NAME
getifaddrs —
get interface
addresses
SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
int
getifaddrs(
struct
ifaddrs **ifap);
void
freeifaddrs(
struct
ifaddrs *ifp);
DESCRIPTION
The
getifaddrs() function stores a reference to a linked list
of the network interfaces on the local machine in the memory referenced by
ifap. The list consists of
ifaddrs
structures, as defined in the include file
<ifaddrs.h>. The
ifaddrs structure contains at least the following entries:
struct ifaddrs *ifa_next; /* Pointer to next struct */
char *ifa_name; /* Interface name */
unsigned int ifa_flags; /* Interface flags */
struct sockaddr *ifa_addr; /* Interface address */
struct sockaddr *ifa_netmask; /* Interface netmask */
struct sockaddr *ifa_broadaddr; /* Interface broadcast address */
struct sockaddr *ifa_dstaddr; /* P2P interface destination */
void *ifa_data; /* Address specific data */
unsigned int ifa_addrflags; /* Address flags */
The
ifa_next
field contains a pointer to the next
structure on the list. This field is
NULL
in last
structure on the list.
The
ifa_name
field contains the interface name.
The
ifa_flags
field contains the interface flags, as set
by
ifconfig(8) utility.
The
ifa_addr
field references either the address of the
interface or the link level address of the interface, if one exists, otherwise
it is
NULL
. (The
sa_family
field of the
ifa_addr
field should be consulted to
determine the format of the
ifa_addr
address.)
The
ifa_netmask
field references the netmask associated
with
ifa_addr
, if one is set, otherwise it is
NULL
.
The
ifa_broadaddr
field, which should only be referenced
for non-P2P interfaces, references the broadcast address associated with
ifa_addr
, if one exists, otherwise it is
NULL
.
The
ifa_dstaddr
field references the destination address
on a P2P interface, if one exists, otherwise it is
NULL
.
The
ifa_data
field references address family specific
data. For
AF_LINK
addresses it contains a pointer to
the
struct if_data (as defined in include file
⟨
net/if.h⟩) which contains various interface
attributes and statistics. For all other address families, it is
NULL
.
The
ifa_addrflags
field contains the address flags,
which are specific to the address family.
The data returned by
getifaddrs() is dynamically allocated and
should be freed using
freeifaddrs() when no longer needed.
RETURN VALUES
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1
is returned and
errno is set to indicate the error.
EXAMPLES
The following example program prints a list of all addresses configured on the
system.
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <ifaddrs.h>
#include <util.h>
#include <err.h>
#include <stdlib.h>
int
main(int argc, char *argv[])
{
struct ifaddrs *ifa, *a;
if (getifaddrs(&ifa) == -1)
err(EXIT_FAILURE, "getifaddrs");
for (a = ifa; a; a = a->ifa_next) {
char buf[1024];
sockaddr_snprintf(buf, sizeof(buf), "%f %a",
a->ifa_addr);
printf("%s %x %s\n", a->ifa_name, a->ifa_flags, buf);
}
freeifaddrs(ifa);
return EXIT_SUCCESS;
}
ERRORS
The
getifaddrs() may fail and set
errno
for any of the errors specified for the library routines
ioctl(2),
socket(2),
malloc(3) or
sysctl(3).
SEE ALSO
ioctl(2),
socket(2),
sysctl(3),
networking(4),
ifconfig(8)
HISTORY
The
getifaddrs implementation first appeared in
BSD/OS.
ifa_addrflags
was added in
NetBSD
8.0.
BUGS
If both
<net/if.h> and
<ifaddrs.h> are being included,
<net/if.h> must be
included before
<ifaddrs.h>.