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 */
u_int ifa_flags; /* Interface flags */
struct sockaddr *ifa_addr; /* Interface address */
struct sockaddr *ifa_netmask; /* Interface netmask */
struct sockaddr *ifa_dstaddr; /* P2P interface destination */
void *ifa_data; /* Address specific data */
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_dstaddr field references the
destination address on a P2P interface, if one exists, otherwise it contains
the broadcast address.
Note that as a convenience, ifa_broadaddr
is defined by a compiler #define directive to be the
same as ifa_dstaddr.
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 contains a pointer to the struct
ifa_data (as defined in include file
<net/if.h>) which contains
per-address interface statistics.
The data returned by
getifaddrs()
is dynamically allocated and should be freed using
freeifaddrs()
when no longer needed.
RETURN VALUES
The getifaddrs() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno is set to indicate the
error.
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
HISTORY
The getifaddrs implementation first
appeared in BSDi BSD/OS.
BUGS
If both <net/if.h>
and <ifaddrs.h> are being
included, <net/if.h>
must be
included before
<ifaddrs.h>.