/// <summary>Decode BER encoded SNMP version 1 trap packet</summary>
/// <param name="buffer">BER encoded buffer</param>
/// <param name="offset">Offset in the packet to start decoding from</param>
/// <returns>Buffer position after the decoded value.</returns>
/// <exception cref="SnmpException">Invalid SNMP Pdu type received. Not an SNMP version 1 Trap PDU.</exception>
/// <exception cref="SnmpException">Invalid Variable Binding list encoding.</exception>
public override int Decode(byte[] buffer, int offset)
{
byte asnType = ParseHeader(buffer, ref offset, out int headerLength);
if (asnType != (byte)EPduType.Trap)
{
throw new SnmpException("Invalid PDU type.");
}
if (headerLength > buffer.Length - offset)
{
throw new OverflowException("Packet is too short.");
}
offset = enterprise.Decode(buffer, offset);
offset = agentAddr.Decode(buffer, offset);
offset = generic.Decode(buffer, offset);
offset = specific.Decode(buffer, offset);
offset = timeStamp.Decode(buffer, offset);
// clean out the current variables
variables.Clear();
offset = variables.Decode(buffer, offset);
return(offset);
}
/// <summary>
/// Decode BER encoded Pdu
/// </summary>
/// <remarks>
/// Decodes the protocol data unit from the passed buffer. If an error
/// occurs during the decoding sequence then an AsnDecodingException is
/// thrown by the method. The value is decoded using the AsnEncoder
/// passed to the object.
/// </remarks>
/// <param name="buffer">BER encoded buffer</param>
/// <param name="offset">The offset byte to begin decoding</param>
/// <returns>Buffer position after the decoded value</returns>
/// <exception cref="OverflowException">Thrown when header points to more data then is available.</exception>
public override int Decode(byte[] buffer, int offset)
{
byte asnType = ParseHeader(buffer, ref offset, out int headerLength);
if (offset + headerLength > buffer.Length)
{
throw new OverflowException("Insufficient data in packet");
}
_asnType = asnType;
// request id
offset = _requestId.Decode(buffer, offset);
// error status
offset = _errorStatus.Decode(buffer, offset);
// error index
offset = _errorIndex.Decode(buffer, offset);
// clean out the current variables
_vbs.Clear();
// decode the Variable binding collection
offset = _vbs.Decode(buffer, offset);
// if Pdu is an SNMP version 2 TRAP, remove sysUpTime and trapObjectID from the VarBinds array
if (Type == PduType.V2Trap || Type == PduType.Inform)
{
if (_vbs.Count > 0)
{
if (_vbs[0].Oid.Equals(SnmpConstants.SysUpTime))
{
_trapTimeStamp.Set(_vbs[0].Value);
_vbs.RemoveAt(0); // remove sysUpTime
}
}
if (_vbs.Count > 0)
{
if (_vbs[0].Oid.Equals(SnmpConstants.TrapObjectId))
{
_trapObjectID.Set((Oid)_vbs[0].Value);
_vbs.RemoveAt(0); // remove sysUpTime
}
}
}
return(offset);
}