3 files changed, 10 insertions, 39 deletions

diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index cc34e74b2..7b80f7519 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -289,8 +289,9 @@ func (h *handshake) synRcvdState(s *segment) *tcpip.Error {
 		}
 
 		// Update timestamp if required. See RFC7323, section-4.3.
-		h.ep.updateRecentTimestamp(s.parsedOptions.TSVal, h.ackNum, s.sequenceNumber)
-
+		if h.ep.sendTSOk && s.parsedOptions.TS {
+			h.ep.updateRecentTimestamp(s.parsedOptions.TSVal, h.ackNum, s.sequenceNumber)
+		}
 		h.state = handshakeCompleted
 		return nil
 	}
@@ -740,16 +741,6 @@ func (e *endpoint) handleSegments() *tcpip.Error {
 			// send window scale.
 			s.window <<= e.snd.sndWndScale
 
-			// If the timestamp option is negotiated and the segment
-			// does not carry a timestamp option then the segment
-			// must be dropped as per
-			// https://tools.ietf.org/html/rfc7323#section-3.2.
-			if e.sendTSOk && !s.parsedOptions.TS {
-				e.stack.Stats().DroppedPackets.Increment()
-				s.decRef()
-				continue
-			}
-
 			// RFC 793, page 41 states that "once in the ESTABLISHED
 			// state all segments must carry current acknowledgment
 			// information."
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index 122c52f32..5c9e76fa1 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -635,14 +635,15 @@ func (s *sender) checkDuplicateAck(seg *segment) (rtx bool) {
 // updating the send-related state.
 func (s *sender) handleRcvdSegment(seg *segment) {
 	// Check if we can extract an RTT measurement from this ack.
-	if !s.ep.sendTSOk && s.rttMeasureSeqNum.LessThan(seg.ackNumber) {
+	if !seg.parsedOptions.TS && s.rttMeasureSeqNum.LessThan(seg.ackNumber) {
 		s.updateRTO(time.Now().Sub(s.rttMeasureTime))
 		s.rttMeasureSeqNum = s.sndNxt
 	}
 
 	// Update Timestamp if required. See RFC7323, section-4.3.
-	s.ep.updateRecentTimestamp(seg.parsedOptions.TSVal, s.maxSentAck, seg.sequenceNumber)
-
+	if s.ep.sendTSOk && seg.parsedOptions.TS {
+		s.ep.updateRecentTimestamp(seg.parsedOptions.TSVal, s.maxSentAck, seg.sequenceNumber)
+	}
 	// Count the duplicates and do the fast retransmit if needed.
 	rtx := s.checkDuplicateAck(seg)
 
diff --git a/pkg/tcpip/transport/tcp/tcp_timestamp_test.go b/pkg/tcpip/transport/tcp/tcp_timestamp_test.go
index b08df0fec..87c640967 100644
--- a/pkg/tcpip/transport/tcp/tcp_timestamp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_timestamp_test.go
@@ -255,7 +255,7 @@ func TestSendGreaterThanMTUWithOptions(t *testing.T) {
 	testBrokenUpWrite(t, c, maxPayload)
 }
 
-func TestSegmentDropWhenTimestampMissing(t *testing.T) {
+func TestSegmentNotDroppedWhenTimestampMissing(t *testing.T) {
 	const maxPayload = 100
 	c := context.New(t, uint32(header.TCPMinimumSize+header.IPv4MinimumSize+maxPayload))
 	defer c.Cleanup()
@@ -270,37 +270,16 @@ func TestSegmentDropWhenTimestampMissing(t *testing.T) {
 	droppedPacketsStat := c.Stack().Stats().DroppedPackets
 	droppedPackets := droppedPacketsStat.Value()
 	data := []byte{1, 2, 3}
-	// Save the sequence number as we will reset it later down
-	// in the test.
-	savedSeqNum := rep.NextSeqNum
+	// Send a packet with no TCP options/timestamp.
 	rep.SendPacket(data, nil)
 
 	select {
 	case <-ch:
-		t.Fatalf("Got data to read when we expect packet to be dropped")
-	case <-time.After(1 * time.Second):
-		// We expect that no data will be available to read.
-	}
-
-	// Assert that DroppedPackets was incremented by 1.
-	if got, want := droppedPacketsStat.Value(), droppedPackets+1; got != want {
-		t.Fatalf("incorrect number of dropped packets, got: %v, want: %v", got, want)
-	}
-
-	droppedPackets = droppedPacketsStat.Value()
-	// Reset the sequence number so that the other endpoint accepts
-	// this segment and does not treat it like an out of order delivery.
-	rep.NextSeqNum = savedSeqNum
-	// Now send a packet with timestamp and we should get the data.
-	rep.SendPacketWithTS(data, rep.TSVal+1)
-
-	select {
-	case <-ch:
 	case <-time.After(1 * time.Second):
 		t.Fatalf("Timed out waiting for data to arrive")
 	}
 
-	// Assert that DroppedPackets was not incremented by 1.
+	// Assert that DroppedPackets was not incremented.
 	if got, want := droppedPacketsStat.Value(), droppedPackets; got != want {
 		t.Fatalf("incorrect number of dropped packets, got: %v, want: %v", got, want)
 	}