ossl_dh_new_by_nid_ex
dh = ossl_dh_new_by_nid_ex(libctx, nid);
return ossl_dh_new_by_nid_ex(NULL, nid);
DH *ossl_dh_new_by_nid_ex(OSSL_LIB_CTX *libctx, int nid);
dh = ossl_dh_new_by_nid_ex(gctx->libctx, gctx->group_nid);