Avoid pseudo endpoint for TSVal generation

PiperOrigin-RevId: 393808461

pkg/tcpip/internal/tcp/BUILD

@@ -0,0 +1,12 @@
+load("//tools:defs.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "tcp",
+    srcs = ["tcp.go"],
+    visibility = ["//pkg/tcpip:__subpackages__"],
+    deps = [
+        "//pkg/tcpip",
+    ],
+)

pkg/tcpip/internal/tcp/tcp.go

@@ -0,0 +1,48 @@
+// Copyright 2021 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 contains internal type definitions that are not expected to be
+// used by anyone else outside pkg/tcpip.
+package tcp
+
+import (
+	"time"
+
+	"gvisor.dev/gvisor/pkg/tcpip"
+)
+
+// TSOffset is an offset applied to the value of the TSVal field in the TCP
+// Timestamp option.
+//
+// +stateify savable
+type TSOffset struct {
+	milliseconds uint32
+}
+
+// NewTSOffset creates a new TSOffset from milliseconds.
+func NewTSOffset(milliseconds uint32) TSOffset {
+	return TSOffset{
+		milliseconds: milliseconds,
+	}
+}
+
+// TSVal applies the offset to now and returns the timestamp in milliseconds.
+func (offset TSOffset) TSVal(now tcpip.MonotonicTime) uint32 {
+	return uint32(now.Sub(tcpip.MonotonicTime{}).Milliseconds()) + offset.milliseconds
+}
+
+// Elapsed calculates the elapsed time given now and the echoed back timestamp.
+func (offset TSOffset) Elapsed(now tcpip.MonotonicTime, tsEcr uint32) time.Duration {
+	return time.Duration(offset.TSVal(now)-tsEcr) * time.Millisecond
+}

pkg/tcpip/stack/BUILD

@@ -85,6 +85,7 @@ go_library(
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/hash/jenkins",
         "//pkg/tcpip/header",
+        "//pkg/tcpip/internal/tcp",
         "//pkg/tcpip/ports",
         "//pkg/tcpip/seqnum",
         "//pkg/tcpip/transport/tcpconntrack",

pkg/tcpip/stack/tcp.go

@@ -19,6 +19,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/internal/tcp"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
 )
 
@@ -402,7 +403,7 @@ type TCPSndBufState struct {
 type TCPEndpointStateInner struct {
 	// TSOffset is a randomized offset added to the value of the TSVal
 	// field in the timestamp option.
-	TSOffset uint32
+	TSOffset tcp.TSOffset
 
 	// SACKPermitted is set to true if the peer sends the TCPSACKPermitted
 	// option in the SYN/SYN-ACK.

pkg/tcpip/transport/tcp/BUILD

@@ -68,6 +68,7 @@ go_library(
         "//pkg/tcpip/hash/jenkins",
         "//pkg/tcpip/header",
         "//pkg/tcpip/header/parse",
+        "//pkg/tcpip/internal/tcp",
         "//pkg/tcpip/ports",
         "//pkg/tcpip/seqnum",
         "//pkg/tcpip/stack",

pkg/tcpip/transport/tcp/accept.go

@@ -606,14 +606,9 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) tcpip.Err
 			MSS:   calculateAdvertisedMSS(e.userMSS, route),
 		}
 		if opts.TS {
-			// Create a barely-sufficient endpoint to calculate the TSVal.
-			pseudoEndpoint := endpoint{
-				TCPEndpointStateInner: stack.TCPEndpointStateInner{
-					TSOffset: e.protocol.tsOffset(s.dstAddr, s.srcAddr),
-				},
-				stack: e.stack,
-			}
-			synOpts.TSVal = pseudoEndpoint.tsValNow()
+			offset := e.protocol.tsOffset(s.dstAddr, s.srcAddr)
+			now := e.stack.Clock().NowMonotonic()
+			synOpts.TSVal = offset.TSVal(now)
 		}
 		cookie := ctx.createCookie(s.id, s.sequenceNumber, encodeMSS(opts.MSS))
 		fields := tcpFields{

pkg/tcpip/transport/tcp/endpoint.go

@@ -2913,7 +2913,7 @@ func (e *endpoint) maybeEnableTimestamp(synOpts header.TCPSynOptions) {
 }
 
 func (e *endpoint) tsVal(now tcpip.MonotonicTime) uint32 {
-	return uint32(now.Sub(tcpip.MonotonicTime{}).Milliseconds()) + e.TSOffset
+	return e.TSOffset.TSVal(now)
 }
 
 func (e *endpoint) tsValNow() uint32 {
@@ -2921,7 +2921,7 @@ func (e *endpoint) tsValNow() uint32 {
 }
 
 func (e *endpoint) elapsed(now tcpip.MonotonicTime, tsEcr uint32) time.Duration {
-	return time.Duration(e.tsVal(now)-tsEcr) * time.Millisecond
+	return e.TSOffset.Elapsed(now, tsEcr)
 }
 
 // maybeEnableSACKPermitted marks the SACKPermitted option enabled for this endpoint

pkg/tcpip/transport/tcp/protocol.go

@@ -26,6 +26,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip/hash/jenkins"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/header/parse"
+	"gvisor.dev/gvisor/pkg/tcpip/internal/tcp"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 	"gvisor.dev/gvisor/pkg/tcpip/transport/raw"
@@ -158,7 +159,7 @@ func (p *protocol) HandleUnknownDestinationPacket(id stack.TransportEndpointID,
 	return stack.UnknownDestinationPacketHandled
 }
 
-func (p *protocol) tsOffset(src, dst tcpip.Address) uint32 {
+func (p *protocol) tsOffset(src, dst tcpip.Address) tcp.TSOffset {
 	// Initialize a random tsOffset that will be added to the recentTS
 	// everytime the timestamp is sent when the Timestamp option is enabled.
 	//
@@ -173,7 +174,7 @@ func (p *protocol) tsOffset(src, dst tcpip.Address) uint32 {
 	// It never returns an error.
 	_, _ = h.Write([]byte(src))
 	_, _ = h.Write([]byte(dst))
-	return h.Sum32()
+	return tcp.NewTSOffset(h.Sum32())
 }
 
 // replyWithReset replies to the given segment with a reset segment.