Merge pull request #53 from jaehnri/main

Add 2-byte prefix with DNS message length in DoQ

transport/quic.go

@@ -2,6 +2,7 @@ package transport
 
 import (
 	"crypto/tls"
+	"encoding/binary"
 	"fmt"
 	"io"
 	"time"
@@ -76,7 +77,11 @@ func QUIC(msg *dns.Msg,
 		return nil, err
 	}
 
-	_, err = stream.Write(buf)
+	// All DNS messages (queries and responses) sent over DoQ connections
+	// MUST be encoded as a 2-octet length field followed by the message
+	// content as specified in [RFC1035].
+	// https://datatracker.ietf.org/doc/html/rfc9250#section-4.2-4
+	_, err = stream.Write(addPrefix(buf))
 	if err != nil {
 		return nil, err
 	}
@@ -96,10 +101,19 @@ func QUIC(msg *dns.Msg,
 	}
 
 	reply := dns.Msg{}
-	err = reply.Unpack(respBuf)
+	err = reply.Unpack(respBuf[2:])
 	if err != nil {
 		return nil, fmt.Errorf("unpacking response from %s: %s", server, err)
 	}
 
 	return &reply, nil
 }
+
+// addPrefix adds a 2-byte prefix with the DNS message length.
+func addPrefix(b []byte) (m []byte) {
+	m = make([]byte, 2+len(b))
+	binary.BigEndian.PutUint16(m, uint16(len(b)))
+	copy(m[2:], b)
+
+	return m
+}