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

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Message-ID: <03415861-593d-6bef-5b50-7a8d87281ea2@6wind.com>
Date:   Fri, 26 Aug 2022 09:55:27 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
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,
        razor@...ckwall.org, 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


Le 25/08/2022 à 17:46, Eyal Birger a écrit :
> 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>
> 
Reviewed-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>