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.TH PCAP_FINDALLDEVS 3PCAP "22 August 2018"

.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(3PCAP)

and

.B pcap_activate(3PCAP)

or with

.BR pcap_open_live(3PCAP) .

(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

.TP

.B PCAP_IF_UP

set if the device is up

.TP

.B PCAP_IF_RUNNING

set if the device is running

.TP

.B PCAP_IF_WIRELESS

set if the device is a wireless interface; this includes IrDA as well as

radio-based networks such as IEEE 802.15.4 and IEEE 802.11, so it

doesn't just mean Wi-Fi

.TP

.B PCAP_IF_CONNECTION_STATUS

a bitmask for an indication of whether the adapter is connected or not;

for wireless interfaces, "connected" means "associated with a network"

.TP

The possible values for the connection status bits are:

.TP

.B PCAP_IF_CONNECTION_STATUS_UNKNOWN

it's unknown whether the adapter is connected or not

.TP

.B PCAP_IF_CONNECTION_STATUS_CONNECTED

the adapter is connected

.TP

.B PCAP_IF_CONNECTION_STATUS_DISCONNECTED

the adapter is disconnected

.TP

.B PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE

the notion of "connected" and "disconnected" don't apply to this

interface; for example, it doesn't apply to a loopback device

.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(3PCAP) ,

which frees the list pointed to by

.IR alldevs .

.SH RETURN VALUE

.B pcap_findalldevs()

returns 0 on success and

.B PCAP_ERROR

on failure; as indicated, finding no

devices is considered success, rather than failure, so 0 will be

returned in that case. If

.B PCAP_ERROR

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 BACKWARD COMPATIBILITY

.PP

The

.B PCAP_IF_UP

and

.B PCAP_IF_RUNNING

constants became available in libpcap release 1.6.1.  The

.BR PCAP_IF_WIRELESS ,

.BR PCAP_IF_CONNECTION_STATUS ,

.BR PCAP_IF_CONNECTION_STATUS_UNKNOWN ,

.BR PCAP_IF_CONNECTION_STATUS_CONNECTED ,

.BR PCAP_IF_CONNECTION_STATUS_DISCONNECTED ,

and

.B PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE

constants became available in libpcap release 1.9.0.

.SH SEE ALSO

pcap(3PCAP)