libssh2_session_abstract man page
libssh2_session_abstract — return a pointer to a session's abstract pointer
void ** libssh2_session_abstract(LIBSSH2_SESSION *session);
session - Session instance as returned by libssh2_session_init_ex(3)
Return a pointer to where the abstract pointer provided to libssh2_session_init_ex(3) is stored. By providing a doubly de-referenced pointer, the internal storage of the session instance may be modified in place.
A pointer to session internal storage who's contents point to previously provided abstract data.