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 31 static 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"); 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 88 cleanup: 89 /* maps, programs, raw sockets will auto cleanup on process exit */ 90 return 0; 91 } 92 93 int main(void) 94 { 95 FILE *f; 96 97 f = popen("ping -c5 localhost", "r"); 98 (void)f; 99 100 return test_sock(); 101 } 102