netdev - Re: [PATCH ipsec-next,v3 2/3] xfrm: interface: support collect metadata mode

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Date:   Fri, 26 Aug 2022 13:42:50 +0300
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     Eyal Birger <eyal.birger@...il.com>, 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,
        nicolas.dichtel@...nd.com, daniel@...earbox.net
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH ipsec-next,v3 2/3] xfrm: interface: support collect
 metadata mode

On 25/08/2022 18:46, 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>
> 
> ----
> 
> v3:
>   - coding improvements suggested by Nikolay Aleksandrov
>   - use RCU_INIT_POINTER() instead of rcu_assign_pointer() in
>     xfrmi_dev_uninit() and rtnl_dereference() in xfrmi_exit_batch_net()
>     as suggested by Nikolay Aleksandrov
>   - omit redundant check on link assignment from metadata as suggested
>     by Nicolas Dichtel
>   - add missing extack message as suggested by Nicolas Dichtel
> 
> v2:
>   - add "link" property as suggested by Nicolas Dichtel
>   - rename xfrm_if_decode_session_params to xfrm_if_decode_session_result
> ---
>  include/net/xfrm.h           |  11 +++-
>  include/uapi/linux/if_link.h |   1 +
>  net/xfrm/xfrm_input.c        |   7 +-
>  net/xfrm/xfrm_interface.c    | 121 +++++++++++++++++++++++++++++------
>  net/xfrm/xfrm_policy.c       |  10 +--
>  5 files changed, 121 insertions(+), 29 deletions(-)
> 


Reviewed-by: Nikolay Aleksandrov <razor@...ckwall.org>