/*
 * This file is part of the Chelsio T3 Ethernet driver for Linux.
 *
 * Copyright (C) 2003-2009 Chelsio Communications.  All rights reserved.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the LICENSE file included in this
 * release for licensing terms and conditions.
 */

#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/if.h>
#include <linux/if_vlan.h>
#include <linux/jhash.h>
#include <net/neighbour.h>
#include "common.h"
#include "t3cdev.h"
#include "cxgb3_defs.h"
#include "l2t.h"
#include "t3_cpl.h"
#include "firmware_exports.h"

#define VLAN_NONE 0xfff

/*
 * Module locking notes:  There is a RW lock protecting the L2 table as a
 * whole plus a spinlock per L2T entry.  Entry lookups and allocations happen
 * under the protection of the table lock, individual entry changes happen
 * while holding that entry's spinlock.  The table lock nests outside the
 * entry locks.  Allocations of new entries take the table lock as writers so
 * no other lookups can happen while allocating new entries.  Entry updates
 * take the table lock as readers so multiple entries can be updated in
 * parallel.  An L2T entry can be dropped by decrementing its reference count
 * and therefore can happen in parallel with entry allocation but no entry
 * can change state or increment its ref count during allocation as both of
 * these perform lookups.
 */

static inline unsigned int vlan_prio(const struct l2t_entry *e)
{
	return e->vlan >> 13;
}

static inline unsigned int arp_hash(u32 key, int ifindex,
				    const struct l2t_data *d)
{
	return jhash_2words(key, ifindex, 0) & (d->nentries - 1);
}

static inline void neigh_replace(struct l2t_entry *e, struct neighbour *n)
{
	neigh_hold(n);
	if (e->neigh)
		neigh_release(e->neigh);
	e->neigh = n;
}

static void setup_l2e(struct t3cdev *dev, struct sk_buff *skb,
		      struct l2t_entry *e)
{
	struct cpl_l2t_write_req *req;

	req = (struct cpl_l2t_write_req *)__skb_put(skb, sizeof(*req));
	req->wr.wr_hi = htonl(V_WR_OP(FW_WROPCODE_FORWARD));
	OPCODE_TID(req) = htonl(MK_OPCODE_TID(CPL_L2T_WRITE_REQ, e->idx));
	req->params = htonl(V_L2T_W_IDX(e->idx) | V_L2T_W_IFF(e->smt_idx) |
			    V_L2T_W_VLAN(e->vlan & VLAN_VID_MASK) |
			    V_L2T_W_PRIO(vlan_prio(e)));
	req->port_idx = e->smt_idx;
	memcpy(req->dst_mac, e->dmac, sizeof(req->dst_mac));
	skb->priority = CPL_PRIORITY_CONTROL;
	cxgb3_ofld_send(dev, skb);
}

/*
 * Set up an L2T entry and send any packets waiting in the arp queue.  The
 * supplied skb is used for the CPL_L2T_WRITE_REQ.  Must be called with the
 * entry locked.
 */
static int setup_l2e_send_pending(struct t3cdev *dev, struct sk_buff *skb,
				  struct l2t_entry *e)
{

	if (!skb) {
		skb = alloc_skb(sizeof(struct cpl_l2t_write_req), GFP_ATOMIC);
		if (!skb)
			return -ENOMEM;
	}

	memcpy(e->dmac, e->neigh->ha, sizeof(e->dmac));
	setup_l2e(dev, skb, e);

	while (e->arpq_head) {
		skb = e->arpq_head;
		e->arpq_head = skb->next;
		skb->next = NULL;
		cxgb3_ofld_send(dev, skb);
	}
	e->arpq_tail = NULL;
	e->state = L2T_STATE_VALID;

	return 0;
}

/*
 * Update an L2T entry.
 * Must be called with the entry locked.
 */
int t3_l2t_update_l2e(struct t3cdev *dev, struct l2t_entry *e)
{
	struct sk_buff * skb = alloc_skb(sizeof(struct cpl_l2t_write_req),
					 GFP_ATOMIC);
	if (!skb)
		return -ENOMEM;

	setup_l2e(dev, skb, e);

	return 0;
}

/*
 * Add a packet to the an L2T entry's queue of packets awaiting resolution.
 * Must be called with the entry's lock held.
 */
static inline void arpq_enqueue(struct l2t_entry *e, struct sk_buff *skb)
{
	skb->next = NULL;
	if (e->arpq_head)
		e->arpq_tail->next = skb;
	else
		e->arpq_head = skb;
	e->arpq_tail = skb;
}

int t3_l2t_send_slow(struct t3cdev *dev, struct sk_buff *skb,
		     struct l2t_entry *e)
{
again:
	switch (e->state) {
	case L2T_STATE_STALE:     /* entry is stale, kick off revalidation */
		neigh_event_send(e->neigh, NULL);
		spin_lock_bh(&e->lock);
		if (e->state == L2T_STATE_STALE)
			e->state = L2T_STATE_VALID;
		spin_unlock_bh(&e->lock);
	case L2T_STATE_VALID:     /* fast-path, send the packet on */
		return cxgb3_ofld_send(dev, skb);
	case L2T_STATE_RESOLVING:
		spin_lock_bh(&e->lock);
		if (e->state != L2T_STATE_RESOLVING) { // ARP already completed
			spin_unlock_bh(&e->lock);
			goto again;
		}
		arpq_enqueue(e, skb);
		spin_unlock_bh(&e->lock);

		/*
		 * Only the first packet added to the arpq should kick off
		 * resolution.  However, because the alloc_skb below can fail,
		 * we allow each packet added to the arpq to retry resolution
		 * as a way of recovering from transient memory exhaustion.
		 * A better way would be to use a work request to retry L2T
		 * entries when there's no memory.
		 */
		if (!neigh_event_send(e->neigh, NULL)) {
			skb = alloc_skb(sizeof(struct cpl_l2t_write_req),
					GFP_ATOMIC);
			if (!skb)
				break;

			spin_lock_bh(&e->lock);
			if (e->arpq_head)
				setup_l2e_send_pending(dev, skb, e);
			else                           /* we lost the race */
				__kfree_skb(skb);
			spin_unlock_bh(&e->lock);
		}
	}
	return 0;
}
EXPORT_SYMBOL(t3_l2t_send_slow);

void t3_l2t_send_event(struct t3cdev *dev, struct l2t_entry *e)
{
again:
	switch (e->state) {
	case L2T_STATE_STALE:     /* entry is stale, kick off revalidation */
		neigh_event_send(e->neigh, NULL);
		spin_lock_bh(&e->lock);
		if (e->state == L2T_STATE_STALE) {
			e->state = L2T_STATE_VALID;
		}
		spin_unlock_bh(&e->lock);
		return;
	case L2T_STATE_VALID:     /* fast-path, send the packet on */
		return;
	case L2T_STATE_RESOLVING:
		spin_lock_bh(&e->lock);
		if (e->state != L2T_STATE_RESOLVING) { // ARP already completed
			spin_unlock_bh(&e->lock);
			goto again;
		}
		spin_unlock_bh(&e->lock);

		/*
		 * Only the first packet added to the arpq should kick off
		 * resolution.  However, because the alloc_skb below can fail,
		 * we allow each packet added to the arpq to retry resolution
		 * as a way of recovering from transient memory exhaustion.
		 * A better way would be to use a work request to retry L2T
		 * entries when there's no memory.
		 */
		neigh_event_send(e->neigh, NULL);
	}
	return;
}
EXPORT_SYMBOL(t3_l2t_send_event);

/*
 * Allocate a free L2T entry.  Must be called with l2t_data.lock held.
 */
static struct l2t_entry *alloc_l2e(struct l2t_data *d)
{
	struct l2t_entry *end, *e, **p;

	if (!atomic_read(&d->nfree))
		return NULL;

	/* there's definitely a free entry */
	for (e = d->rover, end = &d->l2tab[d->nentries]; e != end; ++e)
		if (atomic_read(&e->refcnt) == 0)
			goto found;

	for (e = &d->l2tab[1]; atomic_read(&e->refcnt); ++e) ;
found:
	d->rover = e + 1;
	atomic_dec(&d->nfree);

	/*
	 * The entry we found may be an inactive entry that is
	 * presently in the hash table.  We need to remove it.
	 */
	if (e->state != L2T_STATE_UNUSED) {
		int hash = arp_hash(e->addr, e->ifindex, d);

		for (p = &d->l2tab[hash].first; *p; p = &(*p)->next)
			if (*p == e) {
				*p = e->next;
				break;
			}
		e->state = L2T_STATE_UNUSED;
	}
	return e;
}

/*
 * Called when an L2T entry has no more users.  The entry is left in the hash
 * table since it is likely to be reused but we also bump nfree to indicate
 * that the entry can be reallocated for a different neighbor.  We also drop
 * the existing neighbor reference in case the neighbor is going away and is
 * waiting on our reference.
 *
 * Because entries can be reallocated to other neighbors once their ref count
 * drops to 0 we need to take the entry's lock to avoid races with a new
 * incarnation.
 */
void t3_l2e_free(struct l2t_data *d, struct l2t_entry *e)
{
	spin_lock_bh(&e->lock);
	if (atomic_read(&e->refcnt) == 0) {  /* hasn't been recycled */
		if (e->neigh) {
			neigh_release(e->neigh);
			e->neigh = NULL;
		}
	}
	spin_unlock_bh(&e->lock);
	atomic_inc(&d->nfree);
}
EXPORT_SYMBOL(t3_l2e_free);

/*
 * Update an L2T entry that was previously used for the same next hop as neigh.
 * Must be called with softirqs disabled.
 */
static inline void reuse_entry(struct l2t_entry *e, struct neighbour *neigh)
{
	unsigned int nud_state;

	spin_lock(&e->lock);                /* avoid race with t3_l2t_free */

	if (neigh != e->neigh)
		neigh_replace(e, neigh);
	nud_state = neigh->nud_state;
	if (memcmp(e->dmac, neigh->ha, sizeof(e->dmac)) ||
	    !(nud_state & NUD_VALID))
		e->state = L2T_STATE_RESOLVING;
	else if (nud_state & NUD_CONNECTED)
		e->state = L2T_STATE_VALID;
	else
		e->state = L2T_STATE_STALE;
	spin_unlock(&e->lock);
}

struct l2t_entry *t3_l2t_get(struct t3cdev *cdev, struct neighbour *neigh,
			     struct net_device *dev)
{
	struct l2t_entry *e;
	struct l2t_data *d = L2DATA(cdev);
	u32 addr = *(u32 *) neigh->primary_key;
	int ifidx = neigh->dev->ifindex;
	int hash = arp_hash(addr, ifidx, d);
	struct port_info *p = netdev_priv(dev);
	int smt_idx = p->port_id;

	write_lock_bh(&d->lock);
	for (e = d->l2tab[hash].first; e; e = e->next)
		if (e->addr == addr && e->ifindex == ifidx &&
		    e->smt_idx == smt_idx) {
			l2t_hold(d, e);
			if (atomic_read(&e->refcnt) == 1)
				reuse_entry(e, neigh);
			goto done;
		}

	/* Need to allocate a new entry */
	e = alloc_l2e(d);
	if (e) {
		spin_lock(&e->lock);          /* avoid race with t3_l2t_free */
		e->next = d->l2tab[hash].first;
		d->l2tab[hash].first = e;
		e->state = L2T_STATE_RESOLVING;
		e->addr = addr;
		e->ifindex = ifidx;
		e->smt_idx = smt_idx;
		e->orig_smt_idx = smt_idx;
		e->chan_idx = p->txpkt_intf & 1;
		atomic_set(&e->refcnt, 1);
		neigh_replace(e, neigh);
		if (neigh->dev->priv_flags & IFF_802_1Q_VLAN)
			e->vlan = vlan_dev_vlan_id(neigh->dev);
		else
			e->vlan = VLAN_NONE;
		spin_unlock(&e->lock);
	}
done:
	write_unlock_bh(&d->lock);
	return e;
}
EXPORT_SYMBOL(t3_l2t_get);

/*
 * Called when address resolution fails for an L2T entry to handle packets
 * on the arpq head.  If a packet specifies a failure handler it is invoked,
 * otherwise the packets is sent to the offload device.
 *
 * XXX: maybe we should abandon the latter behavior and just require a failure
 * handler.
 */
static void handle_failed_resolution(struct t3cdev *dev, struct sk_buff *arpq)
{
	while (arpq) {
		struct sk_buff *skb = arpq;
		struct l2t_skb_cb *cb = L2T_SKB_CB(skb);

		arpq = skb->next;
		skb->next = NULL;
		if (cb->arp_failure_handler)
			cb->arp_failure_handler(dev, skb);
		else
			cxgb3_ofld_send(dev, skb);
	}
}

#if defined(NETEVENT) || !defined(OFLD_USE_KPROBES)
/*
 * Called when the host's ARP layer makes a change to some entry that is
 * loaded into the HW L2 table.
 */
void t3_l2t_update(struct t3cdev *dev, struct neighbour *neigh)
{
	struct l2t_entry *e;
	struct sk_buff *arpq = NULL;
	struct l2t_data *d = L2DATA(dev);
	u32 addr = *(u32 *) neigh->primary_key;
	int ifidx = neigh->dev->ifindex;
	int hash = arp_hash(addr, ifidx, d);

	read_lock_bh(&d->lock);
	for (e = d->l2tab[hash].first; e; e = e->next)
		if (e->addr == addr && e->ifindex == ifidx) {
			spin_lock(&e->lock);
			goto found;
		}
	read_unlock_bh(&d->lock);
	return;

found:
	read_unlock(&d->lock);
	if (atomic_read(&e->refcnt)) {
		if (neigh != e->neigh)
			neigh_replace(e, neigh);

		if (e->state == L2T_STATE_RESOLVING) {
			if (neigh->nud_state & NUD_FAILED) {
				arpq = e->arpq_head;
				e->arpq_head = e->arpq_tail = NULL;
			} else if (neigh->nud_state & (NUD_CONNECTED|NUD_STALE))
				setup_l2e_send_pending(dev, NULL, e);
		} else {
			e->state = neigh->nud_state & NUD_CONNECTED ?
				L2T_STATE_VALID : L2T_STATE_STALE;
			if (memcmp(e->dmac, neigh->ha, 6))
				setup_l2e_send_pending(dev, NULL, e);
		}
	}
	spin_unlock_bh(&e->lock);

	if (arpq)
		handle_failed_resolution(dev, arpq);
}
#else
/*
 * Called from a kprobe, interrupts are off.
 */
void t3_l2t_update(struct t3cdev *dev, struct neighbour *neigh)
{
	struct l2t_entry *e;
	struct l2t_data *d = L2DATA(dev);
	u32 addr = *(u32 *) neigh->primary_key;
	int ifidx = neigh->dev->ifindex;
	int hash = arp_hash(addr, ifidx, d);

	read_lock(&d->lock);
	for (e = d->l2tab[hash].first; e; e = e->next)
		if (e->addr == addr && e->ifindex == ifidx) {
			spin_lock(&e->lock);
			if (atomic_read(&e->refcnt)) {
				if (neigh != e->neigh)
					neigh_replace(e, neigh);
				e->tdev = dev;
				mod_timer(&e->update_timer, jiffies + 1);
			}
			spin_unlock(&e->lock);
			break;
		}
	read_unlock(&d->lock);
}

static void update_timer_cb(unsigned long data)
{
	struct sk_buff *arpq = NULL;
	struct l2t_entry *e = (struct l2t_entry *)data;
	struct neighbour *neigh;
	struct t3cdev *dev = e->tdev;

	spin_lock(&e->lock);
	neigh = e->neigh;
	if (neigh)
		neigh_hold(neigh);
	spin_unlock(&e->lock);

	if (!neigh)
		return;

	read_lock(&neigh->lock);
	spin_lock(&e->lock);

	if (atomic_read(&e->refcnt) && neigh == e->neigh) {
		if (e->state == L2T_STATE_RESOLVING) {
			if (neigh->nud_state & NUD_FAILED) {
				arpq = e->arpq_head;
				e->arpq_head = e->arpq_tail = NULL;
			} else if ((neigh->nud_state &
				    (NUD_CONNECTED|NUD_STALE)) && e->arpq_head)
				setup_l2e_send_pending(dev, NULL, e);
		} else {
			e->state = neigh->nud_state & NUD_CONNECTED ?
				L2T_STATE_VALID : L2T_STATE_STALE;
			if (memcmp(e->dmac, neigh->ha, sizeof(e->dmac)))
				setup_l2e_send_pending(dev, NULL, e);
		}
	}
	spin_unlock(&e->lock);
	read_unlock(&neigh->lock);
	neigh_release(neigh);

	if (arpq)
		handle_failed_resolution(dev, arpq);
}
#endif

struct l2t_data *t3_init_l2t(unsigned int l2t_capacity)
{
	struct l2t_data *d;
	int i, size = sizeof(*d) + l2t_capacity * sizeof(struct l2t_entry);

	d = cxgb_alloc_mem(size);
	if (!d)
		return NULL;

	d->nentries = l2t_capacity;
	d->rover = &d->l2tab[1];	/* entry 0 is not used */
	atomic_set(&d->nfree, l2t_capacity - 1);
	rwlock_init(&d->lock);

	for (i = 0; i < l2t_capacity; ++i) {
		d->l2tab[i].idx = i;
		d->l2tab[i].state = L2T_STATE_UNUSED;
		spin_lock_init(&d->l2tab[i].lock);
		atomic_set(&d->l2tab[i].refcnt, 0);
#ifndef NETEVENT
#ifdef OFLD_USE_KPROBES
		setup_timer(&d->l2tab[i].update_timer, update_timer_cb,
			    (unsigned long)&d->l2tab[i]);
#endif
#endif
	}
	return d;
}

void t3_free_l2t(struct l2t_data *d)
{
#ifndef NETEVENT
#ifdef OFLD_USE_KPROBES
	int i;

	/* Stop all L2T timers */
	for (i = 0; i < d->nentries; ++i)
		del_timer_sync(&d->l2tab[i].update_timer);
#endif
#endif
	cxgb_free_mem(d);
}

#ifdef CONFIG_PROC_FS
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>

static inline void *l2t_get_idx(struct seq_file *seq, loff_t pos)
{
	struct l2t_data *d = seq->private;

	return pos >= d->nentries ? NULL : &d->l2tab[pos];
}

static void *l2t_seq_start(struct seq_file *seq, loff_t *pos)
{
	return *pos ? l2t_get_idx(seq, *pos) : SEQ_START_TOKEN;
}

static void *l2t_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	v = l2t_get_idx(seq, *pos + 1);
	if (v)
		++*pos;
	return v;
}

static void l2t_seq_stop(struct seq_file *seq, void *v)
{
}

static char l2e_state(const struct l2t_entry *e)
{
	switch (e->state) {
	case L2T_STATE_VALID: return 'V';  /* valid, fast-path entry */
	case L2T_STATE_STALE: return 'S';  /* needs revalidation, but usable */
	case L2T_STATE_RESOLVING:
		return e->arpq_head ? 'A' : 'R';
	default:
		return 'U';
	}
}

static int l2t_seq_show(struct seq_file *seq, void *v)
{
	if (v == SEQ_START_TOKEN)
		seq_puts(seq, "Index IP address      Ethernet address   VLAN  "
			 "Prio  State   Users SMTIDX  Port\n");
	else {
		char ip[20];
		struct l2t_entry *e = v;

		spin_lock_bh(&e->lock);
		sprintf(ip, "%u.%u.%u.%u", NIPQUAD(e->addr));
		seq_printf(seq, "%-5u %-15s %02x:%02x:%02x:%02x:%02x:%02x  %4d"
			   "  %3u     %c   %7u   %4u %s\n",
			   e->idx, ip, e->dmac[0], e->dmac[1], e->dmac[2],
			   e->dmac[3], e->dmac[4], e->dmac[5],
			   e->vlan & VLAN_VID_MASK, vlan_prio(e),
			   l2e_state(e), atomic_read(&e->refcnt), e->smt_idx,
			   e->neigh ? e->neigh->dev->name : "");
		spin_unlock_bh(&e->lock);
	}
	return 0;
}

static struct seq_operations l2t_seq_ops = {
	.start = l2t_seq_start,
	.next = l2t_seq_next,
	.stop = l2t_seq_stop,
	.show = l2t_seq_show
};

static int l2t_seq_open(struct inode *inode, struct file *file)
{
	int rc = seq_open(file, &l2t_seq_ops);

	if (!rc) {
		struct proc_dir_entry *dp = PDE(inode);
		struct seq_file *seq = file->private_data;

		seq->private = dp->data;
	}
	return rc;
}

static struct file_operations l2t_seq_fops = {
	.owner = THIS_MODULE,
	.open = l2t_seq_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = seq_release,
};

/*
 * Create the proc entries for the L2 table under dir.
 */
int t3_l2t_proc_setup(struct proc_dir_entry *dir, struct l2t_data *d)
{
	struct proc_dir_entry *p;

	if (!dir)
		return -EINVAL;

	p = create_proc_entry("l2t", S_IRUGO, dir);
	if (!p)
		return -ENOMEM;

	p->proc_fops = &l2t_seq_fops;
	p->data = d;
	return 0;
}

void t3_l2t_proc_free(struct proc_dir_entry *dir)
{
	if (dir)
		remove_proc_entry("l2t", dir);
}
#endif