Fast DNS implementation for Go
Features
- 0 Dependency
- Similar Interface with net/http
- Fast DoH Server Co-create with fasthttp
- Fast DNS Client with rich features
- Fast eDNS options
- Compatible metrics with coredns
- High Performance
- 0-allocs dns request parser
- 0-allocs dns records marshaller
- worker pool + message pool
- prefork + reuse_port + set_affinity
Getting Started
DNS Server
package main
import (
"log/slog"
"net"
"net/netip"
"os"
"github.com/phuslu/fastdns"
)
type DNSHandler struct {
Debug bool
}
func (h *DNSHandler) ServeDNS(rw fastdns.ResponseWriter, req *fastdns.Message) {
if h.Debug {
slog.Info("serve dns request", "domain", req.Domain, "class", req.Question.Class, "type", req.Question.Type)
}
switch req.Question.Type {
case fastdns.TypeA:
req.SetResponseHeader(fastdns.RcodeNoError, 1)
req.AppendHOST1(600, netip.AddrFrom4([4]byte{8, 8, 8, 8}))
case fastdns.TypeAAAA:
ips := []netip.Addr{netip.MustParseAddr("2001:4860:4860::8888")}
req.SetResponseHeader(fastdns.RcodeNoError, uint16(len(ips)))
req.AppendHOST(600, ips)
case fastdns.TypeCNAME:
cnames, ips := []string{"dns.google"}, []netip.Addr{netip.MustParseAddr("8.8.8.8")}
req.SetResponseHeader(fastdns.RcodeNoError, uint16(len(cnames)+len(ips)))
req.AppendCNAME(600, cnames, ips)
case fastdns.TypeSRV:
srvs := []net.SRV{{"www.google.com", 443, 1000, 1000}}
req.SetResponseHeader(fastdns.RcodeNoError, uint16(len(srvs)))
req.AppendSRV(600, srvs)
case fastdns.TypeNS:
nameservers := []net.NS{{"ns1.google.com"}, {"ns2.google.com"}}
req.SetResponseHeader(fastdns.RcodeNoError, uint16(len(nameservers)))
req.AppendNS(600, nameservers)
case fastdns.TypeSOA:
mname := net.NS{Host: "ns1.google.com"}
rname := net.NS{Host: "dns-admin.google.com"}
req.SetResponseHeader(fastdns.RcodeNoError, 1)
req.AppendSOA(600, mname, rname, 42, 900, 900, 1800, 60)
case fastdns.TypeMX:
mxs := []net.MX{{"mail.gmail.com", 10}, {"smtp.gmail.com", 10}}
req.SetResponseHeader(fastdns.RcodeNoError, uint16(len(mxs)))
req.AppendMX(600, mxs)
case fastdns.TypePTR:
ptr := "ptr.google.com"
req.SetResponseHeader(fastdns.RcodeNoError, 1)
req.AppendPTR(600, ptr)
case fastdns.TypeTXT:
txt := "iamatxtrecord"
req.SetResponseHeader(fastdns.RcodeNoError, 1)
req.AppendTXT(600, txt)
default:
req.SetResponseHeader(fastdns.RcodeFormErr, 0)
}
_, _ = rw.Write(req.Raw)
}
func main() {
addr := ":53"
server := &fastdns.ForkServer{
Handler: &DNSHandler{
Debug: os.Getenv("DEBUG") != "",
},
Stats: &fastdns.CoreStats{
Prefix: "coredns_",
Family: "1",
Proto: "udp",
Server: "dns://" + addr,
Zone: ".",
},
ErrorLog: slog.Default(),
}
err := server.ListenAndServe(addr)
if err != nil {
slog.Error("dnsserver serve failed", "error", err)
}
}
DoH/eDNS Client
package main
import (
"context"
"crypto/tls"
"fmt"
"net/http"
"net/netip"
"net/url"
"time"
"github.com/phuslu/fastdns"
)
func main() {
endpoint, _ := url.Parse("https://8.8.8.8/dns-query")
client := &fastdns.Client{
Addr: endpoint.String(),
Dialer: &fastdns.HTTPDialer{
Endpoint: endpoint,
Header: http.Header{
"content-type": []string{"application/dns-message"},
"user-agent": []string{"fastdns/1.0"},
},
Transport: &http.Transport{
ForceAttemptHTTP2: true,
MaxIdleConns: 100,
IdleConnTimeout: 90 * time.Second,
TLSHandshakeTimeout: 10 * time.Second,
TLSClientConfig: &tls.Config{
NextProtos: []string{"h2"},
InsecureSkipVerify: false,
ServerName: endpoint.Hostname(),
ClientSessionCache: tls.NewLRUClientSessionCache(1024),
},
},
},
}
ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
defer cancel()
ctx = fastdns.WithClientSubnet(ctx, netip.MustParsePrefix("1.2.4.8/24"))
fmt.Println(client.LookupNetIP(ctx, "ip4", "www.google.com"))
fmt.Println(client.LookupHTTPS(ctx, "phus.lu"))
}
DNS/eDNS Client Tool
$ go install github.com/phuslu/fastdns/cmd/fastdig@master
$ fastdig www.google.com @https://8.8.8.8/dns-query +subnet=1.2.3.0/24
; <<>> DiG 0.0.1-fastdns-go1.25.0 <<>> www.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 589
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;www.google.com. IN A
;; ANSWER SECTION:
www.google.com. 300 IN A 142.250.9.147
www.google.com. 300 IN A 142.250.9.104
www.google.com. 300 IN A 142.250.9.99
www.google.com. 300 IN A 142.250.9.105
www.google.com. 300 IN A 142.250.9.106
www.google.com. 300 IN A 142.250.9.103
;; Query time: 30 msec
;; SERVER: https://8.8.8.8/dns-query#53(https://8.8.8.8/dns-query)
;; WHEN: Sat Oct 11 00:44:09 +08 2025
;; MSG SIZE rcvd: 150
DoH Server Example
$ go install github.com/phuslu/fastdns/cmd/fastdoh@master
$ fastdoh :8080
High Performance
A Performance result as below, for daily benchmark results see github actions
# go test -v -run=none -benchmem -bench=.
goos: linux
goarch: amd64
pkg: github.com/phuslu/fastdns
cpu: AMD EPYC 7763 64-Core Processor
BenchmarkMessageParseMessage-4 80922766 14.68 ns/op 0 B/op 0 allocs/op
BenchmarkMessageEncodeDomain-4 100000000 12.78 ns/op 0 B/op 0 allocs/op
BenchmarkMessageSetQuestion-4 40993672 30.27 ns/op 0 B/op 0 allocs/op
BenchmarkMessageSetResponseHeader-4 320204428 3.606 ns/op 0 B/op 0 allocs/op
BenchmarkMessageDecodeName-4 52074597 23.07 ns/op 0 B/op 0 allocs/op
BenchmarkMessageAppendHOST-4 183561132 6.544 ns/op 0 B/op 0 allocs/op
BenchmarkMessageAppendCNAME-4 42692521 27.77 ns/op 0 B/op 0 allocs/op
BenchmarkMessageAppendSRV-4 50555230 23.85 ns/op 0 B/op 0 allocs/op
BenchmarkMessageAppendNS-4 32065906 36.33 ns/op 0 B/op 0 allocs/op
BenchmarkMessageAppendSOA-4 26630746 45.05 ns/op 0 B/op 0 allocs/op
BenchmarkMessageAppendPTR-4 54242904 22.74 ns/op 0 B/op 0 allocs/op
BenchmarkMessageAppendMX-4 61512556 19.59 ns/op 0 B/op 0 allocs/op
BenchmarkMessageAppendTXT-4 166240762 7.213 ns/op 0 B/op 0 allocs/op
BenchmarkServerHandlerHOST1-4 152072834 7.914 ns/op 0 B/op 0 allocs/op
BenchmarkServerHandlerHOST-4 130878036 8.404 ns/op 0 B/op 0 allocs/op
BenchmarkServerHandlerCNAME-4 36238018 33.11 ns/op 0 B/op 0 allocs/op
BenchmarkServerHandlerSRV-4 47581225 25.69 ns/op 0 B/op 0 allocs/op
BenchmarkServerHandlerNS-4 30977643 39.82 ns/op 0 B/op 0 allocs/op
BenchmarkServerHandlerSOA-4 22182384 54.29 ns/op 0 B/op 0 allocs/op
BenchmarkServerHandlerMX-4 42502989 28.91 ns/op 0 B/op 0 allocs/op
BenchmarkServerHandlerPTR-4 40598533 28.77 ns/op 0 B/op 0 allocs/op
BenchmarkServerHandlerTXT-4 100000000 14.72 ns/op 0 B/op 0 allocs/op
BenchmarkServerUpdateStats-4 39958220 30.05 ns/op 0 B/op 0 allocs/op
BenchmarkServerAppendOpenMetrics-4 465868 2662 ns/op 0 B/op 0 allocs/op
PASS
ok github.com/phuslu/fastdns
Here is the real-world flamegraph 
when fastdns server reaches 1.4M QPS on a single machine with Xeon 4216 and Intel X710.
Acknowledgment
This dns server is inspired by fasthttp, rawdns and miekg/dns.