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

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Message-ID: <551D82BA.1010809@plumgrid.com>
Date:	Thu, 02 Apr 2015 10:56:10 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Jiri Pirko <jiri@...nulli.us>
CC:	Daniel Borkmann <daniel@...earbox.net>,
	"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 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.

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