1#include <uapi/linux/bpf.h>
2#include <uapi/linux/if_ether.h>
3#include <uapi/linux/if_packet.h>
4#include <uapi/linux/ip.h>
5#include <bpf/bpf_helpers.h>
6#include "bpf_legacy.h"
7
8struct {
9 __uint(type, BPF_MAP_TYPE_ARRAY);
10 __type(key, u32);
11 __type(value, long);
12 __uint(max_entries, 256);
13} my_map SEC(".maps");
14
15SEC("socket1")
16int bpf_prog1(struct __sk_buff *skb)
17{
18 int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
19 long *value;
20
21 if (skb->pkt_type != PACKET_OUTGOING)
22 return 0;
23
24 value = bpf_map_lookup_elem(&my_map, &index);
25 if (value)
26 __sync_fetch_and_add(value, skb->len);
27
28 return 0;
29}
30char _license[] SEC("license") = "GPL";
31

source code of linux/samples/bpf/sockex1_kern.c