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187 lines
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187 lines
5.1 KiB
Plaintext
.\" @(#) $Header: /tcpdump/master/libpcap/pcap_findalldevs.3pcap,v 1.3 2008-04-06 02:53:22 guy Exp $
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.\"
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.\" Copyright (c) 1994, 1996, 1997
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that: (1) source code distributions
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.\" retain the above copyright notice and this paragraph in its entirety, (2)
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.\" distributions including binary code include the above copyright notice and
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.\" this paragraph in its entirety in the documentation or other materials
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.\" provided with the distribution, and (3) all advertising materials mentioning
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.\" features or use of this software display the following acknowledgement:
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.\" ``This product includes software developed by the University of California,
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.\" Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
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.\" the University nor the names of its contributors may be used to endorse
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.\" or promote products derived from this software without specific prior
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.\" written permission.
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.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
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.\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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.\"
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.TH PCAP_FINDALLDEVS 3PCAP "22 August 2010"
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.SH NAME
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pcap_findalldevs, pcap_freealldevs \- get a list of capture devices, and
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free that list
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.SH SYNOPSIS
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.nf
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.ft B
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#include <pcap/pcap.h>
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.ft
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.LP
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.nf
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.ft B
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char errbuf[PCAP_ERRBUF_SIZE];
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.ft
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.LP
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.ft B
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int pcap_findalldevs(pcap_if_t **alldevsp, char *errbuf);
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void pcap_freealldevs(pcap_if_t *alldevs);
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.ft
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.fi
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.SH DESCRIPTION
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.B pcap_findalldevs()
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constructs a list of network devices that can be opened with
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.B pcap_create()
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and
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.B pcap_activate()
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or with
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.BR pcap_open_live() .
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(Note that there may be network devices that cannot be opened by the
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process calling
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.BR pcap_findalldevs() ,
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because, for example, that process does not have sufficient privileges
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to open them for capturing; if so, those devices will not appear on the
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list.)
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If
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.B pcap_findalldevs()
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succeeds, the pointer pointed to by
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.I alldevsp
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is set to point to the first element of the list, or to
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.B NULL
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if no devices were found (this is considered success).
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Each element of the list is of type
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.BR pcap_if_t ,
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and has the following members:
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.RS
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.TP
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.B next
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if not
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.BR NULL ,
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a pointer to the next element in the list;
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.B NULL
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for the last element of the list
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.TP
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.B name
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a pointer to a string giving a name for the device to pass to
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.B pcap_open_live()
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.TP
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.B description
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if not
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.BR NULL ,
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a pointer to a string giving a human-readable description of the device
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.TP
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.B addresses
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a pointer to the first element of a list of network addresses for the
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device,
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or
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.B NULL
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if the device has no addresses
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.TP
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.B flags
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device flags:
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.RS
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.TP
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.B PCAP_IF_LOOPBACK
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set if the device is a loopback interface
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.RE
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.RE
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.PP
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Each element of the list of addresses is of type
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.BR pcap_addr_t ,
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and has the following members:
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.RS
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.TP
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.B next
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if not
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.BR NULL ,
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a pointer to the next element in the list;
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.B NULL
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for the last element of the list
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.TP
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.B addr
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a pointer to a
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.B "struct sockaddr"
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containing an address
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.TP
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.B netmask
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if not
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.BR NULL ,
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a pointer to a
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.B "struct sockaddr"
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that contains the netmask corresponding to the address pointed to by
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.B addr
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.TP
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.B broadaddr
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if not
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.BR NULL ,
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a pointer to a
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.B "struct sockaddr"
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that contains the broadcast address corresponding to the address pointed
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to by
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.BR addr ;
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may be null if the device doesn't support broadcasts
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.TP
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.B dstaddr
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if not
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.BR NULL ,
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a pointer to a
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.B "struct sockaddr"
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that contains the destination address corresponding to the address pointed
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to by
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.BR addr ;
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may be null if the device isn't a point-to-point interface
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.RE
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.PP
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Note that the addresses in the list of addresses might be IPv4
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addresses, IPv6 addresses, or some other type of addresses, so you must
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check the
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.B sa_family
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member of the
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.B "struct sockaddr"
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before interpreting the contents of the address; do not assume that the
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addresses are all IPv4 addresses, or even all IPv4 or IPv6 addresses.
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IPv4 addresses have the value
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.BR AF_INET ,
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IPv6 addresses have the value
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.B AF_INET6
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(which older operating systems that don't support IPv6 might not
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define), and other addresses have other values. Whether other addresses
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are returned, and what types they might have is platform-dependent.
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For IPv4 addresses, the
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.B "struct sockaddr"
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pointer can be interpreted as if it pointed to a
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.BR "struct sockaddr_in" ;
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for IPv6 addresses, it can be interpreted as if it pointed to a
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.BR "struct sockaddr_in6".
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.PP
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The list of devices must be freed with
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.BR pcap_freealldevs() ,
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whch frees the list pointed to by
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.IR alldevs .
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.SH RETURN VALUE
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.B pcap_findalldevs()
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returns 0 on success and \-1 on failure; as indicated, finding no
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devices is considered success, rather than failure, so 0 will be
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returned in that case.
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If \-1 is returned,
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.I errbuf
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is filled in with an appropriate error message.
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.I errbuf
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is assumed to be able to hold at least
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.B PCAP_ERRBUF_SIZE
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chars.
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.SH SEE ALSO
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pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP),
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pcap_open_live(3PCAP)
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