[SPDK] Query regarding nvme_tcp_read_data() API.

Hi,
   In the SPDKv20.07, I’ve query on the below code.

In this nvme_tcp_read_data(), if spdk_sock_recv() return “0” i.e. ret = 0, then it treats that condition as FATAL and the caller of  nvme_tcp_read_data() i.e. nvmf_tcp_sock_process(), disconnects the connection.
So, would like to know why this condition is treated as FATAL condition and disconnect is issued [as readv() can return ZERO bytes]?


static int

nvme_tcp_read_data(struct spdk_sock *sock, int bytes,

                   void *buf)

{

        int ret;



        ret = spdk_sock_recv(sock, buf, bytes);



        if (ret > 0) {

                return ret;

        }



        if (ret < 0) {

                if (errno == EAGAIN || errno == EWOULDBLOCK) {

                        return 0;

                }



                /* For connect reset issue, do not output error log */

                if (errno != ECONNRESET) {

                        SPDK_ERRLOG("spdk_sock_recv() failed, errno %d: %s\n",

                                    errno, spdk_strerror(errno));

                }

        }



        /* connection closed */

        return NVME_TCP_CONNECTION_FATAL;

}

Thanks,
Senthil Kumar V.