diff --git a/vendor/github.com/google/gopacket/writer.go b/vendor/github.com/google/gopacket/writer.go
new file mode 100644
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+++ b/vendor/github.com/google/gopacket/writer.go
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+// Copyright 2012 Google, Inc. 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"
+)
+
+// SerializableLayer allows its implementations to be written out as a set of bytes,
+// so those bytes may be sent on the wire or otherwise used by the caller.
+// SerializableLayer is implemented by certain Layer types, and can be encoded to
+// bytes using the LayerWriter object.
+type SerializableLayer interface {
+	// SerializeTo writes this layer to a slice, growing that slice if necessary
+	// to make it fit the layer's data.
+	//  Args:
+	//   b:  SerializeBuffer to write this layer on to.  When called, b.Bytes()
+	//     is the payload this layer should wrap, if any.  Note that this
+	//     layer can either prepend itself (common), append itself
+	//     (uncommon), or both (sometimes padding or footers are required at
+	//     the end of packet data). It's also possible (though probably very
+	//     rarely needed) to overwrite any bytes in the current payload.
+	//     After this call, b.Bytes() should return the byte encoding of
+	//     this layer wrapping the original b.Bytes() payload.
+	//   opts:  options to use while writing out data.
+	//  Returns:
+	//   error if a problem was encountered during encoding.  If an error is
+	//   returned, the bytes in data should be considered invalidated, and
+	//   not used.
+	//
+	// SerializeTo calls SHOULD entirely ignore LayerContents and
+	// LayerPayload.  It just serializes based on struct fields, neither
+	// modifying nor using contents/payload.
+	SerializeTo(b SerializeBuffer, opts SerializeOptions) error
+	// LayerType returns the type of the layer that is being serialized to the buffer
+	LayerType() LayerType
+}
+
+// SerializeOptions provides options for behaviors that SerializableLayers may want to
+// implement.
+type SerializeOptions struct {
+	// FixLengths determines whether, during serialization, layers should fix
+	// the values for any length field that depends on the payload.
+	FixLengths bool
+	// ComputeChecksums determines whether, during serialization, layers
+	// should recompute checksums based on their payloads.
+	ComputeChecksums bool
+}
+
+// SerializeBuffer is a helper used by gopacket for writing out packet layers.
+// SerializeBuffer starts off as an empty []byte.  Subsequent calls to PrependBytes
+// return byte slices before the current Bytes(), AppendBytes returns byte
+// slices after.
+//
+// Byte slices returned by PrependBytes/AppendBytes are NOT zero'd out, so if
+// you want to make sure they're all zeros, set them as such.
+//
+// SerializeBuffer is specifically designed to handle packet writing, where unlike
+// with normal writes it's easier to start writing at the inner-most layer and
+// work out, meaning that we often need to prepend bytes.  This runs counter to
+// typical writes to byte slices using append(), where we only write at the end
+// of the buffer.
+//
+// It can be reused via Clear.  Note, however, that a Clear call will invalidate the
+// byte slices returned by any previous Bytes() call (the same buffer is
+// reused).
+//
+//  1) Reusing a write buffer is generally much faster than creating a new one,
+//     and with the default implementation it avoids additional memory allocations.
+//  2) If a byte slice from a previous Bytes() call will continue to be used,
+//     it's better to create a new SerializeBuffer.
+//
+// The Clear method is specifically designed to minimize memory allocations for
+// similar later workloads on the SerializeBuffer.  IE: if you make a set of
+// Prepend/Append calls, then clear, then make the same calls with the same
+// sizes, the second round (and all future similar rounds) shouldn't allocate
+// any new memory.
+type SerializeBuffer interface {
+	// Bytes returns the contiguous set of bytes collected so far by Prepend/Append
+	// calls.  The slice returned by Bytes will be modified by future Clear calls,
+	// so if you're planning on clearing this SerializeBuffer, you may want to copy
+	// Bytes somewhere safe first.
+	Bytes() []byte
+	// PrependBytes returns a set of bytes which prepends the current bytes in this
+	// buffer.  These bytes start in an indeterminate state, so they should be
+	// overwritten by the caller.  The caller must only call PrependBytes if they
+	// know they're going to immediately overwrite all bytes returned.
+	PrependBytes(num int) ([]byte, error)
+	// AppendBytes returns a set of bytes which appends the current bytes in this
+	// buffer.  These bytes start in an indeterminate state, so they should be
+	// overwritten by the caller.  The caller must only call AppendBytes if they
+	// know they're going to immediately overwrite all bytes returned.
+	AppendBytes(num int) ([]byte, error)
+	// Clear resets the SerializeBuffer to a new, empty buffer.  After a call to clear,
+	// the byte slice returned by any previous call to Bytes() for this buffer
+	// should be considered invalidated.
+	Clear() error
+	// Layers returns all the Layers that have been successfully serialized into this buffer
+	// already.
+	Layers() []LayerType
+	// PushLayer adds the current Layer to the list of Layers that have been serialized
+	// into this buffer.
+	PushLayer(LayerType)
+}
+
+type serializeBuffer struct {
+	data                []byte
+	start               int
+	prepended, appended int
+	layers              []LayerType
+}
+
+// NewSerializeBuffer creates a new instance of the default implementation of
+// the SerializeBuffer interface.
+func NewSerializeBuffer() SerializeBuffer {
+	return &serializeBuffer{}
+}
+
+// NewSerializeBufferExpectedSize creates a new buffer for serialization, optimized for an
+// expected number of bytes prepended/appended.  This tends to decrease the
+// number of memory allocations made by the buffer during writes.
+func NewSerializeBufferExpectedSize(expectedPrependLength, expectedAppendLength int) SerializeBuffer {
+	return &serializeBuffer{
+		data:      make([]byte, expectedPrependLength, expectedPrependLength+expectedAppendLength),
+		start:     expectedPrependLength,
+		prepended: expectedPrependLength,
+		appended:  expectedAppendLength,
+	}
+}
+
+func (w *serializeBuffer) Bytes() []byte {
+	return w.data[w.start:]
+}
+
+func (w *serializeBuffer) PrependBytes(num int) ([]byte, error) {
+	if num < 0 {
+		panic("num < 0")
+	}
+	if w.start < num {
+		toPrepend := w.prepended
+		if toPrepend < num {
+			toPrepend = num
+		}
+		w.prepended += toPrepend
+		length := cap(w.data) + toPrepend
+		newData := make([]byte, length)
+		newStart := w.start + toPrepend
+		copy(newData[newStart:], w.data[w.start:])
+		w.start = newStart
+		w.data = newData[:toPrepend+len(w.data)]
+	}
+	w.start -= num
+	return w.data[w.start : w.start+num], nil
+}
+
+func (w *serializeBuffer) AppendBytes(num int) ([]byte, error) {
+	if num < 0 {
+		panic("num < 0")
+	}
+	initialLength := len(w.data)
+	if cap(w.data)-initialLength < num {
+		toAppend := w.appended
+		if toAppend < num {
+			toAppend = num
+		}
+		w.appended += toAppend
+		newData := make([]byte, cap(w.data)+toAppend)
+		copy(newData[w.start:], w.data[w.start:])
+		w.data = newData[:initialLength]
+	}
+	// Grow the buffer.  We know it'll be under capacity given above.
+	w.data = w.data[:initialLength+num]
+	return w.data[initialLength:], nil
+}
+
+func (w *serializeBuffer) Clear() error {
+	w.start = w.prepended
+	w.data = w.data[:w.start]
+	w.layers = w.layers[:0]
+	return nil
+}
+
+func (w *serializeBuffer) Layers() []LayerType {
+	return w.layers
+}
+
+func (w *serializeBuffer) PushLayer(l LayerType) {
+	w.layers = append(w.layers, l)
+}
+
+// SerializeLayers clears the given write buffer, then writes all layers into it so
+// they correctly wrap each other.  Note that by clearing the buffer, it
+// invalidates all slices previously returned by w.Bytes()
+//
+// Example:
+//   buf := gopacket.NewSerializeBuffer()
+//   opts := gopacket.SerializeOptions{}
+//   gopacket.SerializeLayers(buf, opts, a, b, c)
+//   firstPayload := buf.Bytes()  // contains byte representation of a(b(c))
+//   gopacket.SerializeLayers(buf, opts, d, e, f)
+//   secondPayload := buf.Bytes()  // contains byte representation of d(e(f)). firstPayload is now invalidated, since the SerializeLayers call Clears buf.
+func SerializeLayers(w SerializeBuffer, opts SerializeOptions, layers ...SerializableLayer) error {
+	w.Clear()
+	for i := len(layers) - 1; i >= 0; i-- {
+		layer := layers[i]
+		err := layer.SerializeTo(w, opts)
+		if err != nil {
+			return err
+		}
+		w.PushLayer(layer.LayerType())
+	}
+	return nil
+}
+
+// SerializeMultiLayers clears the given write buffer, then writes all layers into it so
+// they correctly wrap each other.  Note that by clearing the buffer, it
+// invalidates all slices previously returned by w.Bytes()
+//
+// Example:
+//   buf := gopacket.NewSerializeBuffer()
+//   opts := gopacket.SerializeOptions{}
+//   gopacket.SerializeLayers(buf, opts, a, b, c)
+//   firstPayload := buf.Bytes()  // contains byte representation of a(b(c))
+//   gopacket.SerializeLayers(buf, opts, d, e, f)
+//   secondPayload := buf.Bytes()  // contains byte representation of d(e(f)). firstPayload is now invalidated, since the SerializeLayers call Clears buf.
+func SerializeMultiLayers(w SerializeBuffer, opts SerializeOptions, layers []SerializableLayer) error {
+	w.Clear()
+	for i := len(layers) - 1; i >= 0; i-- {
+		layer := layers[i]
+		err := layer.SerializeTo(w, opts)
+		if err != nil {
+			return err
+		}
+		w.PushLayer(layer.LayerType())
+	}
+	return nil
+}
+
+// SerializePacket is a convenience function that calls SerializeLayers
+// on packet's Layers().
+// It returns an error if one of the packet layers is not a SerializableLayer.
+func SerializePacket(buf SerializeBuffer, opts SerializeOptions, packet Packet) error {
+	sls := []SerializableLayer{}
+	for _, layer := range packet.Layers() {
+		sl, ok := layer.(SerializableLayer)
+		if !ok {
+			return fmt.Errorf("layer %s is not serializable", layer.LayerType().String())
+		}
+		sls = append(sls, sl)
+	}
+	return SerializeLayers(buf, opts, sls...)
+}