gethostbyname

/*
 * Document-method: gethostbyname
 * call-seq: Socket.gethostbyname(host) => hostent
 *
 * Resolve +host+ and return name and address information for it, similarly to
 * gethostbyname(3). +host+ can be a domain name or the presentation format of
 * an address.
 *
 * Returns an array of information similar to that found in a +struct hostent+:
 *   - cannonical name: the cannonical name for host in the DNS, or a
 *     string representing the address
 *   - aliases: an array of aliases for the canonical name, there may be no aliases
 *   - address family: usually one of Socket::AF_INET or Socket::AF_INET6
 *   - address: a string, the binary value of the +struct sockaddr+ for this name, in
 *     the indicated address family
 *   - ...: if there are multiple addresses for this host,  a series of
 *     strings/+struct sockaddr+s may follow, not all necessarily in the same
 *     address family. Note that the fact that they may not be all in the same
 *     address family is a departure from the behaviour of gethostbyname(3).
 *
 * Note: I believe that the fact that the multiple addresses returned are not
 * necessarily in the same address family may be a bug, since if this function
 * actually called gethostbyname(3), ALL the addresses returned in the trailing
 * address list (h_addr_list from struct hostent) would be of the same address
 * family!  Examples from my system, OS X 10.3:
 *
 *   ["localhost", [], 30, "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\001", "\177\000\000\001"]
 *     and
 *   ["ensemble.local", [], 30, "\376\200\000\004\000\000\000\000\002\003\223\377\376\255\010\214", "\300\250{\232" ]
 *
 * Similar information can be returned by Socket.getaddrinfo if called as:
 *
 *    Socket.getaddrinfo(+host+, 0, Socket::AF_UNSPEC, Socket::SOCK_STREAM, nil, Socket::AI_CANONNAME)
 *
 * == Examples
 *   
 *   Socket.gethostbyname "example.com"                                                           
 *   => ["example.com", [], 2, "\300\000\"\246"]
 *   
 * This name has no DNS aliases, and a single IPv4 address.
 *   
 *   Socket.gethostbyname "smtp.telus.net"
 *   => ["smtp.svc.telus.net", ["smtp.telus.net"], 2, "\307\271\334\371"]
 *   
 * This name is an an alias so the canonical name is returned, as well as the
 * alias and a single IPv4 address.
 *   
 *   Socket.gethostbyname "localhost"
 *   => ["localhost", [], 30, "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\001", "\177\000\000\001"]
 *   
 * This machine has no aliases, returns an IPv6 address, and has an additional IPv4 address.
 *
 * +host+ can also be an IP address in presentation format, in which case a
 * reverse lookup is done on the address:
 *
 *   Socket.gethostbyname("127.0.0.1")
 *   => ["localhost", [], 2, "\177\000\000\001"]
 *
 *   Socket.gethostbyname("192.0.34.166")
 *   => ["www.example.com", [], 2, "\300\000\"\246"]
 *
 *
 * == See
 * See: Socket.getaddrinfo
 */
static VALUE
sock_s_gethostbyname(obj, host)
    VALUE obj, host;
{
    rb_secure(3);
    return make_hostent(host, sock_addrinfo(host, Qnil, SOCK_STREAM, AI_CANONNAME), sock_sockaddr);
}