bpf/progs/udp_limit.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002
0003 #include <sys/socket.h>
0004 #include <linux/bpf.h>
0005 #include <bpf/bpf_helpers.h>
0006
0007 int invocations = 0, in_use = 0;
0008
0009 struct {
0010     __uint(type, BPF_MAP_TYPE_SK_STORAGE);
0011     __uint(map_flags, BPF_F_NO_PREALLOC);
0012     __type(key, int);
0013     __type(value, int);
0014 } sk_map SEC(".maps");
0015
0016 SEC("cgroup/sock_create")
0017 int sock(struct bpf_sock *ctx)
0018 {
0019     int *sk_storage;
0020     __u32 key;
0021
0022     if (ctx->type != SOCK_DGRAM)
0023         return 1;
0024
0025     sk_storage = bpf_sk_storage_get(&sk_map, ctx, 0,
0026                     BPF_SK_STORAGE_GET_F_CREATE);
0027     if (!sk_storage)
0028         return 0;
0029     *sk_storage = 0xdeadbeef;
0030
0031     __sync_fetch_and_add(&invocations, 1);
0032
0033     if (in_use > 0) {
0034         /* BPF_CGROUP_INET_SOCK_RELEASE is _not_ called
0035          * when we return an error from the BPF
0036          * program!
0037          */
0038         return 0;
0039     }
0040
0041     __sync_fetch_and_add(&in_use, 1);
0042     return 1;
0043 }
0044
0045 SEC("cgroup/sock_release")
0046 int sock_release(struct bpf_sock *ctx)
0047 {
0048     int *sk_storage;
0049     __u32 key;
0050
0051     if (ctx->type != SOCK_DGRAM)
0052         return 1;
0053
0054     sk_storage = bpf_sk_storage_get(&sk_map, ctx, 0, 0);
0055     if (!sk_storage || *sk_storage != 0xdeadbeef)
0056         return 0;
0057
0058     __sync_fetch_and_add(&invocations, 1);
0059     __sync_fetch_and_add(&in_use, -1);
0060     return 1;
0061 }