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