Re: I didn't understand Packet Classifier Element

You were clean like water.

Thank you.

Emerson Barea

2015-07-18 18:04 GMT-03:00 Lars Bro <[email protected]>:

> Hi Emerson,
>
> The values dd/hhhhhhhh... are interpreted like this:
>
>
> dd is a byte offset in decimal and hhhhhhh... is a binary value in hex
> format.
>
> so, 12/0806 means that at offset 12, two bytes are expected, namely 0x0806
> This will match an ARP message, since the packet type is in byte 12 of an
> Ethernet packet. However, if it is an ARP message, byte 20 and 21 will tell
> the type. They have to be 0x0001 for request and 0x0002 for reply. Forgive
> me if I mixed them up.
>
> So, 12/0806 20/0001 means an ARP message that is a request.
>
> The expressions are separated by comma, and each expression has its own
> output.
>
> So, the whole classifier above means: "ARP requests to output 0, ARP
> responses to output 1, IP to output 2 and all the rest (-) to output 3"
>
> yours,
> Lars Bro
>
> On Sat, Jul 18, 2015 at 5:05 PM, Emerson Barea <[email protected]>
> wrote:
>
>> Hi there.
>>
>> Please, could someone explain to me how Packet Classifier Element works?
>> For example, I want to understant how this command knows what is the arp
>> request, response and IP packet.
>>
>> c0 :: Classifier(12/0806 20/0001,
>>                  12/0806 20/0002,
>>                  12/0800,
>>                  -);
>>
>> I didn't understant the offset/value definition.
>>
>> Thank you.
>>
>> Emerson Barea
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>
>