Custom pointer passed to ssl_ctx callback
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_DATA, void *pointer);
Data pointer to pass to the ssl context callback set by the option CURLOPT_SSL_CTX_FUNCTION(3), this is the pointer you'll get as third parameter.
All TLS based protocols: HTTPS, FTPS, IMAPS, POP3, SMTPS etc.
Added in 7.11.0. Only used with the OpenSSL backend.
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.