PCAP_COMPILE(3) Library Functions Manual PCAP_COMPILE(3)
pcap_compile - compile a filter expression
int pcap_compile(pcap_t *p, struct bpf_program *fp,
const char *str, int optimize, bpf_u_int32 netmask);
pcap_compile() is used to compile the string str into a filter program.
See pcap-filter(7) for the syntax of that string. program is a pointer
to a bpf_program struct and is filled in by pcap_compile(). optimize
controls whether optimization on the resulting code is performed.
netmask specifies the IPv4 netmask of the network on which packets are
being captured; it is used only when checking for IPv4 broadcast
addresses in the filter program. If the netmask of the network on
which packets are being captured isn't known to the program, or if
packets are being captured on the Linux "any" pseudo-interface that can
capture on more than one network, a value of PCAP_NETMASK_UNKNOWN can
be supplied; tests for IPv4 broadcast addreses will fail to compile,
but all other tests in the filter program will be OK.
pcap_compile() returns 0 on success and -1 on failure. If -1 is
returned, pcap_geterr() or pcap_perror() may be called with p as an
argument to fetch or display the error text.
pcap(3), pcap_setfilter(3), pcap_freecode(3), pcap_geterr(3), pcap-
5 April 2008 PCAP_COMPILE(3)