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Re: [babel] About mandatory bits

Toke Høiland-Jørgensen <toke@toke.dk> Thu, 20 April 2017 09:05 UTC

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To: Juliusz Chroboczek <jch@irif.fr>
Cc: babel@ietf.org
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Date: Thu, 20 Apr 2017 11:05:43 +0200
In-Reply-To: <7ivaq0bflk.wl-jch@irif.fr> (Juliusz Chroboczek's message of "Wed, 19 Apr 2017 17:07:51 +0200")
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Subject: Re: [babel] About mandatory bits
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Juliusz Chroboczek <jch@irif.fr> writes:

>> Shouldn't the mandatory bit just be a part of the allocation? I.e.
>> "sub-tlv XX MUST be sent as mandatory", and setting the bit wrong should
>> be considered a format error? That would be the most unambiguous, in my
>> opinion.
>
> The way I think of it is
>
>   TLV numbers 0-127 are non-mandatory;
>   TLV numbers 128-255 are mandatory.

Ah, right. Gotcha. I was thinking of it basically like this:

bool mandatory = tlv[0] & 0x80
u8 type = tlv[0] & 0x7f

where the contents of type would be what was specified in the RFC. That
would lead to two different "TLV type 2" being defined.

But if it's defined in terms of ranges of TLV numbers I see no problem
in assigning them separately :)

-Toke

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