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
34 char bpf_log_buf[BPF_LOG_BUF_SIZE];
35
test_sock(void)36 static 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
98 cleanup:
99 /* maps, programs, raw sockets will auto cleanup on process exit */
100 return 0;
101 }
102
main(void)103 int 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