Hi Steffen, On Fri, Nov 27, 2020 at 11:44 AM Steffen Klassert <steffen.klass...@secunet.com> wrote: > > On Sat, Nov 21, 2020 at 04:28:23PM +0200, 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. The dst metadata type used is METADATA_IP_TUNNEL > > since the only needed property is the if_id stored in the tun_id member > > of the ip_tunnel_info->key. > > Can we please have a separate metadata type for xfrm interfaces? > > Sharing such structures turned already out to be a bad idea > on vti interfaces, let's try to avoid that misstake with > xfrm interfaces.
My initial thought was to do that, but it looks like most of the constructs surrounding this facility - tc, nft, ovs, ebpf, ip routing - are built around struct ip_tunnel_info and don't regard other possible metadata types. For xfrm interfaces, the only metadata used is the if_id, which is stored in the metadata tun_id, so I think other than naming consideration, the use of struct ip_tunnel_info does not imply tunneling and does not limit the use of xfrmi to a specific mode of operation. On the other hand, adding a new metadata type would require changing all other places to regard the new metadata type, with a large number of userspace visible changes. > > > 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. This 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.bir...@gmail.com> > > The rest of the patch looks good. Thanks for the review! Eyal.
