selftests/bpf: Add an iterator selftest for bpf_sk_storage_delete

The eBPF program iterates over all entries (well, only one) of a socket
local storage map and deletes them all. The test makes sure that the
entry is indeed deleted.
Signed-off-by: Florent Revest <revest@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201204113609.1850150-4-revest@google.com

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

@@ -20,6 +20,7 @@
 #include "bpf_iter_bpf_percpu_hash_map.skel.h"
 #include "bpf_iter_bpf_array_map.skel.h"
 #include "bpf_iter_bpf_percpu_array_map.skel.h"
+#include "bpf_iter_bpf_sk_storage_helpers.skel.h"
 #include "bpf_iter_bpf_sk_storage_map.skel.h"
 #include "bpf_iter_test_kern5.skel.h"
 #include "bpf_iter_test_kern6.skel.h"
@@ -913,6 +914,67 @@ static void test_bpf_percpu_array_map(void)
 	bpf_iter_bpf_percpu_array_map__destroy(skel);
 }
 
+/* An iterator program deletes all local storage in a map. */
+static void test_bpf_sk_storage_delete(void)
+{
+	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+	struct bpf_iter_bpf_sk_storage_helpers *skel;
+	union bpf_iter_link_info linfo;
+	int err, len, map_fd, iter_fd;
+	struct bpf_link *link;
+	int sock_fd = -1;
+	__u32 val = 42;
+	char buf[64];
+
+	skel = bpf_iter_bpf_sk_storage_helpers__open_and_load();
+	if (CHECK(!skel, "bpf_iter_bpf_sk_storage_helpers__open_and_load",
+		  "skeleton open_and_load failed\n"))
+		return;
+
+	map_fd = bpf_map__fd(skel->maps.sk_stg_map);
+
+	sock_fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (CHECK(sock_fd < 0, "socket", "errno: %d\n", errno))
+		goto out;
+	err = bpf_map_update_elem(map_fd, &sock_fd, &val, BPF_NOEXIST);
+	if (CHECK(err, "map_update", "map_update failed\n"))
+		goto out;
+
+	memset(&linfo, 0, sizeof(linfo));
+	linfo.map.map_fd = map_fd;
+	opts.link_info = &linfo;
+	opts.link_info_len = sizeof(linfo);
+	link = bpf_program__attach_iter(skel->progs.delete_bpf_sk_storage_map,
+					&opts);
+	if (CHECK(IS_ERR(link), "attach_iter", "attach_iter failed\n"))
+		goto out;
+
+	iter_fd = bpf_iter_create(bpf_link__fd(link));
+	if (CHECK(iter_fd < 0, "create_iter", "create_iter failed\n"))
+		goto free_link;
+
+	/* do some tests */
+	while ((len = read(iter_fd, buf, sizeof(buf))) > 0)
+		;
+	if (CHECK(len < 0, "read", "read failed: %s\n", strerror(errno)))
+		goto close_iter;
+
+	/* test results */
+	err = bpf_map_lookup_elem(map_fd, &sock_fd, &val);
+	if (CHECK(!err || errno != ENOENT, "bpf_map_lookup_elem",
+		  "map value wasn't deleted (err=%d, errno=%d)\n", err, errno))
+		goto close_iter;
+
+close_iter:
+	close(iter_fd);
+free_link:
+	bpf_link__destroy(link);
+out:
+	if (sock_fd >= 0)
+		close(sock_fd);
+	bpf_iter_bpf_sk_storage_helpers__destroy(skel);
+}
+
 static void test_bpf_sk_storage_map(void)
 {
 	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
@@ -1067,6 +1129,8 @@ void test_bpf_iter(void)
 		test_bpf_percpu_array_map();
 	if (test__start_subtest("bpf_sk_storage_map"))
 		test_bpf_sk_storage_map();
+	if (test__start_subtest("bpf_sk_storage_delete"))
+		test_bpf_sk_storage_delete();
 	if (test__start_subtest("rdonly-buf-out-of-bound"))
 		test_rdonly_buf_out_of_bound();
 	if (test__start_subtest("buf-neg-offset"))

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Google LLC. */
+#include "bpf_iter.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, int);
+} sk_stg_map SEC(".maps");
+
+SEC("iter/bpf_sk_storage_map")
+int delete_bpf_sk_storage_map(struct bpf_iter__bpf_sk_storage_map *ctx)
+{
+	if (ctx->sk)
+		bpf_sk_storage_delete(&sk_stg_map, ctx->sk);
+
+	return 0;
+}