pcap_setnonblock(3pcap) — Linux manual page



NAME         top

       pcap_setnonblock, pcap_getnonblock - set or get the state of non-
       blocking mode on a capture device

SYNOPSIS         top

       #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);

DESCRIPTION         top

       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.

RETURN VALUE         top

       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.

SEE ALSO         top

       pcap(3PCAP), pcap_next_ex(3PCAP), pcap_geterr(3PCAP)

COLOPHON         top

       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 2023-12-22.
       (At that time, the date of the most recent commit that was found
       in the repository was 2023-12-13.)  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

                              5 March 2022       PCAP_SETNONBLOCK(3PCAP)