How to implement an agent width Windows SNMP API for a MIB containing SNMP tables? thanks.

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VisualC++

SNMP

I have implemented a SNMP agent by windows snmp api with reference to an article How to develop a SNMP extension agent DLL[^]. Several oids must be organized to be a SNMP table. I did it like this:
This class represent a oid.

class VeMIB_ENTRY
{
public:
	AsnObjectIdentifier m_asnOid;
	VeMIB_ENTRY*		m_pMibNext;

	VeMIB_ENTRY(VeMIB_ENTRY* pMibNext,UINT unLength,UINT asnOid,...)
	{
		m_asnOid.idLength = unLength;
		m_asnOid.ids = new UINT[unLength];
		memcpy(m_asnOid.ids,&asnOid,unLength*sizeof(UINT));
		m_pMibNext = pMibNext;
	}

	VeMIB_ENTRY(VeMIB_ENTRY* pMibNext,UINT unLength,UINT asnOid[])
	{
		m_asnOid.idLength = unLength;
		m_asnOid.ids = new UINT[unLength];
		memcpy(m_asnOid.ids,asnOid,unLength*sizeof(UINT));
		m_pMibNext = pMibNext;
	}

	virtual ~VeMIB_ENTRY() 
	{ 
		delete[] m_asnOid.ids; 
	}

	virtual int  GetStorageValue( AsnAny* pasnValue ) {return SNMP_ERRORSTATUS_NOERROR;}
	virtual int  SetStorageValue( const AsnAny* pasnValue ) {return SNMP_ERRORSTATUS_READONLY;}

private:
	VeMIB_ENTRY( const VeMIB_ENTRY& ) {};
	VeMIB_ENTRY& operator=( const VeMIB_ENTRY& ) {};
};

class VeNullValue:
	public VeMIB_ENTRY
{
public:
	VeNullValue(VeMIB_ENTRY *pMibNext,UINT unLength,UINT asnOid,...)
		:VeMIB_ENTRY(pMibNext,unLength,&asnOid)
	{
	}

	virtual int  GetStorageValue(AsnAny* pasnValue) 
	{
		pasnValue->asnType = ASN_NULL;

		return SNMP_ERRORSTATUS_NOERROR;
	}

	virtual int  SetStorageValue( const AsnAny* pasnValue ) {return SNMP_ERRORSTATUS_NOERROR;}
};

class VeEntryValue:
	public VeMIB_ENTRY
{
private:
	const TCHAR* m_szMsg;
public:
	VeEntryValue(VeMIB_ENTRY *pMibNext,UINT unLength,UINT asnOid,...)
		:VeMIB_ENTRY(pMibNext,unLength,&asnOid)
	{
		m_szMsg = _T("entry");
	}

	virtual int  GetStorageValue(AsnAny* pasnValue) 
	{
		pasnValue->asnType = ASN_SEQUENCE;
		pasnValue->asnValue.sequence.length = _tcslen(m_szMsg)*sizeof(TCHAR);
		pasnValue->asnValue.sequence.stream 
			= (unsigned char*)SnmpUtilMemAlloc(pasnValue->asnValue.sequence.length);

		memcpy(pasnValue->asnValue.string.stream,m_szMsg,pasnValue->asnValue.sequence.length);

		pasnValue->asnValue.sequence.dynamic = TRUE;
		return SNMP_ERRORSTATUS_NOERROR;
	}

	virtual int  SetStorageValue( const AsnAny* pasnValue ) {return SNMP_ERRORSTATUS_NOERROR;}
};

MIB is organised like this.

UINT g_unMyOIDPrefix[] = {1, 3, 6, 1, 4, 1, 31492};
CMap<AsnObjectIdentifier*,AsnObjectIdentifier*,VeMIB_ENTRY*,VeMIB_ENTRY*> g_VeMIB;

void  InitialVeMIB()
{
	VeMIB_ENTRY *pMibEntry = NULL;
	VeMIB_ENTRY *pMibEntryNext = NULL;

	g_VeMIB.InitHashTable(100);

#define ADD_MIB_ITEM(type,length,...)            \
	pMibEntry = new type(pMibEntryNext,length,##__VA_ARGS__);\
	g_VeMIB.SetAt(&(pMibEntry->m_asnOid),pMibEntry);\
	pMibEntryNext = pMibEntry

	ADD_MIB_ITEM(VeMIB_ENTRY ,7,3,1,1,1,10,1,5);
	ADD_MIB_ITEM(VeMIB_ENTRY ,7,3,1,1,1,10,1,4);
	ADD_MIB_ITEM(VeMIB_ENTRY ,7,3,1,1,1,10,1,3);
	ADD_MIB_ITEM(VeMIB_ENTRY ,1,7,3,1,1,1,10,1,2);
	ADD_MIB_ITEM(VeMIB_ENTRY ,7,3,1,1,1,10,1,1);
	ADD_MIB_ITEM(VeEntryValue,6,3,1,1,1,10,1);
	ADD_MIB_ITEM(VeNullValue,5,3,1,1,1,10);
}

If it is correctly implemented,one can use command line like snmputil walk localhost public .1.3.6.1.4.1.31492.3.1.1.1.10 or snmp4j -c -v 2c -Ot localhost .1.3.6.1.4.1.31492.3.1.1.1.10 to query the table. But now i can use command line snmp4j -c -v 2c -Ot localhost .1.3.6.1.4.1.31492.3.1.1.1.10.1 query the table with an error number 2 returned.

It may also concerned with SnmpExtensionQuery. Its source code provide as follow.

BOOL SNMP_FUNC_TYPE SnmpExtensionQuery(BYTE bPduType, SnmpVarBindList *pVarBindList, AsnInteger32 *pErrorStatus, AsnInteger32 *pErrorIndex)
{
	int nRet = 0;

	*pErrorStatus = SNMP_ERRORSTATUS_NOERROR;
	*pErrorIndex = 0;

	for(UINT i=0;i<pVarBindList->len;i++)
	{
		*pErrorStatus = SNMP_ERRORSTATUS_NOERROR;

		VeMIB_ENTRY* pMIBItem = GetVeMIBItem(&pVarBindList->list[i]);
		if (pMIBItem != NULL)
		{
			// what type of request we are getting?
			switch(bPduType)
			{
			case SNMP_PDU_GET:// // gets the variable value passed variable in pVarBindList
				*pErrorStatus = pMIBItem->GetStorageValue(&(pVarBindList->list[i].value));
				if(*pErrorStatus != SNMP_ERRORSTATUS_NOERROR)
					*pErrorIndex++;
				break;
			case SNMP_PDU_GETNEXT: // gets the next variable related to the passed variable in pVarBindList
				*pErrorStatus = SNMP_ERRORSTATUS_NOSUCHNAME;
				if(pMIBItem->m_pMibNext != NULL)
				{
					SnmpUtilOidFree(&pVarBindList->list[i].name);			
					SnmpUtilOidCpy(&pVarBindList->list[i].name, &MIB_OidPrefix);
					SnmpUtilOidAppend(&pVarBindList->list[i].name, &pMIBItem->m_pMibNext->m_asnOid);
					*pErrorStatus = pMIBItem->m_pMibNext->GetStorageValue(&(pVarBindList->list[i].value));
				}
				else

				if(*pErrorStatus != SNMP_ERRORSTATUS_NOERROR)
					*pErrorIndex++;
				break;
			case SNMP_PDU_SET: // sets a variable
				*pErrorStatus = pMIBItem->SetStorageValue(&(pVarBindList->list[i].value));
				if(*pErrorStatus != SNMP_ERRORSTATUS_NOERROR)
					*pErrorIndex++;
				break;
			default:
				*pErrorStatus = SNMP_ERRORSTATUS_NOSUCHNAME;
				*pErrorIndex++;
			};
		}
		else
		{
			*pErrorStatus = SNMP_ERRORSTATUS_NOSUCHNAME;
			*pErrorIndex++;
		}
	}	

	return SNMPAPI_NOERROR;
}

How it happens, How to implement an agent width Windows SNMP API for a MIB containing SNMP tables?