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Diffstat (limited to 'vendor/github.com/google/gopacket/parser.go')
| -rw-r--r-- | vendor/github.com/google/gopacket/parser.go | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/vendor/github.com/google/gopacket/parser.go b/vendor/github.com/google/gopacket/parser.go new file mode 100644 index 0000000..f786834 --- /dev/null +++ b/vendor/github.com/google/gopacket/parser.go @@ -0,0 +1,198 @@ +// 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" +) + +// DecodingLayer is an interface for packet layers that can decode themselves. +// +// The important part of DecodingLayer is that they decode themselves in-place. +// Calling DecodeFromBytes on a DecodingLayer totally resets the entire layer to +// the new state defined by the data passed in. A returned error leaves the +// DecodingLayer in an unknown intermediate state, thus its fields should not be +// trusted. +// +// Because the DecodingLayer is resetting its own fields, a call to +// DecodeFromBytes should normally not require any memory allocation. +type DecodingLayer interface { + // DecodeFromBytes resets the internal state of this layer to the state + // defined by the passed-in bytes. Slices in the DecodingLayer may + // reference the passed-in data, so care should be taken to copy it + // first should later modification of data be required before the + // DecodingLayer is discarded. + DecodeFromBytes(data []byte, df DecodeFeedback) error + // CanDecode returns the set of LayerTypes this DecodingLayer can + // decode. For Layers that are also DecodingLayers, this will most + // often be that Layer's LayerType(). + CanDecode() LayerClass + // NextLayerType returns the LayerType which should be used to decode + // the LayerPayload. + NextLayerType() LayerType + // LayerPayload is the set of bytes remaining to decode after a call to + // DecodeFromBytes. + LayerPayload() []byte +} + +// DecodingLayerParser parses a given set of layer types. See DecodeLayers for +// more information on how DecodingLayerParser should be used. +type DecodingLayerParser struct { + // DecodingLayerParserOptions is the set of options available to the + // user to define the parser's behavior. + DecodingLayerParserOptions + first LayerType + decoders map[LayerType]DecodingLayer + df DecodeFeedback + // Truncated is set when a decode layer detects that the packet has been + // truncated. + Truncated bool +} + +// AddDecodingLayer adds a decoding layer to the parser. This adds support for +// the decoding layer's CanDecode layers to the parser... should they be +// encountered, they'll be parsed. +func (l *DecodingLayerParser) AddDecodingLayer(d DecodingLayer) { + for _, typ := range d.CanDecode().LayerTypes() { + l.decoders[typ] = d + } +} + +// SetTruncated is used by DecodingLayers to set the Truncated boolean in the +// DecodingLayerParser. Users should simply read Truncated after calling +// DecodeLayers. +func (l *DecodingLayerParser) SetTruncated() { + l.Truncated = true +} + +// NewDecodingLayerParser creates a new DecodingLayerParser and adds in all +// of the given DecodingLayers with AddDecodingLayer. +// +// Each call to DecodeLayers will attempt to decode the given bytes first by +// treating them as a 'first'-type layer, then by using NextLayerType on +// subsequently decoded layers to find the next relevant decoder. Should a +// deoder not be available for the layer type returned by NextLayerType, +// decoding will stop. +func NewDecodingLayerParser(first LayerType, decoders ...DecodingLayer) *DecodingLayerParser { + dlp := &DecodingLayerParser{ + decoders: make(map[LayerType]DecodingLayer), + first: first, + } + dlp.df = dlp // Cast this once to the interface + for _, d := range decoders { + dlp.AddDecodingLayer(d) + } + return dlp +} + +// DecodeLayers decodes as many layers as possible from the given data. It +// initially treats the data as layer type 'typ', then uses NextLayerType on +// each subsequent decoded layer until it gets to a layer type it doesn't know +// how to parse. +// +// For each layer successfully decoded, DecodeLayers appends the layer type to +// the decoded slice. DecodeLayers truncates the 'decoded' slice initially, so +// there's no need to empty it yourself. +// +// This decoding method is about an order of magnitude faster than packet +// decoding, because it only decodes known layers that have already been +// allocated. This means it doesn't need to allocate each layer it returns... +// instead it overwrites the layers that already exist. +// +// Example usage: +// func main() { +// var eth layers.Ethernet +// var ip4 layers.IPv4 +// var ip6 layers.IPv6 +// var tcp layers.TCP +// var udp layers.UDP +// var payload gopacket.Payload +// parser := gopacket.NewDecodingLayerParser(layers.LayerTypeEthernet, ð, &ip4, &ip6, &tcp, &udp, &payload) +// var source gopacket.PacketDataSource = getMyDataSource() +// decodedLayers := make([]gopacket.LayerType, 0, 10) +// for { +// data, _, err := source.ReadPacketData() +// if err == nil { +// fmt.Println("Error reading packet data: ", err) +// continue +// } +// fmt.Println("Decoding packet") +// err = parser.DecodeLayers(data, &decodedLayers) +// for _, typ := range decodedLayers { +// fmt.Println(" Successfully decoded layer type", typ) +// switch typ { +// case layers.LayerTypeEthernet: +// fmt.Println(" Eth ", eth.SrcMAC, eth.DstMAC) +// case layers.LayerTypeIPv4: +// fmt.Println(" IP4 ", ip4.SrcIP, ip4.DstIP) +// case layers.LayerTypeIPv6: +// fmt.Println(" IP6 ", ip6.SrcIP, ip6.DstIP) +// case layers.LayerTypeTCP: +// fmt.Println(" TCP ", tcp.SrcPort, tcp.DstPort) +// case layers.LayerTypeUDP: +// fmt.Println(" UDP ", udp.SrcPort, udp.DstPort) +// } +// } +// if decodedLayers.Truncated { +// fmt.Println(" Packet has been truncated") +// } +// if err != nil { +// fmt.Println(" Error encountered:", err) +// } +// } +// } +// +// If DecodeLayers is unable to decode the next layer type, it will return the +// error UnsupportedLayerType. +func (l *DecodingLayerParser) DecodeLayers(data []byte, decoded *[]LayerType) (err error) { + l.Truncated = false + if !l.IgnorePanic { + defer panicToError(&err) + } + typ := l.first + *decoded = (*decoded)[:0] // Truncated decoded layers. + for len(data) > 0 { + decoder, ok := l.decoders[typ] + if !ok { + return UnsupportedLayerType(typ) + } else if err = decoder.DecodeFromBytes(data, l.df); err != nil { + return err + } + *decoded = append(*decoded, typ) + typ = decoder.NextLayerType() + data = decoder.LayerPayload() + } + return nil +} + +// UnsupportedLayerType is returned by DecodingLayerParser if DecodeLayers +// encounters a layer type that the DecodingLayerParser has no decoder for. +type UnsupportedLayerType LayerType + +// Error implements the error interface, returning a string to say that the +// given layer type is unsupported. +func (e UnsupportedLayerType) Error() string { + return fmt.Sprintf("No decoder for layer type %v", LayerType(e)) +} + +func panicToError(e *error) { + if r := recover(); r != nil { + *e = fmt.Errorf("panic: %v", r) + } +} + +// DecodingLayerParserOptions provides options to affect the behavior of a given +// DecodingLayerParser. +type DecodingLayerParserOptions struct { + // IgnorePanic determines whether a DecodingLayerParser should stop + // panics on its own (by returning them as an error from DecodeLayers) + // or should allow them to raise up the stack. Handling errors does add + // latency to the process of decoding layers, but is much safer for + // callers. IgnorePanic defaults to false, thus if the caller does + // nothing decode panics will be returned as errors. + IgnorePanic bool +} |