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open.go
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open.go
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package msg
import (
"fmt"
"math"
"net/netip"
"github.com/bgpfix/bgpfix/caps"
"github.com/bgpfix/bgpfix/json"
)
// Open represents a BGP OPEN message
type Open struct {
Msg *Msg // parent BGP message
Version byte // must be 4
ASN uint16 // 2-byte local ASN
HoldTime uint16 // proposed hold time
Identifier netip.Addr // router identifier
Params []byte // raw Optional Parameters
ParamsExt bool // true iff Params use extended length
Caps caps.Caps // BGP capabilities, usually parsed from Params
}
const (
OPEN_MINLEN = 29 - HEADLEN // rfc4271/4.2
OPEN_VERSION = 4
OPEN_HOLDTIME = 90
PARAM_CAPS = 2
PARAM_EXTLEN = 255
AS_TRANS = 23456
)
// Init initializes o to use parent m
func (o *Open) Init(m *Msg) {
o.Msg = m
o.Identifier = netip.IPv4Unspecified()
o.Version = OPEN_VERSION
// NB: no o.Caps.Init()
}
// Reset prepares o for re-use
func (o *Open) Reset() {
o.Params = nil
o.ParamsExt = false
o.Caps.Reset()
}
// Parse parses o.Msg.Data as BGP OPEN
func (o *Open) Parse() error {
buf := o.Msg.Data
if len(buf) < OPEN_MINLEN {
return ErrShort
}
o.Version = buf[0]
if o.Version != OPEN_VERSION {
return ErrVersion
}
o.ASN = msb.Uint16(buf[1:3])
o.HoldTime = msb.Uint16(buf[3:5])
o.Identifier = netip.AddrFrom4([4]byte(buf[5:9]))
// parse optional parameters
pslen := int(buf[9])
if pslen > 0 {
params, ext := buf[10:], false
// extended length?
if len(params) >= 3 && params[0] == PARAM_EXTLEN {
ext = true
pslen = int(msb.Uint16(params[1:3]))
params = params[3:]
}
// double-check params length
if len(params) != pslen {
return ErrParams
}
o.Params = params
o.ParamsExt = ext
}
o.Msg.Upper = OPEN
return nil
}
// ParseCaps parses all capability codes from Params to Caps
func (o *Open) ParseCaps() error {
var (
params = o.Params // all parameters
ptyp byte // parameter type
plen int // parameter length
pval []byte // parameter value
cps caps.Caps // parsed capabilities
)
// parse params one-by-one, in practice there's only the
// capabilities param, or we return an error
cps.Init()
for len(params) > 0 {
if o.ParamsExt {
if len(params) < 3 {
return ErrParams
}
ptyp = params[0]
plen = int(msb.Uint16(params[1:3]))
pval = params[3:]
} else {
if len(params) < 2 {
return ErrParams
}
ptyp = params[0]
plen = int(params[1])
pval = params[2:]
}
// double-check param length
if len(pval) < plen {
return ErrParams
} else {
params = pval[plen:]
pval = pval[:plen]
}
// we only support capabilities
if ptyp != PARAM_CAPS {
return ErrParams
}
// parse capabilities
for len(pval) > 0 {
if len(pval) < 2 {
return ErrCaps
}
cc, clen, cval := caps.Code(pval[0]), int(pval[1]), pval[2:]
if len(cval) < clen {
return ErrCaps
} else {
pval = cval[clen:]
cval = cval[:clen]
}
// fetch cap
cap := cps.Use(cc)
if cap == nil {
continue // should not happen
}
// try parsing
if err := cap.Unmarshal(cval, cps); err != nil {
return fmt.Errorf("%s: %w", cc, err)
}
}
}
// store
o.Caps = cps
return nil
}
// SetASN sets local ASN number in o and its AS4
func (o *Open) SetASN(asn int) {
// o'rlly?
if asn < 0 || int64(asn) > math.MaxUint32 {
asn = 0
}
if asn <= math.MaxUint16 {
o.ASN = uint16(asn)
} else {
o.ASN = AS_TRANS
}
if c, ok := o.Caps.Use(caps.CAP_AS4).(*caps.AS4); ok {
c.ASN = uint32(asn)
}
}
// GetASN returns the local ASN, preferably from AS4
func (o *Open) GetASN() int {
if c, ok := o.Caps.Get(caps.CAP_AS4).(*caps.AS4); ok {
return int(c.ASN)
} else {
return int(o.ASN)
}
}
// Marshal marshals o to o.Msg.Data.
func (o *Open) Marshal() error {
// check params length
switch plen := len(o.Params); {
case plen > math.MaxUint16:
return fmt.Errorf("Marshal: Params too long: %w (%d)", ErrLength, plen)
case plen > math.MaxUint8 && !o.ParamsExt:
return fmt.Errorf("Marshal: ParamsExt disabled: %w (%d)", ErrLength, plen)
}
msg := o.Msg
buf := msg.buf[:0]
buf = append(buf, o.Version)
buf = msb.AppendUint16(buf, o.ASN)
buf = msb.AppendUint16(buf, o.HoldTime)
buf = append(buf, o.Identifier.AsSlice()...)
// optional parameters
if o.ParamsExt {
buf = append(buf, 255, PARAM_EXTLEN)
buf = msb.AppendUint16(buf, uint16(len(o.Params)))
} else {
buf = append(buf, byte(len(o.Params)))
}
buf = append(buf, o.Params...)
// done
msg.Type = OPEN
msg.Upper = OPEN
msg.buf = buf
msg.Data = buf
msg.ref = false
return nil
}
// MarshalCaps marshals o.Caps into o.Params. Sets o.ParamsExt.
func (o *Open) MarshalCaps() error {
// NB: avoid o.Params[:0] as it might be referencing another slice
o.Params = nil
// marshal one-by-one
var raw []byte
o.Caps.Each(func(i int, cc caps.Code, c caps.Cap) {
if res := c.Marshal(raw); res != nil {
raw = res
}
})
// done?
if len(raw) == 0 {
return nil
}
// check *parameter* length
switch plen := len(raw) + 2; { // 2 for param Type and Length
case plen > math.MaxUint16:
return fmt.Errorf("MarshalCaps: too long: %w (%d)", ErrLength, plen)
case plen > 255:
o.ParamsExt = true
default:
o.ParamsExt = false // avoid if not neccessary
}
// encode as new o.Params
p := o.Params
p = append(p, PARAM_CAPS)
if o.ParamsExt {
p = msb.AppendUint16(p, uint16(len(raw)))
} else {
p = append(p, byte(len(raw)))
}
p = append(p, raw...)
o.Params = p
return nil
}
// String dumps o to JSON
func (o *Open) String() string {
return string(o.ToJSON(nil))
}
// ToJSON appends JSON representation of o to dst
func (o *Open) ToJSON(dst []byte) []byte {
dst = append(dst, `{"bgp":`...)
dst = json.Byte(dst, o.Version)
dst = append(dst, `,"asn":`...)
dst = json.Int(dst, int(o.ASN))
dst = append(dst, `,"id":`...)
dst = json.Addr(dst, o.Identifier)
dst = append(dst, `,"hold":`...)
dst = json.Uint16(dst, o.HoldTime)
if o.Caps.Valid() {
dst = append(dst, `,"caps":`...)
dst = o.Caps.ToJSON(dst)
} else {
dst = append(dst, `,"params":`...)
dst = json.Hex(dst, o.Params)
}
dst = append(dst, '}')
return dst
}
// FromJSON reads o JSON representation from src
func (o *Open) FromJSON(src []byte) error {
return json.ObjectEach(src, func(key string, val []byte, typ json.Type) (err error) {
switch key {
case "bgp":
o.Version, err = json.UnByte(val)
case "asn":
asn, err := json.UnUint32(val)
if err != nil {
return err
}
o.SetASN(int(asn))
case "id":
o.Identifier, err = json.UnAddr(val)
case "hold":
o.HoldTime, err = json.UnUint16(val)
case "caps":
err = o.Caps.FromJSON(val)
case "params":
o.Params, err = json.UnHex(val, o.Params[:0])
}
return err
})
}