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by Kimmo Suominen.
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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. net-
mask 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 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.
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-filter(7)
24 March 2017 PCAP_COMPILE(3)