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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 (
"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)
}
// TestRetransmits tests retransmits occur at exponentially increasing
// time intervals.
func TestRetransmits(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)
dut.SetSockOptInt(t, acceptFd, unix.IPPROTO_TCP, unix.TCP_NODELAY, 1)
sampleData := []byte("Sample Data")
samplePayload := &testbench.Payload{Bytes: sampleData}
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)
}
// Give a chance for the dut to estimate RTO with RTT from the DATA-ACK.
// TODO(gvisor.dev/issue/2685) Estimate RTO during handshake, after which
// we can skip sending this ACK.
conn.Send(t, testbench.TCP{Flags: testbench.Uint8(header.TCPFlagAck)})
startRTO := time.Second
current := startRTO
first := time.Now()
dut.Send(t, acceptFd, sampleData, 0)
seq := testbench.Uint32(uint32(*conn.RemoteSeqNum(t)))
if _, err := conn.ExpectData(t, &testbench.TCP{SeqNum: seq}, samplePayload, startRTO); err != nil {
t.Fatalf("expected payload was not received: %s", err)
}
// Expect retransmits of the same segment.
for i := 0; i < 5; i++ {
start := time.Now()
if _, err := conn.ExpectData(t, &testbench.TCP{SeqNum: seq}, samplePayload, 2*current); err != nil {
t.Fatalf("expected payload was not received: %s loop %d", err, i)
}
if i == 0 {
startRTO = time.Now().Sub(first)
current = 2 * startRTO
continue
}
// Check if the probes came at exponentially increasing intervals.
if p := time.Since(start); p < current-startRTO {
t.Fatalf("retransmit came sooner interval %d probe %d", p, i)
}
current *= 2
}
}
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