Add tests for RACK

- Added packetimpact tests for RACK.

PiperOrigin-RevId: 353282342

2 files changed, 235 insertions, 0 deletions

diff --git a/test/packetimpact/tests/BUILD b/test/packetimpact/tests/BUILD
index b1b3c578b..6c6f2bdf7 100644
--- a/test/packetimpact/tests/BUILD
+++ b/test/packetimpact/tests/BUILD
@@ -376,6 +376,20 @@ packetimpact_testbench(
     ],
 )
 
+packetimpact_testbench(
+    name = "tcp_rack",
+    srcs = ["tcp_rack_test.go"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/binary",
+        "//pkg/tcpip/header",
+        "//pkg/tcpip/seqnum",
+        "//pkg/usermem",
+        "//test/packetimpact/testbench",
+        "@org_golang_x_sys//unix:go_default_library",
+    ],
+)
+
 validate_all_tests()
 
 [packetimpact_go_test(
diff --git a/test/packetimpact/tests/tcp_rack_test.go b/test/packetimpact/tests/tcp_rack_test.go
new file mode 100644
index 000000000..0a2381c97
--- /dev/null
+++ b/test/packetimpact/tests/tcp_rack_test.go
@@ -0,0 +1,221 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tcp_rack_test
+
+import (
+	"flag"
+	"testing"
+	"time"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/binary"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
+	"gvisor.dev/gvisor/pkg/usermem"
+	"gvisor.dev/gvisor/test/packetimpact/testbench"
+)
+
+func init() {
+	testbench.Initialize(flag.CommandLine)
+}
+
+const (
+	// payloadSize is the size used to send packets.
+	payloadSize = header.TCPDefaultMSS
+
+	// simulatedRTT is the time delay between packets sent and acked to
+	// increase the RTT.
+	simulatedRTT = 30 * time.Millisecond
+
+	// numPktsForRTT is the number of packets sent and acked to establish
+	// RTT.
+	numPktsForRTT = 10
+)
+
+func createSACKConnection(t *testing.T) (testbench.DUT, testbench.TCPIPv4, int32, int32) {
+	dut := testbench.NewDUT(t)
+	listenFd, remotePort := dut.CreateListener(t, unix.SOCK_STREAM, unix.IPPROTO_TCP, 1)
+	conn := dut.Net.NewTCPIPv4(t, testbench.TCP{DstPort: &remotePort}, testbench.TCP{SrcPort: &remotePort})
+
+	// Enable SACK.
+	opts := make([]byte, 40)
+	optsOff := 0
+	optsOff += header.EncodeNOP(opts[optsOff:])
+	optsOff += header.EncodeNOP(opts[optsOff:])
+	optsOff += header.EncodeSACKPermittedOption(opts[optsOff:])
+
+	conn.ConnectWithOptions(t, opts[:optsOff])
+	acceptFd, _ := dut.Accept(t, listenFd)
+	return dut, conn, acceptFd, listenFd
+}
+
+func closeSACKConnection(t *testing.T, dut testbench.DUT, conn testbench.TCPIPv4, acceptFd, listenFd int32) {
+	dut.Close(t, acceptFd)
+	dut.Close(t, listenFd)
+	conn.Close(t)
+}
+
+func getRTTAndRTO(t *testing.T, dut testbench.DUT, acceptFd int32) (rtt, rto time.Duration) {
+	info := linux.TCPInfo{}
+	ret := dut.GetSockOpt(t, acceptFd, unix.SOL_TCP, unix.TCP_INFO, int32(linux.SizeOfTCPInfo))
+	binary.Unmarshal(ret, usermem.ByteOrder, &info)
+	return time.Duration(info.RTT) * time.Microsecond, time.Duration(info.RTO) * time.Microsecond
+}
+
+func sendAndReceive(t *testing.T, dut testbench.DUT, conn testbench.TCPIPv4, numPkts int, acceptFd int32, sendACK bool) time.Time {
+	seqNum1 := *conn.RemoteSeqNum(t)
+	payload := make([]byte, payloadSize)
+	var lastSent time.Time
+	for i, sn := 0, seqNum1; i < numPkts; i++ {
+		lastSent = time.Now()
+		dut.Send(t, acceptFd, payload, 0)
+		gotOne, err := conn.Expect(t, testbench.TCP{SeqNum: testbench.Uint32(uint32(sn))}, time.Second)
+		if err != nil {
+			t.Fatalf("Expect #%d: %s", i+1, err)
+			continue
+		}
+		if gotOne == nil {
+			t.Fatalf("#%d: expected a packet within a second but got none", i+1)
+		}
+		sn.UpdateForward(seqnum.Size(payloadSize))
+
+		if sendACK {
+			time.Sleep(simulatedRTT)
+			conn.Send(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck), AckNum: testbench.Uint32(uint32(sn))})
+		}
+	}
+	return lastSent
+}
+
+// TestRACKTLPAllPacketsLost tests TLP when an entire flight of data is lost.
+func TestRACKTLPAllPacketsLost(t *testing.T) {
+	dut, conn, acceptFd, listenFd := createSACKConnection(t)
+	seqNum1 := *conn.RemoteSeqNum(t)
+
+	// Send ACK for data packets to establish RTT.
+	sendAndReceive(t, dut, conn, numPktsForRTT, acceptFd, true /* sendACK */)
+	seqNum1.UpdateForward(seqnum.Size(numPktsForRTT * payloadSize))
+
+	// We are not sending ACK for these packets.
+	const numPkts = 5
+	lastSent := sendAndReceive(t, dut, conn, numPkts, acceptFd, false /* sendACK */)
+
+	// Probe Timeout (PTO) should be two times RTT. Check that the last
+	// packet is retransmitted after probe timeout.
+	rtt, _ := getRTTAndRTO(t, dut, acceptFd)
+	pto := rtt * 2
+	// We expect the 5th packet (the last unacknowledged packet) to be
+	// retransmitted.
+	tlpProbe := testbench.Uint32(uint32(seqNum1) + uint32((numPkts-1)*payloadSize))
+	if _, err := conn.Expect(t, testbench.TCP{SeqNum: tlpProbe}, time.Second); err != nil {
+		t.Fatalf("expected payload was not received: %s %v %v", err, rtt, pto)
+	}
+	diff := time.Now().Sub(lastSent)
+	if diff < pto {
+		t.Fatalf("expected payload was received before the probe timeout, got: %v, want: %v", diff, pto)
+	}
+	closeSACKConnection(t, dut, conn, acceptFd, listenFd)
+}
+
+// TestRACKTLPLost tests TLP when there are tail losses.
+// See: https://tools.ietf.org/html/draft-ietf-tcpm-rack-08#section-7.4
+func TestRACKTLPLost(t *testing.T) {
+	dut, conn, acceptFd, listenFd := createSACKConnection(t)
+	seqNum1 := *conn.RemoteSeqNum(t)
+
+	// Send ACK for data packets to establish RTT.
+	sendAndReceive(t, dut, conn, numPktsForRTT, acceptFd, true /* sendACK */)
+	seqNum1.UpdateForward(seqnum.Size(numPktsForRTT * payloadSize))
+
+	// We are not sending ACK for these packets.
+	const numPkts = 10
+	lastSent := sendAndReceive(t, dut, conn, numPkts, acceptFd, false /* sendACK */)
+
+	// Cumulative ACK for #[1-5] packets.
+	ackNum := seqNum1.Add(seqnum.Size(6 * payloadSize))
+	conn.Send(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck), AckNum: testbench.Uint32(uint32(ackNum))})
+
+	// Probe Timeout (PTO) should be two times RTT. Check that the last
+	// packet is retransmitted after probe timeout.
+	rtt, _ := getRTTAndRTO(t, dut, acceptFd)
+	pto := rtt * 2
+	// We expect the 10th packet (the last unacknowledged packet) to be
+	// retransmitted.
+	tlpProbe := testbench.Uint32(uint32(seqNum1) + uint32((numPkts-1)*payloadSize))
+	if _, err := conn.Expect(t, testbench.TCP{SeqNum: tlpProbe}, time.Second); err != nil {
+		t.Fatalf("expected payload was not received: %s", err)
+	}
+	diff := time.Now().Sub(lastSent)
+	if diff < pto {
+		t.Fatalf("expected payload was received before the probe timeout, got: %v, want: %v", diff, pto)
+	}
+	closeSACKConnection(t, dut, conn, acceptFd, listenFd)
+}
+
+// TestRACKTLPWithSACK tests TLP by acknowledging out of order packets.
+// See: https://tools.ietf.org/html/draft-ietf-tcpm-rack-08#section-8.1
+func TestRACKTLPWithSACK(t *testing.T) {
+	dut, conn, acceptFd, listenFd := createSACKConnection(t)
+	seqNum1 := *conn.RemoteSeqNum(t)
+
+	// Send ACK for data packets to establish RTT.
+	sendAndReceive(t, dut, conn, numPktsForRTT, acceptFd, true /* sendACK */)
+	seqNum1.UpdateForward(seqnum.Size(numPktsForRTT * payloadSize))
+
+	// We are not sending ACK for these packets.
+	const numPkts = 3
+	lastSent := sendAndReceive(t, dut, conn, numPkts, acceptFd, false /* sendACK */)
+
+	// SACK for #2 packet.
+	sackBlock := make([]byte, 40)
+	start := seqNum1.Add(seqnum.Size(payloadSize))
+	end := start.Add(seqnum.Size(payloadSize))
+	sbOff := 0
+	sbOff += header.EncodeNOP(sackBlock[sbOff:])
+	sbOff += header.EncodeNOP(sackBlock[sbOff:])
+	sbOff += header.EncodeSACKBlocks([]header.SACKBlock{{
+		start, end,
+	}}, sackBlock[sbOff:])
+	conn.Send(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck), AckNum: testbench.Uint32(uint32(seqNum1)), Options: sackBlock[:sbOff]})
+
+	// RACK marks #1 packet as lost and retransmits it.
+	if _, err := conn.Expect(t, testbench.TCP{SeqNum: testbench.Uint32(uint32(seqNum1))}, time.Second); err != nil {
+		t.Fatalf("expected payload was not received: %s", err)
+	}
+
+	// ACK for #1 packet.
+	conn.Send(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck), AckNum: testbench.Uint32(uint32(end))})
+
+	// Probe Timeout (PTO) should be two times RTT. TLP will trigger for #3
+	// packet. RACK adds an additional timeout of 200ms if the number of
+	// outstanding packets is equal to 1.
+	rtt, rto := getRTTAndRTO(t, dut, acceptFd)
+	pto := rtt*2 + (200 * time.Millisecond)
+	if rto < pto {
+		pto = rto
+	}
+	// We expect the 3rd packet (the last unacknowledged packet) to be
+	// retransmitted.
+	tlpProbe := testbench.Uint32(uint32(seqNum1) + uint32((numPkts-1)*payloadSize))
+	if _, err := conn.Expect(t, testbench.TCP{SeqNum: tlpProbe}, time.Second); err != nil {
+		t.Fatalf("expected payload was not received: %s", err)
+	}
+	diff := time.Now().Sub(lastSent)
+	if diff < pto {
+		t.Fatalf("expected payload was received before the probe timeout, got: %v, want: %v", diff, pto)
+	}
+	closeSACKConnection(t, dut, conn, acceptFd, listenFd)
+}