er_perform(OSSL_CMP_CTX *client_ctx,
                                           const OSSL_CMP_MSG *req);
 OSSL_CMP_SRV_CTX *OSSL_CMP_SRV_CTX_new(OSSL_LIB_CTX *libctx, const char *propq);
 void OSSL_CMP_SRV_CTX_free(OSSL_CMP_SRV_CTX *srv_ctx);

 typedef OSSL_CMP_PKISI *(*OSSL_CMP_SRV_cert_request_cb_t)(
                                                 OSSL_CMP_SRV_CTX *srv_ctx,
                                                 const OSSL_CMP_MSG *req,
                                                 int cert