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by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.
pcap_setnonblock, pcap_getnonblock - set or get the state of non-block-
ing mode on a capture device
int pcap_setnonblock(pcap_t *p, int nonblock, char *errbuf);
int pcap_getnonblock(pcap_t *p, char *errbuf);
pcap_setnonblock() puts a capture handle into ``non-blocking'' mode, or
takes it out of ``non-blocking'' mode, depending on whether the non-
block argument is non-zero or zero. It has no effect on ``savefiles''.
If there is an error, -1 is returned and errbuf is filled in with an
appropriate error message; otherwise, 0 is returned. In ``non-block-
ing'' mode, an attempt to read from the capture descriptor with
pcap_dispatch() will, if no packets are currently available to be read,
return 0 immediately rather than blocking waiting for packets to
arrive. pcap_loop() and pcap_next() will not work in ``non-blocking''
When first activated with pcap_activate() or opened with
pcap_open_live() , a capture handle is not in ``non-blocking mode''; a
call to pcap_setnonblock() is required in order to put it into ``non-
pcap_getnonblock() returns the current ``non-blocking'' state of the
capture descriptor; it always returns 0 on ``savefiles''. If there is
an error, -1 is returned and errbuf is filled in with an appropriate
errbuf is assumed to be able to hold at least PCAP_ERRBUF_SIZE chars.
pcap(3), pcap_loop(3), pcap_next_ex(3), pcap_geterr(3)
18 October 2014 PCAP_SETNONBLOCK(3)