LXR linux/samples/bpf/sock

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