diff options
| -rw-r--r-- | pkg/tcpip/transport/tcp/snd.go | 19 | ||||
| -rw-r--r-- | test/packetimpact/tests/BUILD | 6 | ||||
| -rw-r--r-- | test/packetimpact/tests/tcp_send_window_sizes_piggyback_test.go | 105 | ||||
| -rw-r--r-- | test/packetimpact/tests/tcp_should_piggyback_test.go | 64 |
4 files changed, 126 insertions, 68 deletions
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go index 06dc9b7d7..3a19c4468 100644 --- a/pkg/tcpip/transport/tcp/snd.go +++ b/pkg/tcpip/transport/tcp/snd.go @@ -816,6 +816,25 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se panic("Netstack queues FIN segments without data.") } + segEnd = seg.sequenceNumber.Add(seqnum.Size(seg.data.Size())) + // If the entire segment cannot be accomodated in the receiver + // advertized window, skip splitting and sending of the segment. + // ref: net/ipv4/tcp_output.c::tcp_snd_wnd_test() + // + // Linux checks this for all segment transmits not triggered + // by a probe timer. On this condition, it defers the segment + // split and transmit to a short probe timer. + // ref: include/net/tcp.h::tcp_check_probe_timer() + // ref: net/ipv4/tcp_output.c::tcp_write_wakeup() + // + // Instead of defining a new transmit timer, we attempt to split the + // segment right here if there are no pending segments. + // If there are pending segments, segment transmits are deferred + // to the retransmit timer handler. + if s.sndUna != s.sndNxt && !segEnd.LessThan(end) { + return false + } + if !seg.sequenceNumber.LessThan(end) { return false } diff --git a/test/packetimpact/tests/BUILD b/test/packetimpact/tests/BUILD index 1598c61e9..fb39ee4b8 100644 --- a/test/packetimpact/tests/BUILD +++ b/test/packetimpact/tests/BUILD @@ -124,10 +124,8 @@ packetimpact_go_test( ) packetimpact_go_test( - name = "tcp_should_piggyback", - srcs = ["tcp_should_piggyback_test.go"], - # TODO(b/153680566): Fix netstack then remove the line below. - expect_netstack_failure = True, + name = "tcp_send_window_sizes_piggyback", + srcs = ["tcp_send_window_sizes_piggyback_test.go"], deps = [ "//pkg/tcpip/header", "//test/packetimpact/testbench", diff --git a/test/packetimpact/tests/tcp_send_window_sizes_piggyback_test.go b/test/packetimpact/tests/tcp_send_window_sizes_piggyback_test.go new file mode 100644 index 000000000..b7e91712d --- /dev/null +++ b/test/packetimpact/tests/tcp_send_window_sizes_piggyback_test.go @@ -0,0 +1,105 @@ +// 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_send_window_sizes_piggyback_test + +import ( + "flag" + "fmt" + "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) +} + +// TestSendWindowSizesPiggyback tests cases where segment sizes are close to +// sender window size and checks for ACK piggybacking for each of those case. +func TestSendWindowSizesPiggyback(t *testing.T) { + sampleData := []byte("Sample Data") + segmentSize := uint16(len(sampleData)) + // Advertise receive window sizes that are lesser, equal to or greater than + // enqueued segment size and check for segment transmits. The test attempts + // to enqueue a segment on the dut before acknowledging previous segment and + // lets the dut piggyback any ACKs along with the enqueued segment. + for _, tt := range []struct { + description string + windowSize uint16 + expectedPayload1 []byte + expectedPayload2 []byte + enqueue bool + }{ + // Expect the first segment to be split as it cannot be accomodated in + // the sender window. This means we need not enqueue a new segment after + // the first segment. + {"WindowSmallerThanSegment", segmentSize - 1, sampleData[:(segmentSize - 1)], sampleData[(segmentSize - 1):], false /* enqueue */}, + + {"WindowEqualToSegment", segmentSize, sampleData, sampleData, true /* enqueue */}, + + // Expect the second segment to not be split as its size is greater than + // the available sender window size. The segments should not be split + // when there is pending unacknowledged data and the segment-size is + // greater than available sender window. + {"WindowGreaterThanSegment", segmentSize + 1, sampleData, sampleData, true /* enqueue */}, + } { + t.Run(fmt.Sprintf("%s%d", tt.description, tt.windowSize), func(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, WindowSize: tb.Uint16(tt.windowSize)}, 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) + + expectedTCP := tb.TCP{Flags: tb.Uint8(header.TCPFlagAck | header.TCPFlagPsh)} + + dut.Send(acceptFd, sampleData, 0) + expectedPayload := tb.Payload{Bytes: tt.expectedPayload1} + if _, err := conn.ExpectData(&expectedTCP, &expectedPayload, time.Second); err != nil { + t.Fatalf("Expected %s but didn't get one: %s", tb.Layers{&expectedTCP, &expectedPayload}, err) + } + + // Expect any enqueued segment to be transmitted by the dut along with + // piggybacked ACK for our data. + + if tt.enqueue { + // Enqueue a segment for the dut to transmit. + dut.Send(acceptFd, sampleData, 0) + } + + // Send ACK for the previous segment along with data for the dut to + // receive and ACK back. Sending this ACK would make room for the dut + // to transmit any enqueued segment. + conn.Send(tb.TCP{Flags: tb.Uint8(header.TCPFlagAck | header.TCPFlagPsh), WindowSize: tb.Uint16(tt.windowSize)}, &tb.Payload{Bytes: sampleData}) + + // Expect the dut to piggyback the ACK for received data along with + // the segment enqueued for transmit. + expectedPayload = tb.Payload{Bytes: tt.expectedPayload2} + if _, err := conn.ExpectData(&expectedTCP, &expectedPayload, time.Second); err != nil { + t.Fatalf("Expected %s but didn't get one: %s", tb.Layers{&expectedTCP, &expectedPayload}, err) + } + }) + } +} diff --git a/test/packetimpact/tests/tcp_should_piggyback_test.go b/test/packetimpact/tests/tcp_should_piggyback_test.go deleted file mode 100644 index 0240dc2f9..000000000 --- a/test/packetimpact/tests/tcp_should_piggyback_test.go +++ /dev/null @@ -1,64 +0,0 @@ -// 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_should_piggyback_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) -} - -func TestPiggyback(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, WindowSize: tb.Uint16(12)}, 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") - - dut.Send(acceptFd, sampleData, 0) - expectedTCP := tb.TCP{Flags: tb.Uint8(header.TCPFlagAck | header.TCPFlagPsh)} - expectedPayload := tb.Payload{Bytes: sampleData} - if _, err := conn.ExpectData(&expectedTCP, &expectedPayload, time.Second); err != nil { - t.Fatalf("Expected %v but didn't get one: %s", tb.Layers{&expectedTCP, &expectedPayload}, err) - } - - // Cause DUT to send us more data as soon as we ACK their first data segment because we have - // a small window. - dut.Send(acceptFd, sampleData, 0) - - // DUT should ACK our segment by piggybacking ACK to their outstanding data segment instead of - // sending a separate ACK packet. - conn.Send(expectedTCP, &expectedPayload) - if _, err := conn.ExpectData(&expectedTCP, &expectedPayload, time.Second); err != nil { - t.Fatalf("Expected %v but didn't get one: %s", tb.Layers{&expectedTCP, &expectedPayload}, err) - } -} |