/* eBPF example program:
   * - creates arraymap in kernel with key 4 bytes and value 8 bytes
   *
   * - loads eBPF program:
   *   r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
   *   *(u32*)(fp - 4) = r0;
   *   // assuming packet is IPv4, lookup ip->proto in a map
   *   value = bpf_map_lookup_elem(map_fd, fp - 4);
   *   if (value)
   *        (*(u64*)value) += 1;
   *
   * - attaches this program to eth0 raw socket
   *
   * - every second user space reads map[tcp], map[udp], map[icmp] to see
   *   how many packets of given protocol were seen on eth0
   */
  #include <stdio.h>
  #include <unistd.h>
  #include <assert.h>
  #include <linux/bpf.h>
  #include <string.h>
  #include <stdlib.h>
  #include <errno.h>
  #include <sys/socket.h>
  #include <arpa/inet.h>
  #include <linux/if_ether.h>
  #include <linux/ip.h>
  #include <stddef.h>
  #include "libbpf.h"

  #include "sock_example.h"

  char bpf_log_buf[BPF_LOG_BUF_SIZE];

  static int test_sock(void)
  {
  	int sock = -1, map_fd, prog_fd, i, key;
  	long long value = 0, tcp_cnt, udp_cnt, icmp_cnt;
  
  	map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(key), sizeof(value),

  				256, 0);

  	if (map_fd < 0) {
  		printf("failed to create map '%s'
  ", strerror(errno));
  		goto cleanup;
  	}
  
  	struct bpf_insn prog[] = {
  		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
  		BPF_LD_ABS(BPF_B, ETH_HLEN + offsetof(struct iphdr, protocol) /* R0 = ip->proto */),
  		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
  		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
  		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
  		BPF_LD_MAP_FD(BPF_REG_1, map_fd),
  		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
  		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
  		BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
  		BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
  		BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */
  		BPF_EXIT_INSN(),
  	};

  	size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);

  	prog_fd = bpf_load_program(BPF_PROG_TYPE_SOCKET_FILTER, prog, insns_cnt,

  				   "GPL", 0, bpf_log_buf, BPF_LOG_BUF_SIZE);

  	if (prog_fd < 0) {
  		printf("failed to load prog '%s'
  ", strerror(errno));
  		goto cleanup;
  	}
  
  	sock = open_raw_sock("lo");
  
  	if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
  		       sizeof(prog_fd)) < 0) {
  		printf("setsockopt %s
  ", strerror(errno));
  		goto cleanup;
  	}
  
  	for (i = 0; i < 10; i++) {
  		key = IPPROTO_TCP;

  		assert(bpf_map_lookup_elem(map_fd, &key, &tcp_cnt) == 0);

  
  		key = IPPROTO_UDP;

  		assert(bpf_map_lookup_elem(map_fd, &key, &udp_cnt) == 0);

  
  		key = IPPROTO_ICMP;

  		assert(bpf_map_lookup_elem(map_fd, &key, &icmp_cnt) == 0);

  
  		printf("TCP %lld UDP %lld ICMP %lld packets
  ",
  		       tcp_cnt, udp_cnt, icmp_cnt);
  		sleep(1);
  	}
  
  cleanup:
  	/* maps, programs, raw sockets will auto cleanup on process exit */
  	return 0;
  }
  
  int main(void)
  {
  	FILE *f;
  
  	f = popen("ping -c5 localhost", "r");
  	(void)f;
  
  	return test_sock();
  }