Based on further discussion on curl-library, I reverted yesterday's SOCKS5

code to instead introduce support for a new proxy type called
CURLPROXY_SOCKS5_HOSTNAME that is used to send the host name to the proxy
instead of IP address and there's thus no longer any need for a new
curl_easy_setopt() option.

The default SOCKS5 proxy is again back to sending the IP address to the
proxy.  The new curl command line option for enabling sending host name to a
SOCKS5 proxy is now --socks5-hostname.

lib/socks.c

@@ -390,7 +390,7 @@ CURLcode Curl_SOCKS5(const char *proxy_name,
   curl_socket_t sock = conn->sock[sockindex];
   struct SessionHandle *data = conn->data;
   long timeout;
-  bool socks5_resolve_local = data->set.socks5_resolve_local;
+  bool socks5_resolve_local = data->set.proxytype == CURLPROXY_SOCKS5;
   const size_t hostname_len = strlen(hostname);
   int packetsize = 0;
 

lib/url.c

@@ -2054,14 +2054,6 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
     }
     break;
 
-  case CURLOPT_SOCKS5_RESOLVE_LOCAL:
-    /*
-     * Enable or disable using of SOCKS5 proxy server to resolve domain names
-     * instead of using platform API like gethostbyname_r etc
-     */
-    data->set.socks5_resolve_local = (bool)(0 != va_arg(param, long));
-    break;
-
   default:
     /* unknown tag and its companion, just ignore: */
     result = CURLE_FAILED_INIT; /* correct this */

lib/urldata.h

@@ -1441,9 +1441,6 @@ struct UserDefined {
   long new_directory_perms; /* Permissions to use when creating remote dirs */
   bool proxy_transfer_mode; /* set transfer mode (;type=<a|i>) when doing FTP
                                via an HTTP proxy */
-  bool socks5_resolve_local; /* resolve host names locally even if a SOCKS5
-                                proxy in use.  Valid only if CURLOPT_PROXYTYPE
-                                == CURLPROXY_SOCKS5, otherwise ignored. */
   char *str[STRING_LAST]; /* array of strings, pointing to allocated memory */
 };