I found some info in httpd.c that has call to httpd_post_receive_data()
/** Pass received POST body data to the application and correctly handle
* returning a response document or closing the connection.
* ATTENTION: The application is responsible for the pbuf now, so don't free it!
*
* @param hs http connection state
* @param p pbuf to pass to the application
* @return ERR_OK if passed successfully, another err_t if the response file
* hasn't been found (after POST finished)
*/
static err_t
http_post_rxpbuf(struct http_state *hs, struct pbuf *p)
I guess, now I have to find out how to free pbuf.