linux-kernel - Re: [PATCH net-next v2 8/9] net: filter: rework/optimize internal BPF interpreter's instruction set

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Message-Id: <20140325.201712.1651156258234145348.davem@davemloft.net>
Date:	Tue, 25 Mar 2014 20:17:12 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	dborkman@...hat.com
Cc:	ast@...mgrid.com, netdev@...r.kernel.org, hagen@...u.net,
	keescook@...omium.org, pmoore@...hat.com, mingo@...nel.org,
	hpa@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 8/9] net: filter: rework/optimize internal
 BPF interpreter's instruction set

From: Daniel Borkmann <dborkman@...hat.com>
Date: Tue, 25 Mar 2014 13:10:56 +0100

>   - Conditional jt/jf targets replaced with jt/fall-through,
>     and forward/backward jumps now possible as well

Ummm... does anyone even remember why backwards jumps were not allowed
in the original BPF?

It's to guarentee forward progress in the filter.

Allowing branching backward would allow endless loops.

Please remove this feature.
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