xdp_sample_pkts_kern.c (1566B)
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 9struct { 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 15SEC("xdp_sample") 16int 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 56char _license[] SEC("license") = "GPL"; 57u32 _version SEC("version") = LINUX_VERSION_CODE;