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