netdev - Re: [PATCH 1/9] batman-adv: add UNICAST

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Message-Id: <20121103.152226.244759041688205348.davem@davemloft.net>
Date:	Sat, 03 Nov 2012 15:22:26 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	ordex@...istici.org
Cc:	netdev@...r.kernel.org, b.a.t.m.a.n@...ts.open-mesh.org
Subject: Re: [PATCH 1/9] batman-adv: add UNICAST_4ADDR packet type

From: Antonio Quartulli <ordex@...istici.org>
Date: Sat,  3 Nov 2012 19:48:26 +0100

> The current unicast packet type does not contain the orig source address. This
> patches add a new unicast packet (called UNICAST_4ADDR) which provides two new
> fields: the originator source address and the subtype (the type of the data
> contained in the packet payload). The former is useful to identify the node
> which injected the packet into the network and the latter is useful to avoid
> creating new unicast packet types in the future: a macro defining a new subtype
> will be enough.
> 
> Signed-off-by: Antonio Quartulli <ordex@...istici.org>

Your packet layouts are very poorly designed and I want you to stop
and think seriously about things before extending things further.

All of this __packed stuff is a serious problem.

It means that on RISC system, fields such as your 32-bit sequence
number, will be read and written using byte loads and stores.

This is terrible.

Instead, design the structures so that they are full filled out to
at least 4 byte boundaries, so that they and the contents after
them, are 4 byte aligned too.

Then you won't need to mark all of your packet header structs
with __packed, and therefore the compiler can use full 32-bit
loads and stores to access 32-bit fields.

I'm not applying this series, sorry, it just continues a major
problem that the batman-adv code already has.
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