netdev - Re: [PATCH] Add JMEMCMP to Berkeley Packet Filters

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Date:	Thu, 10 Feb 2011 17:27:15 +0200
From:	Octavian Purdila <tavi.purdila@...il.com>
To:	Ian Molton <ian.molton@...labora.co.uk>
Cc:	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
	rdunlap@...otime.net, isdn@...ux-pingi.de, paulus@...ba.org,
	arnd@...db.de, davem@...emloft.net, herbert@...dor.apana.org.au,
	ebiederm@...ssion.com, alban.crequy@...labora.co.uk,
	astanciu@...acom.com
Subject: Re: [PATCH] Add JMEMCMP to Berkeley Packet Filters

On Thu, Feb 10, 2011 at 3:35 PM, Ian Molton <ian.molton@...labora.co.uk> wrote:
> On 10/02/11 13:24, Eric Dumazet wrote:
>
> Hi!
>
> Thanks for reviewing! :)
>
>>> * Can sk_run_filter() be called in a context where kmalloc(GFP_KERNEL) is
>>>   not allowed (I think not)
>>
>> You cannot use GFP_KERNEL in sk_run_filter() : We run in {soft}irq mode,
>> in input path.
>
> Ok, that can be sorted.
>
>>> * Data section allocated with second call to sock_kmalloc().
>>> * Should the patch be broken into two - one to add the data uploading,
>>>   one to add the JMEMCMP insn. ?
>>
>> May I ask why it is needed at all ?
>
> So we can match strings in packet filters... I don't think I understand the
> question...
>

Adding a data section (some sort of persistent memory storage that the
filter can access) is also useful for creating capture triggers, e.g.
starting capturing after a marker packet has arrived.
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