[PATCH bpf-next v2 5/8] selftests/bpf: Test cgroup_iter.

Yosry Ahmed
2022-06-10T19:44:32Z

From: Hao Luo <haoluo-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

Add a selftest for cgroup_iter. The selftest creates a mini cgroup tree
of the following structure:

ROOT (working cgroup)
|
PARENT
/ \
CHILD1 CHILD2

and tests the following scenarios:

- invalid cgroup fd.
- pre-order walk over descendants from PARENT.
- post-order walk over descendants from PARENT.
- walk of ancestors from PARENT.
- early termination.

Signed-off-by: Hao Luo <haoluo-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Yosry Ahmed <yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
---
.../selftests/bpf/prog_tests/cgroup_iter.c | 190 ++++++++++++++++++
tools/testing/selftests/bpf/progs/bpf_iter.h | 7 +
.../testing/selftests/bpf/progs/cgroup_iter.c | 39 ++++
3 files changed, 236 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
create mode 100644 tools/testing/selftests/bpf/progs/cgroup_iter.c

diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c b/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
new file mode 100644
index 0000000000000..4c8f11f784915
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Google */
+
+#include <test_progs.h>
+#include <bpf/libbpf.h>
+#include <bpf/btf.h>
+#include "cgroup_iter.skel.h"
+#include "cgroup_helpers.h"
+
+#define ROOT 0
+#define PARENT 1
+#define CHILD1 2
+#define CHILD2 3
+#define NUM_CGROUPS 4
+
+#define PROLOGUE "prologue\n"
+#define EPILOGUE "epilogue\n"
+
+#define format_expected_output1(cg_id1) \
+ snprintf(expected_output, sizeof(expected_output), \
+ PROLOGUE "%8llu\n" EPILOGUE, (cg_id1))
+
+#define format_expected_output2(cg_id1, cg_id2) \
+ snprintf(expected_output, sizeof(expected_output), \
+ PROLOGUE "%8llu\n%8llu\n" EPILOGUE, \
+ (cg_id1), (cg_id2))
+
+#define format_expected_output3(cg_id1, cg_id2, cg_id3) \
+ snprintf(expected_output, sizeof(expected_output), \
+ PROLOGUE "%8llu\n%8llu\n%8llu\n" EPILOGUE, \
+ (cg_id1), (cg_id2), (cg_id3))
+
+const char *cg_path[] = {
+ "/", "/parent", "/parent/child1", "/parent/child2"
+};
+
+static int cg_fd[] = {-1, -1, -1, -1};
+static unsigned long long cg_id[] = {0, 0, 0, 0};
+static char expected_output[64];
+
+int setup_cgroups(void)
+{
+ int fd, i = 0;
+
+ for (i = 0; i < NUM_CGROUPS; i++) {
+ fd = create_and_get_cgroup(cg_path[i]);
+ if (fd < 0)
+ return fd;
+
+ cg_fd[i] = fd;
+ cg_id[i] = get_cgroup_id(cg_path[i]);
+ }
+ return 0;
+}
+
+void cleanup_cgroups(void)
+{
+ int i;
+
+ for (i = 0; i < NUM_CGROUPS; i++)
+ close(cg_fd[i]);
+}
+
+static void read_from_cgroup_iter(struct bpf_program *prog, int cgroup_fd,
+ int order, const char *testname)
+{
+ DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+ union bpf_iter_link_info linfo;
+ struct bpf_link *link;
+ int len, iter_fd;
+ static char buf[64];
+
+ memset(&linfo, 0, sizeof(linfo));
+ linfo.cgroup.cgroup_fd = cgroup_fd;
+ linfo.cgroup.traversal_order = order;
+ opts.link_info = &linfo;
+ opts.link_info_len = sizeof(linfo);
+
+ link = bpf_program__attach_iter(prog, &opts);
+ if (!ASSERT_OK_PTR(link, "attach_iter"))
+ return;
+
+ iter_fd = bpf_iter_create(bpf_link__fd(link));
+ if (iter_fd < 0)
+ goto free_link;
+
+ memset(buf, 0, sizeof(buf));
+ while ((len = read(iter_fd, buf, sizeof(buf))) > 0)
+ ;
+
+ ASSERT_STREQ(buf, expected_output, testname);
+
+ close(iter_fd);
+free_link:
+ bpf_link__destroy(link);
+}
+
+/* Invalid cgroup. */
+static void test_invalid_cgroup(struct cgroup_iter *skel)
+{
+
+ DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+ union bpf_iter_link_info linfo;
+ struct bpf_link *link;
+
+ memset(&linfo, 0, sizeof(linfo));
+ linfo.cgroup.cgroup_fd = (__u32)-1;
+ opts.link_info = &linfo;
+ opts.link_info_len = sizeof(linfo);
+
+ link = bpf_program__attach_iter(skel->progs.cgroup_id_printer, &opts);
+ if (!ASSERT_ERR_PTR(link, "attach_iter"))
+ bpf_link__destroy(link);
+}
+
+/* Preorder walk prints parent and child in order. */
+static void test_walk_preorder(struct cgroup_iter *skel)
+{
+ format_expected_output3(cg_id[PARENT], cg_id[CHILD1], cg_id[CHILD2]);
+
+ read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
+ BPF_ITER_CGROUP_PRE, "preorder");
+}
+
+/* Postorder walk prints child and parent in order. */
+static void test_walk_postorder(struct cgroup_iter *skel)
+{
+ format_expected_output3(cg_id[CHILD1], cg_id[CHILD2], cg_id[PARENT]);
+
+ read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
+ BPF_ITER_CGROUP_POST, "postorder");
+}
+
+/* Walking parents prints parent and then root. */
+static void test_walk_parent_up(struct cgroup_iter *skel)
+{
+ /* terminate the walk when ROOT is met. */
+ skel->bss->terminal_cgroup = cg_id[ROOT];
+
+ format_expected_output2(cg_id[PARENT], cg_id[ROOT]);
+
+ read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
+ BPF_ITER_CGROUP_PARENT_UP, "parent_up");
+
+ skel->bss->terminal_cgroup = 0;
+}
+
+/* Early termination prints parent only. */
+static void test_early_termination(struct cgroup_iter *skel)
+{
+ /* terminate the walk after the first element is processed. */
+ skel->bss->terminate_early = 1;
+
+ format_expected_output1(cg_id[PARENT]);
+
+ read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
+ BPF_ITER_CGROUP_PRE, "early_termination");
+
+ skel->bss->terminate_early = 0;
+}
+
+void test_cgroup_iter(void)
+{
+ struct cgroup_iter *skel = NULL;
+
+ if (setup_cgroup_environment() < 0)
+ return;
+
+ if (setup_cgroups() < 0)
+ goto out;
+
+ skel = cgroup_iter__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "cgroup_iter__open_and_load"))
+ goto out;
+
+ if (test__start_subtest("cgroup_iter__invalid_cgroup"))
+ test_invalid_cgroup(skel);
+ if (test__start_subtest("cgroup_iter__preorder"))
+ test_walk_preorder(skel);
+ if (test__start_subtest("cgroup_iter__postorder"))
+ test_walk_postorder(skel);
+ if (test__start_subtest("cgroup_iter__parent_up_walk"))
+ test_walk_parent_up(skel);
+ if (test__start_subtest("cgroup_iter__early_termination"))
+ test_early_termination(skel);
+out:
+ cgroup_iter__destroy(skel);
+ cleanup_cgroups();
+ cleanup_cgroup_environment();
+}
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter.h b/tools/testing/selftests/bpf/progs/bpf_iter.h
index 97ec8bc76ae62..df91f1daf74d3 100644
--- a/tools/testing/selftests/bpf/progs/bpf_iter.h
+++ b/tools/testing/selftests/bpf/progs/bpf_iter.h
@@ -17,6 +17,7 @@
#define bpf_iter__bpf_sk_storage_map bpf_iter__bpf_sk_storage_map___not_used
#define bpf_iter__sockmap bpf_iter__sockmap___not_used
#define bpf_iter__bpf_link bpf_iter__bpf_link___not_used
+#define bpf_iter__cgroup bpf_iter__cgroup__not_used
#define btf_ptr btf_ptr___not_used
#define BTF_F_COMPACT BTF_F_COMPACT___not_used
#define BTF_F_NONAME BTF_F_NONAME___not_used
@@ -39,6 +40,7 @@
#undef bpf_iter__bpf_sk_storage_map
#undef bpf_iter__sockmap
#undef bpf_iter__bpf_link
+#undef bpf_iter__cgroup
#undef btf_ptr
#undef BTF_F_COMPACT
#undef BTF_F_NONAME
@@ -139,6 +141,11 @@ struct bpf_iter__bpf_link {
struct bpf_link *link;
};

+struct bpf_iter__cgroup {
+ struct bpf_iter_meta *meta;
+ struct cgroup *cgroup;
+} __attribute((preserve_access_index));
+
struct btf_ptr {
void *ptr;
__u32 type_id;
diff --git a/tools/testing/selftests/bpf/progs/cgroup_iter.c b/tools/testing/selftests/bpf/progs/cgroup_iter.c
new file mode 100644
index 0000000000000..2a34d146d6df0
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/cgroup_iter.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Google */
+
+#include "bpf_iter.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+volatile int terminate_early = 0;
+volatile u64 terminal_cgroup = 0;
+
+static inline u64 cgroup_id(struct cgroup *cgrp)
+{
+ return cgrp->kn->id;
+}
+
+SEC("iter/cgroup")
+int cgroup_id_printer(struct bpf_iter__cgroup *ctx)
+{
+ struct seq_file *seq = ctx->meta->seq;
+ struct cgroup *cgrp = ctx->cgroup;
+
+ /* epilogue */
+ if (cgrp == NULL) {
+ BPF_SEQ_PRINTF(seq, "epilogue\n");
+ return 0;
+ }
+
+ /* prologue */
+ if (ctx->meta->seq_num == 0)
+ BPF_SEQ_PRINTF(seq, "prologue\n");
+
+ BPF_SEQ_PRINTF(seq, "%8llu\n", cgroup_id(cgrp));
+
+ if (terminal_cgroup == cgroup_id(cgrp))
+ return 1;
+
+ return terminate_early ? 1 : 0;
+}
--
2.36.1.476.g0c4daa206d-goog