/// <summary>Decode received SNMP packet.</summary>
/// <param name="buffer">BER encoded packet buffer</param>
/// <param name="length">BER encoded packet buffer length</param>
/// <returns>Buffer position after the decoded packet.</returns>
/// <exception cref="SnmpException">Thrown when invalid encoding has been found in the packet</exception>
/// <exception cref="OverflowException">Thrown when parsed header points to more data then is available in the packet</exception>
/// <exception cref="SnmpInvalidVersionException">Thrown when parsed packet is not SNMP version 1</exception>
/// <exception cref="SnmpInvalidPduTypeException">Thrown when received PDU is of a type not supported by SNMP version 1</exception>
public override int Decode(byte[] buffer, int length)
{
MutableByte buf = new MutableByte(buffer, length);
int offset = 0;
offset = base.Decode(buffer, buffer.Length);
if (protocolVersion.Value != (int)ESnmpVersion.Ver1)
{
throw new SnmpInvalidVersionException("Invalid protocol version");
}
offset = Community.Decode(buf, offset);
int tmpOffset = offset;
byte asnType = AsnType.ParseHeader(buf, ref tmpOffset, out int headerLength);
// Check packet length
if (headerLength + offset > buf.Length)
{
throw new OverflowException("Insufficient data in packet");
}
if (asnType != (byte)EPduType.Get && asnType != (byte)EPduType.GetNext && asnType != (byte)EPduType.Set && asnType != (byte)EPduType.Response)
{
throw new SnmpInvalidPduTypeException("Invalid SNMP operation received: " + string.Format("0x{0:x2}", asnType));
}
// Now process the Protocol Data Unit
offset = Pdu.Decode(buf, offset);
return(length);
}