selftests/bpf: Add test for CGROUP_STORAGE map on multiple attaches

This test creates a parent cgroup, and a child of that cgroup.
It attaches a cgroup_skb/egress program that simply counts packets,
to a global variable (ARRAY map), and to a CGROUP_STORAGE map.
The program is first attached to the parent cgroup only, then to
parent and child.

The test cases sends a message within the child cgroup, and because
the program is inherited across parent / child cgroups, it will
trigger the egress program for both the parent and child, if they
exist. The program, when looking up a CGROUP_STORAGE map, uses the
cgroup and attach type of the attachment parameters; therefore,
both attaches uses different cgroup storages.

We assert that all packet counts returns what we expects.

Signed-off-by: YiFei Zhu <zhuyifei@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/5a20206afa4606144691c7caa0d1b997cd60dec0.1595565795.git.zhuyifei@google.com

1 files changed, 30 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c b/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c
new file mode 100644
index 000000000000..ec0165d07105
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/cg_storage_multi_egress_only.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright 2020 Google LLC.
+ */
+
+#include <errno.h>
+#include <linux/bpf.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+#include <bpf/bpf_helpers.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_CGROUP_STORAGE);
+	__type(key, struct bpf_cgroup_storage_key);
+	__type(value, __u32);
+} cgroup_storage SEC(".maps");
+
+__u32 invocations = 0;
+
+SEC("cgroup_skb/egress")
+int egress(struct __sk_buff *skb)
+{
+	__u32 *ptr_cg_storage = bpf_get_local_storage(&cgroup_storage, 0);
+
+	__sync_fetch_and_add(ptr_cg_storage, 1);
+	__sync_fetch_and_add(&invocations, 1);
+
+	return 1;
+}