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