1 // SPDX-License-Identifier: GPL-2.0-only
2 
3 #include <sys/socket.h>
4 #include <linux/bpf.h>
5 #include <bpf/bpf_helpers.h>
6 
7 int invocations = 0, in_use = 0;
8 
9 struct {
10 	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
11 	__uint(map_flags, BPF_F_NO_PREALLOC);
12 	__type(key, int);
13 	__type(value, int);
14 } sk_map SEC(".maps");
15 
16 SEC("cgroup/sock_create")
17 int sock(struct bpf_sock *ctx)
18 {
19 	int *sk_storage;
20 
21 	if (ctx->type != SOCK_DGRAM)
22 		return 1;
23 
24 	sk_storage = bpf_sk_storage_get(&sk_map, ctx, 0,
25 					BPF_SK_STORAGE_GET_F_CREATE);
26 	if (!sk_storage)
27 		return 0;
28 	*sk_storage = 0xdeadbeef;
29 
30 	__sync_fetch_and_add(&invocations, 1);
31 
32 	if (in_use > 0) {
33 		/* BPF_CGROUP_INET_SOCK_RELEASE is _not_ called
34 		 * when we return an error from the BPF
35 		 * program!
36 		 */
37 		return 0;
38 	}
39 
40 	__sync_fetch_and_add(&in_use, 1);
41 	return 1;
42 }
43 
44 SEC("cgroup/sock_release")
45 int sock_release(struct bpf_sock *ctx)
46 {
47 	int *sk_storage;
48 
49 	if (ctx->type != SOCK_DGRAM)
50 		return 1;
51 
52 	sk_storage = bpf_sk_storage_get(&sk_map, ctx, 0, 0);
53 	if (!sk_storage || *sk_storage != 0xdeadbeef)
54 		return 0;
55 
56 	__sync_fetch_and_add(&invocations, 1);
57 	__sync_fetch_and_add(&in_use, -1);
58 	return 1;
59 }
60