bionic (3) pcap_findalldevs.3pcap.gz
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() and
pcap_activate() or with pcap_open_live(). (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
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(), which frees the list pointed to by alldevs.
RETURN VALUE
pcap_findalldevs() returns 0 on success and -1 on failure; as indicated, finding no devices is considered
success, rather than failure, so 0 will be returned in that case. If -1 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.
SEE ALSO
pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP), pcap_open_live(3PCAP) 7 April 2014 PCAP_FINDALLDEVS(3PCAP)