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 | |
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(format: "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(format: "failed to load prog '%s'\n" , strerror(errno)); |
72 | goto cleanup; |
73 | } |
74 | |
75 | sock = open_raw_sock(name: "lo" ); |
76 | |
77 | if (setsockopt(fd: sock, SOL_SOCKET, SO_ATTACH_BPF, optval: &prog_fd, |
78 | optlen: sizeof(prog_fd)) < 0) { |
79 | printf(format: "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(format: "TCP %lld UDP %lld ICMP %lld packets\n" , |
94 | tcp_cnt, udp_cnt, icmp_cnt); |
95 | sleep(seconds: 1); |
96 | } |
97 | |
98 | cleanup: |
99 | /* maps, programs, raw sockets will auto cleanup on process exit */ |
100 | return 0; |
101 | } |
102 | |
103 | int main(void) |
104 | { |
105 | FILE *f; |
106 | |
107 | f = popen(command: "ping -4 -c5 localhost" , modes: "r" ); |
108 | (void)f; |
109 | |
110 | return test_sock(); |
111 | } |
112 | |