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GETIFADDRS(3) BSD Library Functions Manual GETIFADDRS(3)
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 struc-
tures, 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_broadaddr; /* Interface broadcast address */
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, other-
wise 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 con-
tains 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 re-
turned 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 rou-
tines ioctl(2), socket(2), malloc(3) or sysctl(3).
BUGS
If both <net/if.h> and <ifaddrs.h> are being included, <net/if.h> must be included before
<ifaddrs.h>.
SEE ALSO
ioctl(2), socket(2), sysctl(3), networking(4), ifconfig(8)
HISTORY
The getifaddrs implementation first appeared in BSDi BSD/OS.
BSD October 12, 1995 BSD
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