tools/testing/selftests/bpf/progs/udp_limit.c

// SPDX-License-Identifier: GPL-2.0-only

#include <sys/socket.h>
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>

int invocations = 0, in_use = 0;

struct {
	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
	__uint(map_flags, BPF_F_NO_PREALLOC);
	__type(key, int);
	__type(value, int);
} sk_map SEC(".maps");

SEC("cgroup/sock_create")
int sock(struct bpf_sock *ctx)
{
	int *sk_storage;

	if (ctx->type != SOCK_DGRAM)
		return 1;

	sk_storage = bpf_sk_storage_get(&sk_map, ctx, 0,
					BPF_SK_STORAGE_GET_F_CREATE);
	if (!sk_storage)
		return 0;
	*sk_storage = 0xdeadbeef;

	__sync_fetch_and_add(&invocations, 1);

	if (in_use > 0) {
		/* BPF_CGROUP_INET_SOCK_RELEASE is _not_ called
		 * when we return an error from the BPF
		 * program!
		 */
		return 0;
	}

	__sync_fetch_and_add(&in_use, 1);
	return 1;
}

SEC("cgroup/sock_release")
int sock_release(struct bpf_sock *ctx)
{
	int *sk_storage;

	if (ctx->type != SOCK_DGRAM)
		return 1;

	sk_storage = bpf_sk_storage_get(&sk_map, ctx, 0, 0);
	if (!sk_storage || *sk_storage != 0xdeadbeef)
		return 0;

	__sync_fetch_and_add(&invocations, 1);
	__sync_fetch_and_add(&in_use, -1);
	return 1;
}