From f1ad2d54ab28dcdaaa5d7aa95d8f1b370b6fd36d Mon Sep 17 00:00:00 2001 From: Mithun Iyer Date: Wed, 13 May 2020 21:25:28 -0700 Subject: Fix TCP segment retransmit timeout handling. As per RFC 1122 and Linux retransmit timeout handling: - The segment retransmit timeout needs to exponentially increase and cap at a predefined value. - TCP connection needs to timeout after a predefined number of segment retransmissions. - TCP connection should not timeout when the retranmission timeout exceeds MaxRTO, predefined upper bound. Fixes #2673 PiperOrigin-RevId: 311463961 --- test/packetimpact/tests/BUILD | 10 +++ test/packetimpact/tests/tcp_retransmits_test.go | 84 +++++++++++++++++++++++++ 2 files changed, 94 insertions(+) create mode 100644 test/packetimpact/tests/tcp_retransmits_test.go (limited to 'test/packetimpact') diff --git a/test/packetimpact/tests/BUILD b/test/packetimpact/tests/BUILD index c25b3b8c1..fff7787c8 100644 --- a/test/packetimpact/tests/BUILD +++ b/test/packetimpact/tests/BUILD @@ -81,6 +81,16 @@ packetimpact_go_test( ], ) +packetimpact_go_test( + name = "tcp_retransmits", + srcs = ["tcp_retransmits_test.go"], + deps = [ + "//pkg/tcpip/header", + "//test/packetimpact/testbench", + "@org_golang_x_sys//unix:go_default_library", + ], +) + packetimpact_go_test( name = "tcp_outside_the_window", srcs = ["tcp_outside_the_window_test.go"], diff --git a/test/packetimpact/tests/tcp_retransmits_test.go b/test/packetimpact/tests/tcp_retransmits_test.go new file mode 100644 index 000000000..c043ad881 --- /dev/null +++ b/test/packetimpact/tests/tcp_retransmits_test.go @@ -0,0 +1,84 @@ +// 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 + } +} -- cgit v1.2.3