netdev - Re: [PATCH] openvswitch: Fix alignment of struct sw_flow

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Message-ID: <CAEP_g=8Phux4eMz_b45XvEddkJKkTkkGzg+jvVKLBx4Ztiu=5w@mail.gmail.com>
Date:	Thu, 5 Sep 2013 12:25:00 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"dev@...nvswitch.org" <dev@...nvswitch.org>,
	Andy Zhou <azhou@...ira.com>, fengguan.wu@...el.com
Subject: Re: [PATCH] openvswitch: Fix alignment of struct sw_flow_key.

On Thu, Sep 5, 2013 at 12:20 PM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> Why don't you abort the loop if a difference is found?
> Or is this a security-related struct where you want to protect against
> timing attacks?

It's more expensive to test for a difference on every iteration in the
common case where the comparison succeeds.

> Furthermore, as you compare the raw bytes, I hope you always
> initialize all gaps in the struct to zero.
> E.g. there's a 2-byte gap immediately after "ip", as the next member
> is 32-bit (except op m68k, where the 32-bit member will be 2-byte aligned).

It's initialized to zero.
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