2 files changed, 123 insertions, 0 deletions
diff --git a/test/packetimpact/tests/BUILD b/test/packetimpact/tests/BUILD
index ce21c079a..373ab8d2f 100644
--- a/test/packetimpact/tests/BUILD
+++ b/test/packetimpact/tests/BUILD
@@ -366,6 +366,16 @@ packetimpact_testbench(
     ],
 )
 
+packetimpact_testbench(
+    name = "tcp_zero_receive_window",
+    srcs = ["tcp_zero_receive_window_test.go"],
+    deps = [
+        "//pkg/tcpip/header",
+        "//test/packetimpact/testbench",
+        "@org_golang_x_sys//unix:go_default_library",
+    ],
+)
+
 validate_all_tests()
 
 [packetimpact_go_test(
diff --git a/test/packetimpact/tests/tcp_zero_receive_window_test.go b/test/packetimpact/tests/tcp_zero_receive_window_test.go
new file mode 100644
index 000000000..cf0431c57
--- /dev/null
+++ b/test/packetimpact/tests/tcp_zero_receive_window_test.go
@@ -0,0 +1,113 @@
+// 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_zero_receive_window_test
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"testing"
+	"time"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/test/packetimpact/testbench"
+)
+
+func init() {
+	testbench.Initialize(flag.CommandLine)
+}
+
+// TestZeroReceiveWindow tests if the DUT sends a zero receive window eventually.
+func TestZeroReceiveWindow(t *testing.T) {
+	for _, payloadLen := range []int{64, 512, 1024} {
+		t.Run(fmt.Sprintf("TestZeroReceiveWindow_with_%dbytes_payload", payloadLen), func(t *testing.T) {
+			dut := testbench.NewDUT(t)
+			listenFd, remotePort := dut.CreateListener(t, unix.SOCK_STREAM, unix.IPPROTO_TCP, 1)
+			defer dut.Close(t, listenFd)
+			conn := dut.Net.NewTCPIPv4(t, testbench.TCP{DstPort: &remotePort}, testbench.TCP{SrcPort: &remotePort})
+			defer conn.Close(t)
+
+			conn.Connect(t)
+			acceptFd, _ := dut.Accept(t, listenFd)
+			defer dut.Close(t, acceptFd)
+
+			dut.SetSockOptInt(t, acceptFd, unix.IPPROTO_TCP, unix.TCP_NODELAY, 1)
+
+			samplePayload := &testbench.Payload{Bytes: make([]byte, payloadLen)} //testbench.GenerateRandomPayload(t, payloadLen)}
+			// Expect the DUT to eventually advertize zero receive window.
+			// The test would timeout otherwise.
+			for {
+				conn.Send(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck | header.TCPFlagPsh)}, samplePayload)
+				gotTCP, err := conn.Expect(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck)}, time.Second)
+				if err != nil {
+					t.Fatalf("expected packet was not received: %s", err)
+				}
+				if *gotTCP.WindowSize == 0 {
+					break
+				}
+			}
+		})
+	}
+}
+
+// TestNonZeroReceiveWindow tests for the DUT to never send a zero receive
+// window when the data is being read from the socket buffer.
+func TestNonZeroReceiveWindow(t *testing.T) {
+	for _, payloadLen := range []int{64, 512, 1024} {
+		t.Run(fmt.Sprintf("TestZeroReceiveWindow_with_%dbytes_payload", payloadLen), func(t *testing.T) {
+			dut := testbench.NewDUT(t)
+			listenFd, remotePort := dut.CreateListener(t, unix.SOCK_STREAM, unix.IPPROTO_TCP, 1)
+			defer dut.Close(t, listenFd)
+			conn := dut.Net.NewTCPIPv4(t, testbench.TCP{DstPort: &remotePort}, testbench.TCP{SrcPort: &remotePort})
+			defer conn.Close(t)
+
+			conn.Connect(t)
+			acceptFd, _ := dut.Accept(t, listenFd)
+			defer dut.Close(t, acceptFd)
+
+			dut.SetSockOptInt(t, acceptFd, unix.IPPROTO_TCP, unix.TCP_NODELAY, 1)
+
+			samplePayload := &testbench.Payload{Bytes: testbench.GenerateRandomPayload(t, payloadLen)}
+			var rcvWindow uint16
+			initRcv := false
+			// This loop keeps a running rcvWindow value from the initial ACK for the data
+			// we sent. Once we have received ACKs with non-zero receive windows, we break
+			// the loop.
+			for {
+				conn.Send(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck | header.TCPFlagPsh)}, samplePayload)
+				gotTCP, err := conn.Expect(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck)}, time.Second)
+				if err != nil {
+					t.Fatalf("expected packet was not received: %s", err)
+				}
+				if ret, _, err := dut.RecvWithErrno(context.Background(), t, acceptFd, int32(payloadLen), 0); ret == -1 {
+					t.Fatalf("dut.RecvWithErrno(ctx, t, %d, %d, 0) = %d,_, %s", acceptFd, payloadLen, ret, err)
+				}
+
+				if *gotTCP.WindowSize == 0 {
+					t.Fatalf("expected non-zero receive window.")
+				}
+				if !initRcv {
+					rcvWindow = uint16(*gotTCP.WindowSize)
+					initRcv = true
+				}
+				if rcvWindow <= uint16(payloadLen) {
+					break
+				}
+				rcvWindow -= uint16(payloadLen)
+			}
+		})
+	}
+}