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// 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_retransmits_test
import (
"bytes"
"flag"
"testing"
"time"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/binary"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/tcpip/header"
"gvisor.dev/gvisor/test/packetimpact/testbench"
)
func init() {
testbench.Initialize(flag.CommandLine)
}
func getRTO(t *testing.T, dut testbench.DUT, acceptFd int32) (rto time.Duration) {
info := linux.TCPInfo{}
infoBytes := dut.GetSockOpt(t, acceptFd, unix.SOL_TCP, unix.TCP_INFO, int32(linux.SizeOfTCPInfo))
if got, want := len(infoBytes), linux.SizeOfTCPInfo; got != want {
t.Fatalf("unexpected size for TCP_INFO, got %d bytes want %d bytes", got, want)
}
binary.Unmarshal(infoBytes, hostarch.ByteOrder, &info)
return time.Duration(info.RTO) * time.Microsecond
}
// TestRetransmits tests retransmits occur at exponentially increasing
// time intervals.
func TestRetransmits(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)
sampleData := []byte("Sample Data")
samplePayload := &testbench.Payload{Bytes: sampleData}
// Give a chance for the dut to estimate RTO with RTT from the DATA-ACK.
// This is to reduce the test run-time from the default initial RTO of 1s.
// TODO(gvisor.dev/issue/2685) Estimate RTO during handshake, after which
// we can skip this data send/recv which is solely to estimate RTO.
dut.Send(t, acceptFd, sampleData, 0)
if _, err := conn.ExpectData(t, &testbench.TCP{}, samplePayload, time.Second); err != nil {
t.Fatalf("expected payload was not received: %s", err)
}
conn.Send(t, testbench.TCP{Flags: testbench.TCPFlags(header.TCPFlagAck | header.TCPFlagPsh)}, samplePayload)
if _, err := conn.ExpectData(t, &testbench.TCP{Flags: testbench.TCPFlags(header.TCPFlagAck)}, nil, time.Second); err != nil {
t.Fatalf("expected packet was not received: %s", err)
}
// Wait for the DUT to receive the data, thus ensuring that the stack has
// estimated RTO before we query RTO via TCP_INFO.
if got := dut.Recv(t, acceptFd, int32(len(sampleData)), 0); !bytes.Equal(got, sampleData) {
t.Fatalf("got dut.Recv(t, %d, %d, 0) = %s, want %s", acceptFd, len(sampleData), got, sampleData)
}
const timeoutCorrection = time.Second
const diffCorrection = 200 * time.Millisecond
rto := getRTO(t, dut, acceptFd)
dut.Send(t, acceptFd, sampleData, 0)
seq := testbench.Uint32(uint32(*conn.RemoteSeqNum(t)))
if _, err := conn.ExpectData(t, &testbench.TCP{SeqNum: seq}, samplePayload, rto+timeoutCorrection); err != nil {
t.Fatalf("expected payload was not received: %s", err)
}
// Expect retransmits of the same segment.
for i := 0; i < 5; i++ {
startTime := time.Now()
rto = getRTO(t, dut, acceptFd)
if _, err := conn.ExpectData(t, &testbench.TCP{SeqNum: seq}, samplePayload, rto+timeoutCorrection); err != nil {
t.Fatalf("expected payload was not received within %s loop %d err %s", rto+timeoutCorrection, i, err)
}
if diff := time.Since(startTime); diff+diffCorrection < rto {
t.Fatalf("retransmit came sooner got: %s want: >= %s probe %d", diff+diffCorrection, rto, i)
}
}
}
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