netdev - Re: [PATCH net-next] tc: bpf: add checksum helpers

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Date:	Thu, 02 Apr 2015 20:01:42 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Alexei Starovoitov <ast@...mgrid.com>,
	Jiri Pirko <jiri@...nulli.us>
CC:	"David S. Miller" <davem@...emloft.net>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	linux-api@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tc: bpf: add checksum helpers

On 04/02/2015 07:56 PM, Alexei Starovoitov wrote:
> On 4/2/2015 10:46 AM, Jiri Pirko wrote:
>> Thu, Apr 02, 2015 at 06:34:59PM CEST, ast@...mgrid.com wrote:
>>> On 4/2/2015 8:21 AM, Daniel Borkmann wrote:
>>>> On 04/02/2015 05:15 PM, Jiri Pirko wrote:
>>>>> Thu, Apr 02, 2015 at 05:00:47PM CEST, daniel@...earbox.net wrote:
>>>>>> On 04/02/2015 02:12 AM, Alexei Starovoitov wrote:
>>>>>>> Commit 608cd71a9c7c ("tc: bpf: generalize pedit action") has added the
>>>>>>> possibility to mangle packet data to BPF programs in the tc pipeline.
>>>>>>> This patch adds two helpers bpf_l3_csum_replace() and
>>>>>>> bpf_l4_csum_replace()
>>>>>>> for fixing up the protocol checksums after the packet mangling.
>>>>>>>
>>>>>>> It also adds 'flags' argument to bpf_skb_store_bytes() helper to avoid
>>>>>>> unnecessary checksum recomputations when BPF programs adjusting l3/l4
>>>>>>> checksums and documents all three helpers in uapi header.
>>>>>>>
>>>>>>> Moreover, a sample program is added to show how BPF programs can
>>>>>>> make use
>>>>>>> of the mangle and csum helpers.
>>>>>>>
>>>>>>> Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
>>>>>>
>>>>>> I think in future we need to find a better place for these helpers,
>>>>>> as they are for cls_bpf and act_bpf.
>>>>>
>>>>> Yeah, makes sense to now have it in net/core/filter.c. How about to
>>>>> create net/bpf dir for these?
>>>>
>>>> I was thinking somewhere under net/sched/, f.e. net/sched/bpf.c
>>>> as probably kernel/bpf/ would end up in too much ifdef pasta. :/
>>>
>>> I would prefer to keep mangle and csum helpers in net/core/filter.c for
>>> now, since it's not clear what networking subsystems beyond TC would
>>> want to use them in the future. Otherwise we'll keep moving them back
>>> and forth.
>>
>> Well, therefore I suggested net/bpf/ dir as a place to store
>> net-subsystem specific bpf stuff.
>
> ahh. misread your earlier statement. yes. makes sense in long term.
> Right now feels too early to create a dir for just 3 functions.
> Eventually half of filter.c probably belongs in there.

Agreed, yeah. I think we should keep that refactoring in mind in
the mid-long term, but I guess a single file somewhere under net/core/
might be enough then.
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