pcap_set_tstamp_precision - set the time stamp precision returned in captures
#include <pcap/pcap.h>
int pcap_set_tstamp_precision(pcap_t *p, int tstamp_precision);
pcap_set_tstamp_precision() sets the precision of the time stamp desired
  for packets captured on the pcap descriptor to the type specified by
  tstamp_precision. It must be called on a pcap descriptor created by
  pcap_create(3) that has not yet been activated by
  pcap_activate(3). Two time stamp precisions are supported, microseconds
  and nanoseconds. One can use options PCAP_TSTAMP_PRECISION_MICRO and
  PCAP_TSTAMP_PRECISION_NANO to request desired precision. By default,
  time stamps are in microseconds.
pcap_set_tstamp_precision() returns 0 on success if the specified time
  stamp precision is expected to be supported by the capture device,
  PCAP_ERROR_TSTAMP_PRECISION_NOTSUP if the capture device does not
  support the requested time stamp precision, PCAP_ERROR_ACTIVATED if
  called on a capture handle that has been activated.
This function became available in libpcap release 1.5.1. In previous releases,
  time stamps from a capture device or savefile are always given in seconds and
  microseconds.
pcap(3), pcap_get_tstamp_precision(3), pcap-tstamp(7)