TUN-6666: Define packet package

This package defines IP and ICMP packet, decoders, encoder and flow

vendor/github.com/google/gopacket/time.go

@@ -0,0 +1,72 @@
+// Copyright 2018 The GoPacket Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the LICENSE file in the root of the source
+// tree.
+
+package gopacket
+
+import (
+	"fmt"
+	"math"
+	"time"
+)
+
+// TimestampResolution represents the resolution of timestamps in Base^Exponent.
+type TimestampResolution struct {
+	Base, Exponent int
+}
+
+func (t TimestampResolution) String() string {
+	return fmt.Sprintf("%d^%d", t.Base, t.Exponent)
+}
+
+// ToDuration returns the smallest representable time difference as a time.Duration
+func (t TimestampResolution) ToDuration() time.Duration {
+	if t.Base == 0 {
+		return 0
+	}
+	if t.Exponent == 0 {
+		return time.Second
+	}
+	switch t.Base {
+	case 10:
+		return time.Duration(math.Pow10(t.Exponent + 9))
+	case 2:
+		if t.Exponent < 0 {
+			return time.Second >> uint(-t.Exponent)
+		}
+		return time.Second << uint(t.Exponent)
+	default:
+		// this might loose precision
+		return time.Duration(float64(time.Second) * math.Pow(float64(t.Base), float64(t.Exponent)))
+	}
+}
+
+// TimestampResolutionInvalid represents an invalid timestamp resolution
+var TimestampResolutionInvalid = TimestampResolution{}
+
+// TimestampResolutionMillisecond is a resolution of 10^-3s
+var TimestampResolutionMillisecond = TimestampResolution{10, -3}
+
+// TimestampResolutionMicrosecond is a resolution of 10^-6s
+var TimestampResolutionMicrosecond = TimestampResolution{10, -6}
+
+// TimestampResolutionNanosecond is a resolution of 10^-9s
+var TimestampResolutionNanosecond = TimestampResolution{10, -9}
+
+// TimestampResolutionNTP is the resolution of NTP timestamps which is 2^-32 ≈ 233 picoseconds
+var TimestampResolutionNTP = TimestampResolution{2, -32}
+
+// TimestampResolutionCaptureInfo is the resolution used in CaptureInfo, which his currently nanosecond
+var TimestampResolutionCaptureInfo = TimestampResolutionNanosecond
+
+// PacketSourceResolution is an interface for packet data sources that
+// support reporting the timestamp resolution of the aqcuired timestamps.
+// Returned timestamps will always have NanosecondTimestampResolution due
+// to the use of time.Time, but scaling might have occured if acquired
+// timestamps have a different resolution.
+type PacketSourceResolution interface {
+	// Resolution returns the timestamp resolution of acquired timestamps before scaling to NanosecondTimestampResolution.
+	Resolution() TimestampResolution
+}