SIOCGIFVERSION (determine if an IPv4 or IPv6 interface has been configured on a TCP/IP stack)

SIOCGIFVERSION determines if a TCP/IP stack in an INET environment has a configured IPv6 or IPv4 source address. (In this case, the loopback address is not considered to be valid as a configured interface.) This information is needed so that appropriate DNS queries can be made (IPv6 address records (AAAA) vs. IPv4 address records (AA)).

Argument: A four-byte area containing flags that provide the following information:

DCL 1 IfVersionInfo Based,        /* SIOCGIFVERSION structure      */
       2 IfVerFlags Bit(16),       /* Stack flags                   */
         3 IfVerIPv6Interfaces Bit(1), /* Are there any IPv6          
                                      interfaces active other than    
                                      loopback                      */
         3 IfVerIPv4Interfaces Bit(1), /* Are there any IPv4          
                                      interfaces active other than    
                                      loopback                      */
         3 IfVerIPv6Supported  Bit(1), /* Is IPv6 supported by this   
                                      stack                         */
         3 *                   Bit(13), /* Available                */
       2 *          Char(2);       /* Available                     */