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

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Date:	Thu, 02 Apr 2015 09:34:59 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Daniel Borkmann <daniel@...earbox.net>,
	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 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.

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