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 structures, as defined in the include file <ifaddrs.h>.  The ifaddrs structure contains at least the fol-
     lowing 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 indi-
     cate 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

     ioctl(2), socket(2), sysctl(3), networking(4), ifconfig(8)

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>.

BSD
								 October 12, 1995							       BSD