// SPDX-License-Identifier: GPL-2.0-or-later
/* Copyright Red Hat
 * Author: Laurent Vivier <lvivier@redhat.com>
 *
 * common_vu.c - vhost-user common UDP and TCP functions
 */

#include <unistd.h>
#include <sys/uio.h>
#include <sys/eventfd.h>
#include <linux/virtio_net.h>

#include "util.h"
#include "passt.h"
#include "tap.h"
#include "vhost_user.h"
#include "pcap.h"
#include "vu_common.h"

/**
 * vu_init_elem() - initialize an array of virtqueue element with 1 iov in each
 * @elem:	Array of virtqueue element to initialize
 * @iov:	Array of iovec to assign to virtqueue element
 * @elem_cnt:	Number of virtqueue element
 */
void vu_init_elem(struct vu_virtq_element *elem, struct iovec *iov, int elem_cnt)
{
	int i;

	for (i = 0; i < elem_cnt; i++) {
		elem[i].out_num = 0;
		elem[i].out_sg = NULL;
		elem[i].in_num = 1;
		elem[i].in_sg = &iov[i];
	}
}

/**
 * vu_collect_one_frame() - collect virtio buffers from a given virtqueue for
 *			    one frame
 * @vdev:		vhost-user device
 * @vq:			virtqueue to collect from
 * @elem:		Array of virtqueue element
 * 			each element must be initialized with one iovec entry
 * 			in the in_sg array.
 * @max_elem:		Number of virtqueue element in the array
 * @size:		Maximum size of the data in the frame
 * @hdrlen:		Size of the frame header
 */
int vu_collect_one_frame(struct vu_dev *vdev, struct vu_virtq *vq,
			 struct vu_virtq_element *elem, int max_elem,
			 size_t size, size_t hdrlen)
{
	return vu_collect(vdev, vq, elem, max_elem, size, hdrlen, size);
}

/**
 * vu_collect() - collect virtio buffers from a given virtqueue
 * @vdev:		vhost-user device
 * @vq:			virtqueue to collect from
 * @elem:		Array of virtqueue element
 * 			each element must be initialized with one iovec entry
 * 			in the in_sg array.
 * @max_elem:		Number of virtqueue element in the array
 * @max_frame_size:	Maximum size of the data in the frame
 * @hdrlen:		Size of the frame header
 * @size:		Total size of the buffers we need to collect
 * 			(if size > max_frame_size, we collect several frame)
 */
int vu_collect(struct vu_dev *vdev, struct vu_virtq *vq,
	       struct vu_virtq_element *elem, int max_elem,
	       size_t max_frame_size, size_t hdrlen, size_t size)
{
	size_t frame_size = 0;
	int elem_cnt = 0;

	/* header is at least virtio_net_hdr_mrg_rxbuf */
	hdrlen += sizeof(struct virtio_net_hdr_mrg_rxbuf);

	while (size > 0 && elem_cnt < max_elem) {
		struct iovec *iov;
		int ret;

		ret = vu_queue_pop(vdev, vq, &elem[elem_cnt]);
		if (ret < 0)
			break;

		if (elem[elem_cnt].in_num < 1) {
			warn("virtio-net receive queue contains no in buffers");
			vu_queue_detach_element(vq);
			break;
		}

		iov = &elem[elem_cnt].in_sg[0];

		ASSERT(iov->iov_len >= hdrlen);

		if (frame_size == 0) {
			/* this is the iovec that will contain frame headers */
			iov->iov_base = (char *)iov->iov_base + hdrlen;
			iov->iov_len -= hdrlen;
		}

		if (iov->iov_len > size)
			iov->iov_len = size;

		frame_size += iov->iov_len;

		if (frame_size >= max_frame_size) {
			/* if the frame size is greater than maximum size
			 * we need to start a new frame
			 */
			iov->iov_len -= frame_size - max_frame_size;
			frame_size = 0;
		} else if (!vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) {
			/* if we don't have feature F_MRG_RXBUF,
			 * the frame cannot be spread over several
			 * virtqueue element
			 */
			frame_size = 0;
		}

		size -= iov->iov_len;
		elem_cnt++;
	}

	return elem_cnt;
}

/**
 * vu_set_vnethdr() - set virtio-net headers in a given iovec
 * @vdev:		vhost-user device
 * @iov:		One iovec to initialize
 * @num_buffers:	Number of guest buffers of the frame
 * @hdrlen:		Size of the frame header
 */
void vu_set_vnethdr(const struct vu_dev *vdev, struct iovec *iov,
		    int num_buffers, size_t hdrlen)
{
	struct virtio_net_hdr_mrg_rxbuf *vnethdr;

	/* header is at least virtio_net_hdr_mrg_rxbuf */
	hdrlen += sizeof(struct virtio_net_hdr_mrg_rxbuf);

	/* NOLINTNEXTLINE(clang-analyzer-core.UndefinedBinaryOperatorResult) */
	iov->iov_base = (char *)iov->iov_base - hdrlen;
	iov->iov_len += hdrlen;

	vnethdr = iov->iov_base;
	vnethdr->hdr = VU_HEADER;
	if (vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
		vnethdr->num_buffers = htole16(num_buffers);
}

/**
 * vu_flush() - flush all the collected buffers to the vhost-user interface
 * @vdev:	vhost-user device
 * @vq:		vhost-user virtqueue
 * @elem:	virtqueue element array to send back to the virqueue
 * @iov_used:	Length of the array
 */
void vu_flush(const struct vu_dev *vdev, struct vu_virtq *vq,
	      struct vu_virtq_element *elem, int elem_cnt)
{
	int i;

	for (i = 0; i < elem_cnt; i++)
		vu_queue_fill(vq, &elem[i], elem[i].in_sg[0].iov_len, i);

	vu_queue_flush(vq, elem_cnt);
	vu_queue_notify(vdev, vq);
}

/**
 * vu_handle_tx() - Receive data from the TX virtqueue
 * @vdev:	vhost-user device
 * @index:	index of the virtqueue
 * @now:	Current timestamp
 */
static void vu_handle_tx(struct vu_dev *vdev, int index,
			 const struct timespec *now)
{
	struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE];
	struct iovec out_sg[VIRTQUEUE_MAX_SIZE];
	struct vu_virtq *vq = &vdev->vq[index];
	int hdrlen = sizeof(struct virtio_net_hdr_mrg_rxbuf);
	int out_sg_count;
	int count;

	if (!VHOST_USER_IS_QUEUE_TX(index)) {
		debug("vhost-user: index %d is not a TX queue", index);
		return;
	}

	tap_flush_pools();

	count = 0;
	out_sg_count = 0;
	while (count < VIRTQUEUE_MAX_SIZE) {
		int ret;

		elem[count].out_num = 1;
		elem[count].out_sg = &out_sg[out_sg_count];
		elem[count].in_num = 0;
		elem[count].in_sg = NULL;
		ret = vu_queue_pop(vdev, vq, &elem[count]);
		if (ret < 0)
			break;
		out_sg_count += elem[count].out_num;

		if (elem[count].out_num < 1) {
			debug("virtio-net header not in first element");
			break;
		}
		ASSERT(elem[count].out_num == 1);

		tap_add_packet(vdev->context,
			       elem[count].out_sg[0].iov_len - hdrlen,
			       (char *)elem[count].out_sg[0].iov_base + hdrlen);
		count++;
	}
	tap_handler(vdev->context, now);

	if (count) {
		int i;

		for (i = 0; i < count; i++)
			vu_queue_fill(vq, &elem[i], 0, i);
		vu_queue_flush(vq, count);
		vu_queue_notify(vdev, vq);
	}
}

/**
 * vu_kick_cb() - Called on a kick event to start to receive data
 * @vdev:	vhost-user device
 * @ref:	epoll reference information
 * @now:	Current timestamp
 */
void vu_kick_cb(struct vu_dev *vdev, union epoll_ref ref,
		const struct timespec *now)
{
	eventfd_t kick_data;
	ssize_t rc;
	int idx;

	for (idx = 0; idx < VHOST_USER_MAX_QUEUES; idx++) {
		if (vdev->vq[idx].kick_fd == ref.fd)
			break;
	}

	if (idx == VHOST_USER_MAX_QUEUES)
		return;

	rc = eventfd_read(ref.fd, &kick_data);
	if (rc == -1)
		die_perror("vhost-user kick eventfd_read()");

	debug("vhost-user: ot kick_data: %016"PRIx64" idx:%d",
	      kick_data, idx);
	if (VHOST_USER_IS_QUEUE_TX(idx))
		vu_handle_tx(vdev, idx, now);
}

/**
 * vu_send_single() - Send a buffer to the front-end using the RX virtqueue
 * @c:		execution context
 * @buf:	address of the buffer
 * @size:	size of the buffer
 *
 * Return: number of bytes sent, -1 if there is an error
 */
int vu_send_single(const struct ctx *c, const void *buf, size_t size)
{
	struct vu_dev *vdev = c->vdev;
	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
	struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE];
	struct iovec in_sg[VIRTQUEUE_MAX_SIZE];
	size_t total;
	int elem_cnt, max_elem;
	int i;

	debug("vu_send_single size %zu", size);

	if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) {
		err("Got packet, but no available descriptors on RX virtq.");
		return 0;
	}

	if (vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
		max_elem = VIRTQUEUE_MAX_SIZE;
	else
		max_elem = 1;

	vu_init_elem(elem, in_sg, max_elem);

	elem_cnt = vu_collect_one_frame(vdev, vq, elem, max_elem, size,
					0);
	total = iov_size(in_sg, elem_cnt);
	if (total < size) {
		debug("vu_send_single: no space to send the data "
		      "elem_cnt %d iov_size %zd", elem_cnt, total);
		goto err;
	}

	vu_set_vnethdr(vdev, in_sg, elem_cnt, 0);

	/* copy data from the buffer to the iovec */
	iov_from_buf(in_sg, elem_cnt, sizeof(struct virtio_net_hdr_mrg_rxbuf),
		     buf, size);

	if (*c->pcap) {
		pcap_iov(in_sg, elem_cnt,
			 sizeof(struct virtio_net_hdr_mrg_rxbuf));
	}

	vu_flush(vdev, vq, elem, elem_cnt);

	debug("vhost-user sent %zu", total);

	return total;
err:
	for (i = 0; i < elem_cnt; i++)
		vu_queue_detach_element(vq);

	return 0;
}