2 files changed, 90 insertions, 0 deletions
diff --git a/test/packetimpact/tests/BUILD b/test/packetimpact/tests/BUILD
index fbfea61e1..94731c64b 100644
--- a/test/packetimpact/tests/BUILD
+++ b/test/packetimpact/tests/BUILD
@@ -340,3 +340,13 @@ packetimpact_go_test(
         "@org_golang_x_sys//unix:go_default_library",
     ],
 )
+
+packetimpact_go_test(
+    name = "tcp_rcv_buf_space",
+    srcs = ["tcp_rcv_buf_space_test.go"],
+    deps = [
+        "//pkg/tcpip/header",
+        "//test/packetimpact/testbench",
+        "@org_golang_x_sys//unix:go_default_library",
+    ],
+)
diff --git a/test/packetimpact/tests/tcp_rcv_buf_space_test.go b/test/packetimpact/tests/tcp_rcv_buf_space_test.go
new file mode 100644
index 000000000..cfbba1e8e
--- /dev/null
+++ b/test/packetimpact/tests/tcp_rcv_buf_space_test.go
@@ -0,0 +1,80 @@
+// 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_rcv_buf_space_test
+
+import (
+	"context"
+	"flag"
+	"syscall"
+	"testing"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/test/packetimpact/testbench"
+)
+
+func init() {
+	testbench.RegisterFlags(flag.CommandLine)
+}
+
+// TestReduceRecvBuf tests that a packet within window is still dropped
+// if the available buffer space drops below the size of the incoming
+// segment.
+func TestReduceRecvBuf(t *testing.T) {
+	dut := testbench.NewDUT(t)
+	defer dut.TearDown()
+	listenFd, remotePort := dut.CreateListener(t, unix.SOCK_STREAM, unix.IPPROTO_TCP, 1)
+	defer dut.Close(t, listenFd)
+	conn := testbench.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)
+
+	// Set a small receive buffer for the test.
+	const rcvBufSz = 4096
+	dut.SetSockOptInt(t, acceptFd, unix.SOL_SOCKET, unix.SO_RCVBUF, rcvBufSz)
+
+	// Retrieve the actual buffer.
+	bufSz := dut.GetSockOptInt(t, acceptFd, unix.SOL_SOCKET, unix.SO_RCVBUF)
+
+	// Generate a payload of 1 more than the actual buffer size used by the
+	// DUT.
+	sampleData := testbench.GenerateRandomPayload(t, int(bufSz)+1)
+	// Send and receive sample data to the dut.
+	const pktSize = 1400
+	for payload := sampleData; len(payload) != 0; {
+		payloadBytes := pktSize
+		if l := len(payload); l < payloadBytes {
+			payloadBytes = l
+		}
+
+		conn.Send(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck)}, []testbench.Layer{&testbench.Payload{Bytes: payload[:payloadBytes]}}...)
+		payload = payload[payloadBytes:]
+	}
+
+	// First read should read < len(sampleData)
+	if ret, _, err := dut.RecvWithErrno(context.Background(), t, acceptFd, int32(len(sampleData)), 0); ret == -1 || int(ret) == len(sampleData) {
+		t.Fatalf("dut.RecvWithErrno(ctx, t, %d, %d, 0) = %d,_, %s", acceptFd, int32(len(sampleData)), ret, err)
+	}
+
+	// Second read should return EAGAIN as the last segment should have been
+	// dropped due to it exceeding the receive buffer space available in the
+	// socket.
+	if ret, got, err := dut.RecvWithErrno(context.Background(), t, acceptFd, int32(len(sampleData)), syscall.MSG_DONTWAIT); got != nil || ret != -1 || err != syscall.EAGAIN {
+		t.Fatalf("expected no packets but got: %s", got)
+	}
+}