selftests/bpf: Update xdp_bpf2bpf test to use new set_attach_target API

Use the new bpf_program__set_attach_target() API in the xdp_bpf2bpf
selftest so it can be referenced as an example on how to use it.
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/158220520562.127661.14289388017034825841.stgit@xdp-tutorial

tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c

@@ -14,7 +14,7 @@ void test_xdp_bpf2bpf(void)
 	struct test_xdp *pkt_skel = NULL;
 	struct test_xdp_bpf2bpf *ftrace_skel = NULL;
 	struct vip key4 = {.protocol = 6, .family = AF_INET};
-	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts);
+	struct bpf_program *prog;
 
 	/* Load XDP program to introspect */
 	pkt_skel = test_xdp__open_and_load();
@@ -27,11 +27,21 @@ void test_xdp_bpf2bpf(void)
 	bpf_map_update_elem(map_fd, &key4, &value4, 0);
 
 	/* Load trace program */
-	opts.attach_prog_fd = pkt_fd,
-	ftrace_skel = test_xdp_bpf2bpf__open_opts(&opts);
+	ftrace_skel = test_xdp_bpf2bpf__open();
 	if (CHECK(!ftrace_skel, "__open", "ftrace skeleton failed\n"))
 		goto out;
 
+	/* Demonstrate the bpf_program__set_attach_target() API rather than
+	 * the load with options, i.e. opts.attach_prog_fd.
+	 */
+	prog = ftrace_skel->progs.trace_on_entry;
+	bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
+	bpf_program__set_attach_target(prog, pkt_fd, "_xdp_tx_iptunnel");
+
+	prog = ftrace_skel->progs.trace_on_exit;
+	bpf_program__set_expected_attach_type(prog, BPF_TRACE_FEXIT);
+	bpf_program__set_attach_target(prog, pkt_fd, "_xdp_tx_iptunnel");
+
 	err = test_xdp_bpf2bpf__load(ftrace_skel);
 	if (CHECK(err, "__load", "ftrace skeleton failed\n"))
 		goto out;

tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c

@@ -28,7 +28,7 @@ struct xdp_buff {
 } __attribute__((preserve_access_index));
 
 __u64 test_result_fentry = 0;
-SEC("fentry/_xdp_tx_iptunnel")
+SEC("fentry/FUNC")
 int BPF_PROG(trace_on_entry, struct xdp_buff *xdp)
 {
 	test_result_fentry = xdp->rxq->dev->ifindex;
@@ -36,7 +36,7 @@ int BPF_PROG(trace_on_entry, struct xdp_buff *xdp)
 }
 
 __u64 test_result_fexit = 0;
-SEC("fexit/_xdp_tx_iptunnel")
+SEC("fexit/FUNC")
 int BPF_PROG(trace_on_exit, struct xdp_buff *xdp, int ret)
 {
 	test_result_fexit = ret;