Test TCP sender behavior against window shrinking

RFC 1122 Section 3.7: A sending TCP MUST be robust against window shrinking,
which may cause the "useable window" to become negative.

PiperOrigin-RevId: 305377072

2 files changed, 70 insertions, 0 deletions

diff --git a/test/packetimpact/tests/BUILD b/test/packetimpact/tests/BUILD
index 9a4d66ea9..a9b2de9b9 100644
--- a/test/packetimpact/tests/BUILD
+++ b/test/packetimpact/tests/BUILD
@@ -28,6 +28,18 @@ packetimpact_go_test(
     ],
 )
 
+packetimpact_go_test(
+    name = "tcp_window_shrink",
+    srcs = ["tcp_window_shrink_test.go"],
+    # TODO(b/153202472): Fix netstack then remove the line below.
+    netstack = False,
+    deps = [
+        "//pkg/tcpip/header",
+        "//test/packetimpact/testbench",
+        "@org_golang_x_sys//unix:go_default_library",
+    ],
+)
+
 sh_binary(
     name = "test_runner",
     srcs = ["test_runner.sh"],
diff --git a/test/packetimpact/tests/tcp_window_shrink_test.go b/test/packetimpact/tests/tcp_window_shrink_test.go
new file mode 100644
index 000000000..b48cc6491
--- /dev/null
+++ b/test/packetimpact/tests/tcp_window_shrink_test.go
@@ -0,0 +1,58 @@
+// 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_window_shrink_test
+
+import (
+	"testing"
+	"time"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	tb "gvisor.dev/gvisor/test/packetimpact/testbench"
+)
+
+func TestWindowShrink(t *testing.T) {
+	dut := tb.NewDUT(t)
+	defer dut.TearDown()
+	listenFd, remotePort := dut.CreateListener(unix.SOCK_STREAM, unix.IPPROTO_TCP, 1)
+	defer dut.Close(listenFd)
+	conn := tb.NewTCPIPv4(t, tb.TCP{DstPort: &remotePort}, tb.TCP{SrcPort: &remotePort})
+	defer conn.Close()
+
+	conn.Handshake()
+	acceptFd, _ := dut.Accept(listenFd)
+	defer dut.Close(acceptFd)
+
+	dut.SetSockOptInt(acceptFd, unix.IPPROTO_TCP, unix.TCP_NODELAY, 1)
+
+	sampleData := []byte("Sample Data")
+
+	dut.Send(acceptFd, sampleData, 0)
+	conn.ExpectData(tb.TCP{}, sampleData, time.Second)
+	conn.Send(tb.TCP{Flags: tb.Uint8(header.TCPFlagAck)})
+
+	dut.Send(acceptFd, sampleData, 0)
+	dut.Send(acceptFd, sampleData, 0)
+	conn.ExpectData(tb.TCP{}, sampleData, time.Second)
+	conn.ExpectData(tb.TCP{}, sampleData, time.Second)
+	// We close our receiving window here
+	conn.Send(tb.TCP{Flags: tb.Uint8(header.TCPFlagAck), WindowSize: tb.Uint16(0)})
+
+	dut.Send(acceptFd, []byte("Sample Data"), 0)
+	// Note: There is another kind of zero-window probing which Windows uses (by sending one
+	// new byte at `RemoteSeqNum`), if netstack wants to go that way, we may want to change
+	// the following lines.
+	conn.ExpectData(tb.TCP{SeqNum: tb.Uint32(uint32(conn.RemoteSeqNum - 1))}, nil, time.Second)
+}