1/* eBPF example program:
2 * - creates arraymap in kernel with key 4 bytes and value 8 bytes
3 *
4 * - loads eBPF program:
5 *   r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
6 *   *(u32*)(fp - 4) = r0;
7 *   // assuming packet is IPv4, lookup ip->proto in a map
8 *   value = bpf_map_lookup_elem(map_fd, fp - 4);
9 *   if (value)
10 *        (*(u64*)value) += 1;
11 *
12 * - attaches this program to eth0 raw socket
13 *
14 * - every second user space reads map[tcp], map[udp], map[icmp] to see
15 *   how many packets of given protocol were seen on eth0
16 */
17#include <stdio.h>
18#include <unistd.h>
19#include <assert.h>
20#include <linux/bpf.h>
21#include <string.h>
22#include <stdlib.h>
23#include <errno.h>
24#include <sys/socket.h>
25#include <arpa/inet.h>
26#include <linux/if_ether.h>
27#include <linux/ip.h>
28#include <stddef.h>
29#include "libbpf.h"
30
31static int test_sock(void)
32{
33	int sock = -1, map_fd, prog_fd, i, key;
34	long long value = 0, tcp_cnt, udp_cnt, icmp_cnt;
35
36	map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(key), sizeof(value),
37				256);
38	if (map_fd < 0) {
39		printf("failed to create map '%s'\n", strerror(errno));
40		goto cleanup;
41	}
42
43	struct bpf_insn prog[] = {
44		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
45		BPF_LD_ABS(BPF_B, ETH_HLEN + offsetof(struct iphdr, protocol) /* R0 = ip->proto */),
46		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
47		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
48		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
49		BPF_LD_MAP_FD(BPF_REG_1, map_fd),
50		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
51		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
52		BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
53		BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
54		BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */
55		BPF_EXIT_INSN(),
56	};
57
58	prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, prog, sizeof(prog),
59				"GPL", 0);
60	if (prog_fd < 0) {
61		printf("failed to load prog '%s'\n", strerror(errno));
62		goto cleanup;
63	}
64
65	sock = open_raw_sock("lo");
66
67	if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
68		       sizeof(prog_fd)) < 0) {
69		printf("setsockopt %s\n", strerror(errno));
70		goto cleanup;
71	}
72
73	for (i = 0; i < 10; i++) {
74		key = IPPROTO_TCP;
75		assert(bpf_lookup_elem(map_fd, &key, &tcp_cnt) == 0);
76
77		key = IPPROTO_UDP;
78		assert(bpf_lookup_elem(map_fd, &key, &udp_cnt) == 0);
79
80		key = IPPROTO_ICMP;
81		assert(bpf_lookup_elem(map_fd, &key, &icmp_cnt) == 0);
82
83		printf("TCP %lld UDP %lld ICMP %lld packets\n",
84		       tcp_cnt, udp_cnt, icmp_cnt);
85		sleep(1);
86	}
87
88cleanup:
89	/* maps, programs, raw sockets will auto cleanup on process exit */
90	return 0;
91}
92
93int main(void)
94{
95	FILE *f;
96
97	f = popen("ping -c5 localhost", "r");
98	(void)f;
99
100	return test_sock();
101}
102