pcap_setfilter.3pcap - Man Page

#include <pcap/pcap.h>

int pcap_setfilter(pcap_t *p, struct bpf_program *fp);

pcap_setfilter() is used to specify a filter program. fp is a pointer to a bpf_program struct, usually the result of a call to pcap_compile(3PCAP).

pcap_setfilter() returns 0 on success, PCAP_ERROR_NOT_ACTIVATED if called on a capture handle that has been created but not activated, or PCAP_ERROR on other errors.  If PCAP_ERROR is returned, pcap_geterr(3PCAP) or pcap_perror(3PCAP) may be called with p as an argument to fetch or display the error text.

pcap(3PCAP)