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package main
import (
"flag"
"fmt"
"net"
)
func main() {
var resolver string
flag.StringVar(&resolver, "resolver", "1.1.1.1:53", "DNS resolver to forward queries to")
flag.Parse()
udpAddr, err := net.ResolveUDPAddr("udp", "127.0.0.1:2053")
if err != nil {
fmt.Println("Failed to resol[]byteve UDP address:", err)
return
}
udpConn, err := net.ListenUDP("udp", udpAddr)
if err != nil {
fmt.Println("Failed to bind to address:", err)
return
}
defer udpConn.Close()
buf := make([]byte, 512)
for {
size, source, err := udpConn.ReadFromUDP(buf)
if err != nil {
fmt.Println("Error receiving data:", err)
break
}
receivedData := string(buf[:size])
fmt.Printf("Received %d bytes from %s: %s\n", size, source, receivedData)
requestHeader := ParseHeader(buf[:size])
questions, _ := ParseQuestions(buf[:size], requestHeader.QDCOUNT)
answers := ForwardQuestions(resolver, questions, requestHeader.ID)
rcode := uint8(4)
if requestHeader.OPCODE == 0 {
rcode = 0
}
header := DNSHeader{
ID: requestHeader.ID,
QR: 1,
OPCODE: requestHeader.OPCODE,
AA: 0,
TC: 0,
RD: requestHeader.RD,
RA: 0,
Z: 0,
RCODE: rcode,
QDCOUNT: 0,
ANCOUNT: 0,
NSCOUNT: requestHeader.NSCOUNT,
ARCOUNT: requestHeader.ARCOUNT,
}
response := MakeMessage(header)
for _, question := range questions {
response.AddQuestion(question)
}
for _, answer := range answers {
response.AddAnswer(answer)
}
_, err = udpConn.WriteToUDP(response.Bytes(), source)
if err != nil {
fmt.Println("Failed to send response:", err)
}
}
}
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