PCAP_FINDALLDEVS(3PCAP) PCAP_FINDALLDEVS(3PCAP)

NAME

pcap_findalldevs, pcap_freealldevs - get a list of capture devices,
and free that list

SYNOPSIS

#include <pcap/pcap.h>

char errbuf[PCAP_ERRBUF_SIZE];

int pcap_findalldevs(pcap_if_t **alldevsp, char *errbuf);
void pcap_freealldevs(pcap_if_t *alldevs);

DESCRIPTION

pcap_findalldevs() constructs a list of network devices that can be
opened with pcap_create(3PCAP) and pcap_activate(3PCAP) or with
pcap_open_live(3PCAP). (Note that there may be network devices that
cannot be opened by the process calling 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.) alldevsp is a pointer to a pcap_if_t *; errbuf is a buffer
large enough to hold at least PCAP_ERRBUF_SIZE chars.

If pcap_findalldevs() succeeds, the pointer pointed to by alldevsp is
set to point to the first element of the list, or to NULL if no
devices were found (this is considered success). Each element of the
list is of type pcap_if_t, and has the following members:

next if not NULL, a pointer to the next element in the list;
NULL for the last element of the list

name a pointer to a string giving a name for the device to
pass to pcap_open_live()

description
if not NULL, a pointer to a string giving a human-
readable description of the device

addresses
a pointer to the first element of a list of network
addresses for the device, or NULL if the device has no
addresses

flags device flags:

PCAP_IF_LOOPBACK
set if the device is a loopback interface

PCAP_IF_UP
set if the device is up

PCAP_IF_RUNNING
set if the device is running

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

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"

The possible values for the connection status bits are:

PCAP_IF_CONNECTION_STATUS_UNKNOWN
it's unknown whether the adapter is connected or
not

PCAP_IF_CONNECTION_STATUS_CONNECTED
the adapter is connected

PCAP_IF_CONNECTION_STATUS_DISCONNECTED
the adapter is disconnected

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

Each element of the list of addresses is of type pcap_addr_t, and has
the following members:

next if not NULL, a pointer to the next element in the list;
NULL for the last element of the list

addr a pointer to a struct sockaddr containing an address

netmask
if not NULL, a pointer to a struct sockaddr that
contains the netmask corresponding to the address
pointed to by addr

broadaddr
if not NULL, a pointer to a struct sockaddr that
contains the broadcast address corresponding to the
address pointed to by addr; may be NULL if the device
doesn't support broadcasts

dstaddr
if not NULL, a pointer to a struct sockaddr that
contains the destination address corresponding to the
address pointed to by addr; may be NULL if the device
isn't a point-to-point interface

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 sa_family member of the 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 AF_INET, IPv6 addresses have the value
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. Namely, link-layer addresses, such as Ethernet MAC
addresses, have the value AF_PACKET (on Linux) or AF_LINK (on AIX,
FreeBSD, Haiku, illumos, macOS, NetBSD and OpenBSD) or are not
returned at all (on GNU/Hurd and Solaris).

For IPv4 addresses, the struct sockaddr pointer can be interpreted as
if it pointed to a struct sockaddr_in; for IPv6 addresses, it can be
interpreted as if it pointed to a struct sockaddr_in6. For link-
layer addresses, it can be interpreted as if it pointed to a struct
sockaddr_ll (for AF_PACKET) or a struct sockaddr_dl (for AF_LINK).

The list of devices must be freed with pcap_freealldevs(3PCAP), which
frees the list pointed to by alldevs.

RETURN VALUE

pcap_findalldevs() returns 0 on success and PCAP_ERROR on failure; as
indicated, finding no devices is considered success, rather than
failure, so 0 will be returned in that case. If PCAP_ERROR is
returned, errbuf is filled in with an appropriate error message, and
the pointer pointed to by alldevsp is set to NULL.

BACKWARD COMPATIBILITY

The PCAP_IF_UP and PCAP_IF_RUNNING constants became available in
libpcap release 1.6.1. The PCAP_IF_WIRELESS,
PCAP_IF_CONNECTION_STATUS, PCAP_IF_CONNECTION_STATUS_UNKNOWN,
PCAP_IF_CONNECTION_STATUS_CONNECTED,
PCAP_IF_CONNECTION_STATUS_DISCONNECTED, and
PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE constants became available
in libpcap release 1.9.0.

SEE ALSO

pcap(3PCAP)

9 August 2024 PCAP_FINDALLDEVS(3PCAP)