implemented dns question structure and serialization

internal/dns/question.go

@@ -1 +1,33 @@
 package dns
+
+import (
+	"encoding/binary"
+	"strings"
+)
+
+type DNSQuestion struct {
+	QName  string
+	QType  uint16
+	QClass uint16
+}
+
+// convert dns question into a byte slice
+func (q *DNSQuestion) Serialize() []byte {
+	buf := EncodeQName(q.QName)
+	question := make([]byte, 4)
+	binary.BigEndian.PutUint16(question[0:2], q.QType)
+	binary.BigEndian.PutUint16(question[2:4], q.QClass)
+	return append(buf, question...)
+}
+
+// encode a domain name to dns format
+func EncodeQName(domain string) []byte {
+	parts := strings.Split(domain, ".")
+	var encoded []byte
+	for _, part := range parts {
+		encoded = append(encoded, byte(len(part)))
+		encoded = append(encoded, part...)
+	}
+	encoded = append(encoded, 0)
+	return encoded
+}