Hangbin Liu <liuhangbin@xxxxxxxxx> writes: > This patch is for xdp multicast support. which has been discussed before[0], > The goal is to be able to implement an OVS-like data plane in XDP, i.e., > a software switch that can forward XDP frames to multiple ports. > > To achieve this, an application needs to specify a group of interfaces > to forward a packet to. It is also common to want to exclude one or more > physical interfaces from the forwarding operation - e.g., to forward a > packet to all interfaces in the multicast group except the interface it > arrived on. While this could be done simply by adding more groups, this > quickly leads to a combinatorial explosion in the number of groups an > application has to maintain. > > To avoid the combinatorial explosion, we propose to include the ability > to specify an "exclude group" as part of the forwarding operation. This > needs to be a group (instead of just a single port index), because there > may have multi interfaces you want to exclude. > > Thus, the logical forwarding operation becomes a "set difference" > operation, i.e. "forward to all ports in group A that are not also in > group B". This series implements such an operation using device maps to > represent the groups. This means that the XDP program specifies two > device maps, one containing the list of netdevs to redirect to, and the > other containing the exclude list. > > To achieve this, I re-implement a new helper bpf_redirect_map_multi() > to accept two maps, the forwarding map and exclude map. If user > don't want to use exclude map and just want simply stop redirecting back > to ingress device, they can use flag BPF_F_EXCLUDE_INGRESS. > > The 2nd and 3rd patches are for usage sample and testing purpose, so there > is no effort has been made on performance optimisation. I did same tests > with pktgen(pkt size 64) to compire with xdp_redirect_map(). Here is the > test result(the veth peer has a dummy xdp program with XDP_DROP directly): > > Version | Test | Native | Generic > 5.8 rc1 | xdp_redirect_map i40e->i40e | 10.0M | 1.9M > 5.8 rc1 | xdp_redirect_map i40e->veth | 12.7M | 1.6M > 5.8 rc1 + patch | xdp_redirect_map i40e->i40e | 10.0M | 1.9M > 5.8 rc1 + patch | xdp_redirect_map i40e->veth | 12.3M | 1.6M > 5.8 rc1 + patch | xdp_redirect_map_multi i40e->i40e | 7.2M | 1.5M > 5.8 rc1 + patch | xdp_redirect_map_multi i40e->veth | 8.5M | 1.3M > 5.8 rc1 + patch | xdp_redirect_map_multi i40e->i40e+veth | 3.0M | 0.98M > > The bpf_redirect_map_multi() is slower than bpf_redirect_map() as we loop > the arrays and do clone skb/xdpf. The native path is slower than generic > path as we send skbs by pktgen. So the result looks reasonable. > > Last but not least, thanks a lot to Jiri, Eelco, Toke and Jesper for > suggestions and help on implementation. > > [0] https://xdp-project.net/#Handling-multicast > > v7: Fix helper flag check > Limit the *ex_map* to use DEVMAP_HASH only and update function > dev_in_exclude_map() to get better performance. Did it help? The performance numbers in the table above are the same as in v6... -Toke
