netdev - RE: [PATCH] qlcnic: dont assume NET_IP

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Message-ID: <99737F4847ED0A48AECC9F4A1974A4B80F86F80270@MNEXMB2.qlogic.org>
Date:	Tue, 21 Sep 2010 03:19:21 -0500
From:	Amit Salecha <amit.salecha@...gic.com>
To:	David Miller <davem@...emloft.net>
CC:	"eric.dumazet@...il.com" <eric.dumazet@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ameen Rahman <ameen.rahman@...gic.com>,
	Anirban Chakraborty <anirban.chakraborty@...gic.com>
Subject: RE: [PATCH] qlcnic: dont assume NET_IP_ALIGN is 2



> -----Original Message-----
> From: David Miller [mailto:davem@...emloft.net]
> Sent: Monday, September 20, 2010 9:29 PM
> To: Amit Salecha
> Cc: eric.dumazet@...il.com; netdev@...r.kernel.org; Ameen Rahman;
> Anirban Chakraborty
> Subject: Re: [PATCH] qlcnic: dont assume NET_IP_ALIGN is 2
> 
> From: Amit Salecha <amit.salecha@...gic.com>
> Date: Mon, 20 Sep 2010 06:16:31 -0500
> 
> > Though I have one doubt. We are allocating larger packets than the
> actual data used.
> > Doesn't it will break accounting ?
> 
> No, it will "fix" accounting.
> 
> You must charge to the SKB all of the non-shared memory that was
> allocated to the SKB.
> 
> This means even if the packet only uses 128 bytes of the SKB
> data area, you must still account for the full blob of linear
> memory that was allocated for the SKB data area in skb->truesize.
> 
> Otherwise remote attackers could consume enormous amounts of memory by
> tricking our socket accounting via carefully sized packets.

Wont this affect throughput ?
As problem discuss in this thread http://www.mail-archive.com/netdev@vger.kernel.org/msg06848.html, it can affect tcp window scaling.

-Amit
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