pcap_breakloop(3) - NetBSD Manual Pages

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PCAP_BREAKLOOP(3)                                            PCAP_BREAKLOOP(3)

pcap_breakloop - force a pcap_dispatch() or pcap_loop() call to return
#include <pcap/pcap.h> void pcap_breakloop(pcap_t *);
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 con- sole 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 com- pletes. 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 in systems that support POSIX threads. Note that pcap_next() and pcap_next_ex() will, on some platforms, loop reading packets from the OS; that loop will not necessarily be termi- nated 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 posi- tive number is returned, the flag is not cleared, so a subsequent call will return -2 and clear the flag.
pcap(3), pcap_loop(3), pcap_next_ex(3) 5 April 2008 PCAP_BREAKLOOP(3)
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