Man pages matching name curlinfo_content_length_upload in section 3:

CURLINFO_CONTENT_LENGTH_UPLOAD.3.en	debian 10 / libcurl4-doc
CURLINFO_CONTENT_LENGTH_UPLOAD.3.en	debian 11 / libcurl4-doc
CURLINFO_CONTENT_LENGTH_UPLOAD.3.en	debian 12 / libcurl4-doc