samples/bpf/xdp_sample_pkts_kern.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/ptrace.h>
   3 #include <linux/version.h>
   4 #include <uapi/linux/bpf.h>
   5 #include "bpf_helpers.h"
   6
   7 #define SAMPLE_SIZE 64ul
   8 #define MAX_CPUS 128
   9
  10 #define bpf_printk(fmt, ...)                                    \
  11 ({                                                              \
  12                char ____fmt[] = fmt;                            \
  13                bpf_trace_printk(____fmt, sizeof(____fmt),       \
  14                                 ##__VA_ARGS__);                 \
  15 })
  16
  17 struct bpf_map_def SEC("maps") my_map = {
  18         .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
  19         .key_size = sizeof(int),
  20         .value_size = sizeof(u32),
  21         .max_entries = MAX_CPUS,
  22 };
  23
  24 SEC("xdp_sample")
  25 int xdp_sample_prog(struct xdp_md *ctx)
  26 {
  27         void *data_end = (void *)(long)ctx->data_end;
  28         void *data = (void *)(long)ctx->data;
  29
  30         /* Metadata will be in the perf event before the packet data. */
  31         struct S {
  32                 u16 cookie;
  33                 u16 pkt_len;
  34         } __packed metadata;
  35
  36         if (data < data_end) {
  37                 /* The XDP perf_event_output handler will use the upper 32 bits
  38                  * of the flags argument as a number of bytes to include of the
  39                  * packet payload in the event data. If the size is too big, the
  40                  * call to bpf_perf_event_output will fail and return -EFAULT.
  41                  *
  42                  * See bpf_xdp_event_output in net/core/filter.c.
  43                  *
  44                  * The BPF_F_CURRENT_CPU flag means that the event output fd
  45                  * will be indexed by the CPU number in the event map.
  46                  */
  47                 u64 flags = BPF_F_CURRENT_CPU;
  48                 u16 sample_size;
  49                 int ret;
  50
  51                 metadata.cookie = 0xdead;
  52                 metadata.pkt_len = (u16)(data_end - data);
  53                 sample_size = min(metadata.pkt_len, SAMPLE_SIZE);
  54                 flags |= (u64)sample_size << 32;
  55
  56                 ret = bpf_perf_event_output(ctx, &my_map, flags,
  57                                             &metadata, sizeof(metadata));
  58                 if (ret)
  59                         bpf_printk("perf_event_output failed: %d\n", ret);
  60         }
  61
  62         return XDP_PASS;
  63 }
  64
  65 char _license[] SEC("license") = "GPL";
  66 u32 _version SEC("version") = LINUX_VERSION_CODE;