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|
// Command dnsd is a simple DNS server for my network. It has O(n) lookup times.
package main
import (
"bufio"
"flag"
"fmt"
"log"
"net/http"
"os"
"os/signal"
"syscall"
"time"
"github.com/miekg/dns"
"github.com/mmikulicic/stringlist"
"within.website/x/internal"
"within.website/x/web"
)
var (
port = flag.String("port", "53", "UDP port to listen on for DNS")
server = flag.String("forward-server", "1.1.1.1:53", "forward DNS server")
zoneURLs = stringlist.Flag("zone-url", "DNS zonefiles to load")
)
var (
defaultZoneURLS = []string{
"https://xena.greedo.xeserv.us/files/akua.zone",
"https://xena.greedo.xeserv.us/files/adblock.zone",
}
)
func monitorURLs(urls []string) {
etags := make(map[string]string)
t := time.NewTicker(time.Minute)
defer t.Stop()
for {
select {
case <-t.C:
for _, urli := range urls {
resp, err := http.Get(urli)
if err != nil {
panic(err)
}
et := resp.Header.Get("ETag")
ot, ok := etags[urli]
if !ok {
log.Printf("stored %s:%s", urli, et)
etags[urli] = et
}
if ok && et != ot {
log.Fatalf("url %s has new etag %s and wanted old etag %s", urli, et, ot)
}
}
}
}
}
func main() {
internal.HandleStartup()
if len(*zoneURLs) == 0 {
*zoneURLs = defaultZoneURLS
}
go monitorURLs(*zoneURLs)
for _, zurl := range *zoneURLs {
log.Printf("conf: -zone-url=%s", zurl)
}
log.Printf("conf: -port=%s", *port)
log.Printf("conf: -forward-server=%s", *server)
rrs := []dns.RR{}
ns := []dns.RR{}
txt, err := dns.NewRR("user-agent. 10 CH TXT " + fmt.Sprintf("%q", web.GenUserAgent()))
if err != nil {
log.Fatal(err)
}
for _, zurl := range *zoneURLs {
resp, err := http.Get(zurl)
if err != nil {
panic(err)
}
reader := bufio.NewReaderSize(resp.Body, 2048)
var i int
zp := dns.NewZoneParser(reader, "", zurl)
for rr, ok := zp.Next(); ok; rr, ok = zp.Next() {
rrs = append(rrs, rr)
if rr.Header().Rrtype == dns.TypeNS {
ns = append(ns, rr)
}
i++
}
if zp.Err() != nil {
panic(zp.Err())
}
resp.Body.Close()
log.Printf("%s: %d records", zurl, i)
}
dns.HandleFunc(".", func(w dns.ResponseWriter, r *dns.Msg) {
m := new(dns.Msg)
m.SetReply(r)
m.Authoritative = true
for _, q := range r.Question {
answers := []dns.RR{}
for _, rr := range rrs {
rh := rr.Header()
if rh.Rrtype == dns.TypeCNAME && q.Name == rh.Name {
answers = append(answers, rr)
for _, a := range resolver("127.0.0.1:"+*port, rr.(*dns.CNAME).Target, q.Qtype) {
answers = append(answers, a)
}
}
if q.Name == rh.Name && q.Qtype == rh.Rrtype && q.Qclass == rh.Class {
answers = append(answers, rr)
}
}
if len(answers) == 0 && *server != "" {
for _, a := range resolver(*server, q.Name, q.Qtype) {
answers = append(answers, a)
}
} else {
m.Ns = ns
m.Extra = []dns.RR{txt}
}
for _, a := range answers {
m.Answer = append(m.Answer, a)
}
}
w.WriteMsg(m)
})
go func() {
srv := &dns.Server{Addr: ":" + *port, Net: "udp"}
if err := srv.ListenAndServe(); err != nil {
log.Fatalf("Failed to set udp listener %s\n", err.Error())
}
}()
sig := make(chan os.Signal)
signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
s := <-sig
log.Fatalf("Signal (%v) received, stopping\n", s)
}
func resolver(server, fqdn string, r_type uint16) []dns.RR {
m1 := new(dns.Msg)
m1.Id = dns.Id()
m1.SetQuestion(fqdn, r_type)
in, err := dns.Exchange(m1, server)
if err == nil {
return in.Answer
}
return []dns.RR{}
}
|
