build_request
int (*build_request)(struct ceph_auth_client *ac, void *buf, void *end);
ret = ac->ops->build_request(ac, p + sizeof(u32), end);
ret = build_request(ac, true, reply_buf, reply_len);
ret = build_request(ac, true, msg_buf, msg_len);
ret = build_request(ac, false, buf, buf_len);
.build_request = build_request,
.build_request = ceph_x_build_request,
build_request(req, argv[1]);