| GETIFADDRS(3) | Library Functions Manual | GETIFADDRS(3) |
getifaddrs, freeifaddrs —
#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
int
getifaddrs(struct
ifaddrs **ifap);
void
freeifaddrs(struct
ifaddrs *ifp);
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.
#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;
}
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).
getifaddrs implementation first appeared in
BSD/OS.
ifa_addrflags was added in
NetBSD 8.0.
<net/if.h> and
<ifaddrs.h> are being
included, <net/if.h>
must be included before
<ifaddrs.h>.
| September 15, 2016 | NetBSD 9.3 |