pcap_findalldevs, pcap_freealldevs - get a list of capture devices, and free
that list
#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);
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.) 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. 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.
The list of devices must be freed with
pcap_freealldevs(3PCAP), which frees the list pointed to by
alldevs.
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. errbuf is
assumed to be able to hold at least PCAP_ERRBUF_SIZE chars.
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.