func parseParamProb(proto int, b []byte) (MessageBody, error) {
	if len(b) < 4 {
		return nil, errMessageTooShort
	}
	p := &ParamProb{}
	if proto == iana.ProtocolIPv6ICMP {
		p.Pointer = uintptr(binary.BigEndian.Uint32(b[:4]))
		p.Data = make([]byte, len(b)-4)
		copy(p.Data, b[4:])
		return p, nil
	}
	p.Pointer = uintptr(b[0])
	var err error
	p.Data, p.Extensions, err = parseMultipartMessageBody(proto, b)
	if err != nil {
		return nil, err
	}
	return p, nil
}
parseParamProb parses b as an ICMP parameter problem message body.
package icmp
import (
	"encoding/binary"
	"golang.org/x/net/internal/iana"
)
type ParamProb struct {
	Pointer    uintptr      
	Data       []byte       
	Extensions []Extension  
}
func (p *ParamProb) Len(proto int) int {
	if p == nil {
		return 0
	}
	l, _ := multipartMessageBodyDataLen(proto, p.Data, p.Extensions)
	return 4 + l
}
func (p *ParamProb) Marshal(proto int) ([]byte, error) {
	if proto == iana.ProtocolIPv6ICMP {
		b := make([]byte, p.Len(proto))
		binary.BigEndian.PutUint32(b[:4], uint32(p.Pointer))
		copy(b[4:], p.Data)
		return b, nil
	}
	b, err := marshalMultipartMessageBody(proto, p.Data, p.Extensions)
	if err != nil {
		return nil, err
	}
	b[0] = byte(p.Pointer)
	return b, nil
}