Re: [PATCH 1/9] batman-adv: add UNICAST_4ADDR packet type

[David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>]

From: Antonio Quartulli <ordex-GaUfNO9RBHfsrOwW+9ziJQ@public.gmane.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-GaUfNO9RBHfsrOwW+9ziJQ@public.gmane.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.