refactor: DNS

dns/transport/predefined.go

@@ -0,0 +1,83 @@
+package transport
+
+import (
+	"context"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/dns"
+	"github.com/sagernet/sing-box/log"
+	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common"
+	E "github.com/sagernet/sing/common/exceptions"
+
+	mDNS "github.com/miekg/dns"
+)
+
+var _ adapter.DNSTransport = (*PredefinedTransport)(nil)
+
+func RegisterPredefined(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.PredefinedDNSServerOptions](registry, C.DNSTypePreDefined, NewPredefined)
+}
+
+type PredefinedTransport struct {
+	dns.TransportAdapter
+	responses []*predefinedResponse
+}
+
+type predefinedResponse struct {
+	questions []mDNS.Question
+	answer    *mDNS.Msg
+}
+
+func NewPredefined(ctx context.Context, logger log.ContextLogger, tag string, options option.PredefinedDNSServerOptions) (adapter.DNSTransport, error) {
+	var responses []*predefinedResponse
+	for _, response := range options.Responses {
+		questions, msg, err := response.Build()
+		if err != nil {
+			return nil, err
+		}
+		responses = append(responses, &predefinedResponse{
+			questions: questions,
+			answer:    msg,
+		})
+	}
+	if len(responses) == 0 {
+		return nil, E.New("empty predefined responses")
+	}
+	return &PredefinedTransport{
+		TransportAdapter: dns.NewTransportAdapter(C.DNSTypePreDefined, tag, nil),
+		responses:        responses,
+	}, nil
+}
+
+func (t *PredefinedTransport) Reset() {
+}
+
+func (t *PredefinedTransport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	for _, response := range t.responses {
+		for _, question := range response.questions {
+			if func() bool {
+				if question.Name == "" && question.Qtype == mDNS.TypeNone {
+					return true
+				} else if question.Name == "" {
+					return common.Any(message.Question, func(it mDNS.Question) bool {
+						return it.Qtype == question.Qtype
+					})
+				} else if question.Qtype == mDNS.TypeNone {
+					return common.Any(message.Question, func(it mDNS.Question) bool {
+						return it.Name == question.Name
+					})
+				} else {
+					return common.Contains(message.Question, question)
+				}
+			}() {
+				copyAnswer := *response.answer
+				copyAnswer.Id = message.Id
+				copyAnswer.Question = message.Question
+				return &copyAnswer, nil
+			}
+		}
+	}
+	return nil, dns.RCodeNameError
+}