Manpages - 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’’. If there is an error, *PCAP_ERROR is returned and errbuf is filled in with an appropriate error message; otherwise, 0 is returned.

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; *pacp_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_getnonblock*() returns the current ``non-blocking’’ state of the capture descriptor; it always returns *0 on ``savefiles’’. If there is an error, PCAP_ERROR is returned and errbuf is filled in with an appropriate error message.

errbuf is assumed to be able to hold at least PCAP_ERRBUF_SIZE chars.

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