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 loopback interface "lo" 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 "lo"
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 <bpf/bpf.h>
30#include "bpf_insn.h"
31#include "sock_example.h"
32#include "bpf_util.h"
33
34char bpf_log_buf[BPF_LOG_BUF_SIZE];
35
36static int test_sock(void)
37{
38	int sock = -1, map_fd, prog_fd, i, key;
39	long long value = 0, tcp_cnt, udp_cnt, icmp_cnt;
40
41	map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(key), sizeof(value),
42				256, NULL);
43	if (map_fd < 0) {
44		printf("failed to create map '%s'\n", strerror(errno));
45		goto cleanup;
46	}
47
48	struct bpf_insn prog[] = {
49		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
50		BPF_LD_ABS(BPF_B, ETH_HLEN + offsetof(struct iphdr, protocol) /* R0 = ip->proto */),
51		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
52		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
53		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
54		BPF_LD_MAP_FD(BPF_REG_1, map_fd),
55		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
56		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
57		BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
58		BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
59		BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */
60		BPF_EXIT_INSN(),
61	};
62	size_t insns_cnt = ARRAY_SIZE(prog);
63	LIBBPF_OPTS(bpf_prog_load_opts, opts,
64		.log_buf = bpf_log_buf,
65		.log_size = BPF_LOG_BUF_SIZE,
66	);
67
68	prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL",
69				prog, insns_cnt, &opts);
70	if (prog_fd < 0) {
71		printf("failed to load prog '%s'\n", strerror(errno));
72		goto cleanup;
73	}
74
75	sock = open_raw_sock("lo");
76
77	if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
78		       sizeof(prog_fd)) < 0) {
79		printf("setsockopt %s\n", strerror(errno));
80		goto cleanup;
81	}
82
83	for (i = 0; i < 10; i++) {
84		key = IPPROTO_TCP;
85		assert(bpf_map_lookup_elem(map_fd, &key, &tcp_cnt) == 0);
86
87		key = IPPROTO_UDP;
88		assert(bpf_map_lookup_elem(map_fd, &key, &udp_cnt) == 0);
89
90		key = IPPROTO_ICMP;
91		assert(bpf_map_lookup_elem(map_fd, &key, &icmp_cnt) == 0);
92
93		printf("TCP %lld UDP %lld ICMP %lld packets\n",
94		       tcp_cnt, udp_cnt, icmp_cnt);
95		sleep(1);
96	}
97
98cleanup:
99	/* maps, programs, raw sockets will auto cleanup on process exit */
100	return 0;
101}
102
103int main(void)
104{
105	FILE *f;
106
107	f = popen("ping -4 -c5 localhost", "r");
108	(void)f;
109
110	return test_sock();
111}
112