netdev - Re: [PATCH net-next v2] net: filter: add insn for loading internal transport header offset

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Date:	Wed, 14 May 2014 11:51:18 -0700
From:	Chema Gonzalez <chema@...gle.com>
To:	David Miller <davem@...emloft.net>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2] net: filter: add insn for loading internal
 transport header offset

Just realized flow_keys_init() returns a zero'ed flow_keys, which is
not inited. I renamed the function flow_keys_reset(). Sending v3.

-Chema


On Wed, May 14, 2014 at 11:42 AM, Chema Gonzalez <chema@...gle.com> wrote:
> On Mon, May 5, 2014 at 12:12 PM, David Miller <davem@...emloft.net> wrote:
>> From: Chema Gonzalez <chema@...gle.com>
>> Date: Mon, 5 May 2014 11:42:00 -0700
>>
>>> On Fri, May 2, 2014 at 7:52 PM, David Miller <davem@...emloft.net> wrote:
>>>> We can probably add an extension to AF_PACKET which provides the flow
>>>> key at the end of the tpacket3_hdr if a certain socket option is set.
>>>>
>>>> That would provide the transport header as well as a side effect, and
>>>> be much more powerful and efficient than this particular BPF
>>>> instruction.
>>> I'm not sure whether I follow this. The goal is to be able to access
>>> the inner-most headers inside BPF, not in userland by calling
>>> getsockopt().
>>
>> You're missing my entire point.
>>
>> You can use AF_PACKET mmap() rings and in those ring entries all of the
>> flow dissection information can be put in the ring entry headers before
>> the packet contents.  Ports, header offsets, everything.
> I added a flow_keys variable in the packet runner function
> (__sk_run_filter()) stack, and modified __skb_get_poff() to try to get
> the results from there instead of calling the flow dissector every
> time you call it. That will allow the packet filter to only perform a
> single call to the flow dissector per packet.
>
> I reworked the toff patch to use the same flow dissector output
> approach (and share it with the poff load), and added a tproto patch.
>
> Patches coming now.
>
> -Chema
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