PCAP_SETNONBLOCK
Section: Misc. Reference Manual Pages (3PCAP)
Updated: 30 November 2023
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NAME
pcap_setnonblock, pcap_getnonblock - set or get the state of
no-blocking 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 ``no-blocking'' mode, or takes it out
of ``no-blocking'' mode, depending on whether the
nonblock
argument is no-zero or zero. It has no effect on ``savefiles''.
errbuf
is a buffer large enough to hold at least
PCAP_ERRBUF_SIZE
chars.
In
``no-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;
pcap_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 ``no-blocking mode''; a call to
pcap_setnonblock()
is required in order to put it into ``no-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 ``no-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(3PCAP),
pcap_next_ex(3PCAP),
pcap_geterr(3PCAP)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- SEE ALSO
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