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46 lines
1.2 KiB
Go
46 lines
1.2 KiB
Go
// Copyright 2012 Google, Inc. 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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// Loopback contains the header for loopback encapsulation. This header is
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// used by both BSD and OpenBSD style loopback decoding (pcap's DLT_NULL
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// and DLT_LOOP, respectively).
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type Loopback struct {
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BaseLayer
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Family ProtocolFamily
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}
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// LayerType returns LayerTypeLoopback.
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func (l *Loopback) LayerType() gopacket.LayerType { return LayerTypeLoopback }
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func decodeLoopback(data []byte, p gopacket.PacketBuilder) error {
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// The protocol could be either big-endian or little-endian, we're
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// not sure. But we're PRETTY sure that the value is less than
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// 256, so we can check the first two bytes.
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var prot uint32
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if data[0] == 0 && data[1] == 0 {
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prot = binary.BigEndian.Uint32(data[:4])
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} else {
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prot = binary.LittleEndian.Uint32(data[:4])
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}
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if prot > 0xFF {
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return fmt.Errorf("Invalid loopback protocol %q", data[:4])
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}
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l := &Loopback{
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BaseLayer: BaseLayer{data[:4], data[4:]},
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Family: ProtocolFamily(prot),
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}
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p.AddLayer(l)
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return p.NextDecoder(l.Family)
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}
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