netdev - Re: [B.A.T.M.A.N.] pull request: batman-adv 2011-11-26

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Message-ID: <20111203015528.GB3148@ritirata.org>
Date:	Sat, 3 Dec 2011 02:55:29 +0100
From:	Antonio Quartulli <ordex@...istici.org>
To:	David Miller <davem@...emloft.net>
Cc:	lindner_marek@...oo.de, netdev@...r.kernel.org,
	b.a.t.m.a.n@...ts.open-mesh.org
Subject: Re: [B.A.T.M.A.N.] pull request: batman-adv 2011-11-26

On Fri, Dec 02, 2011 at 12:57:25 -0500, David Miller wrote:
> From: Antonio Quartulli <ordex@...istici.org>
> Date: Fri, 2 Dec 2011 18:12:16 +0100
> 
> > First of all I think you are referring to patch 08/10, in which I moved a
> > skb_linearise() operation.
> > 
> > To be sure it is really needed, I backtracked the code flow and noted down any
> > eventual psbk_may_pull() (or any other linearisation operation). The result is:
> > 
> > => in batman_skb_recv()
> > 	- pskb_may_pull(2)
> >   => in recv_tt_query()
> >   	  - pskb_may_pull(sizeof(header))
> > 	  - skb_linearise()
> > 
> > Actually it seems we haven't any useless linearisation.
> > Would you mind explain us where you actually found the problem, please?
> > 
> > It might also be that I misunderstood your advice.
> 
> You only need to call pskb_may_pull() on the parts of the packet you want to
> access directly to parse headers etc.
> 
> If you use that interface properly, you never need to linearize, ever.

Sorry for being too generic: we actually invoke skb_linearise() because
we want to access the whole skb.

We first call pskb_may_pull() to pull the header only and then, under certain
conditions, we linearise the whole skb to access it all. Should I use
pskb_may_pull() even in this case?

Sorry for stealing you so much time on this issue, but I would like to fully
understand it in order to avoid any further mistake.


Thank you again.

Best Regards,

-- 
Antonio Quartulli

..each of us alone is worth nothing..
Ernesto "Che" Guevara
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