selftests/bpf: Test cgroup_iter.

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.
 - process only a single object (i.e. PARENT).
 - early termination.

Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/r/20220824233117.1312810-3-haoluo@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dump.c b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
index 84c1cfaa2b027bebc4715757c5536569e2498d92..a1bae92be1fc99c95516e2faf5b2ecb4d16721d7 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/btf_dump.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
@@ -764,7 +764,7 @@ static void test_btf_dump_struct_data(struct btf *btf, struct btf_dump *d,
 
        /* union with nested struct */
        TEST_BTF_DUMP_DATA(btf, d, "union", str, union bpf_iter_link_info, BTF_F_COMPACT,
-                          "(union bpf_iter_link_info){.map = (struct){.map_fd = (__u32)1,},.cgroup = (struct){.order = (__u32)1,.cgroup_fd = (__u32)1,},}",
+                          "(union bpf_iter_link_info){.map = (struct){.map_fd = (__u32)1,},.cgroup = (struct){.order = (enum bpf_cgroup_iter_order)BPF_ITER_SELF_ONLY,.cgroup_fd = (__u32)1,},}",
                           { .cgroup = { .order = 1, .cgroup_fd = 1, }});
 
        /* struct skb with nested structs/unions; because type output is so

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 (file)
index 0000000..38958c3
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/cgroup_iter.c
@@ -0,0 +1,224 @@
+// 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"
+
+static 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];
+
+static 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;
+}
+
+static 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[128];
+       size_t left;
+       char *p;
+
+       memset(&linfo, 0, sizeof(linfo));
+       linfo.cgroup.cgroup_fd = cgroup_fd;
+       linfo.cgroup.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));
+       left = ARRAY_SIZE(buf);
+       p = buf;
+       while ((len = read(iter_fd, p, left)) > 0) {
+               p += len;
+               left -= len;
+       }
+
+       ASSERT_STREQ(buf, expected_output, testname);
+
+       /* read() after iter finishes should be ok. */
+       if (len == 0)
+               ASSERT_OK(read(iter_fd, buf, sizeof(buf)), "second_read");
+
+       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);
+       ASSERT_ERR_PTR(link, "attach_iter");
+       bpf_link__destroy(link);
+}
+
+/* Specifying both cgroup_fd and cgroup_id is invalid. */
+static void test_invalid_cgroup_spec(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)cg_fd[PARENT];
+       linfo.cgroup.cgroup_id = (__u64)cg_id[PARENT];
+       opts.link_info = &linfo;
+       opts.link_info_len = sizeof(linfo);
+
+       link = bpf_program__attach_iter(skel->progs.cgroup_id_printer, &opts);
+       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)
+{
+       snprintf(expected_output, sizeof(expected_output),
+                PROLOGUE "%8llu\n%8llu\n%8llu\n" EPILOGUE,
+                cg_id[PARENT], cg_id[CHILD1], cg_id[CHILD2]);
+
+       read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
+                             BPF_ITER_DESCENDANTS_PRE, "preorder");
+}
+
+/* Postorder walk prints child and parent in order. */
+static void test_walk_postorder(struct cgroup_iter *skel)
+{
+       snprintf(expected_output, sizeof(expected_output),
+                PROLOGUE "%8llu\n%8llu\n%8llu\n" EPILOGUE,
+                cg_id[CHILD1], cg_id[CHILD2], cg_id[PARENT]);
+
+       read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
+                             BPF_ITER_DESCENDANTS_POST, "postorder");
+}
+
+/* Walking parents prints parent and then root. */
+static void test_walk_ancestors_up(struct cgroup_iter *skel)
+{
+       /* terminate the walk when ROOT is met. */
+       skel->bss->terminal_cgroup = cg_id[ROOT];
+
+       snprintf(expected_output, sizeof(expected_output),
+                PROLOGUE "%8llu\n%8llu\n" EPILOGUE,
+                cg_id[PARENT], cg_id[ROOT]);
+
+       read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
+                             BPF_ITER_ANCESTORS_UP, "ancestors_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;
+
+       snprintf(expected_output, sizeof(expected_output),
+                PROLOGUE "%8llu\n" EPILOGUE, cg_id[PARENT]);
+
+       read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
+                             BPF_ITER_DESCENDANTS_PRE, "early_termination");
+
+       skel->bss->terminate_early = 0;
+}
+
+/* Waling self prints self only. */
+static void test_walk_self_only(struct cgroup_iter *skel)
+{
+       snprintf(expected_output, sizeof(expected_output),
+                PROLOGUE "%8llu\n" EPILOGUE, cg_id[PARENT]);
+
+       read_from_cgroup_iter(skel->progs.cgroup_id_printer, cg_fd[PARENT],
+                             BPF_ITER_SELF_ONLY, "self_only");
+}
+
+void test_cgroup_iter(void)
+{
+       struct cgroup_iter *skel = NULL;
+
+       if (setup_cgroup_environment())
+               return;
+
+       if (setup_cgroups())
+               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__invalid_cgroup_spec"))
+               test_invalid_cgroup_spec(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__ancestors_up_walk"))
+               test_walk_ancestors_up(skel);
+       if (test__start_subtest("cgroup_iter__early_termination"))
+               test_early_termination(skel);
+       if (test__start_subtest("cgroup_iter__self_only"))
+               test_walk_self_only(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 e9846606690d7e70d9a9a149fdf3e4bf15490ab8..c41ee80533ca219a59cf5640eb008df2b6c10380 100644 (file)
--- 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
@@ -40,6 +41,7 @@
 #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
@@ -141,6 +143,11 @@ 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 (file)
index 0000000..de03997
--- /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";
+int terminate_early = 0;
+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;
+}