mirror of https://github.com/subgraph/fw-daemon
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
81 lines
2.2 KiB
81 lines
2.2 KiB
// 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 layers
|
|
|
|
import (
|
|
"encoding/binary"
|
|
"errors"
|
|
"fmt"
|
|
|
|
"github.com/google/gopacket"
|
|
)
|
|
|
|
// Loopback contains the header for loopback encapsulation. This header is
|
|
// used by both BSD and OpenBSD style loopback decoding (pcap's DLT_NULL
|
|
// and DLT_LOOP, respectively).
|
|
type Loopback struct {
|
|
BaseLayer
|
|
Family ProtocolFamily
|
|
}
|
|
|
|
// LayerType returns LayerTypeLoopback.
|
|
func (l *Loopback) LayerType() gopacket.LayerType { return LayerTypeLoopback }
|
|
|
|
// DecodeFromBytes decodes the given bytes into this layer.
|
|
func (l *Loopback) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
|
|
if len(data) < 4 {
|
|
return errors.New("Loopback packet too small")
|
|
}
|
|
|
|
// The protocol could be either big-endian or little-endian, we're
|
|
// not sure. But we're PRETTY sure that the value is less than
|
|
// 256, so we can check the first two bytes.
|
|
var prot uint32
|
|
if data[0] == 0 && data[1] == 0 {
|
|
prot = binary.BigEndian.Uint32(data[:4])
|
|
} else {
|
|
prot = binary.LittleEndian.Uint32(data[:4])
|
|
}
|
|
if prot > 0xFF {
|
|
return fmt.Errorf("Invalid loopback protocol %q", data[:4])
|
|
}
|
|
|
|
l.Family = ProtocolFamily(prot)
|
|
l.BaseLayer = BaseLayer{data[:4], data[4:]}
|
|
return nil
|
|
}
|
|
|
|
// CanDecode returns the set of layer types that this DecodingLayer can decode.
|
|
func (l *Loopback) CanDecode() gopacket.LayerClass {
|
|
return LayerTypeLoopback
|
|
}
|
|
|
|
// NextLayerType returns the layer type contained by this DecodingLayer.
|
|
func (l *Loopback) NextLayerType() gopacket.LayerType {
|
|
return l.Family.LayerType()
|
|
}
|
|
|
|
// SerializeTo writes the serialized form of this layer into the
|
|
// SerializationBuffer, implementing gopacket.SerializableLayer.
|
|
func (l *Loopback) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
|
|
bytes, err := b.PrependBytes(4)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
binary.LittleEndian.PutUint32(bytes, uint32(l.Family))
|
|
return nil
|
|
}
|
|
|
|
func decodeLoopback(data []byte, p gopacket.PacketBuilder) error {
|
|
l := Loopback{}
|
|
if err := l.DecodeFromBytes(data, gopacket.NilDecodeFeedback); err != nil {
|
|
return err
|
|
}
|
|
p.AddLayer(&l)
|
|
return p.NextDecoder(l.Family)
|
|
}
|