selftests/bpf: Add a test case for loading BPF_SK_SKB_VERDICT

This adds a test case to ensure BPF_SK_SKB_VERDICT and
BPF_SK_STREAM_VERDICT will never be attached at the same time.
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210331023237.41094-17-xiyou.wangcong@gmail.com

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

@@ -7,6 +7,7 @@
 #include "test_skmsg_load_helpers.skel.h"
 #include "test_sockmap_update.skel.h"
 #include "test_sockmap_invalid_update.skel.h"
+#include "test_sockmap_skb_verdict_attach.skel.h"
 #include "bpf_iter_sockmap.skel.h"
 
 #define TCP_REPAIR		19	/* TCP sock is under repair right now */
@@ -281,6 +282,39 @@ static void test_sockmap_copy(enum bpf_map_type map_type)
 	bpf_iter_sockmap__destroy(skel);
 }
 
+static void test_sockmap_skb_verdict_attach(enum bpf_attach_type first,
+					    enum bpf_attach_type second)
+{
+	struct test_sockmap_skb_verdict_attach *skel;
+	int err, map, verdict;
+
+	skel = test_sockmap_skb_verdict_attach__open_and_load();
+	if (CHECK_FAIL(!skel)) {
+		perror("test_sockmap_skb_verdict_attach__open_and_load");
+		return;
+	}
+
+	verdict = bpf_program__fd(skel->progs.prog_skb_verdict);
+	map = bpf_map__fd(skel->maps.sock_map);
+
+	err = bpf_prog_attach(verdict, map, first, 0);
+	if (CHECK_FAIL(err)) {
+		perror("bpf_prog_attach");
+		goto out;
+	}
+
+	err = bpf_prog_attach(verdict, map, second, 0);
+	assert(err == -1 && errno == EBUSY);
+
+	err = bpf_prog_detach2(verdict, map, first);
+	if (CHECK_FAIL(err)) {
+		perror("bpf_prog_detach2");
+		goto out;
+	}
+out:
+	test_sockmap_skb_verdict_attach__destroy(skel);
+}
+
 void test_sockmap_basic(void)
 {
 	if (test__start_subtest("sockmap create_update_free"))
@@ -301,4 +335,10 @@ void test_sockmap_basic(void)
 		test_sockmap_copy(BPF_MAP_TYPE_SOCKMAP);
 	if (test__start_subtest("sockhash copy"))
 		test_sockmap_copy(BPF_MAP_TYPE_SOCKHASH);
+	if (test__start_subtest("sockmap skb_verdict attach")) {
+		test_sockmap_skb_verdict_attach(BPF_SK_SKB_VERDICT,
+						BPF_SK_SKB_STREAM_VERDICT);
+		test_sockmap_skb_verdict_attach(BPF_SK_SKB_STREAM_VERDICT,
+						BPF_SK_SKB_VERDICT);
+	}
 }

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

+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 2);
+	__type(key, __u32);
+	__type(value, __u64);
+} sock_map SEC(".maps");
+
+SEC("sk_skb/skb_verdict")
+int prog_skb_verdict(struct __sk_buff *skb)
+{
+	return SK_DROP;
+}
+
+char _license[] SEC("license") = "GPL";