[RFC bpf-next PATCH] samples/bpf: xdp1 add XDP hardware offload option

[Jesper Dangaard Brouer <brouer@redhat.com>]

Trying to use XDP hardware offloading via XDP_FLAGS_HW_MODE
and setting the ifindex in prog_load_attr.ifindex before
loading the BPF code via bpf_prog_load_xattr().

This unfortunately does not seem to work...
- Am I doing something wrong?

Notice, I also disable the map BPF_MAP_TYPE_PERCPU_ARRAY
to make sure it was not related to the map (not supporting
offloading).

Failed with:
 # ./xdp1 -O $(</sys/class/net/enp130s0np1/ifindex)
 libbpf: load bpf program failed: Invalid argument
 libbpf: failed to load program 'xdp1'
 libbpf: failed to load object './xdp1_kern.o'

Tested on kernel 4.18.0-2.el8.x86_64 with driver nfp
 Ethernet controller: Netronome Systems, Inc. Device 4000
---
 samples/bpf/xdp1_kern.c |    8 +++++---
 samples/bpf/xdp1_user.c |   12 ++++++++++--
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/samples/bpf/xdp1_kern.c b/samples/bpf/xdp1_kern.c
index 219742106bfd..1b577b7dba1e 100644
--- a/samples/bpf/xdp1_kern.c
+++ b/samples/bpf/xdp1_kern.c
@@ -14,12 +14,14 @@
 #include <linux/ipv6.h>
 #include "bpf_helpers.h"
 
+/*
 struct bpf_map_def SEC("maps") rxcnt = {
 	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
 	.key_size = sizeof(u32),
 	.value_size = sizeof(long),
 	.max_entries = 256,
 };
+*/
 
 static int parse_ipv4(void *data, u64 nh_off, void *data_end)
 {
@@ -83,9 +85,9 @@ int xdp_prog1(struct xdp_md *ctx)
 	else
 		ipproto = 0;
 
-	value = bpf_map_lookup_elem(&rxcnt, &ipproto);
-	if (value)
-		*value += 1;
+//	value = bpf_map_lookup_elem(&rxcnt, &ipproto);
+//	if (value)
+//		*value += 1;
 
 	return rc;
 }
diff --git a/samples/bpf/xdp1_user.c b/samples/bpf/xdp1_user.c
index b02c531510ed..a362b5adfcf0 100644
--- a/samples/bpf/xdp1_user.c
+++ b/samples/bpf/xdp1_user.c
@@ -64,7 +64,8 @@ static void usage(const char *prog)
 		"usage: %s [OPTS] IFINDEX\n\n"
 		"OPTS:\n"
 		"    -S    use skb-mode\n"
-		"    -N    enforce native mode\n",
+		"    -N    enforce native mode\n"
+		"    -O    offload mode\n",
 		prog);
 }
 
@@ -74,7 +75,7 @@ int main(int argc, char **argv)
 	struct bpf_prog_load_attr prog_load_attr = {
 		.prog_type	= BPF_PROG_TYPE_XDP,
 	};
-	const char *optstr = "SN";
+	const char *optstr = "SNO";
 	int prog_fd, map_fd, opt;
 	struct bpf_object *obj;
 	struct bpf_map *map;
@@ -88,6 +89,9 @@ int main(int argc, char **argv)
 		case 'N':
 			xdp_flags |= XDP_FLAGS_DRV_MODE;
 			break;
+		case 'O':
+			xdp_flags |= XDP_FLAGS_HW_MODE;
+			break;
 		default:
 			usage(basename(argv[0]));
 			return 1;
@@ -109,6 +113,10 @@ int main(int argc, char **argv)
 	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
 	prog_load_attr.file = filename;
 
+	/* For HW offload provide ifindex when loading BPF code */
+	if (xdp_flags & XDP_FLAGS_HW_MODE) {
+		prog_load_attr.ifindex = ifindex;
+	}
 	if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
 		return 1;