/*
 * Virtual network driver for conversing with remote driver backends.
 *
 * Copyright (c) 2002-2005, K A Fraser
 * Copyright (c) 2005, XenSource Ltd
 *
 * 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 <linux/module.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/ethtool.h>
#include <linux/if_ether.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/moduleparam.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <net/ip.h>

#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/page.h>
#include <xen/grant_table.h>

#include <xen/interface/io/netif.h>
#include <xen/interface/memory.h>
#include <xen/interface/grant_table.h>

static const struct ethtool_ops xennet_ethtool_ops;

struct netfront_cb {
	struct page *page;
	unsigned offset;
};

#define NETFRONT_SKB_CB(skb)	((struct netfront_cb *)((skb)->cb))

#define RX_COPY_THRESHOLD 256

#define GRANT_INVALID_REF	0

#define NET_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
#define NET_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, PAGE_SIZE)
#define TX_MAX_TARGET min_t(int, NET_RX_RING_SIZE, 256)

struct netfront_stats {
	u64			rx_packets;
	u64			tx_packets;
	u64			rx_bytes;
	u64			tx_bytes;
	struct u64_stats_sync	syncp;
};

struct netfront_info {
	struct list_head list;
	struct net_device *netdev;

	struct napi_struct napi;

	unsigned int evtchn;
	struct xenbus_device *xbdev;

	spinlock_t   tx_lock;
	struct xen_netif_tx_front_ring tx;
	int tx_ring_ref;

	/*
	 * {tx,rx}_skbs store outstanding skbuffs. Free tx_skb entries
	 * are linked from tx_skb_freelist through skb_entry.link.
	 *
	 *  NB. Freelist index entries are always going to be less than
	 *  PAGE_OFFSET, whereas pointers to skbs will always be equal or
	 *  greater than PAGE_OFFSET: we use this property to distinguish
	 *  them.
	 */
	union skb_entry {
		struct sk_buff *skb;
		unsigned long link;
	} tx_skbs[NET_TX_RING_SIZE];
	grant_ref_t gref_tx_head;
	grant_ref_t grant_tx_ref[NET_TX_RING_SIZE];
	unsigned tx_skb_freelist;

	spinlock_t   rx_lock ____cacheline_aligned_in_smp;
	struct xen_netif_rx_front_ring rx;
	int rx_ring_ref;

	/* Receive-ring batched refills. */
#define RX_MIN_TARGET 8
#define RX_DFL_MIN_TARGET 64
#define RX_MAX_TARGET min_t(int, NET_RX_RING_SIZE, 256)
	unsigned rx_min_target, rx_max_target, rx_target;
	struct sk_buff_head rx_batch;

	struct timer_list rx_refill_timer;

	struct sk_buff *rx_skbs[NET_RX_RING_SIZE];
	grant_ref_t gref_rx_head;
	grant_ref_t grant_rx_ref[NET_RX_RING_SIZE];

	unsigned long rx_pfn_array[NET_RX_RING_SIZE];
	struct multicall_entry rx_mcl[NET_RX_RING_SIZE+1];
	struct mmu_update rx_mmu[NET_RX_RING_SIZE];

	/* Statistics */
	struct netfront_stats __percpu *stats;

	unsigned long rx_gso_checksum_fixup;
};

struct netfront_rx_info {
	struct xen_netif_rx_response rx;
	struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX - 1];
};

static void skb_entry_set_link(union skb_entry *list, unsigned short id)
{
	list->link = id;
}

static int skb_entry_is_link(const union skb_entry *list)
{
	BUILD_BUG_ON(sizeof(list->skb) != sizeof(list->link));
	return (unsigned long)list->skb < PAGE_OFFSET;
}

/*
 * Access macros for acquiring freeing slots in tx_skbs[].
 */

static void add_id_to_freelist(unsigned *head, union skb_entry *list,
			       unsigned short id)
{
	skb_entry_set_link(&list[id], *head);
	*head = id;
}

static unsigned short get_id_from_freelist(unsigned *head,
					   union skb_entry *list)
{
	unsigned int id = *head;
	*head = list[id].link;
	return id;
}

static int xennet_rxidx(RING_IDX idx)
{
	return idx & (NET_RX_RING_SIZE - 1);
}

static struct sk_buff *xennet_get_rx_skb(struct netfront_info *np,
					 RING_IDX ri)
{
	int i = xennet_rxidx(ri);
	struct sk_buff *skb = np->rx_skbs[i];
	np->rx_skbs[i] = NULL;
	return skb;
}

static grant_ref_t xennet_get_rx_ref(struct netfront_info *np,
					    RING_IDX ri)
{
	int i = xennet_rxidx(ri);
	grant_ref_t ref = np->grant_rx_ref[i];
	np->grant_rx_ref[i] = GRANT_INVALID_REF;
	return ref;
}

#ifdef CONFIG_SYSFS
static int xennet_sysfs_addif(struct net_device *netdev);
static void xennet_sysfs_delif(struct net_device *netdev);
#else /* !CONFIG_SYSFS */
#define xennet_sysfs_addif(dev) (0)
#define xennet_sysfs_delif(dev) do { } while (0)
#endif

static int xennet_can_sg(struct net_device *dev)
{
	return dev->features & NETIF_F_SG;
}


static void rx_refill_timeout(unsigned long data)
{
	struct net_device *dev = (struct net_device *)data;
	struct netfront_info *np = netdev_priv(dev);
	napi_schedule(&np->napi);
}

static int netfront_tx_slot_available(struct netfront_info *np)
{
	return (np->tx.req_prod_pvt - np->tx.rsp_cons) <
		(TX_MAX_TARGET - MAX_SKB_FRAGS - 2);
}

static void xennet_maybe_wake_tx(struct net_device *dev)
{
	struct netfront_info *np = netdev_priv(dev);

	if (unlikely(netif_queue_stopped(dev)) &&
	    netfront_tx_slot_available(np) &&
	    likely(netif_running(dev)))
		netif_wake_queue(dev);
}

static void xennet_alloc_rx_buffers(struct net_device *dev)
{
	unsigned short id;
	struct netfront_info *np = netdev_priv(dev);
	struct sk_buff *skb;
	struct page *page;
	int i, batch_target, notify;
	RING_IDX req_prod = np->rx.req_prod_pvt;
	grant_ref_t ref;
	unsigned long pfn;
	void *vaddr;
	struct xen_netif_rx_request *req;

	if (unlikely(!netif_carrier_ok(dev)))
		return;

	/*
	 * Allocate skbuffs greedily, even though we batch updates to the
	 * receive ring. This creates a less bursty demand on the memory
	 * allocator, so should reduce the chance of failed allocation requests
	 * both for ourself and for other kernel subsystems.
	 */
	batch_target = np->rx_target - (req_prod - np->rx.rsp_cons);
	for (i = skb_queue_len(&np->rx_batch); i < batch_target; i++) {
		skb = __netdev_alloc_skb(dev, RX_COPY_THRESHOLD + NET_IP_ALIGN,
					 GFP_ATOMIC | __GFP_NOWARN);
		if (unlikely(!skb))
			goto no_skb;

		/* Align ip header to a 16 bytes boundary */
		skb_reserve(skb, NET_IP_ALIGN);

		page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
		if (!page) {
			kfree_skb(skb);
no_skb:
			/* Any skbuffs queued for refill? Force them out. */
			if (i != 0)
				goto refill;
			/* Could not allocate any skbuffs. Try again later. */
			mod_timer(&np->rx_refill_timer,
				  jiffies + (HZ/10));
			break;
		}

		skb_shinfo(skb)->frags[0].page = page;
		skb_shinfo(skb)->nr_frags = 1;
		__skb_queue_tail(&np->rx_batch, skb);
	}

	/* Is the batch large enough to be worthwhile? */
	if (i < (np->rx_target/2)) {
		if (req_prod > np->rx.sring->req_prod)
			goto push;
		return;
	}

	/* Adjust our fill target if we risked running out of buffers. */
	if (((req_prod - np->rx.sring->rsp_prod) < (np->rx_target / 4)) &&
	    ((np->rx_target *= 2) > np->rx_max_target))
		np->rx_target = np->rx_max_target;

 refill:
	for (i = 0; ; i++) {
		skb = __skb_dequeue(&np->rx_batch);
		if (skb == NULL)
			break;

		skb->dev = dev;

		id = xennet_rxidx(req_prod + i);

		BUG_ON(np->rx_skbs[id]);
		np->rx_skbs[id] = skb;

		ref = gnttab_claim_grant_reference(&np->gref_rx_head);
		BUG_ON((signed short)ref < 0);
		np->grant_rx_ref[id] = ref;

		pfn = page_to_pfn(skb_shinfo(skb)->frags[0].page);
		vaddr = page_address(skb_shinfo(skb)->frags[0].page);

		req = RING_GET_REQUEST(&np->rx, req_prod + i);
		gnttab_grant_foreign_access_ref(ref,