On 7/9/20 3:30 AM, Hangbin Liu wrote:
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 a physical interface can be part of a logical grouping, such as a bond device. 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.
Could you move this description as part of patch 1/3 instead of cover letter? Mostly given this helps understanding the rationale wrt exclusion map which is otherwise lacking from just looking at the patch itself. Assuming you have a bond, how does this look in practice for your mentioned ovs-like data plane in XDP? The map for 'group A' is shared among all XDP progs and the map for 'group B' is managed per prog? The BPF_F_EXCLUDE_INGRESS is clear, but how would this look wrt forwarding from a phys dev /to/ the bond iface w/ XDP? Also, what about tc BPF helper support for the case where not every device might have native XDP (but they could still share the maps)?
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 v6: converted helper return types from int to long v5: a) Check devmap_get_next_key() return value. b) Pass through flags to __bpf_tx_xdp_map() instead of bool value. c) In function dev_map_enqueue_multi(), consume xdpf for the last obj instead of the first on. d) Update helper description and code comments to explain that we use NULL target value to distinguish multicast and unicast forwarding. e) Update memory model, memory id and frame_sz in xdpf_clone(). f) Split the tests from sample and add a bpf kernel selftest patch. v4: Fix bpf_xdp_redirect_map_multi_proto arg2_type typo v3: Based on Toke's suggestion, do the following update a) Update bpf_redirect_map_multi() description in bpf.h. b) Fix exclude_ifindex checking order in dev_in_exclude_map(). c) Fix one more xdpf clone in dev_map_enqueue_multi(). d) Go find next one in dev_map_enqueue_multi() if the interface is not able to forward instead of abort the whole loop. e) Remove READ_ONCE/WRITE_ONCE for ex_map. v2: Add new syscall bpf_xdp_redirect_map_multi() which could accept include/exclude maps directly. Hangbin Liu (3): xdp: add a new helper for dev map multicast support sample/bpf: add xdp_redirect_map_multicast test selftests/bpf: add xdp_redirect_multi test include/linux/bpf.h | 20 ++ include/linux/filter.h | 1 + include/net/xdp.h | 1 + include/uapi/linux/bpf.h | 22 +++ kernel/bpf/devmap.c | 154 ++++++++++++++++ kernel/bpf/verifier.c | 6 + net/core/filter.c | 109 ++++++++++- net/core/xdp.c | 29 +++ samples/bpf/Makefile | 3 + samples/bpf/xdp_redirect_map_multi_kern.c | 57 ++++++ samples/bpf/xdp_redirect_map_multi_user.c | 166 +++++++++++++++++ tools/include/uapi/linux/bpf.h | 22 +++ tools/testing/selftests/bpf/Makefile | 4 +- .../bpf/progs/xdp_redirect_multi_kern.c | 90 +++++++++ .../selftests/bpf/test_xdp_redirect_multi.sh | 164 +++++++++++++++++ .../selftests/bpf/xdp_redirect_multi.c | 173 ++++++++++++++++++ 16 files changed, 1015 insertions(+), 6 deletions(-) create mode 100644 samples/bpf/xdp_redirect_map_multi_kern.c create mode 100644 samples/bpf/xdp_redirect_map_multi_user.c create mode 100644 tools/testing/selftests/bpf/progs/xdp_redirect_multi_kern.c create mode 100755 tools/testing/selftests/bpf/test_xdp_redirect_multi.sh create mode 100644 tools/testing/selftests/bpf/xdp_redirect_multi.c
