Use the packet trace timestamps in netflow records

Instead of the current time.
Equally, copy the incoming stream (on the in channel) timestamps.

The aggregate segment will take the first timestamp as flow start and
the last timestamp as flow end from all the connected sub-flows for the
final flow (at least when the packet trace/flow data is sorted by time).

segments/filter/aggregate/flowcache.go

@@ -265,10 +265,10 @@ func (f *FlowExporter) Insert(pkt gopacket.Packet) {
 	f.mutex.Lock()
 	if record, exists = f.cache[key]; !exists {
 		f.cache[key] = new(FlowRecord)
-		f.cache[key].TimeReceived = time.Now()
+		f.cache[key].TimeReceived = pkt.Metadata().Timestamp
 		record = f.cache[key]
 	}
-	record.LastUpdated = time.Now()
+	record.LastUpdated = pkt.Metadata().Timestamp
 	record.SamplerAddress = f.samplerAddress
 	record.Packets = append(record.Packets, pkt)
 
@@ -291,10 +291,10 @@ func (f *FlowExporter) InsertFlow(flow *pb.EnrichedFlow) {
 	f.mutex.Lock()
 	if record, exists = f.cache[key]; !exists {
 		f.cache[key] = new(FlowRecord)
-		f.cache[key].TimeReceived = time.Now()
+		f.cache[key].TimeReceived = time.Unix(int64(flow.TimeFlowStart), 0)
 		record = f.cache[key]
 	}
-	record.LastUpdated = time.Now()
+	record.LastUpdated = time.Unix(int64(flow.TimeFlowEnd), 0)
 	record.SamplerAddress = f.samplerAddress
 	record.Flows = append(record.Flows, flow)
 }