PCAP_FINDALLDEVS(3) FreeBSD Library Functions Manual PCAP_FINDALLDEVS(3)
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(3) and pcap_activate(3) or with
pcap_open_live(3). (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(3), 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(3)
9 August 2024 PCAP_FINDALLDEVS(3)