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msg.go
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// Package msg represents BGP messages.
//
// This package can read/write BGP messages in wire and JSON formats.
package msg
import (
"bytes"
"io"
"strconv"
"time"
"github.com/bgpfix/bgpfix/binary"
"github.com/bgpfix/bgpfix/caps"
"github.com/bgpfix/bgpfix/json"
)
// Msg represents a BGP message.
// Use NewMsg to get a new valid object.
type Msg struct {
// internal
ref bool // true iff Data is a reference we don't own
buf []byte // internal buffer
// optional metadata
Dst Dst // message destination
Seq int64 // sequence number
Time time.Time // message timestamp
// raw contents
Type Type // message type
Data []byte // message data (referenced or owned), can be nil
// upper layer
Upper Type // which of the upper layer is valid?
Dirty bool // if true, probably needs a marshal (Data does not reflect Upper)
Open Open // parsed BGP OPEN message
Update Update // parsed BGP UPDATE message
// for optional use beyond this pkg
Value Value // NB: not affected by Reset()
}
// Value represents an optional, arbitrary value attached to a message
type Value interface {
// ToJSON appends JSON representation of the value to dst
ToJSON(dst []byte) []byte
// FromJSON reads from JSON representation in src
FromJSON(src []byte) error
}
// BGP message destination (message direction)
type Dst byte
//go:generate go run github.com/dmarkham/enumer -type Dst -trimprefix DST_
const (
DST_LR Dst = 0 // no particular destination (ie. both L and R)
DST_L Dst = 1 // destined for L ("left" or "local")
DST_R Dst = 2 // destined for R ("right" or "remote")
)
// BGP message type
type Type byte
//go:generate go run github.com/dmarkham/enumer -type Type
const (
INVALID Type = 0 // NOT DEFINED / INVALID
OPEN Type = 1 // OPEN
UPDATE Type = 2 // UPDATE
NOTIFY Type = 3 // NOTFICATION
KEEPALIVE Type = 4 // KEEPALIVE
REFRESH Type = 5 // ROUTE-REFRESH RFC2918
)
const (
// BGP header length, per rfc4271/4.1
HEADLEN = 19 // = marker(16) + length(2) + type(1)
// BGP maximum message length, per rfc4271
MAXLEN = 4096
// BGP maximum extended message length, per rfc8654
MAXLEN_EXT = 65535
// JSON date and time format
JSON_TIME = `2006-01-02T15:04:05.000`
)
var (
msb = binary.Msb
bgp_marker = [...]byte{
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
}
)
// NewMsg returns new empty message
func NewMsg() *Msg {
msg := new(Msg)
msg.Open.Init(msg)
msg.Update.Init(msg)
return msg
}
// Reset clears the message
func (msg *Msg) Reset() *Msg {
switch msg.Upper {
case OPEN:
msg.Open.Reset()
case UPDATE:
msg.Update.Reset()
}
msg.ref = false
if cap(msg.buf) < 1024*1024 {
msg.buf = msg.buf[:0] // NB: re-use iff < 1MiB
} else {
msg.buf = nil
}
msg.Dst = 0
msg.Seq = 0
msg.Time = time.Time{}
msg.Type = 0
msg.Data = nil
msg.Upper = INVALID
msg.Dirty = false
msg.Value = nil
return msg
}
// Length returns total BGP message length, including header
func (msg *Msg) Length() int {
return len(msg.Data) + HEADLEN
}
// Up prepares to make use of and modify the upper layer of given type.
// Does not reset the upper layer struct, though.
func (msg *Msg) Up(typ Type) *Msg {
msg.Type = typ
msg.Upper = typ
msg.Dirty = true
return msg
}
// SetData updates the data to reference given value
func (msg *Msg) SetData(data []byte) *Msg {
msg.Data = data
msg.ref = data != nil
if msg.Upper != INVALID {
msg.Dirty = true
}
return msg
}
// Own tags msg as the owner of referenced data. Does not copy the data.
func (msg *Msg) Own() *Msg {
msg.ref = false
return msg
}
// Disown tags msg as not the owner of data.
func (msg *Msg) Disown() *Msg {
msg.ref = true
return msg
}
// CopyData copies the referenced data iff needed and makes msg the owner
func (msg *Msg) CopyData() *Msg {
if !msg.ref {
return msg // already owned
}
// tag as owned
msg.ref = false
// special case: nothing to do
if msg.Data == nil {
return msg
}
// copy re-using our internal buffer
msg.buf = append(msg.buf[:0], msg.Data...)
msg.Data = msg.buf
msg.ref = false
return msg
}
// Parse parses the BGP message in raw. Does not copy.
// Returns the number of parsed bytes from raw.
func (msg *Msg) Parse(raw []byte) (off int, err error) {
// enough data for marker + length + type?
if len(raw) < HEADLEN {
return off, io.ErrUnexpectedEOF
}
data := raw
// find marker
if !bytes.HasPrefix(data, bgp_marker[:]) {
return off, ErrMarker
}
off = len(bgp_marker)
data = raw[off:]
// read type and length
l := int(msb.Uint16(data[:2]))
msg.Type = Type(data[2])
off += 3
data = raw[off:]
// check length
dlen := l - HEADLEN
if dlen < 0 {
return off, ErrLength
} else if dlen > len(data) {
return off, io.ErrUnexpectedEOF
}
// reference data, if needed
if dlen > 0 {
msg.ref = true
msg.Data = data[:dlen]
} else {
msg.ref = false
msg.Data = nil
}
// done!
return off + dlen, nil
}
// ParseUpper parses the upper layer iff needed.
// caps can infuence the upper layer decoders.
func (msg *Msg) ParseUpper(caps caps.Caps) error {
if msg.Upper != INVALID {
return nil // already done
}
var err error
switch msg.Type {
case OPEN:
o := &msg.Open
err = o.Parse()
if err != nil {
break
}
err = o.ParseCaps()
case UPDATE:
u := &msg.Update
err = u.Parse()
if err != nil {
break
}
err = u.ParseAttrs(caps)
case KEEPALIVE:
if len(msg.Data) != 0 {
err = ErrLength
}
case NOTIFY, REFRESH:
// err = ErrNotImpl // TODO
default:
err = ErrType
}
if err == nil {
msg.Upper = msg.Type
msg.Dirty = false
}
return err
}
// MarshalUpper marshals the upper layer to msg.Data iff possible and needed.
// caps can infuence the upper layer encoders.
func (msg *Msg) MarshalUpper(caps caps.Caps) error {
if !msg.Dirty || msg.Upper == INVALID {
return nil // not needed or not possible
}
var err error
switch msg.Type {
case OPEN:
o := &msg.Open
err = o.MarshalCaps()
if err != nil {
break
}
err = o.Marshal()
case UPDATE:
u := &msg.Update
err = u.MarshalAttrs(caps)
if err != nil {
break
}
err = u.Marshal(caps)
case KEEPALIVE:
msg.SetData(nil)
default:
err = ErrType
}
if err == nil {
msg.Dirty = false
}
return err
}
// WriteTo marshals the BGP message to w, implementing io.WriterTo
func (msg *Msg) WriteTo(w io.Writer) (n int64, err error) {
var m int
// data length ok?
l := msg.Length()
if l > MAXLEN {
return 0, ErrLength
}
// write the marker
m, err = w.Write(bgp_marker[:])
if err != nil {
return
}
n += int64(m)
// write length
m, err = msb.WriteUint16(w, uint16(l))
if err != nil {
return
}
n += int64(m)
// write type
m, err = msb.WriteUint8(w, uint8(msg.Type))
if err != nil {
return
}
n += int64(m)
// write data?
if len(msg.Data) > 0 {
m, err = w.Write(msg.Data)
if err != nil {
return
}
n += int64(m)
}
// done
return
}
// String dumps msg to JSON
func (msg *Msg) String() string {
return string(msg.ToJSON(nil))
}
// ToJSON appends JSON representation of msg to dst (may be nil to allocate)
func (msg *Msg) ToJSON(dst []byte) []byte {
dst = append(dst, `["`...)
// [0] direction
dst = append(dst, msg.Dst.String()...) // TODO: or number
dst = append(dst, `",`...)
// [1] sequence number (for dir)
dst = strconv.AppendInt(dst, msg.Seq, 10)
dst = append(dst, `,"`...)
// [2] time
dst = append(dst, msg.Time.Format(JSON_TIME)...)
dst = append(dst, `",`...)
// [3] length (w/out the header)
if msg.Dirty && msg.Type != KEEPALIVE {
dst = append(dst, `-1`...)
} else {
dst = strconv.AppendUint(dst, uint64(len(msg.Data)), 10)
}
// [4] type
dst = append(dst, `,"`...)
dst = append(dst, msg.Type.String()...) // TODO: or number
dst = append(dst, `",`...)
// [5] data (or upper layer)
switch msg.Upper {
case OPEN:
dst = msg.Open.ToJSON(dst)
case UPDATE:
dst = msg.Update.ToJSON(dst)
case KEEPALIVE:
dst = append(dst, json.Null...)
case NOTIFY:
dst = append(dst, `"`...)
dst = append(dst, msg.Data[2:]...) // FIXME
dst = append(dst, `"`...)
default:
dst = json.Hex(dst, msg.Data)
}
// [6] value TODO: json serialize
dst = append(dst, ',')
if msg.Value != nil {
dst = msg.Value.ToJSON(dst)
} else {
dst = append(dst, `null`...)
}
dst = append(dst, ']')
return dst
}
// FromJSON reads msg JSON representation from src
func (msg *Msg) FromJSON(src []byte) (reterr error) {
return json.ArrayEach(src, func(key int, val []byte, typ json.Type) (err error) {
switch key {
case 0: // dst TODO: better
if typ == json.STRING {
msg.Dst, err = DstString(json.S(val))
} else if typ == json.NUMBER {
var v byte
v, err = json.UnByte(val)
msg.Dst = Dst(v)
}
case 1: // seq number
msg.Seq, err = strconv.ParseInt(json.S(val), 10, 64)
case 2: // time
if typ == json.STRING && len(val) > 0 {
msg.Time, err = time.Parse(JSON_TIME, json.S(val))
}
// NB: ignore [3] = wire length
case 4: // type TODO: better
if typ == json.STRING {
msg.Type, err = TypeString(json.S(val))
} else if typ == json.NUMBER {
var v byte
v, err = json.UnByte(val)
msg.Type = Type(v)
}
if msg.Type != INVALID {
msg.Up(msg.Type)
}
case 5: // upper layer
if typ == json.STRING {
msg.buf, err = json.UnHex(val, msg.buf[:0])
msg.Data = msg.buf
msg.ref = false
msg.Upper = INVALID
} else {
switch msg.Type {
case OPEN:
err = msg.Open.FromJSON(val)
case UPDATE:
err = msg.Update.FromJSON(val)
default:
err = ErrTODO // TODO
}
}
case 6: // value
if msg.Value != nil && typ != json.NULL {
err = msg.Value.FromJSON(val)
}
}
return err
})
}