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
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(), whch 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)