Add protocol version field to Response struct

ntp.go

@@ -169,6 +169,11 @@ func (h *header) setLeap(li LeapIndicator) {
 	h.LiVnMode = (h.LiVnMode & 0x3f) | uint8(li)<<6
 }
 
+// getVersion returns the version value in the header.
+func (h *header) getVersion() int {
+	return int((h.LiVnMode >> 3) & 0x7)
+}
+
 // getMode returns the mode value in the header.
 func (h *header) getMode() mode {
 	return mode(h.LiVnMode & 0x07)
@@ -261,6 +266,9 @@ type Response struct {
 	// Precision is the reported precision of the server's clock.
 	Precision time.Duration
 
+	// Version is the NTP protocol version number reported by the server.
+	Version int
+
 	// Stratum is the "stratum level" of the server. The smaller the number,
 	// the closer the server is to the reference clock. Stratum 1 servers are
 	// attached directly to the reference clock. A stratum value of 0
@@ -693,6 +701,7 @@ func generateResponse(h *header, recvTime ntpTime, authErr error) *Response {
 		ClockOffset:    offset(h.OriginTime, h.ReceiveTime, h.TransmitTime, recvTime),
 		RTT:            rtt(h.OriginTime, h.ReceiveTime, h.TransmitTime, recvTime),
 		Precision:      toInterval(h.Precision),
+		Version:        h.getVersion(),
 		Stratum:        h.Stratum,
 		ReferenceID:    h.ReferenceID,
 		ReferenceTime:  h.ReferenceTime.Time(),

ntp_test.go

@@ -68,6 +68,7 @@ func logResponse(t *testing.T, r *Response) {
 	t.Logf("[%s]  SystemTime: %s", host, now.Format(timeFormat))
 	t.Logf("[%s]   ~TrueTime: %s", host, now.Add(r.ClockOffset).Format(timeFormat))
 	t.Logf("[%s]    XmitTime: %s", host, r.Time.Format(timeFormat))
+	t.Logf("[%s]     Version: %d", host, r.Version)
 	t.Logf("[%s]     Stratum: %d", host, r.Stratum)
 	t.Logf("[%s]       RefID: %s (0x%08x)", host, r.ReferenceString(), r.ReferenceID)
 	t.Logf("[%s]     RefTime: %s", host, r.ReferenceTime.Format(timeFormat))