mirror of
https://github.com/netbirdio/netbird.git
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1d9feab2d9
Works only with userspace implementation: 1. Configure host to solve DNS requests via a fake DSN server address in the Netbird network. 2. Add to firewall catch rule for these DNS requests. 3. Resolve these DNS requests and respond by writing directly to wireguard device.
104 lines
2.6 KiB
Go
104 lines
2.6 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 err
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}
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_, err = r.Write(buff)
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return err
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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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