refactoring
This commit is contained in:
parent
0f716a3c49
commit
8c4d8c1d49
@ -1,9 +1,9 @@
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package dnsProxy
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import (
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"context"
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"encoding/hex"
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"fmt"
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"github.com/coreos/go-iptables/iptables"
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"log"
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"net"
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"time"
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@ -11,147 +11,111 @@ import (
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const (
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DNSMaxUDPPackageSize = 4096
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DNSMaxTCPPackageSize = 65536
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)
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type DNSProxy struct {
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listenAddr string
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upstreamAddr string
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udpConn *net.UDPConn
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listenPort uint16
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udpConn *net.UDPConn
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targetDNSServerAddress string
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MsgHandler func(*Message)
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}
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func (p DNSProxy) Close() error {
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ipt, err := iptables.New()
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if err != nil {
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log.Fatalf("iptables init fail: %v", err)
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}
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err = ipt.DeleteIfExists("nat", "PREROUTING", "-j", "KVAS2_DNSOVERRIDE")
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if err != nil {
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log.Fatalf("failed to attaching chain: %v", err)
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}
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err = ipt.ClearAndDeleteChain("nat", "KVAS2_DNSOVERRIDE")
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if err != nil {
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log.Fatalf("failed to delete chain: %v", err)
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}
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return nil
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//return p.udpConn.Close()
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}
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func (p DNSProxy) sendToUpstream(isTCP bool, request []byte) ([]byte, error) {
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protocol := "udp"
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if isTCP {
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protocol = "tcp"
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}
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conn, err := net.Dial(protocol, p.upstreamAddr)
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if err != nil {
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return nil, fmt.Errorf("failed to dial upstream DNS: %w", err)
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}
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defer conn.Close()
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_, err = conn.Write(request)
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if err != nil {
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return nil, fmt.Errorf("failed to send request to upstream DNS: %w", err)
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}
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err = conn.SetReadDeadline(time.Now().Add(5 * time.Second))
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if err != nil {
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return nil, fmt.Errorf("failed to set timeout: %w", err)
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}
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var response []byte
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if !isTCP {
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response = make([]byte, DNSMaxUDPPackageSize)
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} else {
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response = make([]byte, DNSMaxTCPPackageSize)
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}
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n, err := conn.Read(response)
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if err != nil {
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return nil, fmt.Errorf("failed to read response from upstream DNS: %w", err)
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}
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return response[:n], nil
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}
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func (p DNSProxy) handleDNSRequest(clientAddr *net.UDPAddr, buffer []byte) {
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upstreamResponse, err := p.sendToUpstream(false, buffer)
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if err != nil {
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log.Printf("Failed to get response from upstream DNS: %v", err)
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return
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}
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log.Printf("Response: %s", hex.EncodeToString(upstreamResponse))
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msg, err := ParseResponse(upstreamResponse)
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if err == nil {
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if p.MsgHandler != nil {
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p.MsgHandler(msg)
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}
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} else {
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log.Printf("error while parsing response: %v", err)
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}
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_, err = p.udpConn.WriteToUDP(upstreamResponse, clientAddr)
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if err != nil {
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log.Printf("Failed to send DNS response: %v", err)
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}
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}
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func (p DNSProxy) Listen() error {
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func (p DNSProxy) Listen(ctx context.Context) error {
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var err error
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ipt, err := iptables.New()
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if err != nil {
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log.Fatalf("iptables init fail: %v", err)
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}
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err = ipt.ClearChain("nat", "KVAS2_DNSOVERRIDE")
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if err != nil {
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log.Fatalf("failed to clean chain: %v", err)
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}
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err = ipt.AppendUnique("nat", "KVAS2_DNSOVERRIDE", "-p", "udp", "--dport", "53", "-j", "REDIRECT", "--to-port", "7548")
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if err != nil {
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log.Fatalf("failed to create rule: %v", err)
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}
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err = ipt.InsertUnique("nat", "PREROUTING", 1, "-j", "KVAS2_DNSOVERRIDE")
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if err != nil {
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log.Fatalf("failed to attaching chain: %v", err)
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}
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udpAddr, err := net.ResolveUDPAddr("udp", p.listenAddr)
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udpAddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf(":%d", p.listenPort))
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if err != nil {
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return fmt.Errorf("failed to resolve UDP address: %v", err)
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}
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p.udpConn, err = net.ListenUDP("udp", udpAddr)
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if err != nil {
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return fmt.Errorf("failed to listen on UDP: %v", err)
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return fmt.Errorf("failed to listen UDP address: %v", err)
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}
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defer func() {
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if p.udpConn != nil {
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err := p.udpConn.Close()
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if err != nil {
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log.Printf("failed to close UDP connection: %v", err)
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}
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}
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}()
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for {
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buffer := make([]byte, DNSMaxUDPPackageSize)
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n, clientAddr, err := p.udpConn.ReadFromUDP(buffer)
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if err != nil {
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log.Printf("Failed to read from UDP: %v", err)
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continue
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select {
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case <-ctx.Done():
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log.Println("Shutting down DNS proxy...")
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return nil
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default:
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buffer := make([]byte, DNSMaxUDPPackageSize)
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n, clientAddr, err := p.udpConn.ReadFromUDP(buffer)
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if err != nil {
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log.Printf("failed to read UDP packet: %v", err)
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continue
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}
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go p.handleDNSRequest(clientAddr, buffer[:n])
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}
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go p.handleDNSRequest(clientAddr, buffer[:n])
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}
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}
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func New(listenAddr string, listenPort uint16, upstreamAddr string, upstreamPort uint16) *DNSProxy {
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func (p DNSProxy) handleDNSRequest(clientAddr *net.UDPAddr, buffer []byte) {
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conn, err := net.Dial("udp", p.targetDNSServerAddress)
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if err != nil {
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log.Printf("failed to dial target DNS: %v", err)
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return
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}
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defer conn.Close()
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_, err = conn.Write(buffer)
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if err != nil {
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// TODO: Error log level
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log.Printf("failed to send request to target DNS: %v", err)
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return
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}
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err = conn.SetReadDeadline(time.Now().Add(5 * time.Second))
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if err != nil {
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// TODO: Error log level
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log.Printf("failed to set read deadline: %v", err)
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return
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}
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response := make([]byte, DNSMaxUDPPackageSize)
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n, err := conn.Read(response)
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if err != nil {
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// TODO: Error log level
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log.Printf("failed to read response from target DNS: %v", err)
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return
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}
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// TODO: Debug log level
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log.Printf("Response: %s", hex.EncodeToString(response[:n]))
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msg, err := ParseResponse(response[:n])
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if err == nil {
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if p.MsgHandler != nil {
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p.MsgHandler(msg)
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}
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} else {
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// TODO: Warn log level
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log.Printf("error while parsing DNS message: %v", err)
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}
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_, err = p.udpConn.WriteToUDP(response[:n], clientAddr)
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if err != nil {
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// TODO: Error log level
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log.Printf("failed to send DNS message: %v", err)
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return
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}
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}
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func New(listenPort uint16, targetDNSServerAddress string) *DNSProxy {
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return &DNSProxy{
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listenAddr: fmt.Sprintf("%s:%d", listenAddr, listenPort),
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upstreamAddr: fmt.Sprintf("%s:%d", upstreamAddr, upstreamPort),
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listenPort: listenPort,
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targetDNSServerAddress: targetDNSServerAddress,
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}
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}
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60
iptables-helper/iptables-helper.go
Normal file
60
iptables-helper/iptables-helper.go
Normal file
@ -0,0 +1,60 @@
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package iptablesHelper
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import (
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"fmt"
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"strconv"
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"github.com/coreos/go-iptables/iptables"
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)
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type DNSOverrider struct {
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ipt *iptables.IPTables
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chainName string
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destPort uint16
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}
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func (o DNSOverrider) Enable() error {
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err := o.ipt.ClearChain("nat", o.chainName)
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if err != nil {
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return fmt.Errorf("failed to clear chain: %w", err)
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}
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err = o.ipt.AppendUnique("nat", o.chainName, "-p", "udp", "--dport", "53", "-j", "REDIRECT", "--to-port", strconv.Itoa(int(o.destPort)))
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if err != nil {
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return fmt.Errorf("failed to create rule: %w", err)
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}
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err = o.ipt.InsertUnique("nat", "PREROUTING", 1, "-j", o.chainName)
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if err != nil {
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return fmt.Errorf("failed to linking chain: %w", err)
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}
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return nil
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}
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func (o DNSOverrider) Disable() error {
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err := o.ipt.DeleteIfExists("nat", "PREROUTING", "-j", o.chainName)
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if err != nil {
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return fmt.Errorf("failed to unlinking chain: %w", err)
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}
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err = o.ipt.ClearAndDeleteChain("nat", o.chainName)
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if err != nil {
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return fmt.Errorf("failed to delete chain: %w", err)
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}
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return nil
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}
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func NewDNSOverrider(chainName string, destPort uint16) (*DNSOverrider, error) {
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ipt, err := iptables.New()
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if err != nil {
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return nil, fmt.Errorf("iptables init fail: %w", err)
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}
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return &DNSOverrider{
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ipt: ipt,
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chainName: chainName,
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destPort: destPort,
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}, nil
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}
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105
main.go
105
main.go
@ -1,73 +1,98 @@
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package main
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import (
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"context"
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"fmt"
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dnsProxy "kvas2-go/dns-proxy"
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ruleComposer "kvas2-go/rule-composer"
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"log"
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"os"
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"os/signal"
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"syscall"
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dnsProxy "kvas2-go/dns-proxy"
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iptablesHelper "kvas2-go/iptables-helper"
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ruleComposer "kvas2-go/rule-composer"
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)
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var (
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ChainPostfix = "KVAS2"
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ListenPort = uint16(7548)
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UsableDNSServerAddress = "127.0.0.1"
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UsableDNSServerPort = uint16(53)
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TargetDNSServerAddress = "127.0.0.1:53"
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)
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func main() {
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records := ruleComposer.NewRecords()
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proxy := dnsProxy.New("", ListenPort, UsableDNSServerAddress, UsableDNSServerPort)
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proxy.MsgHandler = func(msg *dnsProxy.Message) {
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for _, q := range msg.QD {
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fmt.Printf("%x: <- Request name: %s\n", msg.ID, q.QName.String())
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fmt.Printf("%x: DBG (Before) Known addresses for: %s\n", msg.ID, q.QName.String())
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for idx, addr := range records.GetARecords(q.QName.String(), true) {
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fmt.Printf("%x: #%d: %s\n", msg.ID, idx, addr.String())
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}
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}
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for _, a := range msg.AN {
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switch v := a.(type) {
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case dnsProxy.Address:
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fmt.Printf("%x: -> A: Name: %s; Address: %s; TTL: %d\n", msg.ID, v.Name, v.Address.String(), v.TTL)
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records.PutARecord(v.Name.String(), v.Address, int64(v.TTL))
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case dnsProxy.CName:
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fmt.Printf("%x: -> CNAME: Name: %s; CName: %s\n", msg.ID, v.Name, v.CName)
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records.PutCNameRecord(v.Name.String(), v.CName.String(), int64(v.TTL))
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default:
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fmt.Printf("%x: -> Unknown: %x\n", msg.ID, v.EncodeResource())
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}
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}
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for _, a := range msg.NS {
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fmt.Printf("%x: -> NS: %x\n", msg.ID, a.EncodeResource())
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}
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for _, a := range msg.AR {
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fmt.Printf("%x: -> NS: %x\n", msg.ID, a.EncodeResource())
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}
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for _, q := range msg.QD {
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fmt.Printf("%x: DBG (After) Known addresses for: %s\n", msg.ID, q.QName.String())
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for idx, addr := range records.GetARecords(q.QName.String(), true) {
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fmt.Printf("%x: #%d: %s\n", msg.ID, idx, addr.String())
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}
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}
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proxy := dnsProxy.New(ListenPort, TargetDNSServerAddress)
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dnsOverrider, err := iptablesHelper.NewDNSOverrider(fmt.Sprintf("%s_DNSOVERRIDER", ChainPostfix), ListenPort)
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if err != nil {
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log.Fatalf("failed to initialize DNS overrider: %v", err)
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}
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proxy.MsgHandler = func(msg *dnsProxy.Message) {
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printKnownRecords := func() {
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for _, q := range msg.QD {
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fmt.Printf("%04x: DBG Known addresses for: %s\n", msg.ID, q.QName.String())
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for idx, addr := range records.GetARecords(q.QName.String(), true) {
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fmt.Printf("%04x: #%d: %s\n", msg.ID, idx, addr.String())
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}
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}
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}
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parseResponseRecord := func(rr dnsProxy.ResourceRecord) {
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switch v := rr.(type) {
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case dnsProxy.Address:
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fmt.Printf("%04x: -> A: Name: %s; Address: %s; TTL: %d\n", msg.ID, v.Name, v.Address.String(), v.TTL)
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records.PutARecord(v.Name.String(), v.Address, int64(v.TTL))
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case dnsProxy.CName:
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fmt.Printf("%04x: -> CNAME: Name: %s; CName: %s\n", msg.ID, v.Name, v.CName)
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records.PutCNameRecord(v.Name.String(), v.CName.String(), int64(v.TTL))
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default:
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fmt.Printf("%04x: -> Unknown: %x\n", msg.ID, v.EncodeResource())
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}
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}
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printKnownRecords()
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for _, q := range msg.QD {
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fmt.Printf("%04x: <- Request name: %s\n", msg.ID, q.QName.String())
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}
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for _, a := range msg.AN {
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parseResponseRecord(a)
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}
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for _, a := range msg.NS {
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parseResponseRecord(a)
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}
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for _, a := range msg.AR {
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parseResponseRecord(a)
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}
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printKnownRecords()
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}
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ctx, cancel := context.WithCancel(context.Background())
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go func() {
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err := proxy.Listen()
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err := proxy.Listen(ctx)
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if err != nil {
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log.Fatal(err)
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}
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}()
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err = dnsOverrider.Enable()
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if err != nil {
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log.Fatalf("failed to override DNS: %v", err)
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}
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fmt.Printf("Started service on port '%d'\n", ListenPort)
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c := make(chan os.Signal, 1)
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signal.Notify(c, os.Interrupt, syscall.SIGTERM)
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for {
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select {
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case <-c:
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proxy.Close()
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fmt.Printf("Graceful shutdown...")
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cancel()
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err = dnsOverrider.Disable()
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if err != nil {
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log.Fatalf("failed to rollback override DNS changes: %v", err)
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}
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return
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}
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}
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