samples/bpf: extend test_cgrp2_attach2 test to use cgroup storage

The test_cgrp2_attach test covers bpf cgroup attachment code well,
so let's re-use it for testing allocation/releasing of cgroup storage.

The extension is pretty straightforward: the bpf program will use
the cgroup storage to save the number of transmitted bytes.

Expected output:
  $ ./test_cgrp2_attach2
  Attached DROP prog. This ping in cgroup /foo should fail...
  ping: sendmsg: Operation not permitted
  Attached DROP prog. This ping in cgroup /foo/bar should fail...
  ping: sendmsg: Operation not permitted
  Attached PASS prog. This ping in cgroup /foo/bar should pass...
  Detached PASS from /foo/bar while DROP is attached to /foo.
  This ping in cgroup /foo/bar should fail...
  ping: sendmsg: Operation not permitted
  Attached PASS from /foo/bar and detached DROP from /foo.
  This ping in cgroup /foo/bar should pass...
  ### override:PASS
  ### multi: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>

samples/bpf/test_cgrp2_attach2.c

@@ -8,7 +8,8 @@
  *   information. The number of invocations of the program, which maps
  *   to the number of packets received, is stored to key 0. Key 1 is
  *   incremented on each iteration by the number of bytes stored in
- *   the skb.
+ *   the skb. The program also stores the number of received bytes
+ *   in the cgroup storage.
  *
  * - Attaches the new program to a cgroup using BPF_PROG_ATTACH
  *
@@ -21,12 +22,15 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
+#include <sys/resource.h>
+#include <sys/time.h>
 #include <unistd.h>
 
 #include <linux/bpf.h>
 #include <bpf/bpf.h>
 
 #include "bpf_insn.h"
+#include "bpf_rlimit.h"
 #include "cgroup_helpers.h"
 
 #define FOO		"/foo"
@@ -205,6 +209,8 @@ static int map_fd = -1;
 
 static int prog_load_cnt(int verdict, int val)
 {
+	int cgroup_storage_fd;
+
 	if (map_fd < 0)
 		map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, 4, 8, 1, 0);
 	if (map_fd < 0) {
@@ -212,6 +218,13 @@ static int prog_load_cnt(int verdict, int val)
 		return -1;
 	}
 
+	cgroup_storage_fd = bpf_create_map(BPF_MAP_TYPE_CGROUP_STORAGE,
+				sizeof(struct bpf_cgroup_storage_key), 8, 0, 0);
+	if (cgroup_storage_fd < 0) {
+		printf("failed to create map '%s'\n", strerror(errno));
+		return -1;
+	}
+
 	struct bpf_insn prog[] = {
 		BPF_MOV32_IMM(BPF_REG_0, 0),
 		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
@@ -222,6 +235,11 @@ static int prog_load_cnt(int verdict, int val)
 		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
 		BPF_MOV64_IMM(BPF_REG_1, val), /* r1 = 1 */
 		BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
+		BPF_LD_MAP_FD(BPF_REG_1, cgroup_storage_fd),
+		BPF_MOV64_IMM(BPF_REG_2, 0),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_local_storage),
+		BPF_MOV64_IMM(BPF_REG_1, val),
+		BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_W, BPF_REG_0, BPF_REG_1, 0, 0),
 		BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
 		BPF_EXIT_INSN(),
 	};
@@ -237,6 +255,7 @@ static int prog_load_cnt(int verdict, int val)
 		printf("Output from verifier:\n%s\n-------\n", bpf_log_buf);
 		return 0;
 	}
+	close(cgroup_storage_fd);
 	return ret;
 }