- Phil Blundell added the CURLOPT_SCOPE option, as well as adjusted the URL

parser to allow numerical IPv6-addresses to be specified with the scope
  given, as per RFC4007 - with a percent letter that itself needs to be URL
  escaped. For example, for an address of fe80::1234%1 the HTTP URL is:
  "http://[fe80::1234%251]/"

lib/connect.c

@@ -773,6 +773,13 @@ singleipconnect(struct connectdata *conn,
 
   *connected = FALSE; /* default is not connected */
 
+#ifdef CURLRES_IPV6
+  if (conn->scope && (addr->family == AF_INET6)) {
+    struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)&addr->addr;
+    in6->sin6_scope_id = conn->scope;
+  }
+#endif
+
   /* FIXME: do we have Curl_printable_address-like with struct sockaddr* as
      argument? */
 #if defined(HAVE_SYS_UN_H) && defined(AF_UNIX)

lib/url.c

@@ -2091,6 +2091,15 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
     }
     break;
 
+  case CURLOPT_ADDRESS_SCOPE:
+    /*
+     * We always get longs when passed plain numericals, but for this value we
+     * know that an unsigned int will always hold the value so we blindly
+     * typecast to this type
+     */
+    data->set.scope = (unsigned int) va_arg(param, long);
+    break;
+
   default:
     /* unknown tag and its companion, just ignore: */
     result = CURLE_FAILED_INIT; /* correct this */
@@ -3080,6 +3089,24 @@ static CURLcode ParseURLAndFillConnection(struct SessionHandle *data,
     path[0] = '/';
   }
 
+  if (conn->host.name[0] == '[' && !data->state.this_is_a_follow) {
+    /* This looks like an IPv6 address literal.  See if there is an address
+       scope.  */
+    char *percent = strstr (conn->host.name, "%25");
+    if (percent) {
+      char *endp;
+      conn->scope = strtoul (percent + 3, &endp, 10);
+      if (*endp == ']') {
+        /* The address scope was well formed.  Knock it out of the hostname.  */
+        strcpy (percent, "]");
+      }
+    }
+  }
+
+  if (data->set.scope)
+    /* Override any scope that was set above.  */
+    conn->scope = data->set.scope;
+
   /*
    * So if the URL was A://B/C,
    *   conn->protostr is A

lib/urldata.h

@@ -903,6 +903,8 @@ struct connectdata {
      set. */
   char *ip_addr_str;
 
+  unsigned int scope;    /* address scope for IPv6 */
+
   char protostr[16];  /* store the protocol string in this buffer */
   int socktype;  /* SOCK_STREAM or SOCK_DGRAM */
 
@@ -1478,6 +1480,7 @@ struct UserDefined {
   bool proxy_transfer_mode; /* set transfer mode (;type=<a|i>) when doing FTP
                                via an HTTP proxy */
   char *str[STRING_LAST]; /* array of strings, pointing to allocated memory */
+  unsigned int scope;    /* address scope for IPv6 */
 };
 
 struct Names {