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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"
tb "gvisor.dev/gvisor/test/packetimpact/testbench"
)
func init() {
tb.RegisterFlags(flag.CommandLine)
}
// TestRetransmits tests retransmits occur at exponentially increasing
// time intervals.
func TestRetransmits(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")
samplePayload := &tb.Payload{Bytes: sampleData}
dut.Send(acceptFd, sampleData, 0)
if _, err := conn.ExpectData(&tb.TCP{}, samplePayload, time.Second); err != nil {
t.Fatalf("expected a packet with payload %v: %s", samplePayload, 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(tb.TCP{Flags: tb.Uint8(header.TCPFlagAck)})
startRTO := time.Second
current := startRTO
first := time.Now()
dut.Send(acceptFd, sampleData, 0)
seq := tb.Uint32(uint32(*conn.RemoteSeqNum()))
if _, err := conn.ExpectData(&tb.TCP{SeqNum: seq}, samplePayload, startRTO); err != nil {
t.Fatalf("expected a packet with payload %v: %s", samplePayload, err)
}
// Expect retransmits of the same segment.
for i := 0; i < 5; i++ {
start := time.Now()
if _, err := conn.ExpectData(&tb.TCP{SeqNum: seq}, samplePayload, 2*current); err != nil {
t.Fatalf("expected a packet with payload %v: %s loop %d", samplePayload, 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\n", p, i)
}
current *= 2
}
}
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