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20 .TH PCAP_BREAKLOOP 3PCAP "25 July 2018"
22 pcap_breakloop \- force a pcap_dispatch() or pcap_loop() call to return
26 #include <pcap/pcap.h>
30 void pcap_breakloop(pcap_t *);
35 sets a flag that will force
36 .B pcap_dispatch(3PCAP)
39 to return rather than looping; they will return the number of packets
40 that have been processed so far, or
42 if no packets have been processed so far.
44 This routine is safe to use inside a signal handler on UNIX or a console
45 control handler on Windows, as it merely sets a flag that is checked
48 The flag is checked in loops reading packets from the OS - a signal by
49 itself will not necessarily terminate those loops - as well as in loops
50 processing a set of packets returned by the OS.
52 Note that if you are catching signals on UNIX systems that support
53 restarting system calls after a signal, and calling pcap_breakloop()
54 in the signal handler, you must specify, when catching those signals,
55 that system calls should NOT be restarted by that signal. Otherwise,
56 if the signal interrupted a call reading packets in a live capture,
57 when your signal handler returns after calling pcap_breakloop(), the
58 call will be restarted, and the loop will not terminate until more
59 packets arrive and the call completes.
63 Note also that, in a multi-threaded application, if one thread is
64 blocked in pcap_dispatch(), pcap_loop(), pcap_next(3PCAP), or pcap_next_ex(3PCAP),
65 a call to pcap_breakloop() in a different thread will not unblock that
68 You will need to use whatever mechanism the OS provides for
69 breaking a thread out of blocking calls in order to unblock the thread,
70 such as thread cancellation or thread signalling in systems that support
77 on which the thread is blocked on Windows. Asynchronous procedure calls
78 will not work on Windows, as a thread blocked on a
80 will not be in an alertable state.
87 will, on some platforms, loop reading packets from the OS; that loop
88 will not necessarily be terminated by a signal, so
90 should be used to terminate packet processing even if
97 does not guarantee that no further packets will be processed by
101 after it is called; at most one more packet might be processed.
109 the flag is cleared, so a subsequent call will resume reading packets.
110 If a positive number is returned, the flag is not cleared, so a
111 subsequent call will return