When CURLOPT_READDATA is specified, not only must we set CURLOPT_READFUNCTION, but we must also set CURLOPT_SEEKFUNCTION to ensure that the data can be resent if there's a redirect.
When CURLOPT_READDATA is specified, not only must we set CURLOPT_READFUNCTION, but we must also set CURLOPT_SEEKFUNCTION to ensure that the data can be resent if there's a redirect.