Function read_fd_message

dpdk/lib/vhost/socket.c:107–160

* return bytes# of read on success or negative val on failure. Update fdnum * with number of fds read. */

 * with number of fds read.
 */
int
read_fd_message(char *ifname, int sockfd, char *buf, int buflen, int *fds, int max_fds,
		int *fd_num)
{
	struct iovec iov;
	struct msghdr msgh;
	char control[CMSG_SPACE(max_fds * sizeof(int))];
	struct cmsghdr *cmsg;
	int got_fds = 0;
	int ret;

	*fd_num = 0;

	memset(&msgh, 0, sizeof(msgh));
	iov.iov_base = buf;
	iov.iov_len  = buflen;

	msgh.msg_iov = &iov;
	msgh.msg_iovlen = 1;
	msgh.msg_control = control;
	msgh.msg_controllen = sizeof(control);

	ret = recvmsg(sockfd, &msgh, 0);
	if (ret <= 0) {
		if (ret)
			VHOST_LOG_CONFIG(ifname, ERR, "recvmsg failed on fd %d (%s)\n",
				sockfd, strerror(errno));
		return ret;
	}

	if (msgh.msg_flags & MSG_TRUNC)
		VHOST_LOG_CONFIG(ifname, ERR, "truncated msg (fd %d)\n", sockfd);

	/* MSG_CTRUNC may be caused by LSM misconfiguration */
	if (msgh.msg_flags & MSG_CTRUNC)
		VHOST_LOG_CONFIG(ifname, ERR, "truncated control data (fd %d)\n", sockfd);

	for (cmsg = CMSG_FIRSTHDR(&msgh); cmsg != NULL;
		cmsg = CMSG_NXTHDR(&msgh, cmsg)) {
		if ((cmsg->cmsg_level == SOL_SOCKET) &&
			(cmsg->cmsg_type == SCM_RIGHTS)) {
			got_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
			*fd_num = got_fds;
			memcpy(fds, CMSG_DATA(cmsg), got_fds * sizeof(int));
			break;
		}
	}

	/* Clear out unused file descriptors */
	while (got_fds < max_fds)
		fds[got_fds++] = -1;

	return ret;
}

int
send_fd_message(char *ifname, int sockfd, char *buf, int buflen, int *fds, int fd_num)