tools/bpf: add a testcase for MAP_GET_NEXT_KEY command of LPM_TRIE map

A test case is added in tools/testing/selftests/bpf/test_lpm_map.c
for MAP_GET_NEXT_KEY command. A four node trie, which
is described in kernel/bpf/lpm_trie.c, is built and the
MAP_GET_NEXT_KEY results are checked.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/test_lpm_map.c

@@ -521,6 +521,126 @@ static void test_lpm_delete(void)
 	close(map_fd);
 }
 
+static void test_lpm_get_next_key(void)
+{
+	struct bpf_lpm_trie_key *key_p, *next_key_p;
+	size_t key_size;
+	__u32 value = 0;
+	int map_fd;
+
+	key_size = sizeof(*key_p) + sizeof(__u32);
+	key_p = alloca(key_size);
+	next_key_p = alloca(key_size);
+
+	map_fd = bpf_create_map(BPF_MAP_TYPE_LPM_TRIE, key_size, sizeof(value),
+				100, BPF_F_NO_PREALLOC);
+	assert(map_fd >= 0);
+
+	/* empty tree. get_next_key should return ENOENT */
+	assert(bpf_map_get_next_key(map_fd, NULL, key_p) == -1 &&
+	       errno == ENOENT);
+
+	/* get and verify the first key, get the second one should fail. */
+	key_p->prefixlen = 16;
+	inet_pton(AF_INET, "192.168.0.0", key_p->data);
+	assert(bpf_map_update_elem(map_fd, key_p, &value, 0) == 0);
+
+	memset(key_p, 0, key_size);
+	assert(bpf_map_get_next_key(map_fd, NULL, key_p) == 0);
+	assert(key_p->prefixlen == 16 && key_p->data[0] == 192 &&
+	       key_p->data[1] == 168);
+
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == -1 &&
+	       errno == ENOENT);
+
+	/* no exact matching key should get the first one in post order. */
+	key_p->prefixlen = 8;
+	assert(bpf_map_get_next_key(map_fd, NULL, key_p) == 0);
+	assert(key_p->prefixlen == 16 && key_p->data[0] == 192 &&
+	       key_p->data[1] == 168);
+
+	/* add one more element (total two) */
+	key_p->prefixlen = 24;
+	inet_pton(AF_INET, "192.168.0.0", key_p->data);
+	assert(bpf_map_update_elem(map_fd, key_p, &value, 0) == 0);
+
+	memset(key_p, 0, key_size);
+	assert(bpf_map_get_next_key(map_fd, NULL, key_p) == 0);
+	assert(key_p->prefixlen == 24 && key_p->data[0] == 192 &&
+	       key_p->data[1] == 168 && key_p->data[2] == 0);
+
+	memset(next_key_p, 0, key_size);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == 0);
+	assert(next_key_p->prefixlen == 16 && next_key_p->data[0] == 192 &&
+	       next_key_p->data[1] == 168);
+
+	memcpy(key_p, next_key_p, key_size);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == -1 &&
+	       errno == ENOENT);
+
+	/* Add one more element (total three) */
+	key_p->prefixlen = 24;
+	inet_pton(AF_INET, "192.168.128.0", key_p->data);
+	assert(bpf_map_update_elem(map_fd, key_p, &value, 0) == 0);
+
+	memset(key_p, 0, key_size);
+	assert(bpf_map_get_next_key(map_fd, NULL, key_p) == 0);
+	assert(key_p->prefixlen == 24 && key_p->data[0] == 192 &&
+	       key_p->data[1] == 168 && key_p->data[2] == 0);
+
+	memset(next_key_p, 0, key_size);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == 0);
+	assert(next_key_p->prefixlen == 24 && next_key_p->data[0] == 192 &&
+	       next_key_p->data[1] == 168 && next_key_p->data[2] == 128);
+
+	memcpy(key_p, next_key_p, key_size);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == 0);
+	assert(next_key_p->prefixlen == 16 && next_key_p->data[0] == 192 &&
+	       next_key_p->data[1] == 168);
+
+	memcpy(key_p, next_key_p, key_size);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == -1 &&
+	       errno == ENOENT);
+
+	/* Add one more element (total four) */
+	key_p->prefixlen = 24;
+	inet_pton(AF_INET, "192.168.1.0", key_p->data);
+	assert(bpf_map_update_elem(map_fd, key_p, &value, 0) == 0);
+
+	memset(key_p, 0, key_size);
+	assert(bpf_map_get_next_key(map_fd, NULL, key_p) == 0);
+	assert(key_p->prefixlen == 24 && key_p->data[0] == 192 &&
+	       key_p->data[1] == 168 && key_p->data[2] == 0);
+
+	memset(next_key_p, 0, key_size);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == 0);
+	assert(next_key_p->prefixlen == 24 && next_key_p->data[0] == 192 &&
+	       next_key_p->data[1] == 168 && next_key_p->data[2] == 1);
+
+	memcpy(key_p, next_key_p, key_size);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == 0);
+	assert(next_key_p->prefixlen == 24 && next_key_p->data[0] == 192 &&
+	       next_key_p->data[1] == 168 && next_key_p->data[2] == 128);
+
+	memcpy(key_p, next_key_p, key_size);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == 0);
+	assert(next_key_p->prefixlen == 16 && next_key_p->data[0] == 192 &&
+	       next_key_p->data[1] == 168);
+
+	memcpy(key_p, next_key_p, key_size);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == -1 &&
+	       errno == ENOENT);
+
+	/* no exact matching key should return the first one in post order */
+	key_p->prefixlen = 22;
+	inet_pton(AF_INET, "192.168.1.0", key_p->data);
+	assert(bpf_map_get_next_key(map_fd, key_p, next_key_p) == 0);
+	assert(next_key_p->prefixlen == 24 && next_key_p->data[0] == 192 &&
+	       next_key_p->data[1] == 168 && next_key_p->data[2] == 0);
+
+	close(map_fd);
+}
+
 int main(void)
 {
 	struct rlimit limit  = { RLIM_INFINITY, RLIM_INFINITY };
@@ -545,6 +665,8 @@ int main(void)
 
 	test_lpm_delete();
 
+	test_lpm_get_next_key();
+
 	printf("test_lpm: OK\n");
 	return 0;
 }