github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/test/packetimpact/tests/tcp_rcv_buf_space_test.go (about)

     1  // Copyright 2020 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package tcp_rcv_buf_space_test
    16  
    17  import (
    18  	"context"
    19  	"flag"
    20  	"testing"
    21  
    22  	"golang.org/x/sys/unix"
    23  	"github.com/SagerNet/gvisor/pkg/tcpip/header"
    24  	"github.com/SagerNet/gvisor/test/packetimpact/testbench"
    25  )
    26  
    27  func init() {
    28  	testbench.Initialize(flag.CommandLine)
    29  }
    30  
    31  // TestReduceRecvBuf tests that a packet within window is still dropped
    32  // if the available buffer space drops below the size of the incoming
    33  // segment.
    34  func TestReduceRecvBuf(t *testing.T) {
    35  	dut := testbench.NewDUT(t)
    36  	listenFd, remotePort := dut.CreateListener(t, unix.SOCK_STREAM, unix.IPPROTO_TCP, 1)
    37  	defer dut.Close(t, listenFd)
    38  	conn := dut.Net.NewTCPIPv4(t, testbench.TCP{DstPort: &remotePort}, testbench.TCP{SrcPort: &remotePort})
    39  	defer conn.Close(t)
    40  
    41  	conn.Connect(t)
    42  	acceptFd, _ := dut.Accept(t, listenFd)
    43  	defer dut.Close(t, acceptFd)
    44  
    45  	// Set a small receive buffer for the test.
    46  	const rcvBufSz = 4096
    47  	dut.SetSockOptInt(t, acceptFd, unix.SOL_SOCKET, unix.SO_RCVBUF, rcvBufSz)
    48  
    49  	// Retrieve the actual buffer.
    50  	bufSz := dut.GetSockOptInt(t, acceptFd, unix.SOL_SOCKET, unix.SO_RCVBUF)
    51  
    52  	// Generate a payload of 1 more than the actual buffer size used by the
    53  	// DUT.
    54  	sampleData := testbench.GenerateRandomPayload(t, int(bufSz)+1)
    55  	// Send and receive sample data to the dut.
    56  	const pktSize = 1400
    57  	for payload := sampleData; len(payload) != 0; {
    58  		payloadBytes := pktSize
    59  		if l := len(payload); l < payloadBytes {
    60  			payloadBytes = l
    61  		}
    62  
    63  		conn.Send(t, testbench.TCP{Flags: testbench.TCPFlags(header.TCPFlagAck)}, []testbench.Layer{&testbench.Payload{Bytes: payload[:payloadBytes]}}...)
    64  		payload = payload[payloadBytes:]
    65  	}
    66  
    67  	// First read should read < len(sampleData)
    68  	if ret, _, err := dut.RecvWithErrno(context.Background(), t, acceptFd, int32(len(sampleData)), 0); ret == -1 || int(ret) == len(sampleData) {
    69  		t.Fatalf("dut.RecvWithErrno(ctx, t, %d, %d, 0) = %d,_, %s", acceptFd, int32(len(sampleData)), ret, err)
    70  	}
    71  
    72  	// Second read should return EAGAIN as the last segment should have been
    73  	// dropped due to it exceeding the receive buffer space available in the
    74  	// socket.
    75  	if ret, got, err := dut.RecvWithErrno(context.Background(), t, acceptFd, int32(len(sampleData)), unix.MSG_DONTWAIT); got != nil || ret != -1 || err != unix.EAGAIN {
    76  		t.Fatalf("expected no packets but got: %s", got)
    77  	}
    78  }