paramprob.go

Documentation: golang.org/x/net/icmp

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package icmp
     6  
     7  import (
     8  	"encoding/binary"
     9  
    10  	"golang.org/x/net/internal/iana"
    11  	"golang.org/x/net/ipv4"
    12  )
    13  
    14  // A ParamProb represents an ICMP parameter problem message body.
    15  type ParamProb struct {
    16  	Pointer    uintptr     // offset within the data where the error was detected
    17  	Data       []byte      // data, known as original datagram field
    18  	Extensions []Extension // extensions
    19  }
    20  
    21  // Len implements the Len method of MessageBody interface.
    22  func (p *ParamProb) Len(proto int) int {
    23  	if p == nil {
    24  		return 0
    25  	}
    26  	l, _ := multipartMessageBodyDataLen(proto, true, p.Data, p.Extensions)
    27  	return l
    28  }
    29  
    30  // Marshal implements the Marshal method of MessageBody interface.
    31  func (p *ParamProb) Marshal(proto int) ([]byte, error) {
    32  	switch proto {
    33  	case iana.ProtocolICMP:
    34  		if !validExtensions(ipv4.ICMPTypeParameterProblem, p.Extensions) {
    35  			return nil, errInvalidExtension
    36  		}
    37  		b, err := marshalMultipartMessageBody(proto, true, p.Data, p.Extensions)
    38  		if err != nil {
    39  			return nil, err
    40  		}
    41  		b[0] = byte(p.Pointer)
    42  		return b, nil
    43  	case iana.ProtocolIPv6ICMP:
    44  		b := make([]byte, p.Len(proto))
    45  		binary.BigEndian.PutUint32(b[:4], uint32(p.Pointer))
    46  		copy(b[4:], p.Data)
    47  		return b, nil
    48  	default:
    49  		return nil, errInvalidProtocol
    50  	}
    51  }
    52  
    53  // parseParamProb parses b as an ICMP parameter problem message body.
    54  func parseParamProb(proto int, typ Type, b []byte) (MessageBody, error) {
    55  	if len(b) < 4 {
    56  		return nil, errMessageTooShort
    57  	}
    58  	p := &ParamProb{}
    59  	if proto == iana.ProtocolIPv6ICMP {
    60  		p.Pointer = uintptr(binary.BigEndian.Uint32(b[:4]))
    61  		p.Data = make([]byte, len(b)-4)
    62  		copy(p.Data, b[4:])
    63  		return p, nil
    64  	}
    65  	p.Pointer = uintptr(b[0])
    66  	var err error
    67  	p.Data, p.Extensions, err = parseMultipartMessageBody(proto, typ, b)
    68  	if err != nil {
    69  		return nil, err
    70  	}
    71  	return p, nil
    72  }
    73
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