C - What is `(struct timeval *)state` in a variable declaration

Question

I'm trying to understand a code example that uses pcap to get the flow statistics while capturing packets, like delay. And in the declaration of a variable there is this line:

struct timeval *old_ts = (struct timeval *)state;

The example is in the link: Gathering Statistics on the network traffic

The code snippet in question is this:

void dispatcher_handler(u_char *state,
  const struct pcap_pkthdr *header,
  const u_char *pkt_data)
{
  struct timeval *old_ts = (struct timeval *)state;
  u_int delay;
  LARGE_INTEGER Bps,Pps;
  struct tm ltime;
  char timestr[16];
  time_t local_tv_sec;

  /* Calculate the delay in microseconds from the last sample. This value
   * is obtained from the timestamp that the associated with the sample. */
  delay = (header->ts.tv_sec - old_ts->tv_sec) * 1000000
    - old_ts->tv_usec + header->ts.tv_usec;
  /* Get the number of Bits per second */
  Bps.QuadPart=(((*(LONGLONG*)(pkt_data + 8)) * 8 * 1000000) / (delay));
  /*                                            ^      ^
                                                  |      |
                                                  |      | 
                                                  |      |
                         converts bytes in bits --       |
                                                         |
                    delay is expressed in microseconds --
  */

  /* Get the number of Packets per second */
  Pps.QuadPart=(((*(LONGLONG*)(pkt_data)) * 1000000) / (delay));

  /* Convert the timestamp to readable format */
  local_tv_sec = header->ts.tv_sec;
  localtime_s(&ltime, &local_tv_sec);
  strftime( timestr, sizeof timestr, "%H:%M:%S", &ltime);

  /* Print timestamp*/
  printf("%s ", timestr);

  /* Print the samples */
  printf("BPS=%I64u ", Bps.QuadPart);
  printf("PPS=%I64u\n", Pps.QuadPart);

  //store current timestamp
  old_ts->tv_sec=header->ts.tv_sec;
  old_ts->tv_usec=header->ts.tv_usec;
}

Can you help me understand this line and this function? Thanks in advance for your help.