159 lines
5.2 KiB
Plaintext
159 lines
5.2 KiB
Plaintext
.\" @(#) $Header: /tcpdump/master/libpcap/pcap_loop.3pcap,v 1.4 2008-12-25 02:01:32 guy Exp $
|
|
.\"
|
|
.\" 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_LOOP 3PCAP "24 December 2008"
|
|
.SH NAME
|
|
pcap_loop, pcap_dispatch \- process packets from a live capture or savefile
|
|
.SH SYNOPSIS
|
|
.nf
|
|
.ft B
|
|
#include <pcap/pcap.h>
|
|
.ft
|
|
.LP
|
|
.ft B
|
|
typedef void (*pcap_handler)(u_char *user, const struct pcap_pkthdr *h,
|
|
.ti +8
|
|
const u_char *bytes);
|
|
.ft
|
|
.LP
|
|
.ft B
|
|
int pcap_loop(pcap_t *p, int cnt,
|
|
.ti +8
|
|
pcap_handler callback, u_char *user);
|
|
int pcap_dispatch(pcap_t *p, int cnt,
|
|
.ti +8
|
|
pcap_handler callback, u_char *user);
|
|
.ft
|
|
.fi
|
|
.SH DESCRIPTION
|
|
.B pcap_loop()
|
|
processes packets from a live capture or ``savefile'' until
|
|
.I cnt
|
|
packets are processed, the end of the ``savefile'' is
|
|
reached when reading from a ``savefile'',
|
|
.B pcap_breakloop()
|
|
is called, or an error occurs.
|
|
It does
|
|
.B not
|
|
return when live read timeouts occur.
|
|
A value of \-1 or 0 for
|
|
.I cnt
|
|
is equivalent to infinity, so that packets are processed until another
|
|
ending condition occurs.
|
|
.PP
|
|
.B pcap_dispatch()
|
|
processes packets from a live capture or ``savefile'' until
|
|
.I cnt
|
|
packets are processed, the end of the current bufferful of packets is
|
|
reached when doing a live capture, the end of the ``savefile'' is
|
|
reached when reading from a ``savefile'',
|
|
.B pcap_breakloop()
|
|
is called, or an error occurs.
|
|
Thus, when doing a live capture,
|
|
.I cnt
|
|
is the maximum number of packets to process before returning, but is not
|
|
a minimum number; when reading a live capture, only one
|
|
bufferful of packets is read at a time, so fewer than
|
|
.I cnt
|
|
packets may be processed. A value of \-1 or 0 for
|
|
.I cnt
|
|
causes all the packets received in one buffer to be processed when
|
|
reading a live capture, and causes all the packets in the file to be
|
|
processed when reading a ``savefile''.
|
|
.PP
|
|
.ft B
|
|
(In older versions of libpcap, the behavior when
|
|
\fIcnt\fP
|
|
was 0 was undefined; different platforms and devices behaved
|
|
differently, so code that must work with older versions of libpcap
|
|
should use \-1, not 0, as the value of
|
|
\fIcnt\fP.)
|
|
.ft R
|
|
.PP
|
|
.I callback
|
|
specifies a
|
|
.I pcap_handler
|
|
routine to be called with three arguments:
|
|
a
|
|
.I u_char
|
|
pointer which is passed in the
|
|
.I user
|
|
argument to
|
|
.B pcap_loop()
|
|
or
|
|
.BR pcap_dispatch() ,
|
|
a
|
|
.I const struct pcap_pkthdr
|
|
pointer pointing to the packet time stamp and lengths, and a
|
|
.I const u_char
|
|
pointer to the first
|
|
.B caplen
|
|
(as given in the
|
|
.I struct pcap_pkthdr
|
|
a pointer to which is passed to the callback routine)
|
|
bytes of data from the packet. The
|
|
.I struct pcap_pkthdr
|
|
and the packet data are not to be freed by the callback routine, and are
|
|
not guaranteed to be valid after the callback routine returns; if the
|
|
code needs them to be valid after the callback, it must make a copy of
|
|
them.
|
|
.SH RETURN VALUE
|
|
.B pcap_loop()
|
|
returns 0 if
|
|
.I cnt
|
|
is exhausted or if, when reading from a ``savefile'', no more packets
|
|
are available. It returns \-1 if an error occurs or \-2 if the loop
|
|
terminated due to a call to
|
|
.B pcap_breakloop()
|
|
before any packets were processed.
|
|
It does
|
|
.B not
|
|
return when live read timeouts occur; instead, it attempts to read more
|
|
packets.
|
|
.PP
|
|
.B pcap_dispatch()
|
|
returns the number of packets processed on success; this can be 0 if no
|
|
packets were read from a live capture (if, for example, they were
|
|
discarded because they didn't pass the packet filter, or if, on
|
|
platforms that support a read timeout that starts before any packets
|
|
arrive, the timeout expires before any packets arrive, or if the file
|
|
descriptor for the capture device is in non-blocking mode and no packets
|
|
were available to be read) or if no more packets are available in a
|
|
``savefile.'' It returns \-1 if an error occurs or \-2 if the loop
|
|
terminated due to a call to
|
|
.B pcap_breakloop()
|
|
before any packets were processed.
|
|
.ft B
|
|
If your application uses pcap_breakloop(),
|
|
make sure that you explicitly check for \-1 and \-2, rather than just
|
|
checking for a return value < 0.
|
|
.ft R
|
|
.PP
|
|
If \-1 is returned,
|
|
.B pcap_geterr()
|
|
or
|
|
.B pcap_perror()
|
|
may be called with
|
|
.I p
|
|
as an argument to fetch or display the error text.
|
|
.SH SEE ALSO
|
|
pcap(3PCAP), pcap_geterr(3PCAP), pcap_breakloop(3PCAP)
|