xdp: sample program for new bpf_redirect helper

This implements a sample program for testing bpf_redirect. It reports
the number of packets redirected per second and as input takes the
ifindex of the device to run the xdp program on and the ifindex of the
interface to redirect packets to.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Tested-by: Andy Gospodarek <andy@greyhouse.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

samples/bpf/Makefile

@@ -37,6 +37,7 @@ hostprogs-y += xdp_tx_iptunnel
 hostprogs-y += test_map_in_map
 hostprogs-y += per_socket_stats_example
 hostprogs-y += load_sock_ops
+hostprogs-y += xdp_redirect
 
 # Libbpf dependencies
 LIBBPF := ../../tools/lib/bpf/bpf.o
@@ -78,6 +79,7 @@ lwt_len_hist-objs := bpf_load.o $(LIBBPF) lwt_len_hist_user.o
 xdp_tx_iptunnel-objs := bpf_load.o $(LIBBPF) xdp_tx_iptunnel_user.o
 test_map_in_map-objs := bpf_load.o $(LIBBPF) test_map_in_map_user.o
 per_socket_stats_example-objs := $(LIBBPF) cookie_uid_helper_example.o
+xdp_redirect-objs := bpf_load.o $(LIBBPF) xdp_redirect_user.o
 
 # Tell kbuild to always build the programs
 always := $(hostprogs-y)
@@ -119,6 +121,7 @@ always += tcp_bufs_kern.o
 always += tcp_cong_kern.o
 always += tcp_iw_kern.o
 always += tcp_clamp_kern.o
+always += xdp_redirect_kern.o
 
 HOSTCFLAGS += -I$(objtree)/usr/include
 HOSTCFLAGS += -I$(srctree)/tools/lib/
@@ -155,6 +158,7 @@ HOSTLOADLIBES_tc_l2_redirect += -l elf
 HOSTLOADLIBES_lwt_len_hist += -l elf
 HOSTLOADLIBES_xdp_tx_iptunnel += -lelf
 HOSTLOADLIBES_test_map_in_map += -lelf
+HOSTLOADLIBES_xdp_redirect += -lelf
 
 # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
 #  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang