/*
 * 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.
 */

#ifndef __XEN_NETBACK__COMMON_H__
#define __XEN_NETBACK__COMMON_H__

#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__

#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/io.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/wait.h>
#include <linux/sched.h>

#include <xen/interface/io/netif.h>
#include <xen/interface/grant_table.h>
#include <xen/grant_table.h>
#include <xen/xenbus.h>
#include <linux/debugfs.h>

typedef unsigned int pending_ring_idx_t;
#define INVALID_PENDING_RING_IDX (~0U)

struct pending_tx_info {
	struct xen_netif_tx_request req; /* tx request */
	/* Callback data for released SKBs. The callback is always
	 * xenvif_zerocopy_callback, desc contains the pending_idx, which is
	 * also an index in pending_tx_info array. It is initialized in
	 * xenvif_alloc and it never changes.
	 * skb_shinfo(skb)->destructor_arg points to the first mapped slot's
	 * callback_struct in this array of struct pending_tx_info's, then ctx
	 * to the next, or NULL if there is no more slot for this skb.
	 * ubuf_to_vif is a helper which finds the struct xenvif from a pointer
	 * to this field.
	 */
	struct ubuf_info callback_struct;
};

#define XEN_NETIF_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
#define XEN_NETIF_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, PAGE_SIZE)

struct xenvif_rx_meta {
	int id;
	int size;
	int gso_type;
	int gso_size;
};

#define GSO_BIT(type) \
	(1 << XEN_NETIF_GSO_TYPE_ ## type)

/* Discriminate from any valid pending_idx value. */
#define INVALID_PENDING_IDX 0xFFFF

#define MAX_BUFFER_OFFSET PAGE_SIZE

#define MAX_PENDING_REQS XEN_NETIF_TX_RING_SIZE

/* It's possible for an skb to have a maximal number of frags
 * but still be less than MAX_BUFFER_OFFSET in size. Thus the
 * worst-case number of copy operations is MAX_SKB_FRAGS per
 * ring slot.
 */
#define MAX_GRANT_COPY_OPS (MAX_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE)

#define NETBACK_INVALID_HANDLE -1

/* To avoid confusion, we define XEN_NETBK_LEGACY_SLOTS_MAX indicating
 * the maximum slots a valid packet can use. Now this value is defined
 * to be XEN_NETIF_NR_SLOTS_MIN, which is supposed to be supported by
 * all backend.
 */
#define XEN_NETBK_LEGACY_SLOTS_MAX XEN_NETIF_NR_SLOTS_MIN

/* Queue name is interface name with "-qNNN" appended */
#define QUEUE_NAME_SIZE (IFNAMSIZ + 5)

/* IRQ name is queue name with "-tx" or "-rx" appended */
#define IRQ_NAME_SIZE (QUEUE_NAME_SIZE + 3)

struct xenvif;

struct xenvif_stats {
	/* Stats fields to be updated per-queue.
	 * A subset of struct net_device_stats that contains only the
	 * fields that are updated in netback.c for each queue.
	 */
	unsigned int rx_bytes;
	unsigned int rx_packets;
	unsigned int tx_bytes;
	unsigned int tx_packets;

	/* Additional stats used by xenvif */
	unsigned long rx_gso_checksum_fixup;
	unsigned long tx_zerocopy_sent;
	unsigned long tx_zerocopy_success;
	unsigned long tx_zerocopy_fail;
	unsigned long tx_frag_overflow;
};

struct xenvif_queue { /* Per-queue data for xenvif */
	unsigned int id; /* Queue ID, 0-based */
	char name[QUEUE_NAME_SIZE]; /* DEVNAME-qN */
	struct xenvif *vif; /* Parent VIF */

	/* Use NAPI for guest TX */
	struct napi_struct napi;
	/* When feature-split-event-channels = 0, tx_irq = rx_irq. */
	unsigned int tx_irq;
	/* Only used when feature-split-event-channels = 1 */
	char tx_irq_name[IRQ_NAME_SIZE]; /* DEVNAME-qN-tx */
	struct xen_netif_tx_back_ring tx;
	struct sk_buff_head tx_queue;
	struct page *mmap_pages[MAX_PENDING_REQS];
	pending_ring_idx_t pending_prod;
	pending_ring_idx_t pending_cons;
	u16 pending_ring[MAX_PENDING_REQS];
	struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
	grant_handle_t grant_tx_handle[MAX_PENDING_REQS];

	struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
	struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
	struct gnttab_unmap_grant_ref tx_unmap_ops[MAX_PENDING_REQS];
	/* passed to gnttab_[un]map_refs with pages under (un)mapping */
	struct page *pages_to_map[MAX_PENDING_REQS];
	struct page *pages_to_unmap[MAX_PENDING_REQS];

	/* This prevents zerocopy callbacks  to race over dealloc_ring */
	spinlock_t callback_lock;
	/* This prevents dealloc thread and NAPI instance to race over response
	 * creation and pending_ring in xenvif_idx_release. In xenvif_tx_err
	 * it only protect response creation
	 */
	spinlock_t response_lock;
	pending_ring_idx_t dealloc_prod;
	pending_ring_idx_t dealloc_cons;
	u16 dealloc_ring[MAX_PENDING_REQS];
	struct task_struct *dealloc_task;
	wait_queue_head_t dealloc_wq;
	atomic_t inflight_packets;

	/* Use kthread for guest RX */
	struct task_struct *task;
	wait_queue_head_t wq;
	/* When feature-split-event-channels = 0, tx_irq = rx_irq. */
	unsigned int rx_irq;
	/* Only used when feature-split-event-channels = 1 */
	char rx_irq_name[IRQ_NAME_SIZE]; /* DEVNAME-qN-rx */
	struct xen_netif_rx_back_ring rx;
	struct sk_buff_head rx_queue;

	unsigned int rx_queue_max;
	unsigned int rx_queue_len;
	unsigned long last_rx_time;
	bool stalled;

	struct gnttab_copy grant_copy_op[MAX_GRANT_COPY_OPS];

	/* We create one meta structure per ring request we consume, so
	 * the maximum number is the same as the ring size.
	 */
	struct xenvif_rx_meta meta[XEN_NETIF_RX_RING_SIZE];

	/* Transmit shaping: allow 'credit_bytes' every 'credit_usec'. */
	unsigned long   credit_bytes;
	unsigned long   credit_usec;
	unsigned long   remaining_credit;
	struct timer_list credit_timeout;
	u64 credit_window_start;

	/* Statistics */
	struct xenvif_stats stats;
};

/* Maximum number of Rx slots a to-guest packet may use, including the
 * slot needed for GSO meta-data.
 */
#define XEN_NETBK_RX_SLOTS_MAX (MAX_SKB_FRAGS + 1)

enum state_bit_shift {
	/* This bit marks that the vif is connected */
	VIF_STATUS_CONNECTED,
};

struct xenvif {
	/* Unique identifier for this interface. */
	domid_t          domid;
	unsigned int     handle;

	u8               fe_dev_addr[6];

	/* Frontend feature information. */
	int gso_mask;
	int gso_prefix_mask;

	u8 can_sg:1;
	u8 ip_csum:1;
	u8 ipv6_csum:1;

	/* Is this interface disabled? True when backend discovers
	 * frontend is rogue.
	 */
	bool disabled;
	unsigned long status;
	unsigned long drain_timeout;
	unsigned long stall_timeout;

	/* Queues */
	struct xenvif_queue *queues;
	unsigned int num_queues; /* active queues, resource allocated */
	unsigned int stalled_queues;

	struct xenbus_watch credit_watch;

	spinlock_t lock;

#ifdef CONFIG_DEBUG_FS
	struct dentry *xenvif_dbg_root;
#endif

	/* Miscellaneous private stuff. */
	struct net_device *dev;
};

struct xenvif_rx_cb {
	unsigned long expires;
	int meta_slots_used;
};

#define XENVIF_RX_CB(skb) ((struct xenvif_rx_cb *)(skb)->cb)

static inline struct xenbus_device *xenvif_to_xenbus_device(struct xenvif *vif)
{
	return to_xenbus_device(vif->dev->dev.parent);
}

void xenvif_tx_credit_callback(unsigned long data);

struct xenvif *xenvif_alloc(struct device *parent,
			    domid_t domid,
			    unsigned int handle);

int xenvif_init_queue(struct xenvif_queue *queue);
void xenvif_deinit_queue(struct xenvif_queue *queue);

int xenvif_connect(struct xenvif_queue *queue, unsigned long tx_ring_ref,
		   unsigned long rx_ring_ref, unsigned int tx_evtchn,
		   unsigned int rx_evtchn);
void xenvif_disconnect(struct xenvif *vif);
void xenvif_free(struct xenvif *vif);

int xenvif_xenbus_init(void);
void xenvif_xenbus_fini(void);

int xenvif_schedulable(struct xenvif *vif);

int xenvif_queue_stopped(struct xenvif_queue *queue);
void xenvif_wake_queue(struct xenvif_queue *queue);

/* (Un)Map communication rings. */
void xenvif_unmap_frontend_rings(struct xenvif_queue *queue);
int xenvif_map_frontend_rings(struct xenvif_queue *queue,
			      grant_ref_t tx_ring_ref,
			      grant_ref_t rx_ring_ref);

/* Check for SKBs from frontend and schedule backend processing */
void xenvif_napi_schedule_or_enable_events(struct xenvif_queue *queue);

/* Prevent the device from generating any further traffic. */
void xenvif_carrier_off(struct xenvif *vif);

int xenvif_tx_action(struct xenvif_queue *queue, int budget);

int xenvif_kthread_guest_rx(void *data);
void xenvif_kick_thread(struct xenvif_queue *queue);

int xenvif_dealloc_kthread(void *data);

void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb);

/* Determine whether the needed number of slots (req) are available,
 * and set req_event if not.
 */
bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue, int needed);

void xenvif_carrier_on(struct xenvif *vif);

/* Callback from stack when TX packet can be released */
void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success);

/* Unmap a pending page and release it back to the guest */
void xenvif_idx_unmap(struct xenvif_queue *queue, u16 pending_idx);

static inline pending_ring_idx_t nr_pending_reqs(struct xenvif_queue *queue)
{
	return MAX_PENDING_REQS -
		queue->pending_prod + queue->pending_cons;
}

/* Callback from stack when TX packet can be released */
void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success);

irqreturn_t xenvif_interrupt(int irq, void *dev_id);

extern bool separate_tx_rx_irq;

extern unsigned int rx_drain_timeout_msecs;
extern unsigned int rx_stall_timeout_msecs;
extern unsigned int xenvif_max_queues;

#ifdef CONFIG_DEBUG_FS
extern struct dentry *xen_netback_dbg_root;
#endif

void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue,
				 struct sk_buff *skb);
void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue);

#endif /* __XEN_NETBACK__COMMON_H__ */