linux/samples/bpf/sockex1_kern.c
Alexei Starovoitov a80857822b samples: bpf: trivial eBPF program in C
this example does the same task as previous socket example
in assembler, but this one does it in C.

eBPF program in kernel does:
    /* assume that packet is IPv4, load one byte of IP->proto */
    int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
    long *value;

    value = bpf_map_lookup_elem(&my_map, &index);
    if (value)
        __sync_fetch_and_add(value, 1);

Corresponding user space reads map[tcp], map[udp], map[icmp]
and prints protocol stats every second

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-12-05 21:47:33 -08:00

26 lines
553 B
C

#include <uapi/linux/bpf.h>
#include <uapi/linux/if_ether.h>
#include <uapi/linux/ip.h>
#include "bpf_helpers.h"
struct bpf_map_def SEC("maps") my_map = {
.type = BPF_MAP_TYPE_ARRAY,
.key_size = sizeof(u32),
.value_size = sizeof(long),
.max_entries = 256,
};
SEC("socket1")
int bpf_prog1(struct sk_buff *skb)
{
int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
long *value;
value = bpf_map_lookup_elem(&my_map, &index);
if (value)
__sync_fetch_and_add(value, 1);
return 0;
}
char _license[] SEC("license") = "GPL";