implemented dns header structure and serialization

internal/dns/header.go

@@ -1 +1,37 @@
 package dns
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	"log"
+)
+
+type DNSHeader struct {
+	ID      uint16
+	Flags   uint16
+	QDCount uint16
+	ANCount uint16
+	NSCount uint16
+	ARCount uint16
+}
+
+// Serialize converts the DNSHeader into a byte slice
+func (h *DNSHeader) Serialize() []byte {
+	buf := make([]byte, 12)
+	binary.BigEndian.PutUint16(buf[0:2], h.ID)
+	binary.BigEndian.PutUint16(buf[2:4], h.Flags)
+	binary.BigEndian.PutUint16(buf[4:6], h.QDCount)
+	binary.BigEndian.PutUint16(buf[6:8], h.ARCount)
+	binary.BigEndian.PutUint16(buf[8:10], h.NSCount)
+	binary.BigEndian.PutUint16(buf[10:12], h.ARCount)
+	return buf
+}
+
+// genertae a random 16bit identifier
+func GenerateRandomID() uint16 {
+	var id [2]byte
+	if _, err := rand.Read(id[:]); err != nil {
+		log.Fatalf("Failed to generate random ID: %v", err)
+	}
+	return binary.BigEndian.Uint16(id[:])
+}