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// Copyright 2012 Google, Inc. All rights reserved.
// Copyright 2009-2011 Andreas Krennmair. 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 layers
import (
"encoding/binary"
"fmt"
"github.com/google/gopacket"
)
// Dot1Q is the packet layer for 802.1Q VLAN headers.
type Dot1Q struct {
BaseLayer
Priority uint8
DropEligible bool
VLANIdentifier uint16
Type EthernetType
}
// LayerType returns gopacket.LayerTypeDot1Q
func (d *Dot1Q) LayerType() gopacket.LayerType { return LayerTypeDot1Q }
// DecodeFromBytes decodes the given bytes into this layer.
func (d *Dot1Q) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
d.Priority = (data[0] & 0xE0) >> 5
d.DropEligible = data[0]&0x10 != 0
d.VLANIdentifier = binary.BigEndian.Uint16(data[:2]) & 0x0FFF
d.Type = EthernetType(binary.BigEndian.Uint16(data[2:4]))
d.BaseLayer = BaseLayer{Contents: data[:4], Payload: data[4:]}
return nil
}
// CanDecode returns the set of layer types that this DecodingLayer can decode.
func (d *Dot1Q) CanDecode() gopacket.LayerClass {
return LayerTypeDot1Q
}
// NextLayerType returns the layer type contained by this DecodingLayer.
func (d *Dot1Q) NextLayerType() gopacket.LayerType {
return d.Type.LayerType()
}
func decodeDot1Q(data []byte, p gopacket.PacketBuilder) error {
d := &Dot1Q{}
return decodingLayerDecoder(d, data, p)
}
// SerializeTo writes the serialized form of this layer into the
// SerializationBuffer, implementing gopacket.SerializableLayer.
// See the docs for gopacket.SerializableLayer for more info.
func (d *Dot1Q) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
bytes, err := b.PrependBytes(4)
if err != nil {
return err
}
if d.VLANIdentifier > 0xFFF {
return fmt.Errorf("vlan identifier %v is too high", d.VLANIdentifier)
}
firstBytes := uint16(d.Priority)<<13 | d.VLANIdentifier
if d.DropEligible {
firstBytes |= 0x1000
}
binary.BigEndian.PutUint16(bytes, firstBytes)
binary.BigEndian.PutUint16(bytes[2:], uint16(d.Type))
return nil
}
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