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Diffstat (limited to 'vendor/github.com/google/gopacket/flows.go')
-rw-r--r-- | vendor/github.com/google/gopacket/flows.go | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/vendor/github.com/google/gopacket/flows.go b/vendor/github.com/google/gopacket/flows.go new file mode 100644 index 0000000..7203ead --- /dev/null +++ b/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 lexigraphically. +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) |