netdev - Re: [PATCH net-next 0/8] Add complementary BPF conditional jump instructions

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Message-Id: <20121231.143715.1238174487756359071.davem@davemloft.net>
Date:	Mon, 31 Dec 2012 14:37:15 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	dborkman@...hat.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/8] Add complementary BPF conditional jump
 instructions

From: Daniel Borkmann <dborkman@...hat.com>
Date: Mon, 31 Dec 2012 14:59:40 +0100

> This set adds adds jump operations for lt (<), le (<=), ne (!=) that
> compare A with K resp. X in order to facilitate filter programming
> with conditional jumps, as also available in McCanne et. al's BPF+
> paper (``BPF+: Exploiting Global Data-flow Optimization in a Generalized
> Packet Filter Architecture'').
> 
> Also, follow-up BPF JIT implementations for x86, Sparc and PowerPC
> are added in this set.

Whilst I agree that adding NE jumps adds great value and closes a
serious gap, the rest can be synthesized by simply swapping the
arguments and using a comparison that does already exist.

Why isn't that sufficient?
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