netdev - Re: [patch net-next v3] tc: introduce OpenFlow classifier

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20150412.194443.1571071793033525091.davem@davemloft.net>
Date:	Sun, 12 Apr 2015 19:44:43 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	jiri@...nulli.us
Cc:	alexei.starovoitov@...il.com, netdev@...r.kernel.org,
	jhs@...atatu.com, tgraf@...g.ch, jesse@...ira.com
Subject: Re: [patch net-next v3] tc: introduce OpenFlow classifier

From: Jiri Pirko <jiri@...nulli.us>
Date: Sun, 12 Apr 2015 09:53:51 +0200

> Sat, Apr 11, 2015 at 06:12:25PM CEST, alexei.starovoitov@...il.com wrote:
>>On Fri, Apr 10, 2015 at 02:45:17PM +0200, Jiri Pirko wrote:
>>> Okay. That was misunderstanding. I was thinking about using existing
>>> flow_dissect. There are couple things which I'm scared of:
>>> - there are eventually many fields to be added to dissection function and to
>>>   the structure as well. Not sure how acceptable that would be for
>>>   performance reasons when flow_dissect is used by different users...
>>
>>I share the same concern. I think flow_dissect is too performance
>>critical to reuse by expanding 'struct flow_keys'.
>>I think it would be better to generalize ovs's key_extract() into
>>common piece of code that TC classifier and ovs datapath can use.
>>It uses kernel internal 'struct sw_flow_key' which we can tweak to
>>accommodate more users. It's already gigantic at 392 bytes, so
>>split and a bit of diet would help too.
> 
> Yep, those are few next topics on my agenda.

This argument kinda ignores the fact that full flow dissection is run
on _every_ single RX packet on basically all Intel chipsets.

Therefore, I cannot take seriously someone saying that it is too much
overhead for a classifier.

And if it is that expensive, fix it, because that helps everyone not
just your special thing.

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html