mirror of
https://github.com/netbirdio/netbird.git
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107 lines
2.7 KiB
Go
107 lines
2.7 KiB
Go
package dns
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import (
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"fmt"
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"net"
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"github.com/google/gopacket"
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"github.com/google/gopacket/layers"
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"github.com/miekg/dns"
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"golang.zx2c4.com/wireguard/tun"
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)
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type responseWriter struct {
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local net.Addr
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remote net.Addr
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packet gopacket.Packet
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device tun.Device
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}
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// LocalAddr returns the net.Addr of the server
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func (r *responseWriter) LocalAddr() net.Addr {
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return r.local
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}
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// RemoteAddr returns the net.Addr of the client that sent the current request.
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func (r *responseWriter) RemoteAddr() net.Addr {
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return r.remote
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}
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// WriteMsg writes a reply back to the client.
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func (r *responseWriter) WriteMsg(msg *dns.Msg) error {
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buff, err := msg.Pack()
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if err != nil {
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return fmt.Errorf("pack: %w", err)
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}
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if _, err := r.Write(buff); err != nil {
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return fmt.Errorf("write: %w", err)
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}
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return nil
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}
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// Write writes a raw buffer back to the client.
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func (r *responseWriter) Write(data []byte) (int, error) {
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var ip gopacket.SerializableLayer
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// Get the UDP layer
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udpLayer := r.packet.Layer(layers.LayerTypeUDP)
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udp := udpLayer.(*layers.UDP)
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// Swap the source and destination addresses for the response
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udp.SrcPort, udp.DstPort = udp.DstPort, udp.SrcPort
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// Check if it's an IPv4 packet
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if ipv4Layer := r.packet.Layer(layers.LayerTypeIPv4); ipv4Layer != nil {
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ipv4 := ipv4Layer.(*layers.IPv4)
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ipv4.SrcIP, ipv4.DstIP = ipv4.DstIP, ipv4.SrcIP
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ip = ipv4
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} else if ipv6Layer := r.packet.Layer(layers.LayerTypeIPv6); ipv6Layer != nil {
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ipv6 := ipv6Layer.(*layers.IPv6)
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ipv6.SrcIP, ipv6.DstIP = ipv6.DstIP, ipv6.SrcIP
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ip = ipv6
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}
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if err := udp.SetNetworkLayerForChecksum(ip.(gopacket.NetworkLayer)); err != nil {
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return 0, fmt.Errorf("failed to set network layer for checksum: %v", err)
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}
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// Serialize the packet
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buffer := gopacket.NewSerializeBuffer()
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options := gopacket.SerializeOptions{
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ComputeChecksums: true,
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FixLengths: true,
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}
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payload := gopacket.Payload(data)
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err := gopacket.SerializeLayers(buffer, options, ip, udp, payload)
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if err != nil {
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return 0, fmt.Errorf("failed to serialize packet: %v", err)
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}
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send := buffer.Bytes()
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sendBuffer := make([]byte, 40, len(send)+40)
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sendBuffer = append(sendBuffer, send...)
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return r.device.Write([][]byte{sendBuffer}, 40)
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}
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// Close closes the connection.
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func (r *responseWriter) Close() error {
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return nil
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}
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// TsigStatus returns the status of the Tsig.
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func (r *responseWriter) TsigStatus() error {
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return nil
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}
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// TsigTimersOnly sets the tsig timers only boolean.
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func (r *responseWriter) TsigTimersOnly(bool) {
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}
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// Hijack lets the caller take over the connection.
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// After a call to Hijack(), the DNS package will not do anything with the connection.
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func (r *responseWriter) Hijack() {
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}
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