TUN-6666: Define packet package

This package defines IP and ICMP packet, decoders, encoder and flow

vendor/github.com/google/gopacket/flows.go

@@ -0,0 +1,236 @@
+// 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"
+	"fmt"
+	"strconv"
+)
+
+// MaxEndpointSize determines the maximum size in bytes of an endpoint address.
+//
+// Endpoints/Flows have a problem:  They need to be hashable.  Therefore, they
+// can't use a byte slice.  The two obvious choices are to use a string or a
+// byte array.  Strings work great, but string creation requires memory
+// allocation, which can be slow.  Arrays work great, but have a fixed size.  We
+// originally used the former, now we've switched to the latter.  Use of a fixed
+// byte-array doubles the speed of constructing a flow (due to not needing to
+// allocate).  This is a huge increase... too much for us to pass up.
+//
+// The end result of this, though, is that an endpoint/flow can't be created
+// using more than MaxEndpointSize bytes per address.
+const MaxEndpointSize = 16
+
+// Endpoint is the set of bytes used to address packets at various layers.
+// See LinkLayer, NetworkLayer, and TransportLayer specifications.
+// Endpoints are usable as map keys.
+type Endpoint struct {
+	typ EndpointType
+	len int
+	raw [MaxEndpointSize]byte
+}
+
+// EndpointType returns the endpoint type associated with this endpoint.
+func (a Endpoint) EndpointType() EndpointType { return a.typ }
+
+// Raw returns the raw bytes of this endpoint.  These aren't human-readable
+// most of the time, but they are faster than calling String.
+func (a Endpoint) Raw() []byte { return a.raw[:a.len] }
+
+// LessThan provides a stable ordering for all endpoints.  It sorts first based
+// on the EndpointType of an endpoint, then based on the raw bytes of that
+// endpoint.
+//
+// For some endpoints, the actual comparison may not make sense, however this
+// ordering does provide useful information for most Endpoint types.
+// Ordering is based first on endpoint type, then on raw endpoint bytes.
+// Endpoint bytes are sorted lexicographically.
+func (a Endpoint) LessThan(b Endpoint) bool {
+	return a.typ < b.typ || (a.typ == b.typ && bytes.Compare(a.raw[:a.len], b.raw[:b.len]) < 0)
+}
+
+// fnvHash is used by our FastHash functions, and implements the FNV hash
+// created by Glenn Fowler, Landon Curt Noll, and Phong Vo.
+// See http://isthe.com/chongo/tech/comp/fnv/.
+func fnvHash(s []byte) (h uint64) {
+	h = fnvBasis
+	for i := 0; i < len(s); i++ {
+		h ^= uint64(s[i])
+		h *= fnvPrime
+	}
+	return
+}
+
+const fnvBasis = 14695981039346656037
+const fnvPrime = 1099511628211
+
+// FastHash provides a quick hashing function for an endpoint, useful if you'd
+// like to split up endpoints by modulos or other load-balancing techniques.
+// It uses a variant of Fowler-Noll-Vo hashing.
+//
+// The output of FastHash is not guaranteed to remain the same through future
+// code revisions, so should not be used to key values in persistent storage.
+func (a Endpoint) FastHash() (h uint64) {
+	h = fnvHash(a.raw[:a.len])
+	h ^= uint64(a.typ)
+	h *= fnvPrime
+	return
+}
+
+// NewEndpoint creates a new Endpoint object.
+//
+// The size of raw must be less than MaxEndpointSize, otherwise this function
+// will panic.
+func NewEndpoint(typ EndpointType, raw []byte) (e Endpoint) {
+	e.len = len(raw)
+	if e.len > MaxEndpointSize {
+		panic("raw byte length greater than MaxEndpointSize")
+	}
+	e.typ = typ
+	copy(e.raw[:], raw)
+	return
+}
+
+// EndpointTypeMetadata is used to register a new endpoint type.
+type EndpointTypeMetadata struct {
+	// Name is the string returned by an EndpointType's String function.
+	Name string
+	// Formatter is called from an Endpoint's String function to format the raw
+	// bytes in an Endpoint into a human-readable string.
+	Formatter func([]byte) string
+}
+
+// EndpointType is the type of a gopacket Endpoint.  This type determines how
+// the bytes stored in the endpoint should be interpreted.
+type EndpointType int64
+
+var endpointTypes = map[EndpointType]EndpointTypeMetadata{}
+
+// RegisterEndpointType creates a new EndpointType and registers it globally.
+// It MUST be passed a unique number, or it will panic.  Numbers 0-999 are
+// reserved for gopacket's use.
+func RegisterEndpointType(num int, meta EndpointTypeMetadata) EndpointType {
+	t := EndpointType(num)
+	if _, ok := endpointTypes[t]; ok {
+		panic("Endpoint type number already in use")
+	}
+	endpointTypes[t] = meta
+	return t
+}
+
+func (e EndpointType) String() string {
+	if t, ok := endpointTypes[e]; ok {
+		return t.Name
+	}
+	return strconv.Itoa(int(e))
+}
+
+func (a Endpoint) String() string {
+	if t, ok := endpointTypes[a.typ]; ok && t.Formatter != nil {
+		return t.Formatter(a.raw[:a.len])
+	}
+	return fmt.Sprintf("%v:%v", a.typ, a.raw)
+}
+
+// Flow represents the direction of traffic for a packet layer, as a source and destination Endpoint.
+// Flows are usable as map keys.
+type Flow struct {
+	typ        EndpointType
+	slen, dlen int
+	src, dst   [MaxEndpointSize]byte
+}
+
+// FlowFromEndpoints creates a new flow by pasting together two endpoints.
+// The endpoints must have the same EndpointType, or this function will return
+// an error.
+func FlowFromEndpoints(src, dst Endpoint) (_ Flow, err error) {
+	if src.typ != dst.typ {
+		err = fmt.Errorf("Mismatched endpoint types: %v->%v", src.typ, dst.typ)
+		return
+	}
+	return Flow{src.typ, src.len, dst.len, src.raw, dst.raw}, nil
+}
+
+// FastHash provides a quick hashing function for a flow, useful if you'd
+// like to split up flows by modulos or other load-balancing techniques.
+// It uses a variant of Fowler-Noll-Vo hashing, and is guaranteed to collide
+// with its reverse flow.  IE: the flow A->B will have the same hash as the flow
+// B->A.
+//
+// The output of FastHash is not guaranteed to remain the same through future
+// code revisions, so should not be used to key values in persistent storage.
+func (f Flow) FastHash() (h uint64) {
+	// This combination must be commutative.  We don't use ^, since that would
+	// give the same hash for all A->A flows.
+	h = fnvHash(f.src[:f.slen]) + fnvHash(f.dst[:f.dlen])
+	h ^= uint64(f.typ)
+	h *= fnvPrime
+	return
+}
+
+// String returns a human-readable representation of this flow, in the form
+// "Src->Dst"
+func (f Flow) String() string {
+	s, d := f.Endpoints()
+	return fmt.Sprintf("%v->%v", s, d)
+}
+
+// EndpointType returns the EndpointType for this Flow.
+func (f Flow) EndpointType() EndpointType {
+	return f.typ
+}
+
+// Endpoints returns the two Endpoints for this flow.
+func (f Flow) Endpoints() (src, dst Endpoint) {
+	return Endpoint{f.typ, f.slen, f.src}, Endpoint{f.typ, f.dlen, f.dst}
+}
+
+// Src returns the source Endpoint for this flow.
+func (f Flow) Src() (src Endpoint) {
+	src, _ = f.Endpoints()
+	return
+}
+
+// Dst returns the destination Endpoint for this flow.
+func (f Flow) Dst() (dst Endpoint) {
+	_, dst = f.Endpoints()
+	return
+}
+
+// Reverse returns a new flow with endpoints reversed.
+func (f Flow) Reverse() Flow {
+	return Flow{f.typ, f.dlen, f.slen, f.dst, f.src}
+}
+
+// NewFlow creates a new flow.
+//
+// src and dst must have length <= MaxEndpointSize, otherwise NewFlow will
+// panic.
+func NewFlow(t EndpointType, src, dst []byte) (f Flow) {
+	f.slen = len(src)
+	f.dlen = len(dst)
+	if f.slen > MaxEndpointSize || f.dlen > MaxEndpointSize {
+		panic("flow raw byte length greater than MaxEndpointSize")
+	}
+	f.typ = t
+	copy(f.src[:], src)
+	copy(f.dst[:], dst)
+	return
+}
+
+// EndpointInvalid is an endpoint type used for invalid endpoints, IE endpoints
+// that are specified incorrectly during creation.
+var EndpointInvalid = RegisterEndpointType(0, EndpointTypeMetadata{Name: "invalid", Formatter: func(b []byte) string {
+	return fmt.Sprintf("%v", b)
+}})
+
+// InvalidEndpoint is a singleton Endpoint of type EndpointInvalid.
+var InvalidEndpoint = NewEndpoint(EndpointInvalid, nil)
+
+// InvalidFlow is a singleton Flow of type EndpointInvalid.
+var InvalidFlow = NewFlow(EndpointInvalid, nil, nil)