refactor: DNS

dns/transport/hosts/hosts.go

@@ -0,0 +1,63 @@
+package hosts
+
+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"
+
+	mDNS "github.com/miekg/dns"
+)
+
+func RegisterTransport(registry *dns.TransportRegistry) {
+	dns.RegisterTransport[option.HostsDNSServerOptions](registry, C.DNSTypeHosts, NewTransport)
+}
+
+var _ adapter.DNSTransport = (*Transport)(nil)
+
+type Transport struct {
+	dns.TransportAdapter
+	files []*File
+}
+
+func NewTransport(ctx context.Context, logger log.ContextLogger, tag string, options option.HostsDNSServerOptions) (adapter.DNSTransport, error) {
+	var files []*File
+	if len(options.Path) == 0 {
+		files = append(files, NewFile(DefaultPath))
+	} else {
+		for _, path := range options.Path {
+			files = append(files, NewFile(path))
+		}
+	}
+	return &Transport{
+		TransportAdapter: dns.NewTransportAdapter(C.DNSTypeHosts, tag, nil),
+		files:            files,
+	}, nil
+}
+
+func (t *Transport) Reset() {
+}
+
+func (t *Transport) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
+	question := message.Question[0]
+	domain := dns.FqdnToDomain(question.Name)
+	if question.Qtype == mDNS.TypeA || question.Qtype == mDNS.TypeAAAA {
+		for _, file := range t.files {
+			addresses := file.Lookup(domain)
+			if len(addresses) > 0 {
+				return dns.FixedResponse(message.Id, question, addresses, C.DefaultDNSTTL), nil
+			}
+		}
+	}
+	return &mDNS.Msg{
+		MsgHdr: mDNS.MsgHdr{
+			Id:       message.Id,
+			Rcode:    mDNS.RcodeNameError,
+			Response: true,
+		},
+		Question: []mDNS.Question{question},
+	}, nil
+}