CURLOPT_FTP_SKIP_PASV_IP (3) - Linux Man Pages
CURLOPT_FTP_SKIP_PASV_IP: ignore the IP address in the PASV response
NAMECURLOPT_FTP_SKIP_PASV_IP - ignore the IP address in the PASV response
DESCRIPTIONPass a long. If skip is set to 1, it instructs libcurl to not use the IP address the server suggests in its 227-response to libcurl's PASV command when libcurl connects the data connection. Instead libcurl will re-use the same IP address it already uses for the control connection. But it will use the port number from the 227-response.
This option thus allows libcurl to work around broken server installations that due to NATs, firewalls or incompetence report the wrong IP address back.