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Diffstat (limited to 'vendor/github.com/google/gopacket/packet.go')
| -rw-r--r-- | vendor/github.com/google/gopacket/packet.go | 838 |
1 files changed, 838 insertions, 0 deletions
diff --git a/vendor/github.com/google/gopacket/packet.go b/vendor/github.com/google/gopacket/packet.go new file mode 100644 index 0000000..76b62d8 --- /dev/null +++ b/vendor/github.com/google/gopacket/packet.go @@ -0,0 +1,838 @@ +// 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 ( + "bytes" + "encoding/hex" + "errors" + "fmt" + "io" + "os" + "reflect" + "runtime/debug" + "strings" + "time" +) + +// CaptureInfo provides standardized information about a packet captured off +// the wire or read from a file. +type CaptureInfo struct { + // Timestamp is the time the packet was captured, if that is known. + Timestamp time.Time + // CaptureLength is the total number of bytes read off of the wire. + CaptureLength int + // Length is the size of the original packet. Should always be >= + // CaptureLength. + Length int + // InterfaceIndex + InterfaceIndex int +} + +// PacketMetadata contains metadata for a packet. +type PacketMetadata struct { + CaptureInfo + // Truncated is true if packet decoding logic detects that there are fewer + // bytes in the packet than are detailed in various headers (for example, if + // the number of bytes in the IPv4 contents/payload is less than IPv4.Length). + // This is also set automatically for packets captured off the wire if + // CaptureInfo.CaptureLength < CaptureInfo.Length. + Truncated bool +} + +// Packet is the primary object used by gopacket. Packets are created by a +// Decoder's Decode call. A packet is made up of a set of Data, which +// is broken into a number of Layers as it is decoded. +type Packet interface { + //// Functions for outputting the packet as a human-readable string: + //// ------------------------------------------------------------------ + // String returns a human-readable string representation of the packet. + // It uses LayerString on each layer to output the layer. + String() string + // Dump returns a verbose human-readable string representation of the packet, + // including a hex dump of all layers. It uses LayerDump on each layer to + // output the layer. + Dump() string + + //// Functions for accessing arbitrary packet layers: + //// ------------------------------------------------------------------ + // Layers returns all layers in this packet, computing them as necessary + Layers() []Layer + // Layer returns the first layer in this packet of the given type, or nil + Layer(LayerType) Layer + // LayerClass returns the first layer in this packet of the given class, + // or nil. + LayerClass(LayerClass) Layer + + //// Functions for accessing specific types of packet layers. These functions + //// return the first layer of each type found within the packet. + //// ------------------------------------------------------------------ + // LinkLayer returns the first link layer in the packet + LinkLayer() LinkLayer + // NetworkLayer returns the first network layer in the packet + NetworkLayer() NetworkLayer + // TransportLayer returns the first transport layer in the packet + TransportLayer() TransportLayer + // ApplicationLayer returns the first application layer in the packet + ApplicationLayer() ApplicationLayer + // ErrorLayer is particularly useful, since it returns nil if the packet + // was fully decoded successfully, and non-nil if an error was encountered + // in decoding and the packet was only partially decoded. Thus, its output + // can be used to determine if the entire packet was able to be decoded. + ErrorLayer() ErrorLayer + + //// Functions for accessing data specific to the packet: + //// ------------------------------------------------------------------ + // Data returns the set of bytes that make up this entire packet. + Data() []byte + // Metadata returns packet metadata associated with this packet. + Metadata() *PacketMetadata +} + +// packet contains all the information we need to fulfill the Packet interface, +// and its two "subclasses" (yes, no such thing in Go, bear with me), +// eagerPacket and lazyPacket, provide eager and lazy decoding logic around the +// various functions needed to access this information. +type packet struct { + // data contains the entire packet data for a packet + data []byte + // initialLayers is space for an initial set of layers already created inside + // the packet. + initialLayers [6]Layer + // layers contains each layer we've already decoded + layers []Layer + // last is the last layer added to the packet + last Layer + // metadata is the PacketMetadata for this packet + metadata PacketMetadata + + decodeOptions DecodeOptions + + // Pointers to the various important layers + link LinkLayer + network NetworkLayer + transport TransportLayer + application ApplicationLayer + failure ErrorLayer +} + +func (p *packet) SetTruncated() { + p.metadata.Truncated = true +} + +func (p *packet) SetLinkLayer(l LinkLayer) { + if p.link == nil { + p.link = l + } +} + +func (p *packet) SetNetworkLayer(l NetworkLayer) { + if p.network == nil { + p.network = l + } +} + +func (p *packet) SetTransportLayer(l TransportLayer) { + if p.transport == nil { + p.transport = l + } +} + +func (p *packet) SetApplicationLayer(l ApplicationLayer) { + if p.application == nil { + p.application = l + } +} + +func (p *packet) SetErrorLayer(l ErrorLayer) { + if p.failure == nil { + p.failure = l + } +} + +func (p *packet) AddLayer(l Layer) { + p.layers = append(p.layers, l) + p.last = l +} + +func (p *packet) DumpPacketData() { + fmt.Fprint(os.Stderr, p.packetDump()) + os.Stderr.Sync() +} + +func (p *packet) Metadata() *PacketMetadata { + return &p.metadata +} + +func (p *packet) Data() []byte { + return p.data +} + +func (p *packet) DecodeOptions() *DecodeOptions { + return &p.decodeOptions +} + +func (p *packet) addFinalDecodeError(err error, stack []byte) { + fail := &DecodeFailure{err: err, stack: stack} + if p.last == nil { + fail.data = p.data + } else { + fail.data = p.last.LayerPayload() + } + p.AddLayer(fail) + p.SetErrorLayer(fail) +} + +func (p *packet) recoverDecodeError() { + if !p.decodeOptions.SkipDecodeRecovery { + if r := recover(); r != nil { + p.addFinalDecodeError(fmt.Errorf("%v", r), debug.Stack()) + } + } +} + +// LayerString outputs an individual layer as a string. The layer is output +// in a single line, with no trailing newline. This function is specifically +// designed to do the right thing for most layers... it follows the following +// rules: +// * If the Layer has a String function, just output that. +// * Otherwise, output all exported fields in the layer, recursing into +// exported slices and structs. +// NOTE: This is NOT THE SAME AS fmt's "%#v". %#v will output both exported +// and unexported fields... many times packet layers contain unexported stuff +// that would just mess up the output of the layer, see for example the +// Payload layer and it's internal 'data' field, which contains a large byte +// array that would really mess up formatting. +func LayerString(l Layer) string { + return fmt.Sprintf("%v\t%s", l.LayerType(), layerString(reflect.ValueOf(l), false, false)) +} + +// Dumper dumps verbose information on a value. If a layer type implements +// Dumper, then its LayerDump() string will include the results in its output. +type Dumper interface { + Dump() string +} + +// LayerDump outputs a very verbose string representation of a layer. Its +// output is a concatenation of LayerString(l) and hex.Dump(l.LayerContents()). +// It contains newlines and ends with a newline. +func LayerDump(l Layer) string { + var b bytes.Buffer + b.WriteString(LayerString(l)) + b.WriteByte('\n') + if d, ok := l.(Dumper); ok { + dump := d.Dump() + if dump != "" { + b.WriteString(dump) + if dump[len(dump)-1] != '\n' { + b.WriteByte('\n') + } + } + } + b.WriteString(hex.Dump(l.LayerContents())) + return b.String() +} + +// layerString outputs, recursively, a layer in a "smart" way. See docs for +// LayerString for more details. +// +// Params: +// i - value to write out +// anonymous: if we're currently recursing an anonymous member of a struct +// writeSpace: if we've already written a value in a struct, and need to +// write a space before writing more. This happens when we write various +// anonymous values, and need to keep writing more. +func layerString(v reflect.Value, anonymous bool, writeSpace bool) string { + // Let String() functions take precedence. + if v.CanInterface() { + if s, ok := v.Interface().(fmt.Stringer); ok { + return s.String() + } + } + // Reflect, and spit out all the exported fields as key=value. + switch v.Type().Kind() { + case reflect.Interface, reflect.Ptr: + if v.IsNil() { + return "nil" + } + r := v.Elem() + return layerString(r, anonymous, writeSpace) + case reflect.Struct: + var b bytes.Buffer + typ := v.Type() + if !anonymous { + b.WriteByte('{') + } + for i := 0; i < v.NumField(); i++ { + // Check if this is upper-case. + ftype := typ.Field(i) + f := v.Field(i) + if ftype.Anonymous { + anonStr := layerString(f, true, writeSpace) + writeSpace = writeSpace || anonStr != "" + b.WriteString(anonStr) + } else if ftype.PkgPath == "" { // exported + if writeSpace { + b.WriteByte(' ') + } + writeSpace = true + fmt.Fprintf(&b, "%s=%s", typ.Field(i).Name, layerString(f, false, writeSpace)) + } + } + if !anonymous { + b.WriteByte('}') + } + return b.String() + case reflect.Slice: + var b bytes.Buffer + b.WriteByte('[') + if v.Len() > 4 { + fmt.Fprintf(&b, "..%d..", v.Len()) + } else { + for j := 0; j < v.Len(); j++ { + if j != 0 { + b.WriteString(", ") + } + b.WriteString(layerString(v.Index(j), false, false)) + } + } + b.WriteByte(']') + return b.String() + } + return fmt.Sprintf("%v", v.Interface()) +} + +const ( + longBytesLength = 128 +) + +// LongBytesGoString returns a string representation of the byte slice shortened +// using the format '<type>{<truncated slice> ... (<n> bytes)}' if it +// exceeds a predetermined length. Can be used to avoid filling the display with +// very long byte strings. +func LongBytesGoString(buf []byte) string { + if len(buf) < longBytesLength { + return fmt.Sprintf("%#v", buf) + } + s := fmt.Sprintf("%#v", buf[:longBytesLength-1]) + s = strings.TrimSuffix(s, "}") + return fmt.Sprintf("%s ... (%d bytes)}", s, len(buf)) +} + +func baseLayerString(value reflect.Value) string { + t := value.Type() + content := value.Field(0) + c := make([]byte, content.Len()) + for i := range c { + c[i] = byte(content.Index(i).Uint()) + } + payload := value.Field(1) + p := make([]byte, payload.Len()) + for i := range p { + p[i] = byte(payload.Index(i).Uint()) + } + return fmt.Sprintf("%s{Contents:%s, Payload:%s}", t.String(), + LongBytesGoString(c), + LongBytesGoString(p)) +} + +func layerGoString(i interface{}, b *bytes.Buffer) { + if s, ok := i.(fmt.GoStringer); ok { + b.WriteString(s.GoString()) + return + } + + var v reflect.Value + var ok bool + if v, ok = i.(reflect.Value); !ok { + v = reflect.ValueOf(i) + } + switch v.Kind() { + case reflect.Ptr, reflect.Interface: + if v.Kind() == reflect.Ptr { + b.WriteByte('&') + } + layerGoString(v.Elem().Interface(), b) + case reflect.Struct: + t := v.Type() + b.WriteString(t.String()) + b.WriteByte('{') + for i := 0; i < v.NumField(); i++ { + if i > 0 { + b.WriteString(", ") + } + if t.Field(i).Name == "BaseLayer" { + fmt.Fprintf(b, "BaseLayer:%s", baseLayerString(v.Field(i))) + } else if v.Field(i).Kind() == reflect.Struct { + fmt.Fprintf(b, "%s:", t.Field(i).Name) + layerGoString(v.Field(i), b) + } else if v.Field(i).Kind() == reflect.Ptr { + b.WriteByte('&') + layerGoString(v.Field(i), b) + } else { + fmt.Fprintf(b, "%s:%#v", t.Field(i).Name, v.Field(i)) + } + } + b.WriteByte('}') + default: + fmt.Fprintf(b, "%#v", i) + } +} + +// LayerGoString returns a representation of the layer in Go syntax, +// taking care to shorten "very long" BaseLayer byte slices +func LayerGoString(l Layer) string { + b := new(bytes.Buffer) + layerGoString(l, b) + return b.String() +} + +func (p *packet) packetString() string { + var b bytes.Buffer + fmt.Fprintf(&b, "PACKET: %d bytes", len(p.Data())) + if p.metadata.Truncated { + b.WriteString(", truncated") + } + if p.metadata.Length > 0 { + fmt.Fprintf(&b, ", wire length %d cap length %d", p.metadata.Length, p.metadata.CaptureLength) + } + if !p.metadata.Timestamp.IsZero() { + fmt.Fprintf(&b, " @ %v", p.metadata.Timestamp) + } + b.WriteByte('\n') + for i, l := range p.layers { + fmt.Fprintf(&b, "- Layer %d (%02d bytes) = %s\n", i+1, len(l.LayerContents()), LayerString(l)) + } + return b.String() +} + +func (p *packet) packetDump() string { + var b bytes.Buffer + fmt.Fprintf(&b, "-- FULL PACKET DATA (%d bytes) ------------------------------------\n%s", len(p.data), hex.Dump(p.data)) + for i, l := range p.layers { + fmt.Fprintf(&b, "--- Layer %d ---\n%s", i+1, LayerDump(l)) + } + return b.String() +} + +// eagerPacket is a packet implementation that does eager decoding. Upon +// initial construction, it decodes all the layers it can from packet data. +// eagerPacket implements Packet and PacketBuilder. +type eagerPacket struct { + packet +} + +var errNilDecoder = errors.New("NextDecoder passed nil decoder, probably an unsupported decode type") + +func (p *eagerPacket) NextDecoder(next Decoder) error { + if next == nil { + return errNilDecoder + } + if p.last == nil { + return errors.New("NextDecoder called, but no layers added yet") + } + d := p.last.LayerPayload() + if len(d) == 0 { + return nil + } + // Since we're eager, immediately call the next decoder. + return next.Decode(d, p) +} +func (p *eagerPacket) initialDecode(dec Decoder) { + defer p.recoverDecodeError() + err := dec.Decode(p.data, p) + if err != nil { + p.addFinalDecodeError(err, nil) + } +} +func (p *eagerPacket) LinkLayer() LinkLayer { + return p.link +} +func (p *eagerPacket) NetworkLayer() NetworkLayer { + return p.network +} +func (p *eagerPacket) TransportLayer() TransportLayer { + return p.transport +} +func (p *eagerPacket) ApplicationLayer() ApplicationLayer { + return p.application +} +func (p *eagerPacket) ErrorLayer() ErrorLayer { + return p.failure +} +func (p *eagerPacket) Layers() []Layer { + return p.layers +} +func (p *eagerPacket) Layer(t LayerType) Layer { + for _, l := range p.layers { + if l.LayerType() == t { + return l + } + } + return nil +} +func (p *eagerPacket) LayerClass(lc LayerClass) Layer { + for _, l := range p.layers { + if lc.Contains(l.LayerType()) { + return l + } + } + return nil +} +func (p *eagerPacket) String() string { return p.packetString() } +func (p *eagerPacket) Dump() string { return p.packetDump() } + +// lazyPacket does lazy decoding on its packet data. On construction it does +// no initial decoding. For each function call, it decodes only as many layers +// as are necessary to compute the return value for that function. +// lazyPacket implements Packet and PacketBuilder. +type lazyPacket struct { + packet + next Decoder +} + +func (p *lazyPacket) NextDecoder(next Decoder) error { + if next == nil { + return errNilDecoder + } + p.next = next + return nil +} +func (p *lazyPacket) decodeNextLayer() { + if p.next == nil { + return + } + d := p.data + if p.last != nil { + d = p.last.LayerPayload() + } + next := p.next + p.next = nil + // We've just set p.next to nil, so if we see we have no data, this should be + // the final call we get to decodeNextLayer if we return here. + if len(d) == 0 { + return + } + defer p.recoverDecodeError() + err := next.Decode(d, p) + if err != nil { + p.addFinalDecodeError(err, nil) + } +} +func (p *lazyPacket) LinkLayer() LinkLayer { + for p.link == nil && p.next != nil { + p.decodeNextLayer() + } + return p.link +} +func (p *lazyPacket) NetworkLayer() NetworkLayer { + for p.network == nil && p.next != nil { + p.decodeNextLayer() + } + return p.network +} +func (p *lazyPacket) TransportLayer() TransportLayer { + for p.transport == nil && p.next != nil { + p.decodeNextLayer() + } + return p.transport +} +func (p *lazyPacket) ApplicationLayer() ApplicationLayer { + for p.application == nil && p.next != nil { + p.decodeNextLayer() + } + return p.application +} +func (p *lazyPacket) ErrorLayer() ErrorLayer { + for p.failure == nil && p.next != nil { + p.decodeNextLayer() + } + return p.failure +} +func (p *lazyPacket) Layers() []Layer { + for p.next != nil { + p.decodeNextLayer() + } + return p.layers +} +func (p *lazyPacket) Layer(t LayerType) Layer { + for _, l := range p.layers { + if l.LayerType() == t { + return l + } + } + numLayers := len(p.layers) + for p.next != nil { + p.decodeNextLayer() + for _, l := range p.layers[numLayers:] { + if l.LayerType() == t { + return l + } + } + numLayers = len(p.layers) + } + return nil +} +func (p *lazyPacket) LayerClass(lc LayerClass) Layer { + for _, l := range p.layers { + if lc.Contains(l.LayerType()) { + return l + } + } + numLayers := len(p.layers) + for p.next != nil { + p.decodeNextLayer() + for _, l := range p.layers[numLayers:] { + if lc.Contains(l.LayerType()) { + return l + } + } + numLayers = len(p.layers) + } + return nil +} +func (p *lazyPacket) String() string { p.Layers(); return p.packetString() } +func (p *lazyPacket) Dump() string { p.Layers(); return p.packetDump() } + +// DecodeOptions tells gopacket how to decode a packet. +type DecodeOptions struct { + // Lazy decoding decodes the minimum number of layers needed to return data + // for a packet at each function call. Be careful using this with concurrent + // packet processors, as each call to packet.* could mutate the packet, and + // two concurrent function calls could interact poorly. + Lazy bool + // NoCopy decoding doesn't copy its input buffer into storage that's owned by + // the packet. If you can guarantee that the bytes underlying the slice + // passed into NewPacket aren't going to be modified, this can be faster. If + // there's any chance that those bytes WILL be changed, this will invalidate + // your packets. + NoCopy bool + // SkipDecodeRecovery skips over panic recovery during packet decoding. + // Normally, when packets decode, if a panic occurs, that panic is captured + // by a recover(), and a DecodeFailure layer is added to the packet detailing + // the issue. If this flag is set, panics are instead allowed to continue up + // the stack. + SkipDecodeRecovery bool + // DecodeStreamsAsDatagrams enables routing of application-level layers in the TCP + // decoder. If true, we should try to decode layers after TCP in single packets. + // This is disabled by default because the reassembly package drives the decoding + // of TCP payload data after reassembly. + DecodeStreamsAsDatagrams bool +} + +// Default decoding provides the safest (but slowest) method for decoding +// packets. It eagerly processes all layers (so it's concurrency-safe) and it +// copies its input buffer upon creation of the packet (so the packet remains +// valid if the underlying slice is modified. Both of these take time, +// though, so beware. If you can guarantee that the packet will only be used +// by one goroutine at a time, set Lazy decoding. If you can guarantee that +// the underlying slice won't change, set NoCopy decoding. +var Default = DecodeOptions{} + +// Lazy is a DecodeOptions with just Lazy set. +var Lazy = DecodeOptions{Lazy: true} + +// NoCopy is a DecodeOptions with just NoCopy set. +var NoCopy = DecodeOptions{NoCopy: true} + +// DecodeStreamsAsDatagrams is a DecodeOptions with just DecodeStreamsAsDatagrams set. +var DecodeStreamsAsDatagrams = DecodeOptions{DecodeStreamsAsDatagrams: true} + +// NewPacket creates a new Packet object from a set of bytes. The +// firstLayerDecoder tells it how to interpret the first layer from the bytes, +// future layers will be generated from that first layer automatically. +func NewPacket(data []byte, firstLayerDecoder Decoder, options DecodeOptions) Packet { + if !options.NoCopy { + dataCopy := make([]byte, len(data)) + copy(dataCopy, data) + data = dataCopy + } + if options.Lazy { + p := &lazyPacket{ + packet: packet{data: data, decodeOptions: options}, + next: firstLayerDecoder, + } + p.layers = p.initialLayers[:0] + // Crazy craziness: + // If the following return statemet is REMOVED, and Lazy is FALSE, then + // eager packet processing becomes 17% FASTER. No, there is no logical + // explanation for this. However, it's such a hacky micro-optimization that + // we really can't rely on it. It appears to have to do with the size the + // compiler guesses for this function's stack space, since one symptom is + // that with the return statement in place, we more than double calls to + // runtime.morestack/runtime.lessstack. We'll hope the compiler gets better + // over time and we get this optimization for free. Until then, we'll have + // to live with slower packet processing. + return p + } + p := &eagerPacket{ + packet: packet{data: data, decodeOptions: options}, + } + p.layers = p.initialLayers[:0] + p.initialDecode(firstLayerDecoder) + return p +} + +// PacketDataSource is an interface for some source of packet data. Users may +// create their own implementations, or use the existing implementations in +// gopacket/pcap (libpcap, allows reading from live interfaces or from +// pcap files) or gopacket/pfring (PF_RING, allows reading from live +// interfaces). +type PacketDataSource interface { + // ReadPacketData returns the next packet available from this data source. + // It returns: + // data: The bytes of an individual packet. + // ci: Metadata about the capture + // err: An error encountered while reading packet data. If err != nil, + // then data/ci will be ignored. + ReadPacketData() (data []byte, ci CaptureInfo, err error) +} + +// ConcatFinitePacketDataSources returns a PacketDataSource that wraps a set +// of internal PacketDataSources, each of which will stop with io.EOF after +// reading a finite number of packets. The returned PacketDataSource will +// return all packets from the first finite source, followed by all packets from +// the second, etc. Once all finite sources have returned io.EOF, the returned +// source will as well. +func ConcatFinitePacketDataSources(pds ...PacketDataSource) PacketDataSource { + c := concat(pds) + return &c +} + +type concat []PacketDataSource + +func (c *concat) ReadPacketData() (data []byte, ci CaptureInfo, err error) { + for len(*c) > 0 { + data, ci, err = (*c)[0].ReadPacketData() + if err == io.EOF { + *c = (*c)[1:] + continue + } + return + } + return nil, CaptureInfo{}, io.EOF +} + +// ZeroCopyPacketDataSource is an interface to pull packet data from sources +// that allow data to be returned without copying to a user-controlled buffer. +// It's very similar to PacketDataSource, except that the caller must be more +// careful in how the returned buffer is handled. +type ZeroCopyPacketDataSource interface { + // ZeroCopyReadPacketData returns the next packet available from this data source. + // It returns: + // data: The bytes of an individual packet. Unlike with + // PacketDataSource's ReadPacketData, the slice returned here points + // to a buffer owned by the data source. In particular, the bytes in + // this buffer may be changed by future calls to + // ZeroCopyReadPacketData. Do not use the returned buffer after + // subsequent ZeroCopyReadPacketData calls. + // ci: Metadata about the capture + // err: An error encountered while reading packet data. If err != nil, + // then data/ci will be ignored. + ZeroCopyReadPacketData() (data []byte, ci CaptureInfo, err error) +} + +// PacketSource reads in packets from a PacketDataSource, decodes them, and +// returns them. +// +// There are currently two different methods for reading packets in through +// a PacketSource: +// +// Reading With Packets Function +// +// This method is the most convenient and easiest to code, but lacks +// flexibility. Packets returns a 'chan Packet', then asynchronously writes +// packets into that channel. Packets uses a blocking channel, and closes +// it if an io.EOF is returned by the underlying PacketDataSource. All other +// PacketDataSource errors are ignored and discarded. +// for packet := range packetSource.Packets() { +// ... +// } +// +// Reading With NextPacket Function +// +// This method is the most flexible, and exposes errors that may be +// encountered by the underlying PacketDataSource. It's also the fastest +// in a tight loop, since it doesn't have the overhead of a channel +// read/write. However, it requires the user to handle errors, most +// importantly the io.EOF error in cases where packets are being read from +// a file. +// for { +// packet, err := packetSource.NextPacket() +// if err == io.EOF { +// break +// } else if err != nil { +// log.Println("Error:", err) +// continue +// } +// handlePacket(packet) // Do something with each packet. +// } +type PacketSource struct { + source PacketDataSource + decoder Decoder + // DecodeOptions is the set of options to use for decoding each piece + // of packet data. This can/should be changed by the user to reflect the + // way packets should be decoded. + DecodeOptions + c chan Packet +} + +// NewPacketSource creates a packet data source. +func NewPacketSource(source PacketDataSource, decoder Decoder) *PacketSource { + return &PacketSource{ + source: source, + decoder: decoder, + } +} + +// NextPacket returns the next decoded packet from the PacketSource. On error, +// it returns a nil packet and a non-nil error. +func (p *PacketSource) NextPacket() (Packet, error) { + data, ci, err := p.source.ReadPacketData() + if err != nil { + return nil, err + } + packet := NewPacket(data, p.decoder, p.DecodeOptions) + m := packet.Metadata() + m.CaptureInfo = ci + m.Truncated = m.Truncated || ci.CaptureLength < ci.Length + return packet, nil +} + +// packetsToChannel reads in all packets from the packet source and sends them +// to the given channel. When it receives an error, it ignores it. When it +// receives an io.EOF, it closes the channel. +func (p *PacketSource) packetsToChannel() { + defer close(p.c) + for { + packet, err := p.NextPacket() + if err == io.EOF { + return + } else if err == nil { + p.c <- packet + } + } +} + +// Packets returns a channel of packets, allowing easy iterating over +// packets. Packets will be asynchronously read in from the underlying +// PacketDataSource and written to the returned channel. If the underlying +// PacketDataSource returns an io.EOF error, the channel will be closed. +// If any other error is encountered, it is ignored. +// +// for packet := range packetSource.Packets() { +// handlePacket(packet) // Do something with each packet. +// } +// +// If called more than once, returns the same channel. +func (p *PacketSource) Packets() chan Packet { + if p.c == nil { + p.c = make(chan Packet, 1000) + go p.packetsToChannel() + } + return p.c +} |