addByteLength(） 不添加字节以在 omnet++ 中发送消息

我为自己的模拟模型编写了一个函数来创建和发送ARP请求。在下面的代码中，我已成功创建了 ARP 数据包并将字节大小设置为 28。现在，当我尝试将这个创建的数据包封装在链路层帧中时tempLinkLayerARPRequestFrame

                tempIPARPRequest = new IPv4ARP("IPv4ARP Request");
                tempIPARPRequest->setSourceIP(tempIPPacket->getSourceIP());
                tempIPARPRequest->setDestinationIP(
                        tempIPPacket->getDestinationIP());
                tempIPARPRequest->addByteLength(28);
                // encapsulate it 
                tempLinkLayerARPRequestFrame= new LinkLayerFrame("LinkARP Request");
                tempLinkLayerARPRequestFrame->setField1(this->Field1);
                tempLinkLayerARPRequestFrame->setField2(this->Field2);

                tempLinkLayerARPRequestFrame->setFrameType(0); //an ARP packet
                tempLinkLayerARPRequestFrame->addByteLength(30); //30Bytes
                tempLinkLayerARPRequestFrame->encapsulate(tempIPARPRequest);
                tempLinkLayerARPRequestFrame->setKind(0);
                send(tempLinkLayerARPRequestFrame->dup(), "toBelowSendQ");
                ARPRequestedCache[tempIPPacket->getDestinationIP()] = true;

但我看到传输的帧大小为 28 字节，而不是 28 + 30 = 58 字节。为什么会发生这种情况或封装函数没有附加字节？

更新

IPv4ARP msg 文件是：

NED 文件：

packet IPv4ARP {
    string SourceIP;
    string DestinationIP;
}

IPv4ARP_m.h：

//
// Generated file, do not edit! Created by nedtool 4.6 from IPv4ARP.msg.
//
#ifndef _IPV4ARP_M_H_
#define _IPV4ARP_M_H_
#include <omnetpp.h>
// nedtool version check
#define MSGC_VERSION 0x0406
#if (MSGC_VERSION!=OMNETPP_VERSION)
#    error Version mismatch! Probably this file was generated by an earlier version of nedtool: 'make clean' should help.
#endif

/**
 * Class generated from <tt>IPv4ARP.msg:19</tt> by nedtool.
 * <pre>
 * //
 * // TODO generated message class
 * //
 * packet IPv4ARP
 * {
 *     string SourceIP;
 *     string DestinationIP;
 * }
 * </pre>
 */
class IPv4ARP : public ::cPacket
{
  protected:
    opp_string SourceIP_var;
    opp_string DestinationIP_var;
  private:
    void copy(const IPv4ARP& other);
  protected:
    // protected and unimplemented operator==(), to prevent accidental usage
    bool operator==(const IPv4ARP&);
  public:
    IPv4ARP(const char *name=NULL, int kind=0);
    IPv4ARP(const IPv4ARP& other);
    virtual ~IPv4ARP();
    IPv4ARP& operator=(const IPv4ARP& other);
    virtual IPv4ARP *dup() const {return new IPv4ARP(*this);}
    virtual void parsimPack(cCommBuffer *b);
    virtual void parsimUnpack(cCommBuffer *b);
    // field getter/setter methods
    virtual const char * getSourceIP() const;
    virtual void setSourceIP(const char * SourceIP);
    virtual const char * getDestinationIP() const;
    virtual void setDestinationIP(const char * DestinationIP);
};
inline void doPacking(cCommBuffer *b, IPv4ARP& obj) {obj.parsimPack(b);}
inline void doUnpacking(cCommBuffer *b, IPv4ARP& obj) {obj.parsimUnpack(b);}

#endif // ifndef _IPV4ARP_M_H_

IPv4ARP_m.cc

//
// Generated file, do not edit! Created by nedtool 4.6 from IPv4ARP.msg.
//
// Disable warnings about unused variables, empty switch stmts, etc:
#ifdef _MSC_VER
#  pragma warning(disable:4101)
#  pragma warning(disable:4065)
#endif
#include <iostream>
#include <sstream>
#include "IPv4ARP_m.h"
USING_NAMESPACE

// Another default rule (prevents compiler from choosing base class' doPacking())
template<typename T>
void doPacking(cCommBuffer *, T& t) {
    throw cRuntimeError("Parsim error: no doPacking() function for type %s or its base class (check .msg and _m.cc/h files!)",opp_typename(typeid(t)));
}
template<typename T>
void doUnpacking(cCommBuffer *, T& t) {
    throw cRuntimeError("Parsim error: no doUnpacking() function for type %s or its base class (check .msg and _m.cc/h files!)",opp_typename(typeid(t)));
}


// Template rule for outputting std::vector<T> types
template<typename T, typename A>
inline std::ostream& operator<<(std::ostream& out, const std::vector<T,A>& vec)
{
    out.put('{');
    for(typename std::vector<T,A>::const_iterator it = vec.begin(); it != vec.end(); ++it)
    {
        if (it != vec.begin()) {
            out.put(','); out.put(' ');
        }
        out << *it;
    }
    out.put('}');
    char buf[32];
    sprintf(buf, " (size=%u)", (unsigned int)vec.size());
    out.write(buf, strlen(buf));
    return out;
}
// Template rule which fires if a struct or class doesn't have operator<<
template<typename T>
inline std::ostream& operator<<(std::ostream& out,const T&) {return out;}
Register_Class(IPv4ARP);
IPv4ARP::IPv4ARP(const char *name, int kind) : ::cPacket(name,kind)
{
    this->SourceIP_var = 0;
    this->DestinationIP_var = 0;
}
IPv4ARP::IPv4ARP(const IPv4ARP& other) : ::cPacket(other)
{
    copy(other);
}
IPv4ARP::~IPv4ARP()
{
}
IPv4ARP& IPv4ARP::operator=(const IPv4ARP& other)
{
    if (this==&other) return *this;
    ::cPacket::operator=(other);
    copy(other);
    return *this;
}
void IPv4ARP::copy(const IPv4ARP& other)
{
    this->SourceIP_var = other.SourceIP_var;
    this->DestinationIP_var = other.DestinationIP_var;
}
void IPv4ARP::parsimPack(cCommBuffer *b)
{
    ::cPacket::parsimPack(b);
    doPacking(b,this->SourceIP_var);
    doPacking(b,this->DestinationIP_var);
}
void IPv4ARP::parsimUnpack(cCommBuffer *b)
{
    ::cPacket::parsimUnpack(b);
    doUnpacking(b,this->SourceIP_var);
    doUnpacking(b,this->DestinationIP_var);
}
const char * IPv4ARP::getSourceIP() const
{
    return SourceIP_var.c_str();
}
void IPv4ARP::setSourceIP(const char * SourceIP)
{
    this->SourceIP_var = SourceIP;
}
const char * IPv4ARP::getDestinationIP() const
{
    return DestinationIP_var.c_str();
}
void IPv4ARP::setDestinationIP(const char * DestinationIP)
{
    this->DestinationIP_var = DestinationIP;
}
class IPv4ARPDescriptor : public cClassDescriptor
{
  public:
    IPv4ARPDescriptor();
    virtual ~IPv4ARPDescriptor();
    virtual bool doesSupport(cObject *obj) const;
    virtual const char *getProperty(const char *propertyname) const;
    virtual int getFieldCount(void *object) const;
    virtual const char *getFieldName(void *object, int field) const;
    virtual int findField(void *object, const char *fieldName) const;
    virtual unsigned int getFieldTypeFlags(void *object, int field) const;
    virtual const char *getFieldTypeString(void *object, int field) const;
    virtual const char *getFieldProperty(void *object, int field, const char *propertyname) const;
    virtual int getArraySize(void *object, int field) const;
    virtual std::string getFieldAsString(void *object, int field, int i) const;
    virtual bool setFieldAsString(void *object, int field, int i, const char *value) const;
    virtual const char *getFieldStructName(void *object, int field) const;
    virtual void *getFieldStructPointer(void *object, int field, int i) const;
};
Register_ClassDescriptor(IPv4ARPDescriptor);
IPv4ARPDescriptor::IPv4ARPDescriptor() : cClassDescriptor("IPv4ARP", "cPacket")
{
}
IPv4ARPDescriptor::~IPv4ARPDescriptor()
{
}
bool IPv4ARPDescriptor::doesSupport(cObject *obj) const
{
    return dynamic_cast<IPv4ARP *>(obj)!=NULL;
}
const char *IPv4ARPDescriptor::getProperty(const char *propertyname) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    return basedesc ? basedesc->getProperty(propertyname) : NULL;
}
int IPv4ARPDescriptor::getFieldCount(void *object) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    return basedesc ? 2+basedesc->getFieldCount(object) : 2;
}
unsigned int IPv4ARPDescriptor::getFieldTypeFlags(void *object, int field) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    if (basedesc) {
        if (field < basedesc->getFieldCount(object))
            return basedesc->getFieldTypeFlags(object, field);
        field -= basedesc->getFieldCount(object);
    }
    static unsigned int fieldTypeFlags[] = {
        FD_ISEDITABLE,
        FD_ISEDITABLE,
    };
    return (field>=0 && field<2) ? fieldTypeFlags[field] : 0;
}
const char *IPv4ARPDescriptor::getFieldName(void *object, int field) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    if (basedesc) {
        if (field < basedesc->getFieldCount(object))
            return basedesc->getFieldName(object, field);
        field -= basedesc->getFieldCount(object);
    }
    static const char *fieldNames[] = {
        "SourceIP",
        "DestinationIP",
    };
    return (field>=0 && field<2) ? fieldNames[field] : NULL;
}
int IPv4ARPDescriptor::findField(void *object, const char *fieldName) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    int base = basedesc ? basedesc->getFieldCount(object) : 0;
    if (fieldName[0]=='S' && strcmp(fieldName, "SourceIP")==0) return base+0;
    if (fieldName[0]=='D' && strcmp(fieldName, "DestinationIP")==0) return base+1;
    return basedesc ? basedesc->findField(object, fieldName) : -1;
}
const char *IPv4ARPDescriptor::getFieldTypeString(void *object, int field) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    if (basedesc) {
        if (field < basedesc->getFieldCount(object))
            return basedesc->getFieldTypeString(object, field);
        field -= basedesc->getFieldCount(object);
    }
    static const char *fieldTypeStrings[] = {
        "string",
        "string",
    };
    return (field>=0 && field<2) ? fieldTypeStrings[field] : NULL;
}
const char *IPv4ARPDescriptor::getFieldProperty(void *object, int field, const char *propertyname) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    if (basedesc) {
        if (field < basedesc->getFieldCount(object))
            return basedesc->getFieldProperty(object, field, propertyname);
        field -= basedesc->getFieldCount(object);
    }
    switch (field) {
        default: return NULL;
    }
}
int IPv4ARPDescriptor::getArraySize(void *object, int field) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    if (basedesc) {
        if (field < basedesc->getFieldCount(object))
            return basedesc->getArraySize(object, field);
        field -= basedesc->getFieldCount(object);
    }
    IPv4ARP *pp = (IPv4ARP *)object; (void)pp;
    switch (field) {
        default: return 0;
    }
}
std::string IPv4ARPDescriptor::getFieldAsString(void *object, int field, int i) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    if (basedesc) {
        if (field < basedesc->getFieldCount(object))
            return basedesc->getFieldAsString(object,field,i);
        field -= basedesc->getFieldCount(object);
    }
    IPv4ARP *pp = (IPv4ARP *)object; (void)pp;
    switch (field) {
        case 0: return oppstring2string(pp->getSourceIP());
        case 1: return oppstring2string(pp->getDestinationIP());
        default: return "";
    }
}
bool IPv4ARPDescriptor::setFieldAsString(void *object, int field, int i, const char *value) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    if (basedesc) {
        if (field < basedesc->getFieldCount(object))
            return basedesc->setFieldAsString(object,field,i,value);
        field -= basedesc->getFieldCount(object);
    }
    IPv4ARP *pp = (IPv4ARP *)object; (void)pp;
    switch (field) {
        case 0: pp->setSourceIP((value)); return true;
        case 1: pp->setDestinationIP((value)); return true;
        default: return false;
    }
}
const char *IPv4ARPDescriptor::getFieldStructName(void *object, int field) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    if (basedesc) {
        if (field < basedesc->getFieldCount(object))
            return basedesc->getFieldStructName(object, field);
        field -= basedesc->getFieldCount(object);
    }
    switch (field) {
        default: return NULL;
    };
}
void *IPv4ARPDescriptor::getFieldStructPointer(void *object, int field, int i) const
{
    cClassDescriptor *basedesc = getBaseClassDescriptor();
    if (basedesc) {
        if (field < basedesc->getFieldCount(object))
            return basedesc->getFieldStructPointer(object, field, i);
        field -= basedesc->getFieldCount(object);
    }
    IPv4ARP *pp = (IPv4ARP *)object; (void)pp;
    switch (field) {
        default: return NULL;
    }
}