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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package icmp
import "encoding/binary"
// MPLSLabel represents an MPLS label stack entry.
type MPLSLabel struct {
Label int // label value
TC int // traffic class; formerly experimental use
S bool // bottom of stack
TTL int // time to live
}
const (
classMPLSLabelStack = 1
typeIncomingMPLSLabelStack = 1
)
// MPLSLabelStack represents an MPLS label stack.
type MPLSLabelStack struct {
Class int // extension object class number
Type int // extension object sub-type
Labels []MPLSLabel
}
// Len implements the Len method of Extension interface.
func (ls *MPLSLabelStack) Len(proto int) int {
return 4 + (4 * len(ls.Labels))
}
// Marshal implements the Marshal method of Extension interface.
func (ls *MPLSLabelStack) Marshal(proto int) ([]byte, error) {
b := make([]byte, ls.Len(proto))
if err := ls.marshal(proto, b); err != nil {
return nil, err
}
return b, nil
}
func (ls *MPLSLabelStack) marshal(proto int, b []byte) error {
l := ls.Len(proto)
binary.BigEndian.PutUint16(b[:2], uint16(l))
b[2], b[3] = classMPLSLabelStack, typeIncomingMPLSLabelStack
off := 4
for _, ll := range ls.Labels {
b[off], b[off+1], b[off+2] = byte(ll.Label>>12), byte(ll.Label>>4&0xff), byte(ll.Label<<4&0xf0)
b[off+2] |= byte(ll.TC << 1 & 0x0e)
if ll.S {
b[off+2] |= 0x1
}
b[off+3] = byte(ll.TTL)
off += 4
}
return nil
}
func parseMPLSLabelStack(b []byte) (Extension, error) {
ls := &MPLSLabelStack{
Class: int(b[2]),
Type: int(b[3]),
}
for b = b[4:]; len(b) >= 4; b = b[4:] {
ll := MPLSLabel{
Label: int(b[0])<<12 | int(b[1])<<4 | int(b[2])>>4,
TC: int(b[2]&0x0e) >> 1,
TTL: int(b[3]),
}
if b[2]&0x1 != 0 {
ll.S = true
}
ls.Labels = append(ls.Labels, ll)
}
return ls, nil
}
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