网络仿真设备

Network Block Device, nbd.c in Linux kernel source.

Written by Pavel Machek, pavel@ucw.cz

完整程序的路径：/usr/src/linux/driver/block/nbd.c

程序段节选：

/*
 *  Send or receive packet.
 */
static int nbd_xmit(int send, int sockfd, char *buf, int size)
{
        int result;
        struct msghdr msg;
        struct iovec iov;
        unsigned long flags;
        sigset_t oldset;

        do {
                iov.iov_base = buf;
                iov.iov_len = size;
                msg.msg_name = NULL;
                msg.msg_namelen = 0;
                msg.msg_iov = &iov;
                msg.msg_iovlen = 1;
                msg.msg_control = NULL;
                msg.msg_controllen = 0;
                msg.msg_namelen = 0;
                msg.msg_flags = 0;

                if (send)
                        result = sendmsg(sockfd, &msg, 0);
                else
                        result = recvmsg(sockfd, &msg, 0);

                           if (result <= 0) break;
                size -= result;
                buf += result;
        } while (size > 0);

        return result;
}