selftest: Add tests for XDP programs in CPUMAP entries

Similar to what have been done for DEVMAP, introduce tests to verify
ability to add a XDP program to an entry in a CPUMAP.
Verify CPUMAP programs can not be attached to devices as a normal
XDP program, and only programs with BPF_XDP_CPUMAP attach type can
be loaded in a CPUMAP.
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/9c632fcea5382ea7b4578bd06b6eddf382c3550b.1594734381.git.lorenzo@kernel.org

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

+// SPDX-License-Identifier: GPL-2.0
+#include <uapi/linux/bpf.h>
+#include <linux/if_link.h>
+#include <test_progs.h>
+
+#include "test_xdp_with_cpumap_helpers.skel.h"
+
+#define IFINDEX_LO	1
+
+void test_xdp_with_cpumap_helpers(void)
+{
+	struct test_xdp_with_cpumap_helpers *skel;
+	struct bpf_prog_info info = {};
+	struct bpf_cpumap_val val = {
+		.qsize = 192,
+	};
+	__u32 duration = 0, idx = 0;
+	__u32 len = sizeof(info);
+	int err, prog_fd, map_fd;
+
+	skel = test_xdp_with_cpumap_helpers__open_and_load();
+	if (CHECK_FAIL(!skel)) {
+		perror("test_xdp_with_cpumap_helpers__open_and_load");
+		return;
+	}
+
+	/* can not attach program with cpumaps that allow programs
+	 * as xdp generic
+	 */
+	prog_fd = bpf_program__fd(skel->progs.xdp_redir_prog);
+	err = bpf_set_link_xdp_fd(IFINDEX_LO, prog_fd, XDP_FLAGS_SKB_MODE);
+	CHECK(err == 0, "Generic attach of program with 8-byte CPUMAP",
+	      "should have failed\n");
+
+	prog_fd = bpf_program__fd(skel->progs.xdp_dummy_cm);
+	map_fd = bpf_map__fd(skel->maps.cpu_map);
+	err = bpf_obj_get_info_by_fd(prog_fd, &info, &len);
+	if (CHECK_FAIL(err))
+		goto out_close;
+
+	val.bpf_prog.fd = prog_fd;
+	err = bpf_map_update_elem(map_fd, &idx, &val, 0);
+	CHECK(err, "Add program to cpumap entry", "err %d errno %d\n",
+	      err, errno);
+
+	err = bpf_map_lookup_elem(map_fd, &idx, &val);
+	CHECK(err, "Read cpumap entry", "err %d errno %d\n", err, errno);
+	CHECK(info.id != val.bpf_prog.id, "Expected program id in cpumap entry",
+	      "expected %u read %u\n", info.id, val.bpf_prog.id);
+
+	/* can not attach BPF_XDP_CPUMAP program to a device */
+	err = bpf_set_link_xdp_fd(IFINDEX_LO, prog_fd, XDP_FLAGS_SKB_MODE);
+	CHECK(err == 0, "Attach of BPF_XDP_CPUMAP program",
+	      "should have failed\n");
+
+	val.qsize = 192;
+	val.bpf_prog.fd = bpf_program__fd(skel->progs.xdp_dummy_prog);
+	err = bpf_map_update_elem(map_fd, &idx, &val, 0);
+	CHECK(err == 0, "Add non-BPF_XDP_CPUMAP program to cpumap entry",
+	      "should have failed\n");
+
+out_close:
+	test_xdp_with_cpumap_helpers__destroy(skel);
+}
+
+void test_xdp_cpumap_attach(void)
+{
+	if (test__start_subtest("cpumap_with_progs"))
+		test_xdp_with_cpumap_helpers();
+}

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

+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+#define IFINDEX_LO	1
+
+struct {
+	__uint(type, BPF_MAP_TYPE_CPUMAP);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(struct bpf_cpumap_val));
+	__uint(max_entries, 4);
+} cpu_map SEC(".maps");
+
+SEC("xdp_redir")
+int xdp_redir_prog(struct xdp_md *ctx)
+{
+	return bpf_redirect_map(&cpu_map, 1, 0);
+}
+
+SEC("xdp_dummy")
+int xdp_dummy_prog(struct xdp_md *ctx)
+{
+	return XDP_PASS;
+}
+
+SEC("xdp_cpumap/dummy_cm")
+int xdp_dummy_cm(struct xdp_md *ctx)
+{
+	if (ctx->ingress_ifindex == IFINDEX_LO)
+		return XDP_DROP;
+
+	return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";