RFC netfilter: Add the capability to offload flowtable in XDP layer

Introduce bpf_xdp_flow_offload_lookup kfunc in order to perform the lookup of a given flowtable entry based on the fib tuple of incoming traffic.
bpf_xdp_flow_offload_lookup can be used as building block to offload in XDP the sw flowtable processing when the hw support is not available.

This series has been tested running the xdp_flowtable_offload eBPF program on an ixgbe 10Gbps NIC (eno2) in order to XDP_REDIRECT the TCP traffic to a veth pair (veth0-veth1) based on the content of the nf_flowtable as soon as the TCP connection is in the established state:

[tcp client] (eno1) == LAN == (eno2) xdp_flowtable_offload [XDP_REDIRECT] --> veth0 == veth1 [tcp server]

table inet filter {
	flowtable ft {
		hook ingress priority filter
		devices = { eno2, veth0 }
	}
	chain forward {
		type filter hook forward priority filter
		meta l4proto { tcp, udp } flow add @ft
	}
}

- sw flowtable [1 TCP stream, T = 300s]: ~ 6.2 Gbps
- xdp flowtable [1 TCP stream, T = 300s]: ~ 7.6 Gbps

Florian Westphal (1):
netfilter: nf_tables: add flowtable map for xdp offload

Lorenzo Bianconi (3):
netfilter: add bpf_xdp_flow_offload_lookup kfunc samples/bpf: Add bpf sample to offload flowtable traffic to xdp selftests/bpf: Add selftest for bpf_xdp_flow_offload_lookup kfunc

 include/net/netfilter/nf_flow_table.h         |  11 +
 net/netfilter/Makefile                        |   5 +
 net/netfilter/nf_flow_table_bpf.c             |  95 +++
 net/netfilter/nf_flow_table_inet.c            |   2 +
 net/netfilter/nf_flow_table_offload.c         | 161 ++++-
 samples/bpf/Makefile                          |   7 +-
 samples/bpf/xdp_flowtable_offload.bpf.c       | 592 ++++++++++++++++++
 samples/bpf/xdp_flowtable_offload_user.c      | 128 ++++
 tools/testing/selftests/bpf/Makefile          |  10 +-
 tools/testing/selftests/bpf/config            |   4 +
 .../selftests/bpf/progs/xdp_flowtable.c       | 142 +++++
 .../selftests/bpf/test_xdp_flowtable.sh       | 112 ++++
 tools/testing/selftests/bpf/xdp_flowtable.c   | 142 +++++
 13 files changed, 1406 insertions(+), 5 deletions(-)
 create mode 100644 net/netfilter/nf_flow_table_bpf.c
 create mode 100644 samples/bpf/xdp_flowtable_offload.bpf.c
 create mode 100644 samples/bpf/xdp_flowtable_offload_user.c
 create mode 100644 tools/testing/selftests/bpf/progs/xdp_flowtable.c
 create mode 100755 tools/testing/selftests/bpf/test_xdp_flowtable.sh
 create mode 100644 tools/testing/selftests/bpf/xdp_flowtable.c

2.45.0