Sample MIB Source File
The MIB source files perform the actual resolving of MIB variables. It contains the following header files: Windows.h, Snmp.h, and Testmib.h.
/*********************************************************************/
#include <windows.h>
#include <snmp.h>
#include "testmib.h" // Contains definitions for the table structure
// describing the MIB.
// If an addition or deletion to the MIB is necessary, there are
// several places in the code that must be checked and possibly
// changed. The last field in each MIB entry is used to point to the
// NEXT leaf variable. If an addition or deletion is made, these
// pointers might need to be updated to reflect the modification.
UINT OID_Prefix[] = {1, 3, 6, 1, 4, 1, 12};
// The prefix to all of these MIB variables is
// 1.3.6.1.4.1.12
AsnObjectIdentifier MIB_OidPrefix =
{OID_SIZEOF(OID_Prefix), OID_Prefix};
UINT MIB_toaster[] = {2};
// Definition of leaf variables under the toaster group. All leaf
// variables have a zero appended to their OID to indicate that it is
// the only instance of this variable and that it exists.
UINT MIB_toasterManufacturer[] = {2, 1, 0};
UINT MIB_toasterModelNumber[] = {2, 2, 0};
UINT MIB_toasterControl[] = {2, 3, 0};
UINT MIB_toasterDoneness[] = {2, 4, 0};
UINT MIB_toasterToastType[] = {2, 5, 0};
// Storage definitions for MIB
char MIB_toasterManStor[] = "Microsoft Corporation";
char MIB_toasterModelStor[] =
"Example SNMP Extension Agent for Windows CE (TOASTER-MIB).";
AsnInteger MIB_toasterControlStor = 1;
AsnInteger MIB_toasterDonenessStor = 2;
AsnInteger MIB_toasterToastTypeStor = 3;
// MIB definiton
MIB_ENTRY Mib[] = {
{{OID_SIZEOF(MIB_toasterManufacturer), MIB_toasterManufacturer},
&MIB_toasterManStor, ASN_RFC1213_DISPSTRING,
MIB_ACCESS_READ, MIB_leaf_func, &Mib[1]},
{{OID_SIZEOF(MIB_toasterModelNumber), MIB_toasterModelNumber},
&MIB_toasterModelStor, ASN_RFC1213_DISPSTRING,
MIB_ACCESS_READ, MIB_leaf_func, &Mib[2]},
{{OID_SIZEOF(MIB_toasterControl), MIB_toasterControl},
&MIB_toasterControlStor, ASN_INTEGER,
MIB_ACCESS_READWRITE, MIB_control_func, &Mib[3]},
{{OID_SIZEOF(MIB_toasterDoneness), MIB_toasterDoneness},
&MIB_toasterDonenessStor, ASN_INTEGER,
MIB_ACCESS_READWRITE, MIB_doneness_func, &Mib[4]},
{{OID_SIZEOF(MIB_toasterToastType), MIB_toasterToastType},
&MIB_toasterToastTypeStor, ASN_INTEGER,
MIB_ACCESS_READWRITE, MIB_toasttype_func, NULL}};
UINT MIB_num_variables = sizeof Mib / sizeof (MIB_ENTRY);
/**********************************************************************
ResolveVarBind
Resolves a single variable binding. Modifies the variable on a GET
or a GET-NEXT.
**********************************************************************/
UINT ResolveVarBind (
IN OUT RFC1157VarBind *VarBind, // Variable Binding to resolve
IN UINT PduAction) // Action that is specified in PDU
{
MIB_ENTRY *MibPtr;
AsnObjectIdentifier TempOid;
int CompResult;
UINT I;
UINT nResult;
// Search for var bind name in the MIB
I = 0;
MibPtr = NULL;
while (MibPtr == NULL && I < MIB_num_variables)
{
// Construct OID with complete prefix for comparison purposes
SnmpUtilOidCpy (&TempOid, &MIB_OidPrefix);
SnmpUtilOidAppend (&TempOid, &Mib[I].Oid);
// Check for OID in MIB - On a GET-NEXT the OID does not have to
// match exactly a variable in the MIB, it must fall only under
// the MIB root.
CompResult = SnmpUtilOidCmp (&VarBind->name, &TempOid);
if (0 > CompResult)
{
// Because there is not an exact match, the only valid action is
// GET-NEXT
if (MIB_ACTION_GETNEXT != PduAction)
{
nResult = SNMP_ERRORSTATUS_NOSUCHNAME;
goto Exit;
}
// Because the match was not exact, but varbind name is within MIB,
// you are at the NEXT MIB variable down from the one that was specified.
PduAction = MIB_ACTION_GET;
MibPtr = &Mib[I];
// Replace var bind name with new name
SnmpUtilOidFree (&VarBind->name);
SnmpUtilOidCpy (&VarBind->name, &MIB_OidPrefix);
SnmpUtilOidAppend (&VarBind->name, &MibPtr->Oid);
}
else
{
// An exact match was found.
if (0 == CompResult)
MibPtr = &Mib[I];
}
// Free OID memory before checking another variable
SnmpUtilOidFree (&TempOid);
I++;
} // while
// If OID not within scope of MIB, then no such name
if (MibPtr == NULL)
{
nResult = SNMP_ERRORSTATUS_NOSUCHNAME;
goto Exit;
}
// Call function to process request. Each MIB entry has a function
// pointer that knows how to process its MIB variable.
nResult = (*MibPtr->MibFunc) (PduAction, MibPtr, VarBind);
// Free temp memory
SnmpUtilOidFree (&TempOid);
Exit:
return nResult;
} // ResolveVarBind
/**********************************************************************
MIB_leaf_func
Performs generic actions on LEAF variables in the MIB.
**********************************************************************/
UINT MIB_leaf_func (
IN UINT Action,
IN MIB_ENTRY *MibPtr,
IN RFC1157VarBind *VarBind)
{
UINT ErrStat;
switch (Action)
{
case MIB_ACTION_GETNEXT:
// If there is no GET-NEXT pointer, this is the end of this MIB
if (MibPtr->MibNext == NULL)
{
ErrStat = SNMP_ERRORSTATUS_NOSUCHNAME;
goto Exit;
}
// Set up varbind name of NEXT MIB variable
SnmpUtilOidFree (&VarBind->name);
SnmpUtilOidCpy (&VarBind->name, &MIB_OidPrefix);
SnmpUtilOidAppend (&VarBind->name, &MibPtr->MibNext->Oid);
// Call function to process request. Each MIB entry has a
// function pointer that knows how to process its MIB variable.
ErrStat = (*MibPtr->MibNext->MibFunc) (MIB_ACTION_GET,
MibPtr->MibNext, VarBind);
break;
case MIB_ACTION_GET:
// Make sure that this variable's ACCESS is GET'able
if (MibPtr->Access != MIB_ACCESS_READ &&
MibPtr->Access != MIB_ACCESS_READWRITE)
{
ErrStat = SNMP_ERRORSTATUS_NOSUCHNAME;
goto Exit;
}
// Set up varbind's return value
VarBind->value.asnType = MibPtr->Type;
switch (VarBind->value.asnType)
{
case ASN_RFC1155_COUNTER:
case ASN_RFC1155_GAUGE:
case ASN_INTEGER:
VarBind->value.asnValue.number =
* (AsnInteger *) (MibPtr->Storage);
break;
case ASN_OCTETSTRING: // Entails ASN_RFC1213_DISPSTRING also.
VarBind->value.asnValue.string.length =
strlen ((LPSTR)MibPtr->Storage);
if (NULL == (VarBind->value.asnValue.string.stream =
SnmpUtilMemAlloc (VarBind->value.asnValue.string.length*
sizeof (char))))
{
ErrStat = SNMP_ERRORSTATUS_GENERR;
goto Exit;
}
memcpy (VarBind->value.asnValue.string.stream,
(LPSTR)MibPtr->Storage,
VarBind->value.asnValue.string.length);
VarBind->value.asnValue.string.dynamic = TRUE;
break;
default:
ErrStat = SNMP_ERRORSTATUS_GENERR;
goto Exit;
}
break;
case MIB_ACTION_SET:
// Make sure that this variable's ACCESS is SET'able
if (MibPtr->Access != MIB_ACCESS_READWRITE &&
MibPtr->Access != MIB_ACCESS_WRITE)
{
ErrStat = SNMP_ERRORSTATUS_NOSUCHNAME;
goto Exit;
}
// Check for proper type before setting
if (MibPtr->Type != VarBind->value.asnType)
{
ErrStat = SNMP_ERRORSTATUS_BADVALUE;
goto Exit;
}
// Save value in MIB
switch (VarBind->value.asnType)
{
case ASN_RFC1155_COUNTER:
case ASN_RFC1155_GAUGE:
case ASN_INTEGER:
* (AsnInteger *) (MibPtr->Storage) =
VarBind->value.asnValue.number;
break;
case ASN_OCTETSTRING: // Entails ASN_RFC1213_DISPSTRING also.
// The storage must be adequate to contain the new string
// including a NULL terminator.
memcpy ((LPSTR)MibPtr->Storage,
VarBind->value.asnValue.string.stream,
VarBind->value.asnValue.string.length);
((LPSTR)MibPtr->Storage)
[VarBind->value.asnValue.string.length] = '\0';
break;
default:
ErrStat = SNMP_ERRORSTATUS_GENERR;
goto Exit;
}
break;
default:
ErrStat = SNMP_ERRORSTATUS_GENERR;
goto Exit;
} // switch
// Signal no error occurred
ErrStat = SNMP_ERRORSTATUS_NOERROR;
Exit:
return ErrStat;
} // MIB_leaf_func
/**********************************************************************
MIB_control_func
Performs specific actions on the toasterControl MIB variable
**********************************************************************/
UINT MIB_control_func (
IN UINT Action,
IN MIB_ENTRY *MibPtr,
IN RFC1157VarBind *VarBind)
{
UINT ErrStat;
switch (Action)
{
case MIB_ACTION_SET:
// Make sure that this variable's ACCESS is SET'able
if (MibPtr->Access != MIB_ACCESS_READWRITE &&
MibPtr->Access != MIB_ACCESS_WRITE)
{
ErrStat = SNMP_ERRORSTATUS_NOSUCHNAME;
goto Exit;
}
// Check for proper type before setting
if (MibPtr->Type != VarBind->value.asnType)
{
ErrStat = SNMP_ERRORSTATUS_BADVALUE;
goto Exit;
}
// Make sure the value is valid
if (MIB_TOASTER_UP > VarBind->value.asnValue.number ||
MIB_TOASTER_DOWN < VarBind->value.asnValue.number)
{
ErrStat = SNMP_ERRORSTATUS_BADVALUE;
goto Exit;
}
// Let fall through purposefully for further processing by
// generic leaf function.
case MIB_ACTION_GETNEXT:
case MIB_ACTION_GET:
// Call the more generic function to perform the action
ErrStat = MIB_leaf_func (Action, MibPtr, VarBind);
break;
default:
ErrStat = SNMP_ERRORSTATUS_GENERR;
goto Exit;
} // switch
Exit:
return ErrStat;
} // MIB_control_func
/**********************************************************************
MIB_doneness_func
Performs specific actions on the toasterDoneness MIB variable
**********************************************************************/
UINT MIB_doneness_func (
IN UINT Action,
IN MIB_ENTRY *MibPtr,
IN RFC1157VarBind *VarBind)
{
UINT ErrStat;
switch (Action)
{
case MIB_ACTION_SET:
// Make sure that this variable's ACCESS is SET'able
if (MibPtr->Access != MIB_ACCESS_READWRITE &&
MibPtr->Access != MIB_ACCESS_WRITE)
{
ErrStat = SNMP_ERRORSTATUS_NOSUCHNAME;
goto Exit;
}
// Check for proper type before setting
if (MibPtr->Type != VarBind->value.asnType)
{
ErrStat = SNMP_ERRORSTATUS_BADVALUE;
goto Exit;
}
// Make sure the value is valid
if (MIB_TOASTER_LIGHTLYWARM > VarBind->value.asnValue.number ||
MIB_TOASTER_BURNT < VarBind->value.asnValue.number)
{
ErrStat = SNMP_ERRORSTATUS_BADVALUE;
goto Exit;
}
// Let fall through purposefully for further processing by
// generic leaf function.
case MIB_ACTION_GETNEXT:
case MIB_ACTION_GET:
// Call the more generic function to perform the action
ErrStat = MIB_leaf_func (Action, MibPtr, VarBind);
break;
default:
ErrStat = SNMP_ERRORSTATUS_GENERR;
goto Exit;
} // switch
Exit:
return ErrStat;
} // MIB_doneness_func
/**********************************************************************
MIB_toasttype_func
Performs specific actions on the toasterToastType MIB variable
**********************************************************************/
UINT MIB_toasttype_func (
IN UINT Action,
IN MIB_ENTRY *MibPtr,
IN RFC1157VarBind *VarBind)
{
UINT ErrStat;
switch (Action)
{
case MIB_ACTION_SET:
// Make sure that this variable's ACCESS is SET'able
if (MibPtr->Access != MIB_ACCESS_READWRITE &&
MibPtr->Access != MIB_ACCESS_WRITE)
{
ErrStat = SNMP_ERRORSTATUS_NOSUCHNAME;
goto Exit;
}
// Check for proper type before setting
if (MibPtr->Type != VarBind->value.asnType)
{
ErrStat = SNMP_ERRORSTATUS_BADVALUE;
goto Exit;
}
// Make sure the value is valid
if (MIB_TOASTER_WHITEBREAD > VarBind->value.asnValue.number ||
MIB_TOASTER_OTHERBREAD < VarBind->value.asnValue.number)
{
ErrStat = SNMP_ERRORSTATUS_BADVALUE;
goto Exit;
}
// Let fall through purposefully for further processing by
// generic leaf function.
case MIB_ACTION_GETNEXT:
case MIB_ACTION_GET:
// Call the more generic function to perform the action
ErrStat = MIB_leaf_func (Action, MibPtr, VarBind);
break;
default:
ErrStat = SNMP_ERRORSTATUS_GENERR;
goto Exit;
} // switch
Exit:
return ErrStat;
} // MIB_toasttype_func
See Also
Last updated on Saturday, April 10, 2004
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