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(7) for the syntax of that string. fp is a pointer to a
bpf_program struct and is filled in by pcap_compile(). optimize con-
trols 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 cap-
tured 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 multi-
ple 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)
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