mirror of
https://git.hardenedbsd.org/hardenedbsd/HardenedBSD.git
synced 2024-12-29 15:10:57 +01:00
128 lines
3.8 KiB
Plaintext
128 lines
3.8 KiB
Plaintext
.\" Copyright (c) 1994, 1996, 1997
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that: (1) source code distributions
|
|
.\" retain the above copyright notice and this paragraph in its entirety, (2)
|
|
.\" distributions including binary code include the above copyright notice and
|
|
.\" this paragraph in its entirety in the documentation or other materials
|
|
.\" provided with the distribution, and (3) all advertising materials mentioning
|
|
.\" features or use of this software display the following acknowledgement:
|
|
.\" ``This product includes software developed by the University of California,
|
|
.\" Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
|
|
.\" the University nor the names of its contributors may be used to endorse
|
|
.\" or promote products derived from this software without specific prior
|
|
.\" written permission.
|
|
.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
|
|
.\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
|
|
.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
|
|
.\"
|
|
.TH PCAP_GET_SELECTABLE_FD 3PCAP "22 July 2011"
|
|
.SH NAME
|
|
pcap_get_selectable_fd \- get a file descriptor on which a select() can
|
|
be done for a live capture
|
|
.SH SYNOPSIS
|
|
.nf
|
|
.ft B
|
|
#include <pcap/pcap.h>
|
|
.ft
|
|
.LP
|
|
.ft B
|
|
int pcap_get_selectable_fd(pcap_t *p);
|
|
.ft
|
|
.fi
|
|
.SH DESCRIPTION
|
|
.B pcap_get_selectable_fd()
|
|
returns, on UNIX, a file descriptor number for a file descriptor on
|
|
which one can
|
|
do a
|
|
.B select()
|
|
or
|
|
.B poll()
|
|
to wait for it to be possible to read packets without blocking, if such
|
|
a descriptor exists, or \-1, if no such descriptor exists. Some network
|
|
devices opened with
|
|
.B pcap_create()
|
|
and
|
|
.BR pcap_activate() ,
|
|
or with
|
|
.BR pcap_open_live() ,
|
|
do not support
|
|
.B select()
|
|
or
|
|
.B poll()
|
|
(for example, regular network devices on FreeBSD 4.3 and 4.4, and Endace
|
|
DAG devices), so \-1 is returned for those devices.
|
|
.PP
|
|
Note that in:
|
|
.IP
|
|
FreeBSD prior to FreeBSD 4.6;
|
|
.IP
|
|
NetBSD prior to NetBSD 3.0;
|
|
.IP
|
|
OpenBSD prior to OpenBSD 2.4;
|
|
.IP
|
|
Mac OS X prior to Mac OS X 10.7;
|
|
.PP
|
|
.B select()
|
|
and
|
|
.B poll()
|
|
do not work correctly on BPF devices;
|
|
.B pcap_get_selectable_fd()
|
|
will return a file descriptor on most of those versions (the exceptions
|
|
being FreeBSD 4.3 and 4.4), but a simple
|
|
.B select()
|
|
or
|
|
.B poll()
|
|
will not indicate that the descriptor is readable until a full buffer's
|
|
worth of packets is received, even if the read timeout expires before
|
|
then. To work around this, an application that uses
|
|
.B select()
|
|
or
|
|
.B poll()
|
|
to wait for packets to arrive must put the
|
|
.B pcap_t
|
|
in non-blocking mode, and must arrange that the
|
|
.B select()
|
|
or
|
|
.B poll()
|
|
have a timeout less than or equal to the read timeout,
|
|
and must try to read packets after that timeout expires, regardless of
|
|
whether
|
|
.B select()
|
|
or
|
|
.B poll()
|
|
indicated that the file descriptor for the
|
|
.B pcap_t
|
|
is ready to be read or not. (That workaround will not work in FreeBSD
|
|
4.3 and later; however, in FreeBSD 4.6 and later,
|
|
.B select()
|
|
and
|
|
.B poll()
|
|
work correctly on BPF devices, so the workaround isn't necessary,
|
|
although it does no harm.)
|
|
.PP
|
|
Note also that
|
|
.B poll()
|
|
doesn't work on character special files, including BPF devices, in Mac
|
|
OS X 10.4 and 10.5, so, while
|
|
.B select()
|
|
can be used on the descriptor returned by
|
|
.BR pcap_get_selectable_fd() ,
|
|
.B poll()
|
|
cannot be used on it those versions of Mac OS X. Kqueues also don't
|
|
work on that descriptor.
|
|
.BR poll() ,
|
|
but not kqueues, work on that descriptor in Mac OS X releases prior to
|
|
10.4;
|
|
.B poll()
|
|
and kqueues work on that descriptor in Mac OS X 10.6 and later.
|
|
.PP
|
|
.B pcap_get_selectable_fd()
|
|
is not available on Windows.
|
|
.SH RETURN VALUE
|
|
A selectable file descriptor is returned if one exists; otherwise, \-1
|
|
is returned.
|
|
.SH SEE ALSO
|
|
pcap(3PCAP), select(2), poll(2)
|