Re: Sending signed values problem

Bill Fenner <[email protected]>
Newsgroups gmane.network.net-snmp.user
Message-ID <CAF4SogbKqyPWUJE4QkLL8cVGunRoUxANnv0+G=v6uOzLAKOd5A@mail.gmail.com>
On Thu, Jun 22, 2017 at 10:37 AM, corvace.fabrizio--- via Net-snmp-users <
[email protected]> wrote:

> Hello,
>
> I'm currently struggling with a data problem.
>
> I have a system where i have to SET a value, the value is of type Integer
> (-32768.32767).
>
> When sending a value over 255 i have no problem with sign, if i scan with
> wireshark i see a transmission of ASN type 2(Integer) with 2 bytes of data,
> and the data is correctly sent with sign.
>
> But whenever i try to send a value that is less that 256, therefore fits
> in a byte, the transmission is still of type 2, but it sends out one single
> byte of data, thus cutting out the range from -129 to -255 and from +128 to
> +255.
>
> I would have thought that since the OID is of type Integer (explicitly
> 16bit) the data would still have been sent as 2bytes.
>
BER encoding is variable length, no matter what the restrictions on the
range of the integer - restrictions like that are managed at a higher layer.

As you surmise, the BER encoding of values from -129 to -255 and +128 to
+255 are two bytes long.

> I tried looking for a way of forcing 2 byte data send, but with no luck.
> Am i missing something?
>
How are you sending your data?  I do not know of a way to force net-snmp to
behave in this incorrect way.

  Bill

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