Re: Fields alignment when extended mask is present

[Roberto Riggio <roberto.riggio-2TmCWn7/4sHOQU1ULcgDhA@public.gmane.org>]

Il 21/02/2011 10:27, Johannes Berg ha scritto:
> On Sun, 2011-02-20 at 11:55 +0100, Roberto Riggio wrote:
>> Hi,
>>
>> I'm generating a radio tap header with extended mask in order to
>> specify a multi rate retry chain. In the first mask i have 4 fields
>> each of them 8 bits long, so no padding problem.
>>
>> In the second, third and forth mask I have only the rate and the retries
>> fields should I use padding between one mask and the next:
>>
>> rate_1 (8)
>> retry_1 (8)
>> pad (8)
>> pad (8)
>> rate_2 (8)
>> retry_2 (8)
>> pad (8)
>> pad (8)
>>
>> or insted:
>>
>> rate_1 (8)
>> retry _1 (8)
>> rate_2 (8)
>> retry _2 (8)
> What's with the "(8)"? Generally, anything in the data portion of
> radiotap needs to be padded to the right position.
(8) was the field length. in the example above i;ve repoted
two different radiotap headers where i specify twice the rate
and the retries field.

of course i know that in this case i will have to put to it-present
bitmasks and i will have to set the bit 31 of the first bitmask to 1.

what i'm not sure is if i have to pad the first "block" to the word
boundary or not.

> johannes
>


-- 
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Roberto Riggio, Ph.D.
CREATE-NET
Network&  Security Solutions for Pervasive Computing Systems (iNSPIRE)
Senior Researcher
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e-mail: roberto.riggio-2TmCWn7/4sHOQU1ULcgDhA@public.gmane.org
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www.create-net.org/~rriggio
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