NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COLOPHON

PCAP_BREAKLOOP(3PCAP)                                  PCAP_BREAKLOOP(3PCAP)

NAME         top

       pcap_breakloop  -  force  a  pcap_dispatch()  or  pcap_loop() call to
       return

SYNOPSIS         top

       #include <pcap/pcap.h>

       void pcap_breakloop(pcap_t *);

DESCRIPTION         top

       pcap_breakloop() sets a flag that will force pcap_dispatch() or
       pcap_loop() to return rather than looping; they will return the
       number of packets that have been processed so far, or -2 if no
       packets have been processed so far.

       This routine is safe to use inside a signal handler on UNIX or a
       console control handler on Windows, as it merely sets a flag that is
       checked within the loop.

       The flag is checked in loops reading packets from the OS - a signal
       by itself will not necessarily terminate those loops - as well as in
       loops processing a set of packets returned by the OS.  Note that if
       you are catching signals on UNIX systems that support restarting
       system calls after a signal, and calling pcap_breakloop() in the
       signal handler, you must specify, when catching those signals, that
       system calls should NOT be restarted by that signal.  Otherwise, if
       the signal interrupted a call reading packets in a live capture, when
       your signal handler returns after calling pcap_breakloop(), the call
       will be restarted, and the loop will not terminate until more packets
       arrive and the call completes.

       Note also that, in a multi-threaded application, if one thread is
       blocked in pcap_dispatch(), pcap_loop(), pcap_next(), or
       pcap_next_ex(), a call to pcap_breakloop() in a different thread will
       not unblock that thread.  You will need to use whatever mechanism the
       OS provides for breaking a thread out of blocking calls in order to
       unblock the thread, such as thread cancellation or thread signalling
       in systems that support POSIX threads, or SetEvent() on the result of
       pcap_getevent() on a pcap_t on which the thread is blocked on
       Windows.  Asynchronous procedure calls will not work on Windows, as a
       thread blocked on a pcap_t will not be in an alertable state.

       Note that pcap_next() and pcap_next_ex() will, on some platforms,
       loop reading packets from the OS; that loop will not necessarily be
       terminated by a signal, so pcap_breakloop() should be used to
       terminate packet processing even if pcap_next() or pcap_next_ex() is
       being used.

       pcap_breakloop() does not guarantee that no further packets will be
       processed by pcap_dispatch() or pcap_loop() after it is called; at
       most one more packet might be processed.

       If -2 is returned from pcap_dispatch() or pcap_loop(), the flag is
       cleared, so a subsequent call will resume reading packets.  If a
       positive number is returned, the flag is not cleared, so a subsequent
       call will return -2 and clear the flag.

SEE ALSO         top

       pcap(3PCAP), pcap_loop(3PCAP), pcap_next_ex(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 2018-02-02.
       (At that time, the date of the most recent commit that was found in
       the repository was 2018-01-31.)  If you discover any rendering prob‐
       lems in this HTML version of the page, or you believe there is a bet‐
       ter 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 man-pages@man7.org

                                8 March 2015           PCAP_BREAKLOOP(3PCAP)