/*
 * Network-device interface management.
 *
 * Copyright (c) 2004-2005, Keir Fraser
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "common.h"

#include <linux/kthread.h>
#include <linux/ethtool.h>
#include <linux/rtnetlink.h>
#include <linux/if_vlan.h>
#include <linux/vmalloc.h>

#include <xen/events.h>
#include <asm/xen/hypercall.h>
#include <xen/balloon.h>

#define XENVIF_QUEUE_LENGTH 32
#define XENVIF_NAPI_WEIGHT  64

int xenvif_schedulable(struct xenvif *vif)
{
	return netif_running(vif->dev) && netif_carrier_ok(vif->dev);
}

static irqreturn_t xenvif_tx_interrupt(int irq, void *dev_id)
{
	struct xenvif *vif = dev_id;

	if (RING_HAS_UNCONSUMED_REQUESTS(&vif->tx))
		napi_schedule(&vif->napi);

	return IRQ_HANDLED;
}

static int xenvif_poll(struct napi_struct *napi, int budget)
{
	struct xenvif *vif = container_of(napi, struct xenvif, napi);
	int work_done;

	/* This vif is rogue, we pretend we've there is nothing to do
	 * for this vif to deschedule it from NAPI. But this interface
	 * will be turned off in thread context later.
	 */
	if (unlikely(vif->disabled)) {
		napi_complete(napi);
		return 0;
	}

	work_done = xenvif_tx_action(vif, budget);

	if (work_done < budget) {
		int more_to_do = 0;
		unsigned long flags;

		/* It is necessary to disable IRQ before calling
		 * RING_HAS_UNCONSUMED_REQUESTS. Otherwise we might
		 * lose event from the frontend.
		 *
		 * Consider:
		 *   RING_HAS_UNCONSUMED_REQUESTS
		 *   <frontend generates event to trigger napi_schedule>
		 *   __napi_complete
		 *
		 * This handler is still in scheduled state so the
		 * event has no effect at all. After __napi_complete
		 * this handler is descheduled and cannot get
		 * scheduled again. We lose event in this case and the ring
		 * will be completely stalled.
		 */

		local_irq_save(flags);

		RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, more_to_do);
		if (!more_to_do)
			__napi_complete(napi);

		local_irq_restore(flags);
	}

	return work_done;
}

static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
{
	struct xenvif *vif = dev_id;

	xenvif_kick_thread(vif);

	return IRQ_HANDLED;
}

static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
{
	xenvif_tx_interrupt(irq, dev_id);
	xenvif_rx_interrupt(irq, dev_id);

	return IRQ_HANDLED;
}

static void xenvif_wake_queue(unsigned long data)
{
	struct xenvif *vif = (struct xenvif *)data;

	if (netif_queue_stopped(vif->dev)) {
		netdev_err(vif->dev, "draining TX queue\n");
		vif->rx_queue_purge = true;
		xenvif_kick_thread(vif);
		netif_wake_queue(vif->dev);
	}
}

static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct xenvif *vif = netdev_priv(dev);
	int min_slots_needed;

	BUG_ON(skb->dev != dev);

	/* Drop the packet if vif is not ready */
	if (vif->task == NULL ||
	    vif->dealloc_task == NULL ||
	    !xenvif_schedulable(vif))
		goto drop;

	/* At best we'll need one slot for the header and one for each
	 * frag.
	 */
	min_slots_needed = 1 + skb_shinfo(skb)->nr_frags;

	/* If the skb is GSO then we'll also need an extra slot for the
	 * metadata.
	 */
	if (skb_is_gso(skb))
		min_slots_needed++;

	/* If the skb can't possibly fit in the remaining slots
	 * then turn off the queue to give the ring a chance to
	 * drain.
	 */
	if (!xenvif_rx_ring_slots_available(vif, min_slots_needed)) {
		vif->wake_queue.function = xenvif_wake_queue;
		vif->wake_queue.data = (unsigned long)vif;
		xenvif_stop_queue(vif);
		mod_timer(&vif->wake_queue,
			jiffies + rx_drain_timeout_jiffies);
	}

	skb_queue_tail(&vif->rx_queue, skb);
	xenvif_kick_thread(vif);

	return NETDEV_TX_OK;

 drop:
	vif->dev->stats.tx_dropped++;
	dev_kfree_skb(skb);
	return NETDEV_TX_OK;
}

static struct net_device_stats *xenvif_get_stats(struct net_device *dev)
{
	struct xenvif *vif = netdev_priv(dev);
	return &vif->dev->stats;
}

static void xenvif_up(struct xenvif *vif)
{
	napi_enable(&vif->napi);
	enable_irq(vif->tx_irq);
	if (vif->tx_irq != vif->rx_irq)
		enable_irq(vif->rx_irq);
	xenvif_check_rx_xenvif(vif);
}

static void xenvif_down(struct xenvif *vif)
{
	napi_disable(&vif->napi);
	disable_irq(vif->tx_irq);
	if (vif->tx_irq != vif->rx_irq)
		disable_irq(vif->rx_irq);
	del_timer_sync(&vif->credit_timeout);
}

static int xenvif_open(struct net_device *dev)
{
	struct xenvif *vif = netdev_priv(dev);
	if (netif_carrier_ok(dev))
		xenvif_up(vif);
	netif_start_queue(dev);
	return 0;
}

static int xenvif_close(struct net_device *dev)
{
	struct xenvif *vif = netdev_priv(dev);
	if (netif_carrier_ok(dev))
		xenvif_down(vif);
	netif_stop_queue(dev);
	return 0;
}

static int xenvif_change_mtu(struct net_device *dev, int mtu)
{
	struct xenvif *vif = netdev_priv(dev);
	int max = vif->can_sg ? 65535 - VLAN_ETH_HLEN : ETH_DATA_LEN;

	if (mtu > max)
		return -EINVAL;
	dev->mtu = mtu;
	return 0;
}

static netdev_features_t xenvif_fix_features(struct net_device *dev,
	netdev_features_t features)
{
	struct xenvif *vif = netdev_priv(dev);

	if (!vif->can_sg)
		features &= ~NETIF_F_SG;
	if (~(vif->gso_mask | vif->gso_prefix_mask) & GSO_BIT(TCPV4))
		features &= ~NETIF_F_TSO;
	if (~(vif->gso_mask | vif->gso_prefix_mask) & GSO_BIT(TCPV6))
		features &= ~NETIF_F_TSO6;
	if (!vif->ip_csum)
		features &= ~NETIF_F_IP_CSUM;
	if (!vif->ipv6_csum)
		features &= ~NETIF_F_IPV6_CSUM;

	return features;
}

static const struct xenvif_stat {
	char name[ETH_GSTRING_LEN];
	u16 offset;
} xenvif_stats[] = {
	{
		"rx_gso_checksum_fixup",
		offsetof(struct xenvif, rx_gso_checksum_fixup)
	},
	/* If (sent != success + fail), there are probably packets never
	 * freed up properly!
	 */
	{
		"tx_zerocopy_sent",
		offsetof(struct xenvif, tx_zerocopy_sent),
	},
	{
		"tx_zerocopy_success",
		offsetof(struct xenvif, tx_zerocopy_success),
	},
	{
		"tx_zerocopy_fail",
		offsetof(struct xenvif, tx_zerocopy_fail)
	},
	/* Number of packets exceeding MAX_SKB_FRAG slots. You should use
	 * a guest with the same MAX_SKB_FRAG
	 */
	{
		"tx_frag_overflow",
		offsetof(struct xenvif, tx_frag_overflow)
	},
};

static int xenvif_get_sset_count(struct net_device *dev, int string_set)
{
	switch (string_set) {
	case ETH_SS_STATS:
		return ARRAY_SIZE(xenvif_stats);
	default:
		return -EINVAL;
	}
}

static void xenvif_get_ethtool_stats(struct net_device *dev,
				     struct ethtool_stats *stats, u64 * data)
{
	void *vif = netdev_priv(dev);
	int i;

	for (i = 0; i < ARRAY_SIZE(xenvif_stats); i++)
		data[i] = *(unsigned long *)(vif + xenvif_stats[i].offset);
}

static void xenvif_get_strings(struct net_device *dev, u32 stringset, u8 * data)
{
	int i;

	switch (stringset) {
	case ETH_SS_STATS:
		for (i = 0; i < ARRAY_SIZE(xenvif_stats); i++)
			memcpy(data + i * ETH_GSTRING_LEN,
			       xenvif_stats[i].name, ETH_GSTRING_LEN);
		break;
	}
}

static const struct ethtool_ops xenvif_ethtool_ops = {
	.get_link	= ethtool_op_get_link,

	.get_sset_count = xenvif_get_sset_count,
	.get_ethtool_stats = xenvif_get_ethtool_stats,
	.get_strings = xenvif_get_strings,
};

static const struct net_device_ops xenvif_netdev_ops = {
	.ndo_start_xmit	= xenvif_start_xmit,
	.ndo_get_stats	= xenvif_get_stats,
	.ndo_open	= xenvif_open,
	.ndo_stop	= xenvif_close,
	.ndo_change_mtu	= xenvif_change_mtu,
	.ndo_fix_features = xenvif_fix_features,
	.ndo_set_mac_address = eth_mac_addr,
	.ndo_validate_addr   = eth_validate_addr,
};

struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
			    unsigned int handle)
{
	int err;
	struct net_device *dev;
	struct xenvif *vif;
	char name[IFNAMSIZ] = {};
	int i;

	snprintf(name, IFNAMSIZ - 1, "vif%u.%u", domid, handle);
	dev = alloc_netdev(sizeof(struct xenvif), name, ether_setup);
	if (dev == NULL) {
		pr_warn("Could not allocate netdev for %s\n", name);
		return ERR_PTR(-ENOMEM);
	}

	SET_NETDEV_DEV(dev, parent);

	vif = netdev_priv(dev);

	vif->grant_copy_op = vmalloc(sizeof(struct gnttab_copy) *
				     MAX_GRANT_COPY_OPS);
	if (vif->grant_copy_op == NULL) {
		pr_warn("Could not allocate grant copy space for %s\n", name);
		free_netdev(dev);
		return ERR_PTR(-ENOMEM);
	}

	vif->domid  = domid;
	vif->handle = handle;
	vif->can_sg = 1;
	vif->ip_csum = 1;
	vif->dev = dev;

	vif->disabled = false;

	vif->credit_bytes = vif->remaining_credit = ~0UL;
	vif->credit_usec  = 0UL;
	init_timer(&vif->credit_timeout);
	vif->credit_window_start = get_jiffies_64();

	init_timer(&vif->wake_queue);

	dev->netdev_ops	= &xenvif_netdev_ops;
	dev->hw_features = NETIF_F_SG |
		NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
		NETIF_F_TSO | NETIF_F_TSO6;
	dev->features = dev->hw_features | NETIF_F_RXCSUM;
	SET_ETHTOOL_OPS(dev, &xenvif_ethtool_ops);

	dev->tx_queue_len = XENVIF_QUEUE_LENGTH;

	skb_queue_head_init(&vif->rx_queue);
	skb_queue_head_init(&vif->tx_queue);

	vif->pending_cons = 0;
	vif->pending_prod = MAX_PENDING_REQS;
	for (i = 0; i < MAX_PENDING_REQS; i++)
		vif->pending_ring[i] = i;
	spin_lock_init(&vif->callback_lock);
	spin_lock_init(&vif->response_lock);
	/* If ballooning is disabled, this will consume real memory, so you
	 * better enable it. The long term solution would be to use just a
	 * bunch of valid page descriptors, without dependency on ballooning
	 */
	err = alloc_xenballooned_pages(MAX_PENDING_REQS,
				       vif->mmap_pages,
				       false);
	if (err) {
		netdev_err(dev, "Could not reserve mmap_pages\n");
		return ERR_PTR(-ENOMEM);
	}
	for (i = 0; i < MAX_PENDING_REQS; i++) {
		vif->pending_tx_info[i].callback_struct = (struct ubuf_info)
			{ .callback = xenvif_zerocopy_callback,
			  .ctx = NULL,
			  .desc = i };
		vif->grant_tx_handle[i] = NETBACK_INVALID_HANDLE;
	}

	/*
	 * Initialise a dummy MAC address. We choose the numerically
	 * largest non-broadcast address to prevent the address getting
	 * stolen by an Ethernet bridge for STP purposes.
	 * (FE:FF:FF:FF:FF:FF)
	 */
	memset(dev->dev_addr, 0xFF, ETH_ALEN);
	dev->dev_addr[0] &= ~0x01;

	netif_napi_add(dev, &vif->napi, xenvif_poll, XENVIF_NAPI_WEIGHT);

	netif_carrier_off(dev);

	err = register_netdev(dev);
	if (err) {
		netdev_warn(dev, "Could not register device: err=%d\n", err);
		free_netdev(dev);
		return ERR_PTR(err);
	}

	netdev_dbg(dev, "Successfully created xenvif\n");

	__module_get(THIS_MODULE);

	return vif;
}

int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
		   unsigned long rx_ring_ref, unsigned int tx_evtchn,
		   unsigned int rx_evtchn)
{
	struct task_struct *task;
	int err = -ENOMEM;

	BUG_ON(vif->tx_irq);
	BUG_ON(vif->task);
	BUG_ON(vif->dealloc_task);

	err = xenvif_map_frontend_rings(vif, tx_ring_ref, rx_ring_ref);
	if (err < 0)
		goto err;

	init_waitqueue_head(&vif->wq);
	init_waitqueue_head(&vif->dealloc_wq);

	if (tx_evtchn == rx_evtchn) {
		/* feature-split-event-channels == 0 */
		err = bind_interdomain_evtchn_to_irqhandler(
			vif->domid, tx_evtchn, xenvif_interrupt, 0,
			vif->dev->name, vif);
		if (err < 0)
			goto err_unmap;
		vif->tx_irq = vif->rx_irq = err;
		disable_irq(vif->tx_irq);
	} else {
		/* feature-split-event-channels == 1 */
		snprintf(vif->tx_irq_name, sizeof(vif->tx_irq_name),
			 "%s-tx", vif->dev->name);
		err = bind_interdomain_evtchn_to_irqhandler(
			vif->domid, tx_evtchn, xenvif_tx_interrupt, 0,
			vif->tx_irq_name, vif);
		if (err < 0)
			goto err_unmap;
		vif->tx_irq = err;
		disable_irq(vif->tx_irq);

		snprintf(vif->rx_irq_name, sizeof(vif->rx_irq_name),
			 "%s-rx", vif->dev->name);
		err = bind_interdomain_evtchn_to_irqhandler(
			vif->domid, rx_evtchn, xenvif_rx_interrupt, 0,
			vif->rx_irq_name, vif);
		if (err < 0)
			goto err_tx_unbind;
		vif->rx_irq = err;
		disable_irq(vif->rx_irq);
	}

	task = kthread_create(xenvif_kthread_guest_rx,
			      (void *)vif, "%s-guest-rx", vif->dev->name);
	if (IS_ERR(task)) {
		pr_warn("Could not allocate kthread for %s\n", vif->dev->name);
		err = PTR_ERR(task);
		goto err_rx_unbind;
	}

	vif->task = task;

	task = kthread_create(xenvif_dealloc_kthread,
			      (void *)vif, "%s-dealloc", vif->dev->name);
	if (IS_ERR(task)) {
		pr_warn("Could not allocate kthread for %s\n", vif->dev->name);
		err = PTR_ERR(task);
		goto err_rx_unbind;
	}

	vif->dealloc_task = task;

	rtnl_lock();
	if (!vif->can_sg && vif->dev->mtu > ETH_DATA_LEN)
		dev_set_mtu(vif->dev, ETH_DATA_LEN);
	netdev_update_features(vif->dev);
	netif_carrier_on(vif->dev);
	if (netif_running(vif->dev))
		xenvif_up(vif);
	rtnl_unlock();

	wake_up_process(vif->task);
	wake_up_process(vif->dealloc_task);

	return 0;

err_rx_unbind:
	unbind_from_irqhandler(vif->rx_irq, vif);
	vif->rx_irq = 0;
err_tx_unbind:
	unbind_from_irqhandler(vif->tx_irq, vif);
	vif->tx_irq = 0;
err_unmap:
	xenvif_unmap_frontend_rings(vif);
err:
	module_put(THIS_MODULE);
	return err;
}

void xenvif_carrier_off(struct xenvif *vif)
{
	struct net_device *dev = vif->dev;

	rtnl_lock();
	netif_carrier_off(dev); /* discard queued packets */
	if (netif_running(dev))
		xenvif_down(vif);
	rtnl_unlock();
}

void xenvif_disconnect(struct xenvif *vif)
{
	if (netif_carrier_ok(vif->dev))
		xenvif_carrier_off(vif);

	if (vif->task) {
		del_timer_sync(&vif->wake_queue);
		kthread_stop(vif->task);
		vif->task = NULL;
	}

	if (vif->dealloc_task) {
		kthread_stop(vif->dealloc_task);
		vif->dealloc_task = NULL;
	}

	if (vif->tx_irq) {
		if (vif->tx_irq == vif->rx_irq)
			unbind_from_irqhandler(vif->tx_irq, vif);
		else {
			unbind_from_irqhandler(vif->tx_irq, vif);
			unbind_from_irqhandler(vif->rx_irq, vif);
		}
		vif->tx_irq = 0;
	}

	xenvif_unmap_frontend_rings(vif);
}

void xenvif_free(struct xenvif *vif)
{
	int i, unmap_timeout = 0;
	/* Here we want to avoid timeout messages if an skb can be legitimately
	 * stuck somewhere else. Realistically this could be an another vif's
	 * internal or QDisc queue. That another vif also has this
	 * rx_drain_timeout_msecs timeout, but the timer only ditches the
	 * internal queue. After that, the QDisc queue can put in worst case
	 * XEN_NETIF_RX_RING_SIZE / MAX_SKB_FRAGS skbs into that another vif's
	 * internal queue, so we need several rounds of such timeouts until we
	 * can be sure that no another vif should have skb's from us. We are
	 * not sending more skb's, so newly stuck packets are not interesting
	 * for us here.
	 */
	unsigned int worst_case_skb_lifetime = (rx_drain_timeout_msecs/1000) *
		DIV_ROUND_UP(XENVIF_QUEUE_LENGTH, (XEN_NETIF_RX_RING_SIZE / MAX_SKB_FRAGS));

	for (i = 0; i < MAX_PENDING_REQS; ++i) {
		if (vif->grant_tx_handle[i] != NETBACK_INVALID_HANDLE) {
			unmap_timeout++;
			schedule_timeout(msecs_to_jiffies(1000));
			if (unmap_timeout > worst_case_skb_lifetime &&
			    net_ratelimit())
				netdev_err(vif->dev,
					   "Page still granted! Index: %x\n",
					   i);
			/* If there are still unmapped pages, reset the loop to
			 * start checking again. We shouldn't exit here until
			 * dealloc thread and NAPI instance release all the
			 * pages. If a kernel bug causes the skbs to stall
			 * somewhere, the interface cannot be brought down
			 * properly.
			 */
			i = -1;
		}
	}

	free_xenballooned_pages(MAX_PENDING_REQS, vif->mmap_pages);

	netif_napi_del(&vif->napi);

	unregister_netdev(vif->dev);

	vfree(vif->grant_copy_op);
	free_netdev(vif->dev);

	module_put(THIS_MODULE);
}