[RFC PATCH 5/6] selftests/bpf: test BPF_MAP_DUMP command on a bpf hashmap

[Brian Vazquez <brianvv@google.com>]

This tests exercise the new command on a bpf hashmap and make sure it
works as expected.

Signed-off-by: Brian Vazquez <brianvv@google.com>
---
 tools/testing/selftests/bpf/test_maps.c | 70 ++++++++++++++++++++++++-
 1 file changed, 68 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c
index a3fbc571280a9..3df72b46fd1d9 100644
--- a/tools/testing/selftests/bpf/test_maps.c
+++ b/tools/testing/selftests/bpf/test_maps.c
@@ -309,6 +309,73 @@ static void test_hashmap_walk(unsigned int task, void *data)
 	close(fd);
 }
 
+static void test_hashmap_dump(void)
+{
+	int fd, i, max_entries = 3;
+	uint64_t keys[max_entries], values[max_entries];
+	uint64_t key, value, next_key;
+	bool next_key_valid = true;
+	void *buf, *elem, *prev_key;
+	u32 buf_len;
+	const int elem_size = sizeof(key) + sizeof(value);
+
+	fd = helper_fill_hashmap(max_entries);
+
+	// Get the elements in the hashmap, and store them in that order
+	assert(bpf_map_get_next_key(fd, NULL, &key) == 0);
+	i = 0;
+	keys[i] = key;
+	for (i = 1; next_key_valid; i++) {
+		next_key_valid = bpf_map_get_next_key(fd, &key, &next_key) == 0;
+		assert(bpf_map_lookup_elem(fd, &key, &values[i - 1]) == 0);
+		keys[i-1] = key;
+		key = next_key;
+	}
+
+	// Alloc memory for the whole table
+	buf = malloc(elem_size * max_entries);
+	assert(buf != NULL);
+
+	// Check that buf_len < elem_size returns EINVAL
+	buf_len = elem_size-1;
+	errno = 0;
+	assert(bpf_map_dump(fd, NULL, buf, &buf_len) == -1 && errno == EINVAL);
+
+	// Check that it returns the first two elements
+	errno = 0;
+	buf_len = elem_size * 2;
+	prev_key = NULL;
+	i = 0;
+	assert(bpf_map_dump(fd, prev_key, buf, &buf_len) == 0 &&
+	       buf_len == 2*elem_size);
+	elem = buf;
+	assert((*(uint64_t *)elem) == keys[i] &&
+	       (*(uint64_t *)(elem + sizeof(key))) == values[i]);
+	elem = buf + elem_size;
+	i++;
+	assert((*(uint64_t *)elem) == keys[i] &&
+	       (*(uint64_t *)(elem + sizeof(key))) == values[i]);
+	i++;
+
+	/* Continue reading from map and verify buf_len only contains 1 element
+	 * even though buf_len is 2 elem_size.
+	 */
+	prev_key = elem;
+	assert(bpf_map_dump(fd, prev_key, buf, &buf_len) == 0 &&
+	       buf_len == elem_size);
+	elem = buf;
+	assert((*(uint64_t *)elem) == keys[i] &&
+	       (*(uint64_t *)(elem + sizeof(key))) == values[i]);
+
+	// Check that there are no more entries after last_key
+	prev_key = &keys[i];
+	assert(bpf_map_dump(fd, prev_key, buf, &buf_len) == -1 &&
+	       errno == ENOENT);
+
+	free(buf);
+	close(fd);
+}
+
 static void test_hashmap_zero_seed(void)
 {
 	int i, first, second, old_flags;
@@ -1668,6 +1735,7 @@ static void run_all_tests(void)
 	test_hashmap_percpu(0, NULL);
 	test_hashmap_walk(0, NULL);
 	test_hashmap_zero_seed();
+	test_hashmap_dump();
 
 	test_arraymap(0, NULL);
 	test_arraymap_percpu(0, NULL);
@@ -1705,11 +1773,9 @@ int main(void)
 
 	map_flags = BPF_F_NO_PREALLOC;
 	run_all_tests();
-
 #define CALL
 #include <map_tests/tests.h>
 #undef CALL
-
 	printf("test_maps: OK, %d SKIPPED\n", skips);
 	return 0;
 }
-- 
2.22.0.410.gd8fdbe21b5-goog