[Olsr-dev] OLSRd 0.6.0 with ETT available
Fri Oct 8 15:40:33 CEST 2010
On Fri October 8 2010 10:11:57 David Lamparter wrote:
> On Thu, Sep 30, 2010 at 02:02:25PM +0200, Henning Rogge wrote:
> > I have a question on your encoding of the ETT values in the Hello/TC
> > messages.
> > In the HELLO messages you seem to be using a 5 byte encoding. OLSR
> > messages have to be 4-byte aligned, so you want to add 3 bytes of
> > padding there. It might crash your nodes on an ARM/MIPS cpu otherwise.
> Um, what kind of crap is this? The padding in OLSR is not only
> unneccessary but even harmful as it wastes airtime.
If you look into the OLSR RFC you will notice two things:
1.) all OLSR messages have a length of 4*x bytes
2.) all fields in OLSR messages are "well aligned"
Even the original ETX extension enlarged the messages by 4 bytes (with 2 bytes
I was pretty sure that it's somewhere in the RFC, but I was unable to find it.
The OLSRd core and most of it's plugins was written with this assumption and
nobody changed it up to version 0.6.0. If you have a message with a length
with is not a multiple of 4, bad things will happen.
We had a case like this last year in Berlin. It took us 3 weeks to find the
problem. After this OLSRd got a check if incoming messages have a "correct"
size... if not the rest of the packet is dropped.
The problem will not be there in 0.7.0, because the new packet parser for
PacketBB (RFC 5444) will handle this stuff.
Diplom-Informatiker Henning Rogge , Fraunhofer-Institut für
Kommunikation, Informationsverarbeitung und Ergonomie FKIE
Neuenahrer Straße 20, 53343 Wachtberg, Germany
Telefon +49 228 9435-961, Fax +49 228 9435 685
GPG: E1C6 0914 490B 3909 D944 F80D 4487 C67C 55EC CFE0
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