avformat/ftp: add log regarding passive mode failure

Signed-off-by: Lukasz Marek <lukasz.m.luki@gmail.com>

libavformat/ftp.c

@@ -270,6 +270,8 @@ static int ftp_passive_mode(FTPContext *s)
   fail:
     av_free(res);
     s->server_data_port = -1;
+    av_log(s, AV_LOG_ERROR, "Set passive mode failed\n"
+                            "Your FTP server may use IPv6 which is not supported yet.\n");
     return AVERROR(EIO);
 }
 
@@ -421,7 +423,7 @@ static int ftp_connect_control_connection(URLContext *h)
         }
 
         if ((err = ftp_type(s)) < 0) {
-            av_dlog(h, "Set content type failed\n");
+            av_log(h, AV_LOG_ERROR, "Set content type failed\n");
             return err;
         }
     }
@@ -437,10 +439,8 @@ static int ftp_connect_data_connection(URLContext *h)
 
     if (!s->conn_data) {
         /* Enter passive mode */
-        if ((err = ftp_passive_mode(s)) < 0) {
-            av_dlog(h, "Set passive mode failed\n");
+        if ((err = ftp_passive_mode(s)) < 0)
             return err;
-        }
         /* Open data connection */
         ff_url_join(buf, sizeof(buf), "tcp", NULL, s->hostname, s->server_data_port, NULL);
         if (s->rw_timeout != -1) {