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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | SEE ALSO | COLOPHON |
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PCAP_SETNONBLOCK(3PCAP) PCAP_SETNONBLOCK(3PCAP)
pcap_setnonblock, pcap_getnonblock - set or get the state of non-
blocking mode on a capture device
#include <pcap/pcap.h>
char errbuf[PCAP_ERRBUF_SIZE];
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 nonblock argument is non-zero or zero. It has no
effect on ``savefiles''. errbuf is a buffer large enough to hold
at least PCAP_ERRBUF_SIZE chars.
In ``non-blocking'' mode, an attempt to read from the capture
descriptor with pcap_dispatch(3PCAP) and pcap_next_ex(3PCAP)
will, if no packets are currently available to be read, return 0
immediately rather than blocking waiting for packets to arrive.
pcap_loop(3PCAP) will loop forever, consuming CPU time when no
packets are currently available; pcap_dispatch() should be used
instead. pcap_next(3PCAP) will return NULL if there are no
packets currently available to read; this is indistinguishable
from an error, so pcap_next_ex() should be used instead.
When first activated with pcap_activate(3PCAP) or opened with
pcap_open_live(3PCAP), a capture handle is not in ``non-blocking
mode''; a call to pcap_setnonblock() is required in order to put
it into ``non-blocking'' mode.
pcap_setnonblock() return 0 on success, PCAP_ERROR_NOT_ACTIVATED
if called on a capture handle that has been created but not
activated, and PCAP_ERROR for other errors. pcap_getnonblock()
returns the current ``non-blocking'' state of the capture
descriptor on success; it always returns 0 on ``savefiles''. It
returns PCAP_ERROR_NOT_ACTIVATED if called on a capture handle
that has been created but not activated, and PCAP_ERROR for other
errors. If PCAP_ERROR is returned, errbuf is filled in with an
appropriate error message.
pcap(3PCAP), pcap_next_ex(3PCAP), pcap_geterr(3PCAP)
This page is part of the libpcap (packet capture library)
project. Information about the project can be found at
⟨http://www.tcpdump.org/⟩. If you have a bug report for this
manual page, see ⟨http://www.tcpdump.org/#patches⟩. This page
was obtained from the project's upstream Git repository
⟨https://github.com/the-tcpdump-group/libpcap.git⟩ on 2024-06-14.
(At that time, the date of the most recent commit that was found
in the repository was 2024-06-04.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
5 March 2022 PCAP_SETNONBLOCK(3PCAP)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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