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

[Jesper Dangaard Brouer]

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;