pcap_setnonblock(3) - NetBSD Manual Pages

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PCAP_SETNONBLOCK(3)                                        PCAP_SETNONBLOCK(3)




NAME

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


SYNOPSIS

       #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

       pcap_setnonblock() puts a capture handle into ``non-blocking'' mode, or
       takes  it  out  of ``non-blocking'' mode, depending on whether the non-
       block 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  descrip-
       tor  with  pcap_dispatch(3) and pcap_next_ex(3) will, if no packets are
       currently available to be read, return 0 immediately rather than block-
       ing waiting for packets to arrive.

       pcap_loop(3)  will loop forever, consuming CPU time when no packets are
       currently  available;   pcap_dispatch()   should   be   used   instead.
       pcap_next(3)  will return NULL if there are no packets currently avail-
       able  to  read;  this  is   indistinguishable   from   an   error,   so
       pcap_next_ex() should be used instead.

       When   first   activated   with   pcap_activate(3)   or   opened   with
       pcap_open_live(3), 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

       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

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



                               30 November 2023            PCAP_SETNONBLOCK(3)