experiment01-tailgrow: Move extra program to bottom

The xdp_loader will default select the first BPF program
in the ELF object to attach.  Move the extra test programs
to bottom and mention them in readme file.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

Author: netoptimizer

experiment01-tailgrow/README.org

@@ -23,3 +23,15 @@ implements this by parsing up-to the IP-layer, and using the
 IP-headers total-length field ([[https://elixir.bootlin.com/linux/v5.6.10/source/include/uapi/linux/ip.h#L97][iphdr->tot_len]]).  See the code for the
 strange bounding checks needed to convince the verifier.  Notice, this
 is limited to IPv4 ICMP packets for testing purposes.
+
+** Side-note: extra programs
+
+Side-note: [[file:xdp_prog_kern.c]] also contains some other smaller
+programs to test =bpf_xdp_adjust_tail= grow works, and to benchmark
+the overhead when doing =XDP_TX=.  Selecting others BPF programs via
+=xdp_loader= option =--prog== like this:
+
+#+begin_src sh
+ sudo ./xdp_loader --dev mlx5p1 --force --prog xdp_tailgrow
+ sudo ./xdp_loader --dev mlx5p1 --force --prog xdp_tailgrow_tx
+#+end_src

experiment01-tailgrow/xdp_prog_kern.c

@@ -12,40 +12,6 @@
 #include "../common/xdp_stats_kern_user.h"
 #include "../common/xdp_stats_kern.h"
 
-SEC("xdp_tailgrow")
-int tailgrow_pass(struct xdp_md *ctx)
-{
-	int offset;
-
-	offset = 10;
-	bpf_xdp_adjust_tail(ctx, offset);
-	return xdp_stats_record_action(ctx, XDP_PASS);
-}
-
-SEC("xdp_pass")
-int xdp_pass_func(struct xdp_md *ctx)
-{
-	return xdp_stats_record_action(ctx, XDP_PASS);
-}
-
-/* For benchmarking tail grow overhead (does a memset)*/
-SEC("xdp_tailgrow_tx")
-int tailgrow_tx(struct xdp_md *ctx)
-{
-	int offset;
-
-	offset = 32;
-	bpf_xdp_adjust_tail(ctx, offset);
-	return xdp_stats_record_action(ctx, XDP_TX);
-}
-
-/* Baseline benchmark of XDP_TX */
-SEC("xdp_tx")
-int xdp_tx_rec(struct xdp_md *ctx)
-{
-	return xdp_stats_record_action(ctx, XDP_TX);
-}
-
 struct my_timestamp {
 	__u16 magic;
 	__u64 time;
@@ -126,4 +92,38 @@ int grow_parse(struct xdp_md *ctx)
 	return xdp_stats_record_action(ctx, action);
 }
 
+SEC("xdp_tailgrow")
+int tailgrow_pass(struct xdp_md *ctx)
+{
+	int offset;
+
+	offset = 10;
+	bpf_xdp_adjust_tail(ctx, offset);
+	return xdp_stats_record_action(ctx, XDP_PASS);
+}
+
+SEC("xdp_pass")
+int xdp_pass_func(struct xdp_md *ctx)
+{
+	return xdp_stats_record_action(ctx, XDP_PASS);
+}
+
+/* For benchmarking tail grow overhead (does a memset)*/
+SEC("xdp_tailgrow_tx")
+int tailgrow_tx(struct xdp_md *ctx)
+{
+	int offset;
+
+	offset = 32;
+	bpf_xdp_adjust_tail(ctx, offset);
+	return xdp_stats_record_action(ctx, XDP_TX);
+}
+
+/* Baseline benchmark of XDP_TX */
+SEC("xdp_tx")
+int xdp_tx_rec(struct xdp_md *ctx)
+{
+	return xdp_stats_record_action(ctx, XDP_TX);
+}
+
 char _license[] SEC("license") = "GPL";