Le 25/08/2022 à 15:46, 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@xxxxxxxxx>
>
> ----
>
> v2:
> - add "link" property as suggested by Nicolas Dichtel
Thanks.
[snip]
> @@ -269,10 +303,24 @@ xfrmi_xmit2(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
> struct net_device *tdev;
> struct xfrm_state *x;
> int err = -1;
> + u32 if_id;
> int mtu;
>
> + if (xi->p.collect_md) {
> + struct xfrm_md_info *md_info = skb_xfrm_md_info(skb);
> +
> + if (unlikely(!md_info))
> + return -EINVAL;
> +
> + if_id = md_info->if_id;
> + if (md_info->link)
> + fl->flowi_oif = md_info->link;
nit: flowi_oif is 0 in case of collect_md, thus the if can be omitted.
[snip]
> @@ -682,12 +746,19 @@ static int xfrmi_changelink(struct net_device *dev, struct nlattr *tb[],
> return -EINVAL;
> }
>
> + if (p.collect_md) {
> + NL_SET_ERR_MSG(extack, "collect_md can't be changed");
> + return -EINVAL;
> + }
> +
> xi = xfrmi_locate(net, &p);
> if (!xi) {
> xi = netdev_priv(dev);
> } else {
> if (xi->dev != dev)
> return -EEXIST;
> + if (xi->p.collect_md)
> + return -EINVAL;
It could be useful to add an extack error msg in this case also.
Regards,
Nicolas
