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 net-
     work 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 deter-
     mine 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 inter-
     face, 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
     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