv6 = expvar.NewInt("stun_read_ipv6")
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stunWrite = expvar.NewInt("stun_write")
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)
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var buf [64 << 10]byte
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for {
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n, addr, err := pc.ReadFrom(buf[:])
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if err != nil {
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log.Printf("STUN ReadFrom: %v", err)
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time.Sleep(time.Second)
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stunReadErrors.Add(1)
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continue
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}
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ua, ok := addr.(*net.UDPAddr)
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if !ok {
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log.Printf("STUN unexpected address %T %v", addr, addr)
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stunReadErrors.Add(1)
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continue
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}
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pkt := buf[:n]
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if !stun.Is(pkt) {
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stunReadNotSTUN.Add(1)
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continue
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}
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txid, err := stun.ParseBindingRequest(pkt)
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if err != nil {
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stunReadNotSTUNValid.Add(1)
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continue
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}
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if ua.IP.To4() != nil {
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stunReadIPv4.Add(1)
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} else {
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stunReadIPv6.Add(1)
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}
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res := stun.Response(txid, ua.IP, uint16(ua.Port))
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_, err = pc.WriteTo(res, addr)
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if err != nil {
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stunWriteErrors.Add(1)
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} else {
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stunWrite.Add(1)
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}
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}
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}
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var validProdHostname = regexp.MustCompile(`^derp(\d+|\-\w+)?\.tailscale\.com\.?$`)
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func prodAutocertHostPolicy(_ context.Context, host string) error {
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if validProdHostname.MatchString(host) {
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return nil
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}
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return errors.New("invalid hostname")
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}
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