diff options
| -rw-r--r-- | pkg/tcpip/stack/stack.go | 1 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/endpoint.go | 1 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/rack.go | 11 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/snd.go | 64 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/tcp_rack_test.go | 415 |
5 files changed, 470 insertions, 22 deletions
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go index ca9f41af4..e0025e0a9 100644 --- a/pkg/tcpip/stack/stack.go +++ b/pkg/tcpip/stack/stack.go @@ -82,6 +82,7 @@ type TCPRACKState struct { FACK seqnum.Value RTT time.Duration Reord bool + DSACKSeen bool } // TCPEndpointID is the unique 4 tuple that identifies a given endpoint. diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go index 194d3a8a4..e78138415 100644 --- a/pkg/tcpip/transport/tcp/endpoint.go +++ b/pkg/tcpip/transport/tcp/endpoint.go @@ -3051,6 +3051,7 @@ func (e *endpoint) completeState() stack.TCPEndpointState { FACK: rc.fack, RTT: rc.rtt, Reord: rc.reorderSeen, + DSACKSeen: rc.dsackSeen, } return s } diff --git a/pkg/tcpip/transport/tcp/rack.go b/pkg/tcpip/transport/tcp/rack.go index d312b1b8b..e0a50a919 100644 --- a/pkg/tcpip/transport/tcp/rack.go +++ b/pkg/tcpip/transport/tcp/rack.go @@ -29,12 +29,12 @@ import ( // // +stateify savable type rackControl struct { + // dsackSeen indicates if the connection has seen a DSACK. + dsackSeen bool + // endSequence is the ending TCP sequence number of rackControl.seg. endSequence seqnum.Value - // dsack indicates if the connection has seen a DSACK. - dsack bool - // fack is the highest selectively or cumulatively acknowledged // sequence. fack seqnum.Value @@ -122,3 +122,8 @@ func (rc *rackControl) detectReorder(seg *segment) { rc.reorderSeen = true } } + +// setDSACKSeen updates rack control if duplicate SACK is seen by the connection. +func (rc *rackControl) setDSACKSeen() { + rc.dsackSeen = true +} diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go index c42d7159a..201cf9aa9 100644 --- a/pkg/tcpip/transport/tcp/snd.go +++ b/pkg/tcpip/transport/tcp/snd.go @@ -1182,25 +1182,29 @@ func (s *sender) detectLoss(seg *segment) (fastRetransmit bool) { // See: https://tools.ietf.org/html/draft-ietf-tcpm-rack-08#section-7.2 // steps 2 and 3. func (s *sender) walkSACK(rcvdSeg *segment) { - if len(rcvdSeg.parsedOptions.SACKBlocks) == 0 { + // Look for DSACK block. + idx := 0 + n := len(rcvdSeg.parsedOptions.SACKBlocks) + if s.checkDSACK(rcvdSeg) { + s.rc.setDSACKSeen() + idx = 1 + n-- + } + + if n == 0 { return } // Sort the SACK blocks. The first block is the most recent unacked // block. The following blocks can be in arbitrary order. - sackBlocks := make([]header.SACKBlock, len(rcvdSeg.parsedOptions.SACKBlocks)) - copy(sackBlocks, rcvdSeg.parsedOptions.SACKBlocks) + sackBlocks := make([]header.SACKBlock, n) + copy(sackBlocks, rcvdSeg.parsedOptions.SACKBlocks[idx:]) sort.Slice(sackBlocks, func(i, j int) bool { return sackBlocks[j].Start.LessThan(sackBlocks[i].Start) }) seg := s.writeList.Front() for _, sb := range sackBlocks { - // This check excludes DSACK blocks. - if sb.Start.LessThanEq(rcvdSeg.ackNumber) || sb.Start.LessThanEq(s.sndUna) || s.sndNxt.LessThan(sb.End) { - continue - } - for seg != nil && seg.sequenceNumber.LessThan(sb.End) && seg.xmitCount != 0 { if sb.Start.LessThanEq(seg.sequenceNumber) && !seg.acked { s.rc.update(seg, rcvdSeg, s.ep.tsOffset) @@ -1212,6 +1216,50 @@ func (s *sender) walkSACK(rcvdSeg *segment) { } } +// checkDSACK checks if a DSACK is reported and updates it in RACK. +func (s *sender) checkDSACK(rcvdSeg *segment) bool { + n := len(rcvdSeg.parsedOptions.SACKBlocks) + if n == 0 { + return false + } + + sb := rcvdSeg.parsedOptions.SACKBlocks[0] + // Check if SACK block is invalid. + if sb.End.LessThan(sb.Start) { + return false + } + + // See: https://tools.ietf.org/html/rfc2883#section-5 DSACK is sent in + // at most one SACK block. DSACK is detected in the below two cases: + // * If the SACK sequence space is less than this cumulative ACK, it is + // an indication that the segment identified by the SACK block has + // been received more than once by the receiver. + // * If the sequence space in the first SACK block is greater than the + // cumulative ACK, then the sender next compares the sequence space + // in the first SACK block with the sequence space in the second SACK + // block, if there is one. This comparison can determine if the first + // SACK block is reporting duplicate data that lies above the + // cumulative ACK. + if sb.Start.LessThan(rcvdSeg.ackNumber) { + return true + } + + if n > 1 { + sb1 := rcvdSeg.parsedOptions.SACKBlocks[1] + if sb1.End.LessThan(sb1.Start) { + return false + } + + // If the first SACK block is fully covered by second SACK + // block, then the first block is a DSACK block. + if sb.End.LessThanEq(sb1.End) && sb1.Start.LessThanEq(sb.Start) { + return true + } + } + + return false +} + // handleRcvdSegment is called when a segment is received; it is responsible for // updating the send-related state. func (s *sender) handleRcvdSegment(rcvdSeg *segment) { diff --git a/pkg/tcpip/transport/tcp/tcp_rack_test.go b/pkg/tcpip/transport/tcp/tcp_rack_test.go index d3f92b48c..9818ffa0f 100644 --- a/pkg/tcpip/transport/tcp/tcp_rack_test.go +++ b/pkg/tcpip/transport/tcp/tcp_rack_test.go @@ -30,15 +30,17 @@ const ( maxPayload = 10 tsOptionSize = 12 maxTCPOptionSize = 40 + mtu = header.TCPMinimumSize + header.IPv4MinimumSize + maxTCPOptionSize + maxPayload ) // TestRACKUpdate tests the RACK related fields are updated when an ACK is // received on a SACK enabled connection. func TestRACKUpdate(t *testing.T) { - c := context.New(t, uint32(header.TCPMinimumSize+header.IPv4MinimumSize+maxTCPOptionSize+maxPayload)) + c := context.New(t, uint32(mtu)) defer c.Cleanup() var xmitTime time.Time + probeDone := make(chan struct{}) c.Stack().AddTCPProbe(func(state stack.TCPEndpointState) { // Validate that the endpoint Sender.RACKState is what we expect. if state.Sender.RACKState.XmitTime.Before(xmitTime) { @@ -54,6 +56,7 @@ func TestRACKUpdate(t *testing.T) { if state.Sender.RACKState.RTT == 0 { t.Fatalf("RACK RTT failed to update when an ACK is received, got RACKState.RTT == 0 want != 0") } + close(probeDone) }) setStackSACKPermitted(t, c, true) createConnectedWithSACKAndTS(c) @@ -73,18 +76,20 @@ func TestRACKUpdate(t *testing.T) { c.ReceiveAndCheckPacketWithOptions(data, bytesRead, maxPayload, tsOptionSize) bytesRead += maxPayload c.SendAck(seqnum.Value(context.TestInitialSequenceNumber).Add(1), bytesRead) - time.Sleep(200 * time.Millisecond) + + // Wait for the probe function to finish processing the ACK before the + // test completes. + <-probeDone } // TestRACKDetectReorder tests that RACK detects packet reordering. func TestRACKDetectReorder(t *testing.T) { - c := context.New(t, uint32(header.TCPMinimumSize+header.IPv4MinimumSize+maxTCPOptionSize+maxPayload)) + c := context.New(t, uint32(mtu)) defer c.Cleanup() - const ackNum = 2 - var n int - ch := make(chan struct{}) + const ackNumToVerify = 2 + probeDone := make(chan struct{}) c.Stack().AddTCPProbe(func(state stack.TCPEndpointState) { gotSeq := state.Sender.RACKState.FACK wantSeq := state.Sender.SndNxt @@ -95,7 +100,7 @@ func TestRACKDetectReorder(t *testing.T) { } n++ - if n < ackNum { + if n < ackNumToVerify { if state.Sender.RACKState.Reord { t.Fatalf("RACK reorder detected when there is no reordering") } @@ -105,11 +110,11 @@ func TestRACKDetectReorder(t *testing.T) { if state.Sender.RACKState.Reord == false { t.Fatalf("RACK reorder detection failed") } - close(ch) + close(probeDone) }) setStackSACKPermitted(t, c, true) createConnectedWithSACKAndTS(c) - data := buffer.NewView(ackNum * maxPayload) + data := buffer.NewView(ackNumToVerify * maxPayload) for i := range data { data[i] = byte(i) } @@ -120,7 +125,7 @@ func TestRACKDetectReorder(t *testing.T) { } bytesRead := 0 - for i := 0; i < ackNum; i++ { + for i := 0; i < ackNumToVerify; i++ { c.ReceiveAndCheckPacketWithOptions(data, bytesRead, maxPayload, tsOptionSize) bytesRead += maxPayload } @@ -133,5 +138,393 @@ func TestRACKDetectReorder(t *testing.T) { // Wait for the probe function to finish processing the ACK before the // test completes. - <-ch + <-probeDone +} + +func sendAndReceive(t *testing.T, c *context.Context, numPackets int) buffer.View { + setStackSACKPermitted(t, c, true) + createConnectedWithSACKAndTS(c) + + data := buffer.NewView(numPackets * maxPayload) + for i := range data { + data[i] = byte(i) + } + + // Write the data. + if _, _, err := c.EP.Write(tcpip.SlicePayload(data), tcpip.WriteOptions{}); err != nil { + t.Fatalf("Write failed: %s", err) + } + + bytesRead := 0 + for i := 0; i < numPackets; i++ { + c.ReceiveAndCheckPacketWithOptions(data, bytesRead, maxPayload, tsOptionSize) + bytesRead += maxPayload + } + + return data +} + +const ( + validDSACKDetected = 1 + failedToDetectDSACK = 2 + invalidDSACKDetected = 3 +) + +func addDSACKSeenCheckerProbe(t *testing.T, c *context.Context, numACK int, probeDone chan int) { + var n int + c.Stack().AddTCPProbe(func(state stack.TCPEndpointState) { + // Validate that RACK detects DSACK. + n++ + if n < numACK { + if state.Sender.RACKState.DSACKSeen { + probeDone <- invalidDSACKDetected + } + return + } + + if !state.Sender.RACKState.DSACKSeen { + probeDone <- failedToDetectDSACK + return + } + probeDone <- validDSACKDetected + }) +} + +// TestRACKDetectDSACK tests that RACK detects DSACK with duplicate segments. +// See: https://tools.ietf.org/html/rfc2883#section-4.1.1. +func TestRACKDetectDSACK(t *testing.T) { + c := context.New(t, uint32(mtu)) + defer c.Cleanup() + + probeDone := make(chan int) + const ackNumToVerify = 2 + addDSACKSeenCheckerProbe(t, c, ackNumToVerify, probeDone) + + numPackets := 8 + data := sendAndReceive(t, c, numPackets) + + // Cumulative ACK for [1-5] packets. + seq := seqnum.Value(context.TestInitialSequenceNumber).Add(1) + bytesRead := 5 * maxPayload + c.SendAck(seq, bytesRead) + + // Expect retransmission of #6 packet. + c.ReceiveAndCheckPacketWithOptions(data, bytesRead, maxPayload, tsOptionSize) + + // Send DSACK block for #6 packet indicating both + // initial and retransmitted packet are received and + // packets [1-7] are received. + start := c.IRS.Add(seqnum.Size(bytesRead)) + end := start.Add(maxPayload) + bytesRead += 2 * maxPayload + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start, end}}) + + // Wait for the probe function to finish processing the + // ACK before the test completes. + err := <-probeDone + switch err { + case failedToDetectDSACK: + t.Fatalf("RACK DSACK detection failed") + case invalidDSACKDetected: + t.Fatalf("RACK DSACK detected when there is no duplicate SACK") + } +} + +// TestRACKDetectDSACKWithOutOfOrder tests that RACK detects DSACK with out of +// order segments. +// See: https://tools.ietf.org/html/rfc2883#section-4.1.2. +func TestRACKDetectDSACKWithOutOfOrder(t *testing.T) { + c := context.New(t, uint32(mtu)) + defer c.Cleanup() + + probeDone := make(chan int) + const ackNumToVerify = 2 + addDSACKSeenCheckerProbe(t, c, ackNumToVerify, probeDone) + + numPackets := 10 + data := sendAndReceive(t, c, numPackets) + + // Cumulative ACK for [1-5] packets. + seq := seqnum.Value(context.TestInitialSequenceNumber).Add(1) + bytesRead := 5 * maxPayload + c.SendAck(seq, bytesRead) + + // Expect retransmission of #6 packet. + c.ReceiveAndCheckPacketWithOptions(data, bytesRead, maxPayload, tsOptionSize) + + // Send DSACK block for #6 packet indicating both + // initial and retransmitted packet are received and + // packets [1-7] are received. + start := c.IRS.Add(seqnum.Size(bytesRead)) + end := start.Add(maxPayload) + bytesRead += 2 * maxPayload + // Send DSACK block for #6 along with out of + // order #9 packet is received. + start1 := c.IRS.Add(seqnum.Size(bytesRead) + maxPayload) + end1 := start1.Add(maxPayload) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start, end}, {start1, end1}}) + + // Wait for the probe function to finish processing the + // ACK before the test completes. + err := <-probeDone + switch err { + case failedToDetectDSACK: + t.Fatalf("RACK DSACK detection failed") + case invalidDSACKDetected: + t.Fatalf("RACK DSACK detected when there is no duplicate SACK") + } +} + +// TestRACKDetectDSACKWithOutOfOrderDup tests that DSACK is detected on a +// duplicate of out of order packet. +// See: https://tools.ietf.org/html/rfc2883#section-4.1.3 +func TestRACKDetectDSACKWithOutOfOrderDup(t *testing.T) { + c := context.New(t, uint32(mtu)) + defer c.Cleanup() + + probeDone := make(chan int) + const ackNumToVerify = 4 + addDSACKSeenCheckerProbe(t, c, ackNumToVerify, probeDone) + + numPackets := 10 + sendAndReceive(t, c, numPackets) + + // ACK [1-5] packets. + seq := seqnum.Value(context.TestInitialSequenceNumber).Add(1) + bytesRead := 5 * maxPayload + c.SendAck(seq, bytesRead) + + // Send SACK indicating #6 packet is missing and received #7 packet. + offset := seqnum.Size(bytesRead + maxPayload) + start := c.IRS.Add(1 + offset) + end := start.Add(maxPayload) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start, end}}) + + // Send SACK with #6 packet is missing and received [7-8] packets. + end = start.Add(2 * maxPayload) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start, end}}) + + // Consider #8 packet is duplicated on the network and send DSACK. + dsackStart := c.IRS.Add(1 + offset + maxPayload) + dsackEnd := dsackStart.Add(maxPayload) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{dsackStart, dsackEnd}, {start, end}}) + + // Wait for the probe function to finish processing the ACK before the + // test completes. + err := <-probeDone + switch err { + case failedToDetectDSACK: + t.Fatalf("RACK DSACK detection failed") + case invalidDSACKDetected: + t.Fatalf("RACK DSACK detected when there is no duplicate SACK") + } +} + +// TestRACKDetectDSACKSingleDup tests DSACK for a single duplicate subsegment. +// See: https://tools.ietf.org/html/rfc2883#section-4.2.1. +func TestRACKDetectDSACKSingleDup(t *testing.T) { + c := context.New(t, uint32(mtu)) + defer c.Cleanup() + + probeDone := make(chan int) + const ackNumToVerify = 4 + addDSACKSeenCheckerProbe(t, c, ackNumToVerify, probeDone) + + numPackets := 4 + data := sendAndReceive(t, c, numPackets) + + // Send ACK for #1 packet. + bytesRead := maxPayload + seq := seqnum.Value(context.TestInitialSequenceNumber).Add(1) + c.SendAck(seq, bytesRead) + + // Missing [2-3] packets and received #4 packet. + seq = seqnum.Value(context.TestInitialSequenceNumber).Add(1) + start := c.IRS.Add(1 + seqnum.Size(3*maxPayload)) + end := start.Add(seqnum.Size(maxPayload)) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start, end}}) + + // Expect retransmission of #2 packet. + c.ReceiveAndCheckPacketWithOptions(data, bytesRead, maxPayload, tsOptionSize) + + // ACK for retransmitted #2 packet. + bytesRead += maxPayload + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start, end}}) + + // Simulate receving delayed subsegment of #2 packet and delayed #3 packet by + // sending DSACK block for the subsegment. + dsackStart := c.IRS.Add(1 + seqnum.Size(bytesRead)) + dsackEnd := dsackStart.Add(seqnum.Size(maxPayload / 2)) + c.SendAckWithSACK(seq, numPackets*maxPayload, []header.SACKBlock{{dsackStart, dsackEnd}}) + + // Wait for the probe function to finish processing the ACK before the + // test completes. + err := <-probeDone + switch err { + case failedToDetectDSACK: + t.Fatalf("RACK DSACK detection failed") + case invalidDSACKDetected: + t.Fatalf("RACK DSACK detected when there is no duplicate SACK") + } +} + +// TestRACKDetectDSACKDupWithCumulativeACK tests DSACK for two non-contiguous +// duplicate subsegments covered by the cumulative acknowledgement. +// See: https://tools.ietf.org/html/rfc2883#section-4.2.2. +func TestRACKDetectDSACKDupWithCumulativeACK(t *testing.T) { + c := context.New(t, uint32(mtu)) + defer c.Cleanup() + + probeDone := make(chan int) + const ackNumToVerify = 5 + addDSACKSeenCheckerProbe(t, c, ackNumToVerify, probeDone) + + numPackets := 6 + data := sendAndReceive(t, c, numPackets) + + // Send ACK for #1 packet. + bytesRead := maxPayload + seq := seqnum.Value(context.TestInitialSequenceNumber).Add(1) + c.SendAck(seq, bytesRead) + + // Missing [2-5] packets and received #6 packet. + seq = seqnum.Value(context.TestInitialSequenceNumber).Add(1) + start := c.IRS.Add(1 + seqnum.Size(5*maxPayload)) + end := start.Add(seqnum.Size(maxPayload)) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start, end}}) + + // Expect retransmission of #2 packet. + c.ReceiveAndCheckPacketWithOptions(data, bytesRead, maxPayload, tsOptionSize) + + // Received delayed #2 packet. + bytesRead += maxPayload + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start, end}}) + + // Received delayed #4 packet. + start1 := c.IRS.Add(1 + seqnum.Size(3*maxPayload)) + end1 := start1.Add(seqnum.Size(maxPayload)) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start1, end1}, {start, end}}) + + // Simulate receiving retransmitted subsegment for #2 packet and delayed #3 + // packet by sending DSACK block for #2 packet. + dsackStart := c.IRS.Add(1 + seqnum.Size(maxPayload)) + dsackEnd := dsackStart.Add(seqnum.Size(maxPayload / 2)) + c.SendAckWithSACK(seq, 4*maxPayload, []header.SACKBlock{{dsackStart, dsackEnd}, {start, end}}) + + // Wait for the probe function to finish processing the ACK before the + // test completes. + err := <-probeDone + switch err { + case failedToDetectDSACK: + t.Fatalf("RACK DSACK detection failed") + case invalidDSACKDetected: + t.Fatalf("RACK DSACK detected when there is no duplicate SACK") + } +} + +// TestRACKDetectDSACKDup tests two non-contiguous duplicate subsegments not +// covered by the cumulative acknowledgement. +// See: https://tools.ietf.org/html/rfc2883#section-4.2.3. +func TestRACKDetectDSACKDup(t *testing.T) { + c := context.New(t, uint32(mtu)) + defer c.Cleanup() + + probeDone := make(chan int) + const ackNumToVerify = 5 + addDSACKSeenCheckerProbe(t, c, ackNumToVerify, probeDone) + + numPackets := 7 + data := sendAndReceive(t, c, numPackets) + + // Send ACK for #1 packet. + bytesRead := maxPayload + seq := seqnum.Value(context.TestInitialSequenceNumber).Add(1) + c.SendAck(seq, bytesRead) + + // Missing [2-6] packets and SACK #7 packet. + seq = seqnum.Value(context.TestInitialSequenceNumber).Add(1) + start := c.IRS.Add(1 + seqnum.Size(6*maxPayload)) + end := start.Add(seqnum.Size(maxPayload)) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start, end}}) + + // Received delayed #3 packet. + start1 := c.IRS.Add(1 + seqnum.Size(2*maxPayload)) + end1 := start1.Add(seqnum.Size(maxPayload)) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start1, end1}, {start, end}}) + + // Expect retransmission of #2 packet. + c.ReceiveAndCheckPacketWithOptions(data, bytesRead, maxPayload, tsOptionSize) + + // Consider #2 packet has been dropped and SACK #4 packet. + start2 := c.IRS.Add(1 + seqnum.Size(3*maxPayload)) + end2 := start2.Add(seqnum.Size(maxPayload)) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start2, end2}, {start1, end1}, {start, end}}) + + // Simulate receiving retransmitted subsegment for #3 packet and delayed #5 + // packet by sending DSACK block for the subsegment. + dsackStart := c.IRS.Add(1 + seqnum.Size(2*maxPayload)) + dsackEnd := dsackStart.Add(seqnum.Size(maxPayload / 2)) + end1 = end1.Add(seqnum.Size(2 * maxPayload)) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{dsackStart, dsackEnd}, {start1, end1}}) + + // Wait for the probe function to finish processing the ACK before the + // test completes. + err := <-probeDone + switch err { + case failedToDetectDSACK: + t.Fatalf("RACK DSACK detection failed") + case invalidDSACKDetected: + t.Fatalf("RACK DSACK detected when there is no duplicate SACK") + } +} + +// TestRACKWithInvalidDSACKBlock tests that DSACK is not detected when DSACK +// is not the first SACK block. +func TestRACKWithInvalidDSACKBlock(t *testing.T) { + c := context.New(t, uint32(mtu)) + defer c.Cleanup() + + probeDone := make(chan struct{}) + const ackNumToVerify = 2 + var n int + c.Stack().AddTCPProbe(func(state stack.TCPEndpointState) { + // Validate that RACK does not detect DSACK when DSACK block is + // not the first SACK block. + n++ + t.Helper() + if state.Sender.RACKState.DSACKSeen { + t.Fatalf("RACK DSACK detected when there is no duplicate SACK") + } + + if n == ackNumToVerify { + close(probeDone) + } + }) + + numPackets := 10 + data := sendAndReceive(t, c, numPackets) + + // Cumulative ACK for [1-5] packets. + seq := seqnum.Value(context.TestInitialSequenceNumber).Add(1) + bytesRead := 5 * maxPayload + c.SendAck(seq, bytesRead) + + // Expect retransmission of #6 packet. + c.ReceiveAndCheckPacketWithOptions(data, bytesRead, maxPayload, tsOptionSize) + + // Send DSACK block for #6 packet indicating both + // initial and retransmitted packet are received and + // packets [1-7] are received. + start := c.IRS.Add(seqnum.Size(bytesRead)) + end := start.Add(maxPayload) + bytesRead += 2 * maxPayload + + // Send DSACK block as second block. + start1 := c.IRS.Add(seqnum.Size(bytesRead) + maxPayload) + end1 := start1.Add(maxPayload) + c.SendAckWithSACK(seq, bytesRead, []header.SACKBlock{{start1, end1}, {start, end}}) + + // Wait for the probe function to finish processing the + // ACK before the test completes. + <-probeDone } |