root/samples/bpf/xdp_sample_pkts_kern.c

DEFINITIONS

1. SEC

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