Plumb monotonic time to netstack

Netstack needs to be portable, so this seems to be preferable to using raw
system calls.

PiperOrigin-RevId: 212917409
Change-Id: I7b2073e7db4b4bf75300717ca23aea4c15be944c

3 files changed, 50 insertions, 9 deletions

diff --git a/pkg/tcpip/BUILD b/pkg/tcpip/BUILD
index 5153bd3b4..daff9a0a0 100644
--- a/pkg/tcpip/BUILD
+++ b/pkg/tcpip/BUILD
@@ -4,7 +4,10 @@ load("//tools/go_stateify:defs.bzl", "go_library", "go_test")
 
 go_library(
     name = "tcpip",
-    srcs = ["tcpip.go"],
+    srcs = [
+        "tcpip.go",
+        "time_unsafe.go",
+    ],
     importpath = "gvisor.googlesource.com/gvisor/pkg/tcpip",
     visibility = ["//visibility:public"],
     deps = [
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 51360b11f..b1bd5117f 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -123,16 +123,11 @@ func (e ErrSaveRejection) Error() string {
 // time, but never for netstack internal timekeeping.
 type Clock interface {
 	// NowNanoseconds returns the current real time as a number of
-	// nanoseconds since some epoch.
+	// nanoseconds since the Unix epoch.
 	NowNanoseconds() int64
-}
-
-// StdClock implements Clock with the time package.
-type StdClock struct{}
 
-// NowNanoseconds implements Clock.NowNanoseconds.
-func (*StdClock) NowNanoseconds() int64 {
-	return time.Now().UnixNano()
+	// NowMonotonic returns a monotonic time value.
+	NowMonotonic() int64
 }
 
 // Address is a byte slice cast as a string that represents the address of a
diff --git a/pkg/tcpip/time_unsafe.go b/pkg/tcpip/time_unsafe.go
new file mode 100644
index 000000000..2102e9633
--- /dev/null
+++ b/pkg/tcpip/time_unsafe.go
@@ -0,0 +1,43 @@
+// Copyright 2018 Google Inc.
+//
+// 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.
+
+// +build go1.9
+// +build !go1.12
+
+package tcpip
+
+import (
+	_ "time"   // Used with go:linkname.
+	_ "unsafe" // Required for go:linkname.
+)
+
+// StdClock implements Clock with the time package.
+type StdClock struct{}
+
+var _ Clock = (*StdClock)(nil)
+
+//go:linkname now time.now
+func now() (sec int64, nsec int32, mono int64)
+
+// NowNanoseconds implements Clock.NowNanoseconds.
+func (*StdClock) NowNanoseconds() int64 {
+	sec, nsec, _ := now()
+	return sec*1e9 + int64(nsec)
+}
+
+// NowMonotonic implements Clock.NowMonotonic.
+func (*StdClock) NowMonotonic() int64 {
+	_, _, mono := now()
+	return mono
+}