Test that we have PAWS mechanism

If there is a Timestamps option in the arriving segment and SEG.TSval
< TS.Recent and if TS.Recent is valid, then treat the arriving segment
as not acceptable: Send an acknowledgement in reply as specified in
RFC-793 page 69 and drop the segment.

https://tools.ietf.org/html/rfc1323#page-19

PiperOrigin-RevId: 312590678

2 files changed, 122 insertions, 0 deletions

diff --git a/test/packetimpact/tests/BUILD b/test/packetimpact/tests/BUILD
index 852ae4a74..c4ffda17e 100644
--- a/test/packetimpact/tests/BUILD
+++ b/test/packetimpact/tests/BUILD
@@ -134,6 +134,19 @@ packetimpact_go_test(
 )
 
 packetimpact_go_test(
+    name = "tcp_paws_mechanism",
+    srcs = ["tcp_paws_mechanism_test.go"],
+    # TODO(b/156682000): Fix netstack then remove the line below.
+    expect_netstack_failure = True,
+    deps = [
+        "//pkg/tcpip/header",
+        "//pkg/tcpip/seqnum",
+        "//test/packetimpact/testbench",
+        "@org_golang_x_sys//unix:go_default_library",
+    ],
+)
+
+packetimpact_go_test(
     name = "tcp_user_timeout",
     srcs = ["tcp_user_timeout_test.go"],
     deps = [
diff --git a/test/packetimpact/tests/tcp_paws_mechanism_test.go b/test/packetimpact/tests/tcp_paws_mechanism_test.go
new file mode 100644
index 000000000..0a668adcf
--- /dev/null
+++ b/test/packetimpact/tests/tcp_paws_mechanism_test.go
@@ -0,0 +1,109 @@
+// 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_paws_mechanism_test
+
+import (
+	"encoding/hex"
+	"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 TestPAWSMechanism(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()
+
+	options := make([]byte, header.TCPOptionTSLength)
+	header.EncodeTSOption(currentTS(), 0, options)
+	conn.Send(tb.TCP{Flags: tb.Uint8(header.TCPFlagSyn), Options: options})
+	synAck, err := conn.Expect(tb.TCP{Flags: tb.Uint8(header.TCPFlagSyn | header.TCPFlagAck)}, time.Second)
+	if err != nil {
+		t.Fatalf("didn't get synack during handshake: %s", err)
+	}
+	parsedSynOpts := header.ParseSynOptions(synAck.Options, true)
+	if !parsedSynOpts.TS {
+		t.Fatalf("expected TSOpt from DUT, options we got:\n%s", hex.Dump(synAck.Options))
+	}
+	tsecr := parsedSynOpts.TSVal
+	header.EncodeTSOption(currentTS(), tsecr, options)
+	conn.Send(tb.TCP{Flags: tb.Uint8(header.TCPFlagAck), Options: options})
+	acceptFD, _ := dut.Accept(listenFD)
+	defer dut.Close(acceptFD)
+
+	sampleData := []byte("Sample Data")
+	sentTSVal := currentTS()
+	header.EncodeTSOption(sentTSVal, tsecr, options)
+	// 3ms here is chosen arbitrarily to make sure we have increasing timestamps
+	// every time we send one, it should not cause any flakiness because timestamps
+	// only need to be non-decreasing.
+	time.Sleep(3 * time.Millisecond)
+	conn.Send(tb.TCP{Flags: tb.Uint8(header.TCPFlagAck), Options: options}, &tb.Payload{Bytes: sampleData})
+
+	gotTCP, err := conn.Expect(tb.TCP{Flags: tb.Uint8(header.TCPFlagAck)}, time.Second)
+	if err != nil {
+		t.Fatalf("expected an ACK but got none: %s", err)
+	}
+
+	parsedOpts := header.ParseTCPOptions(gotTCP.Options)
+	if !parsedOpts.TS {
+		t.Fatalf("expected TS option in response, options we got:\n%s", hex.Dump(gotTCP.Options))
+	}
+	if parsedOpts.TSVal < tsecr {
+		t.Fatalf("TSVal should be non-decreasing, but %d < %d", parsedOpts.TSVal, tsecr)
+	}
+	if parsedOpts.TSEcr != sentTSVal {
+		t.Fatalf("TSEcr should match our sent TSVal, %d != %d", parsedOpts.TSEcr, sentTSVal)
+	}
+	tsecr = parsedOpts.TSVal
+	lastAckNum := gotTCP.AckNum
+
+	badTSVal := sentTSVal - 100
+	header.EncodeTSOption(badTSVal, tsecr, options)
+	// 3ms here is chosen arbitrarily and this time.Sleep() should not cause flakiness
+	// due to the exact same reasoning discussed above.
+	time.Sleep(3 * time.Millisecond)
+	conn.Send(tb.TCP{Flags: tb.Uint8(header.TCPFlagAck), Options: options}, &tb.Payload{Bytes: sampleData})
+
+	gotTCP, err = conn.Expect(tb.TCP{AckNum: lastAckNum, Flags: tb.Uint8(header.TCPFlagAck)}, time.Second)
+	if err != nil {
+		t.Fatalf("expected segment with AckNum %d but got none: %s", lastAckNum, err)
+	}
+	parsedOpts = header.ParseTCPOptions(gotTCP.Options)
+	if !parsedOpts.TS {
+		t.Fatalf("expected TS option in response, options we got:\n%s", hex.Dump(gotTCP.Options))
+	}
+	if parsedOpts.TSVal < tsecr {
+		t.Fatalf("TSVal should be non-decreasing, but %d < %d", parsedOpts.TSVal, tsecr)
+	}
+	if parsedOpts.TSEcr != sentTSVal {
+		t.Fatalf("TSEcr should match our sent TSVal, %d != %d", parsedOpts.TSEcr, sentTSVal)
+	}
+}
+
+func currentTS() uint32 {
+	return uint32(time.Now().UnixNano() / 1e6)
+}