PCAP_COMPILE(3PCAP) PCAP_COMPILE(3PCAP)

NAME

pcap_compile - compile a filter expression

SYNOPSIS

#include <pcap/pcap.h>

int pcap_compile(pcap_t *p, struct bpf_program *fp,
const char *str, int optimize, bpf_u_int32 netmask);

DESCRIPTION

pcap_compile() is used to compile the string str into a filter
program. See pcap-filter(5) for the syntax of that string. fp 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
addresses will fail to compile, but all other tests in the filter
program will be OK.

NOTE: in libpcap 1.8.0 and later, pcap_compile() can be used in
multiple threads within a single process. However, in earlier
versions of libpcap, it is not safe to use pcap_compile() in multiple
threads in a single process without some form of mutual exclusion
allowing only one thread to call it at any given time.

RETURN VALUE

pcap_compile() returns 0 on success and PCAP_ERROR on failure. 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.

BACKWARD COMPATIBILITY

The PCAP_NETMASK_UNKNOWN constant became available in libpcap release
1.1.0.

SEE ALSO

pcap(3PCAP), pcap_setfilter(3PCAP), pcap_freecode(3PCAP)

22 August 2018 PCAP_COMPILE(3PCAP)