Add domain sniffer

common/sniff/dns.go

@@ -0,0 +1,58 @@
+package sniff
+
+import (
+	"context"
+	"encoding/binary"
+	"io"
+	"os"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/buf"
+	"github.com/sagernet/sing/common/task"
+	"golang.org/x/net/dns/dnsmessage"
+)
+
+func StreamDomainNameQuery(readCtx context.Context, reader io.Reader) (*adapter.InboundContext, error) {
+	var length uint16
+	err := binary.Read(reader, binary.BigEndian, &length)
+	if err != nil {
+		return nil, err
+	}
+	if length > 512 {
+		return nil, os.ErrInvalid
+	}
+	_buffer := buf.StackNewSize(int(length))
+	defer common.KeepAlive(_buffer)
+	buffer := common.Dup(_buffer)
+	defer buffer.Release()
+
+	readCtx, cancel := context.WithTimeout(readCtx, time.Millisecond*100)
+	err = task.Run(readCtx, func() error {
+		return common.Error(buffer.ReadFullFrom(reader, buffer.FreeLen()))
+	})
+	cancel()
+	if err != nil {
+		return nil, err
+	}
+	return DomainNameQuery(readCtx, buffer.Bytes())
+}
+
+func DomainNameQuery(ctx context.Context, packet []byte) (*adapter.InboundContext, error) {
+	var parser dnsmessage.Parser
+	_, err := parser.Start(packet)
+	if err != nil {
+		return nil, err
+	}
+	question, err := parser.Question()
+	if err != nil {
+		return nil, os.ErrInvalid
+	}
+	domain := question.Name.String()
+	if question.Class == dnsmessage.ClassINET && (question.Type == dnsmessage.TypeA || question.Type == dnsmessage.TypeAAAA) && IsDomainName(domain) {
+		return &adapter.InboundContext{Protocol: C.ProtocolDNS, Domain: domain}, nil
+	}
+	return nil, os.ErrInvalid
+}