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