pcap_set_immediate_mode - set immediate mode for a not-yet-activated capture
  handle
#include <pcap/pcap.h>
int pcap_set_immediate_mode(pcap_t *p, int immediate_mode);
pcap_set_immediate_mode() sets whether immediate mode should be set on a
  capture handle when the handle is activated. If immediate_mode is
  non-zero, immediate mode will be set, otherwise it will not be set.
pcap_set_immediate_mode() returns 0 on success or
  PCAP_ERROR_ACTIVATED if called on a capture handle that has been
  activated.
pcap(3), pcap_create(3), pcap_activate(3)