2 files changed, 76 insertions, 0 deletions
diff --git a/test/packetimpact/tests/BUILD b/test/packetimpact/tests/BUILD
index 95dd6c440..09e91b832 100644
--- a/test/packetimpact/tests/BUILD
+++ b/test/packetimpact/tests/BUILD
@@ -233,6 +233,16 @@ packetimpact_go_test(
 )
 
 packetimpact_go_test(
+    name = "tcp_handshake_window_size",
+    srcs = ["tcp_handshake_window_size_test.go"],
+    deps = [
+        "//pkg/tcpip/header",
+        "//test/packetimpact/testbench",
+        "@org_golang_x_sys//unix:go_default_library",
+    ],
+)
+
+packetimpact_go_test(
     name = "icmpv6_param_problem",
     srcs = ["icmpv6_param_problem_test.go"],
     # TODO(b/153485026): Fix netstack then remove the line below.
diff --git a/test/packetimpact/tests/tcp_handshake_window_size_test.go b/test/packetimpact/tests/tcp_handshake_window_size_test.go
new file mode 100644
index 000000000..652b530d0
--- /dev/null
+++ b/test/packetimpact/tests/tcp_handshake_window_size_test.go
@@ -0,0 +1,66 @@
+// 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_handshake_window_size_test
+
+import (
+	"flag"
+	"testing"
+	"time"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/test/packetimpact/testbench"
+)
+
+func init() {
+	testbench.RegisterFlags(flag.CommandLine)
+}
+
+// TestTCPHandshakeWindowSize tests if the stack is honoring the window size
+// communicated during handshake.
+func TestTCPHandshakeWindowSize(t *testing.T) {
+	dut := testbench.NewDUT(t)
+	defer dut.TearDown()
+	listenFD, remotePort := dut.CreateListener(unix.SOCK_STREAM, unix.IPPROTO_TCP, 1)
+	defer dut.Close(listenFD)
+	conn := testbench.NewTCPIPv4(t, testbench.TCP{DstPort: &remotePort}, testbench.TCP{SrcPort: &remotePort})
+	defer conn.Close()
+
+	// Start handshake with zero window size.
+	conn.Send(testbench.TCP{Flags: testbench.Uint8(header.TCPFlagSyn), WindowSize: testbench.Uint16(uint16(0))})
+	if _, err := conn.ExpectData(&testbench.TCP{Flags: testbench.Uint8(header.TCPFlagSyn | header.TCPFlagAck)}, nil, time.Second); err != nil {
+		t.Fatalf("expected SYN-ACK: %s", err)
+	}
+	// Update the advertised window size to a non-zero value with the ACK that
+	// completes the handshake.
+	//
+	// Set the window size with MSB set and expect the dut to treat it as
+	// an unsigned value.
+	conn.Send(testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck), WindowSize: testbench.Uint16(uint16(1 << 15))})
+
+	acceptFd, _ := dut.Accept(listenFD)
+	defer dut.Close(acceptFd)
+
+	sampleData := []byte("Sample Data")
+	samplePayload := &testbench.Payload{Bytes: sampleData}
+
+	// Since we advertised a zero window followed by a non-zero window,
+	// expect the dut to honor the recently advertised non-zero window
+	// and actually send out the data instead of probing for zero window.
+	dut.Send(acceptFd, sampleData, 0)
+	if _, err := conn.ExpectNextData(&testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck | header.TCPFlagPsh)}, samplePayload, time.Second); err != nil {
+		t.Fatalf("expected payload was not received: %s", err)
+	}
+}