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pcap_findalldevs.3pcap
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pcap_findalldevs.3pcap
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.\" @(#) $Header: /tcpdump/master/libpcap/pcap_findalldevs.3pcap,v 1.3 2008-04-06 02:53:22 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_FINDALLDEVS 3PCAP "22 August 2010"
.SH NAME
pcap_findalldevs, pcap_freealldevs \- get a list of capture devices, and
free that list
.SH SYNOPSIS
.nf
.ft B
#include <pcap/pcap.h>
.ft
.LP
.nf
.ft B
char errbuf[PCAP_ERRBUF_SIZE];
.ft
.LP
.ft B
int pcap_findalldevs(pcap_if_t **alldevsp, char *errbuf);
void pcap_freealldevs(pcap_if_t *alldevs);
.ft
.fi
.SH DESCRIPTION
.B pcap_findalldevs()
constructs a list of network devices that can be opened with
.B pcap_create()
and
.B pcap_activate()
or with
.BR pcap_open_live() .
(Note that there may be network devices that cannot be opened by the
process calling
.BR pcap_findalldevs() ,
because, for example, that process does not have sufficient privileges
to open them for capturing; if so, those devices will not appear on the
list.)
If
.B pcap_findalldevs()
succeeds, the pointer pointed to by
.I alldevsp
is set to point to the first element of the list, or to
.B NULL
if no devices were found (this is considered success).
Each element of the list is of type
.BR pcap_if_t ,
and has the following members:
.RS
.TP
.B next
if not
.BR NULL ,
a pointer to the next element in the list;
.B NULL
for the last element of the list
.TP
.B name
a pointer to a string giving a name for the device to pass to
.B pcap_open_live()
.TP
.B description
if not
.BR NULL ,
a pointer to a string giving a human-readable description of the device
.TP
.B addresses
a pointer to the first element of a list of network addresses for the
device,
or
.B NULL
if the device has no addresses
.TP
.B flags
device flags:
.RS
.TP
.B PCAP_IF_LOOPBACK
set if the device is a loopback interface
.RE
.RE
.PP
Each element of the list of addresses is of type
.BR pcap_addr_t ,
and has the following members:
.RS
.TP
.B next
if not
.BR NULL ,
a pointer to the next element in the list;
.B NULL
for the last element of the list
.TP
.B addr
a pointer to a
.B "struct sockaddr"
containing an address
.TP
.B netmask
if not
.BR NULL ,
a pointer to a
.B "struct sockaddr"
that contains the netmask corresponding to the address pointed to by
.B addr
.TP
.B broadaddr
if not
.BR NULL ,
a pointer to a
.B "struct sockaddr"
that contains the broadcast address corresponding to the address pointed
to by
.BR addr ;
may be null if the device doesn't support broadcasts
.TP
.B dstaddr
if not
.BR NULL ,
a pointer to a
.B "struct sockaddr"
that contains the destination address corresponding to the address pointed
to by
.BR addr ;
may be null if the device isn't a point-to-point interface
.RE
.PP
Note that the addresses in the list of addresses might be IPv4
addresses, IPv6 addresses, or some other type of addresses, so you must
check the
.B sa_family
member of the
.B "struct sockaddr"
before interpreting the contents of the address; do not assume that the
addresses are all IPv4 addresses, or even all IPv4 or IPv6 addresses.
IPv4 addresses have the value
.BR AF_INET ,
IPv6 addresses have the value
.B AF_INET6
(which older operating systems that don't support IPv6 might not
define), and other addresses have other values. Whether other addresses
are returned, and what types they might have is platform-dependent.
For IPv4 addresses, the
.B "struct sockaddr"
pointer can be interpreted as if it pointed to a
.BR "struct sockaddr_in" ;
for IPv6 addresses, it can be interpreted as if it pointed to a
.BR "struct sockaddr_in6".
.PP
The list of devices must be freed with
.BR pcap_freealldevs() ,
whch frees the list pointed to by
.IR alldevs .
.SH RETURN VALUE
.B pcap_findalldevs()
returns 0 on success and \-1 on failure; as indicated, finding no
devices is considered success, rather than failure, so 0 will be
returned in that case.
If \-1 is returned,
.I errbuf
is filled in with an appropriate error message.
.I errbuf
is assumed to be able to hold at least
.B PCAP_ERRBUF_SIZE
chars.
.SH SEE ALSO
pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP),
pcap_open_live(3PCAP)