139 lines
3.8 KiB
Go
139 lines
3.8 KiB
Go
package dns
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import (
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"context"
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"fmt"
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"net"
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"github.com/hashicorp/go-hclog"
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"github.com/miekg/dns"
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"google.golang.org/grpc"
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"google.golang.org/grpc/codes"
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"google.golang.org/grpc/peer"
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"google.golang.org/grpc/status"
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"github.com/hashicorp/consul/proto-public/pbdns"
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)
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type LocalAddr struct {
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IP net.IP
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Port int
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}
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type Config struct {
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Logger hclog.Logger
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DNSServeMux *dns.ServeMux
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LocalAddr LocalAddr
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}
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type Server struct {
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Config
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}
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func NewServer(cfg Config) *Server {
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return &Server{cfg}
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}
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func (s *Server) Register(grpcServer *grpc.Server) {
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pbdns.RegisterDNSServiceServer(grpcServer, s)
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}
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// BufferResponseWriter writes a DNS response to a byte buffer.
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type BufferResponseWriter struct {
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responseBuffer []byte
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LocalAddress net.Addr
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RemoteAddress net.Addr
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Logger hclog.Logger
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}
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// LocalAddr returns the net.Addr of the server
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func (b *BufferResponseWriter) LocalAddr() net.Addr {
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return b.LocalAddress
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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 (b *BufferResponseWriter) RemoteAddr() net.Addr {
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return b.RemoteAddress
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}
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// WriteMsg writes a reply back to the client.
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func (b *BufferResponseWriter) WriteMsg(m *dns.Msg) error {
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// Pack message to bytes first.
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msgBytes, err := m.Pack()
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if err != nil {
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b.Logger.Error("error packing message", "err", err)
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return err
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}
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b.responseBuffer = msgBytes
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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 (b *BufferResponseWriter) Write(m []byte) (int, error) {
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b.Logger.Debug("Write was called")
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return copy(b.responseBuffer, m), nil
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}
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// Close closes the connection.
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func (b *BufferResponseWriter) Close() error {
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// There's nothing for us to do here as we don't handle the connection.
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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 (b *BufferResponseWriter) TsigStatus() error {
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// TSIG doesn't apply to this response writer.
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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 (b *BufferResponseWriter) TsigTimersOnly(bool) {}
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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 (b *BufferResponseWriter) Hijack() {}
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// Query is a gRPC endpoint that will serve dns requests. It will be consumed primarily by the
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// consul dataplane to proxy dns requests to consul.
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func (s *Server) Query(ctx context.Context, req *pbdns.QueryRequest) (*pbdns.QueryResponse, error) {
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pr, ok := peer.FromContext(ctx)
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if !ok {
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return nil, fmt.Errorf("error retrieving peer information from context")
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}
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var local net.Addr
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var remote net.Addr
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// We do this so that we switch to udp/tcp when handling the request since it will be proxied
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// through consul through gRPC and we need to 'fake' the protocol so that the message is trimmed
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// according to wether it is UDP or TCP.
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switch req.GetProtocol() {
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case pbdns.Protocol_PROTOCOL_TCP:
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remote = pr.Addr
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local = &net.TCPAddr{IP: s.LocalAddr.IP, Port: s.LocalAddr.Port}
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case pbdns.Protocol_PROTOCOL_UDP:
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remoteAddr := pr.Addr.(*net.TCPAddr)
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remote = &net.UDPAddr{IP: remoteAddr.IP, Port: remoteAddr.Port}
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local = &net.UDPAddr{IP: s.LocalAddr.IP, Port: s.LocalAddr.Port}
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default:
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return nil, status.Error(codes.InvalidArgument, fmt.Sprintf("error protocol type not set: %v", req.GetProtocol()))
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}
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respWriter := &BufferResponseWriter{
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LocalAddress: local,
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RemoteAddress: remote,
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Logger: s.Logger,
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}
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msg := &dns.Msg{}
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err := msg.Unpack(req.Msg)
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if err != nil {
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s.Logger.Error("error unpacking message", "err", err)
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return nil, status.Error(codes.Internal, fmt.Sprintf("failure decoding dns request: %s", err.Error()))
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}
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s.DNSServeMux.ServeDNS(respWriter, msg)
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queryResponse := &pbdns.QueryResponse{Msg: respWriter.responseBuffer}
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return queryResponse, nil
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}
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