[RFC-9250]: Add QUIC server support (#6182)

Add DNS-over-QUIC server 

Signed-off-by: jaehnri <joao.henri.cr@gmail.com>
Signed-off-by: João Henri <joao.henri.cr@gmail.com>

core/dnsserver/quic.go

@@ -0,0 +1,60 @@
+package dnsserver
+
+import (
+	"encoding/binary"
+	"net"
+
+	"github.com/miekg/dns"
+	"github.com/quic-go/quic-go"
+)
+
+type DoQWriter struct {
+	localAddr  net.Addr
+	remoteAddr net.Addr
+	stream     quic.Stream
+	Msg        *dns.Msg
+}
+
+func (w *DoQWriter) Write(b []byte) (int, error) {
+	b = AddPrefix(b)
+	return w.stream.Write(b)
+}
+
+func (w *DoQWriter) WriteMsg(m *dns.Msg) error {
+	bytes, err := m.Pack()
+	if err != nil {
+		return err
+	}
+
+	_, err = w.Write(bytes)
+	if err != nil {
+		return err
+	}
+
+	return w.Close()
+}
+
+// Close sends the STREAM FIN signal.
+// The server MUST send the response(s) on the same stream and MUST
+// indicate, after the last response, through the STREAM FIN
+// mechanism that no further data will be sent on that stream.
+// See https://www.rfc-editor.org/rfc/rfc9250#section-4.2-7
+func (w *DoQWriter) Close() error {
+	return w.stream.Close()
+}
+
+// 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
+}
+
+// These methods implement the dns.ResponseWriter interface from Go DNS.
+func (w *DoQWriter) TsigStatus() error     { return nil }
+func (w *DoQWriter) TsigTimersOnly(b bool) {}
+func (w *DoQWriter) Hijack()               {}
+func (w *DoQWriter) LocalAddr() net.Addr   { return w.localAddr }
+func (w *DoQWriter) RemoteAddr() net.Addr  { return w.remoteAddr }