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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 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).

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