tailscale/cmd/derper/bootstrap_dns.go

70 lines
1.3 KiB
Go

// 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 main
import (
"context"
"encoding/json"
"expvar"
"log"
"net"
"net/http"
"strings"
"sync"
"time"
)
var (
dnsMu sync.Mutex
dnsCache = map[string][]net.IP{}
)
var bootstrapDNSRequests = expvar.NewInt("counter_bootstrap_dns_requests")
func refreshBootstrapDNSLoop() {
if *bootstrapDNS == "" {
return
}
for {
refreshBootstrapDNS()
time.Sleep(10 * time.Minute)
}
}
func refreshBootstrapDNS() {
if *bootstrapDNS == "" {
return
}
ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()
names := strings.Split(*bootstrapDNS, ",")
var r net.Resolver
for _, name := range names {
addrs, err := r.LookupIP(ctx, "ip", name)
if err != nil {
log.Printf("bootstrap DNS lookup %q: %v", name, err)
continue
}
dnsMu.Lock()
dnsCache[name] = addrs
dnsMu.Unlock()
}
}
func handleBootstrapDNS(w http.ResponseWriter, r *http.Request) {
bootstrapDNSRequests.Add(1)
dnsMu.Lock()
j, err := json.MarshalIndent(dnsCache, "", "\t")
dnsMu.Unlock()
if err != nil {
log.Printf("bootstrap DNS JSON: %v", err)
http.Error(w, "JSON marshal error", 500)
return
}
w.Header().Set("Content-Type", "application/json")
w.Write(j)
}