sock_example.c 2.9 KB

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  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. char bpf_log_buf[BPF_LOG_BUF_SIZE];
  33. static int test_sock(void)
  34. {
  35. int sock = -1, map_fd, prog_fd, i, key;
  36. long long value = 0, tcp_cnt, udp_cnt, icmp_cnt;
  37. map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(key), sizeof(value),
  38. 256, 0);
  39. if (map_fd < 0) {
  40. printf("failed to create map '%s'\n", strerror(errno));
  41. goto cleanup;
  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. size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
  58. prog_fd = bpf_load_program(BPF_PROG_TYPE_SOCKET_FILTER, prog, insns_cnt,
  59. "GPL", 0, bpf_log_buf, BPF_LOG_BUF_SIZE);
  60. if (prog_fd < 0) {
  61. printf("failed to load prog '%s'\n", strerror(errno));
  62. goto cleanup;
  63. }
  64. sock = open_raw_sock("lo");
  65. if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
  66. sizeof(prog_fd)) < 0) {
  67. printf("setsockopt %s\n", strerror(errno));
  68. goto cleanup;
  69. }
  70. for (i = 0; i < 10; i++) {
  71. key = IPPROTO_TCP;
  72. assert(bpf_map_lookup_elem(map_fd, &key, &tcp_cnt) == 0);
  73. key = IPPROTO_UDP;
  74. assert(bpf_map_lookup_elem(map_fd, &key, &udp_cnt) == 0);
  75. key = IPPROTO_ICMP;
  76. assert(bpf_map_lookup_elem(map_fd, &key, &icmp_cnt) == 0);
  77. printf("TCP %lld UDP %lld ICMP %lld packets\n",
  78. tcp_cnt, udp_cnt, icmp_cnt);
  79. sleep(1);
  80. }
  81. cleanup:
  82. /* maps, programs, raw sockets will auto cleanup on process exit */
  83. return 0;
  84. }
  85. int main(void)
  86. {
  87. FILE *f;
  88. f = popen("ping -4 -c5 localhost", "r");
  89. (void)f;
  90. return test_sock();
  91. }