selftests/bpf: add a cgroup storage test

Implement a test to cover the cgroup storage functionality.
The test implements a bpf program which drops every second packet
by using the cgroup storage as a persistent storage.

The test also use the userspace API to check the data
in the cgroup storage, alter it, and check that the loaded
and attached bpf program sees the update.

Expected output:
  $ ./test_cgroup_storage
  test_cgroup_storage:PASS

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/Makefile

@@ -23,7 +23,7 @@ $(TEST_CUSTOM_PROGS): $(OUTPUT)/%: %.c
 TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
 	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user \
 	test_sock test_btf test_sockmap test_lirc_mode2_user get_cgroup_id_user \
-	test_socket_cookie
+	test_socket_cookie test_cgroup_storage
 
 TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \
 	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \
@@ -66,6 +66,7 @@ $(OUTPUT)/test_sockmap: cgroup_helpers.c
 $(OUTPUT)/test_tcpbpf_user: cgroup_helpers.c
 $(OUTPUT)/test_progs: trace_helpers.c
 $(OUTPUT)/get_cgroup_id_user: cgroup_helpers.c
+$(OUTPUT)/test_cgroup_storage: cgroup_helpers.c
 
 .PHONY: force
 

tools/testing/selftests/bpf/test_cgroup_storage.c

@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <assert.h>
+#include <bpf/bpf.h>
+#include <linux/filter.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "cgroup_helpers.h"
+
+char bpf_log_buf[BPF_LOG_BUF_SIZE];
+
+#define TEST_CGROUP "/test-bpf-cgroup-storage-buf/"
+
+int main(int argc, char **argv)
+{
+	struct bpf_insn prog[] = {
+		BPF_LD_MAP_FD(BPF_REG_1, 0), /* map fd */
+		BPF_MOV64_IMM(BPF_REG_2, 0), /* flags, not used */
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_local_storage),
+		BPF_MOV64_IMM(BPF_REG_1, 1),
+		BPF_STX_XADD(BPF_DW, BPF_REG_0, BPF_REG_1, 0),
+		BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_0, 0),
+		BPF_ALU64_IMM(BPF_AND, BPF_REG_1, 0x1),
+		BPF_MOV64_REG(BPF_REG_0, BPF_REG_1),
+		BPF_EXIT_INSN(),
+	};
+	size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
+	int error = EXIT_FAILURE;
+	int map_fd, prog_fd, cgroup_fd;
+	struct bpf_cgroup_storage_key key;
+	unsigned long long value;
+
+	map_fd = bpf_create_map(BPF_MAP_TYPE_CGROUP_STORAGE, sizeof(key),
+				sizeof(value), 0, 0);
+	if (map_fd < 0) {
+		printf("Failed to create map: %s\n", strerror(errno));
+		goto out;
+	}
+
+	prog[0].imm = map_fd;
+	prog_fd = bpf_load_program(BPF_PROG_TYPE_CGROUP_SKB,
+				   prog, insns_cnt, "GPL", 0,
+				   bpf_log_buf, BPF_LOG_BUF_SIZE);
+	if (prog_fd < 0) {
+		printf("Failed to load bpf program: %s\n", bpf_log_buf);
+		goto out;
+	}
+
+	if (setup_cgroup_environment()) {
+		printf("Failed to setup cgroup environment\n");
+		goto err;
+	}
+
+	/* Create a cgroup, get fd, and join it */
+	cgroup_fd = create_and_get_cgroup(TEST_CGROUP);
+	if (!cgroup_fd) {
+		printf("Failed to create test cgroup\n");
+		goto err;
+	}
+
+	if (join_cgroup(TEST_CGROUP)) {
+		printf("Failed to join cgroup\n");
+		goto err;
+	}
+
+	/* Attach the bpf program */
+	if (bpf_prog_attach(prog_fd, cgroup_fd, BPF_CGROUP_INET_EGRESS, 0)) {
+		printf("Failed to attach bpf program\n");
+		goto err;
+	}
+
+	if (bpf_map_get_next_key(map_fd, NULL, &key)) {
+		printf("Failed to get the first key in cgroup storage\n");
+		goto err;
+	}
+
+	if (bpf_map_lookup_elem(map_fd, &key, &value)) {
+		printf("Failed to lookup cgroup storage\n");
+		goto err;
+	}
+
+	/* Every second packet should be dropped */
+	assert(system("ping localhost -c 1 -W 1 -q > /dev/null") == 0);
+	assert(system("ping localhost -c 1 -W 1 -q > /dev/null"));
+	assert(system("ping localhost -c 1 -W 1 -q > /dev/null") == 0);
+
+	/* Check the counter in the cgroup local storage */
+	if (bpf_map_lookup_elem(map_fd, &key, &value)) {
+		printf("Failed to lookup cgroup storage\n");
+		goto err;
+	}
+
+	if (value != 3) {
+		printf("Unexpected data in the cgroup storage: %llu\n", value);
+		goto err;
+	}
+
+	/* Bump the counter in the cgroup local storage */
+	value++;
+	if (bpf_map_update_elem(map_fd, &key, &value, 0)) {
+		printf("Failed to update the data in the cgroup storage\n");
+		goto err;
+	}
+
+	/* Every second packet should be dropped */
+	assert(system("ping localhost -c 1 -W 1 -q > /dev/null") == 0);
+	assert(system("ping localhost -c 1 -W 1 -q > /dev/null"));
+	assert(system("ping localhost -c 1 -W 1 -q > /dev/null") == 0);
+
+	/* Check the final value of the counter in the cgroup local storage */
+	if (bpf_map_lookup_elem(map_fd, &key, &value)) {
+		printf("Failed to lookup the cgroup storage\n");
+		goto err;
+	}
+
+	if (value != 7) {
+		printf("Unexpected data in the cgroup storage: %llu\n", value);
+		goto err;
+	}
+
+	error = 0;
+	printf("test_cgroup_storage:PASS\n");
+
+err:
+	cleanup_cgroup_environment();
+
+out:
+	return error;
+}