fix node and kubelet start times

pkg/kubelet/util/boottime_util_darwin.go

@@ -0,0 +1,44 @@
+// +build darwin
+
+/*
+Copyright 2018 The Kubernetes 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 util
+
+import (
+	"fmt"
+	"syscall"
+	"time"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// GetBootTime returns the time at which the machine was started, truncated to the nearest second
+func GetBootTime() (time.Time, error) {
+	output, err := unix.SysctlRaw("kern.boottime")
+	if err != nil {
+		return time.Time{}, err
+	}
+	var timeval syscall.Timeval
+	if len(output) != int(unsafe.Sizeof(timeval)) {
+		return time.Time{}, fmt.Errorf("unexpected output when calling syscall kern.bootime.  Expected len(output) to be %v, but got %v",
+			int(unsafe.Sizeof(timeval)), len(output))
+	}
+	timeval = *(*syscall.Timeval)(unsafe.Pointer(&output[0]))
+	sec, nsec := timeval.Unix()
+	return time.Unix(sec, nsec).Truncate(time.Second), nil
+}