netdev - Re: [PATCH ipsec-next,v2 2/3] xfrm: interface: support collect metadata mode

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Message-ID: <3a2c5c4c-a42c-eaae-be0a-b81a63543c0e@blackwall.org>
Date:   Sat, 27 Aug 2022 15:36:58 +0300
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     nicolas.dichtel@...nd.com, Eyal Birger <eyal.birger@...il.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, steffen.klassert@...unet.com,
        herbert@...dor.apana.org.au, dsahern@...nel.org,
        contact@...elbtn.com, pablo@...filter.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, "daniel@...earbox.net" <daniel@...earbox.net>
Subject: Re: [PATCH ipsec-next,v2 2/3] xfrm: interface: support collect
 metadata mode

On 26/08/2022 10:53, Nicolas Dichtel wrote:
> 
> Le 25/08/2022 à 17:14, Eyal Birger a écrit :
>> On Thu, Aug 25, 2022 at 5:24 PM Nikolay Aleksandrov <razor@...ckwall.org> wrote:
>>>
>>> On 25/08/2022 16:46, Eyal Birger wrote:
>>>> This commit adds support for 'collect_md' mode on xfrm interfaces.
>>>>
>>>> Each net can have one collect_md device, created by providing the
>>>> IFLA_XFRM_COLLECT_METADATA flag at creation. This device cannot be
>>>> altered and has no if_id or link device attributes.
>>>>
>>>> On transmit to this device, the if_id is fetched from the attached dst
>>>> metadata on the skb. If exists, the link property is also fetched from
>>>> the metadata. The dst metadata type used is METADATA_XFRM which holds
>>>> these properties.
>>>>
>>>> On the receive side, xfrmi_rcv_cb() populates a dst metadata for each
>>>> packet received and attaches it to the skb. The if_id used in this case is
>>>> fetched from the xfrm state, and the link is fetched from the incoming
>>>> device. This information can later be used by upper layers such as tc,
>>>> ebpf, and ip rules.
>>>>
>>>> Because the skb is scrubed in xfrmi_rcv_cb(), the attachment of the dst
>>>> metadata is postponed until after scrubing. Similarly, xfrm_input() is
>>>> adapted to avoid dropping metadata dsts by only dropping 'valid'
>>>> (skb_valid_dst(skb) == true) dsts.
>>>>
>>>> Policy matching on packets arriving from collect_md xfrmi devices is
>>>> done by using the xfrm state existing in the skb's sec_path.
>>>> The xfrm_if_cb.decode_cb() interface implemented by xfrmi_decode_session()
>>>> is changed to keep the details of the if_id extraction tucked away
>>>> in xfrm_interface.c.
>>>>
>>>> Signed-off-by: Eyal Birger <eyal.birger@...il.com>
>>>>
>>>> ----
>>>>
>>>> v2:
>>>>   - add "link" property as suggested by Nicolas Dichtel
>>>>   - rename xfrm_if_decode_session_params to xfrm_if_decode_session_result
>>>> ---
>>>
>>> (+CC Daniel)
>>>
>>> Hi,
>>> Generally I really like the idea, but I missed to comment the first round. :)
>>> A few comments below..
>>>
>>
>> Thanks for the review!
>>
>>>>  include/net/xfrm.h           |  11 +++-
>> <...snip...>
>>>>
>>>>  static const struct nla_policy xfrmi_policy[IFLA_XFRM_MAX + 1] = {
>>>> -     [IFLA_XFRM_LINK]        = { .type = NLA_U32 },
>>>> -     [IFLA_XFRM_IF_ID]       = { .type = NLA_U32 },
>>>> +     [IFLA_XFRM_UNSPEC]              = { .strict_start_type = IFLA_XFRM_COLLECT_METADATA },
>>>> +     [IFLA_XFRM_LINK]                = { .type = NLA_U32 },
>>>
>>> link is signed, so s32
>>
>> Ack on all comments except this one - I'm a little hesitant to change
>> this one as the change would be unrelated to this series.
> I agree, it's unrelated to this series.

Ohh right, my bad. I somehow confused this for new code. :)

Cheers,
 Nik