GETIFADDRS(3)             OpenBSD Programmer's 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 *ifap);

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 en-
     tries:

         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 */

     ifa_next
             Contains a pointer to the next structure on the list.  This field
             is set to NULL in last structure on the list.

     ifa_name
             Contains the interface name.

     ifa_flags
             Contains the interface flags, as set by ifconfig(8).

     ifa_addr
             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.)

     ifa_netmask
             References the netmask associated with ifa_addr, if one is set,
             otherwise it is NULL.

     ifa_broadaddr
             This field, which should only be referenced for non-P2P inter-
             faces, references the broadcast address associated with ifa_addr,
             if one exists, otherwise it is NULL.

     ifa_dstaddr
             References the destination address on a P2P interface, if one ex-
             ists, otherwise it is NULL.

     ifa_data
             References address family specific data.  For AF_LINK addresses
             it contains a pointer to the struct if_data (as defined in in-
             clude file <net/if.h>) which contains various interface at-
             tributes and statistics.  For all other address families, it con-
             tains 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
     Upon successful completion, a value of 0 is returned.  Otherwise, a value
     of -1 is returned and 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() function first appeared in BSDI BSD/OS.  The function is
     supplied on OpenBSD since OpenBSD 2.7.

BUGS
     If both <net/if.h> and <ifaddrs.h> are being included, <net/if.h> must be
     included before <ifaddrs.h>.

OpenBSD 3.5                    October 12, 1995                              2
