/*
 * This file is part of the Chelsio T4 Ethernet driver for Linux.
 *
 * Copyright (C) 2003-2009 Chelsio Communications.  All rights reserved.
 *
 * Written by Dimitris Michailidis (dm@chelsio.com)
 *
 * 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 <net/8021q/vlan.h>
#include "common.h"
#include "l2t.h"
#include "t4_msg.h"
#include "t4fw_interface.h"
#include "cxgb4_ofld.h"

#define VLAN_NONE 0xfff

/* identifies sync vs async L2T_WRITE_REQs */
#define S_SYNC_WR    12
#define V_SYNC_WR(x) ((x) << S_SYNC_WR)
#define F_SYNC_WR    V_SYNC_WR(1)

enum {
	L2T_STATE_VALID,      /* entry is up to date */
	L2T_STATE_STALE,      /* entry may be used but needs revalidation */
	L2T_STATE_RESOLVING,  /* entry needs address resolution */
	L2T_STATE_SYNC_WRITE, /* synchronous write of entry underway */

	/* when state is one of the below the entry is not hashed */
	L2T_STATE_SWITCHING,  /* entry is being used by a switching filter */
	L2T_STATE_UNUSED      /* entry not in use */
};

struct l2t_data {
	rwlock_t lock;
	atomic_t nfree;             /* number of free entries */
	struct l2t_entry *rover;    /* starting point for next allocation */
	struct l2t_entry l2tab[L2T_SIZE];
};

/*
 * 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.
 *
 * Note: We do not take refereces to net_devices in this module because both
 * the TOE and the sockets already hold references to the interfaces and the
 * lifetime of an L2T entry is fully contained in the lifetime of the TOE.
 */

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

static inline void l2t_hold(struct l2t_data *d, struct l2t_entry *e)
{
	if (atomic_add_return(1, &e->refcnt) == 1)  /* 0 -> 1 transition */
		atomic_dec(&d->nfree);
}

/*
 * To avoid having to check address families we do not allow v4 and v6
 * neighbors to be on the same hash chain.  We keep v4 entries in the first
 * half of available hash buckets and v6 in the second.
 */
enum {
	L2T_SZ_HALF = L2T_SIZE / 2,
	L2T_HASH_MASK = L2T_SZ_HALF - 1
};

static inline unsigned int arp_hash(const u32 *key, int ifindex)
{
	return jhash_2words(*key, ifindex, 0) & L2T_HASH_MASK;
}

static inline unsigned int ipv6_hash(const u32 *key, int ifindex)
{
	u32 xor = key[0] ^ key[1] ^ key[2] ^ key[3];

	return L2T_SZ_HALF + (jhash_2words(xor, ifindex, 0) & L2T_HASH_MASK);
}

static unsigned int addr_hash(const u32 *addr, int addr_len, int ifindex)
{
	return addr_len == 4 ? arp_hash(addr, ifindex) :
			       ipv6_hash(addr, ifindex);
}


static inline unsigned short vlan_dev_get_egress_pri_mask(struct net_device* dev,
                                                           u32 priority)
{
        struct vlan_priority_tci_mapping *mp = 
		vlan_dev_info(dev)->egress_priority_map[(priority & 0xF)];
 
        while (mp) {
		if (mp->priority == priority) {
			return mp->vlan_qos; 
		}	
		mp = mp->next;
	}
	return 0;
}

/*
 * Checks if an L2T entry is for the given IP/IPv6 address.  It does not check
 * whether the L2T entry and the address are of the same address family.
 * Callers ensure an address is only checked against L2T entries of the same
 * family, something made trivial by the separation of IP and IPv6 hash chains
 * mentioned above.  Returns 0 if there's a match,
 */
static int addreq(const struct l2t_entry *e, const u32 *addr)
{
	if (e->v6)
		return (e->addr[0] ^ addr[0]) | (e->addr[1] ^ addr[1]) |
		       (e->addr[2] ^ addr[2]) | (e->addr[3] ^ addr[3]);
	return e->addr[0] ^ addr[0];
}

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

/*
 * Write an L2T entry.  Must be called with the entry locked.
 * The write may be synchronous or asynchronous.
 */
static int write_l2e(struct adapter *adap, struct l2t_entry *e, int sync)
{
	struct sk_buff *skb;
	struct cpl_l2t_write_req *req;

	skb = alloc_skb(sizeof(*req), GFP_ATOMIC);
	if (!skb)
		return -ENOMEM;

	req = (struct cpl_l2t_write_req *)__skb_put(skb, sizeof(*req));
	INIT_TP_WR(req, 0);

	OPCODE_TID(req) = htonl(MK_OPCODE_TID(CPL_L2T_WRITE_REQ,
					e->idx | V_SYNC_WR(sync) |
					V_TID_QID(adap->sge.fw_evtq.abs_id)));
	req->params = htons(V_L2T_W_PORT(e->lport) | V_L2T_W_NOREPLY(!sync));
	req->l2t_idx = htons(e->idx);
	req->vlan = htons(e->vlan);
	if (e->neigh && !(e->neigh->dev->flags & IFF_LOOPBACK))
		memcpy(e->dmac, e->neigh->ha, sizeof(e->dmac));
	memcpy(req->dst_mac, e->dmac, sizeof(req->dst_mac));

	set_wr_txq(skb, CPL_PRIORITY_CONTROL, 0);
	t4_ofld_send(adap, skb);

	if (sync && e->state != L2T_STATE_SWITCHING)
		e->state = L2T_STATE_SYNC_WRITE;

	return 0;
}

/*
 * Send packets waiting in an L2T entry's ARP queue.  Must be called with the
 * entry locked.
 */
static void send_pending(struct adapter *adap, struct l2t_entry *e)
{
	while (e->arpq_head) {
		struct sk_buff *skb = e->arpq_head;

		e->arpq_head = skb->next;
		skb->next = NULL;
		t4_ofld_send(adap, skb);
	}
	e->arpq_tail = NULL;
}

/*
 * Process a CPL_L2T_WRITE_RPL.  Wake up the ARP queue if it completes a
 * synchronous L2T_WRITE.  Note that the TID in the reply is really the L2T
 * index it refers to.
 */
void do_l2t_write_rpl(struct adapter *adap, const struct cpl_l2t_write_rpl *rpl)
{
	unsigned int tid = GET_TID(rpl);
	unsigned int idx = tid & (L2T_SIZE - 1);

	if (unlikely(rpl->status != CPL_ERR_NONE)) {
		CH_ERR(adap,
		       "Unexpected L2T_WRITE_RPL status %u for entry %u\n",
		       rpl->status, idx);
		return;
	}

	if (tid & F_SYNC_WR) {
		struct l2t_entry *e = &adap->l2t->l2tab[idx];

		spin_lock(&e->lock);
		if (e->state != L2T_STATE_SWITCHING) {
			send_pending(adap, e);
			e->state = (e->neigh->nud_state & NUD_STALE) ?
					L2T_STATE_STALE : L2T_STATE_VALID;
		}
		spin_unlock(&e->lock);
	}
}

/*
 * Add a packet to 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 cxgb4_l2t_send(struct net_device *dev, struct sk_buff *skb,
		   struct l2t_entry *e)
{
	struct adapter *adap = netdev2adap(dev);

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 t4_ofld_send(adap, skb);
	case L2T_STATE_RESOLVING:
	case L2T_STATE_SYNC_WRITE:
		spin_lock_bh(&e->lock);
		if (e->state != L2T_STATE_SYNC_WRITE &&
		    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 skb allocation 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 (e->state == L2T_STATE_RESOLVING &&
		    !neigh_event_send(e->neigh, NULL)) {
			spin_lock_bh(&e->lock);
			if (e->state == L2T_STATE_RESOLVING && e->arpq_head)
				write_l2e(adap, e, 1);
			spin_unlock_bh(&e->lock);
		}
	}
	return 0;
}
EXPORT_SYMBOL(cxgb4_l2t_send);

/*
 * 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[L2T_SIZE]; e != end; ++e)
		if (atomic_read(&e->refcnt) == 0)
			goto found;

	for (e = d->l2tab; 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_SWITCHING)
		for (p = &d->l2tab[e->hash].first; *p; p = &(*p)->next)
			if (*p == e) {
				*p = e->next;
				e->next = NULL;
				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.
 */
static void t4_l2e_free(struct l2t_entry *e)
{
	struct l2t_data *d;

	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;
		}
		/*
		 * Don't need to worry about the arpq, an L2T entry can't be
		 * released if any packets are waiting for resolution as we
		 * need to be able to communicate with the device to close a
		 * connection.
		 */
	}
	spin_unlock_bh(&e->lock);

	d = container_of(e, struct l2t_data, l2tab[e->idx]);
	atomic_inc(&d->nfree);
}

void cxgb4_l2t_release(struct l2t_entry *e)
{
	if (atomic_dec_and_test(&e->refcnt))
		t4_l2e_free(e);
}
EXPORT_SYMBOL(cxgb4_l2t_release);

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

	spin_lock(&e->lock);                /* avoid race with t4_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 *cxgb4_l2t_get(struct l2t_data *d, struct neighbour *neigh,
				const struct net_device *physdev , u32 priority)
{
	u8 lport;
	u16 vlan;
	struct l2t_entry *e;
	int addr_len = neigh->tbl->key_len;
	u32 *addr = (u32 *)neigh->primary_key;
	int ifidx = neigh->dev->ifindex;
	int hash = addr_hash(addr, addr_len, ifidx);

	if (neigh->dev->flags & IFF_LOOPBACK)
		lport = netdev2pinfo(physdev)->tx_chan + 4;
	else
		lport = netdev2pinfo(physdev)->lport;

	if (neigh->dev->priv_flags & IFF_802_1Q_VLAN) {
		vlan = vlan_dev_vlan_id(neigh->dev);
		vlan |= vlan_dev_get_egress_pri_mask(neigh->dev , priority);
	} else
		vlan = VLAN_NONE;

	write_lock_bh(&d->lock);
	for (e = d->l2tab[hash].first; e; e = e->next)
		if (!addreq(e, addr) && e->ifindex == ifidx &&
		    e->lport == lport && e->vlan == vlan) {
			l2t_hold(d, e);
			/*
			 * We now have an entry that has previously been used
			 * for this next hop.  If we are the sole owner it
			 * may have been some time since this entry has been
			 * maintained so we need to bring it up to date.
			 * Otherwise the existing users have been updating it.
			 */
			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 t4_l2t_free */
		e->state = L2T_STATE_RESOLVING;
		if (neigh->dev->flags & IFF_LOOPBACK)
			memcpy(e->dmac, physdev->dev_addr, ETH_ALEN); 
		memcpy(e->addr, addr, addr_len);
		e->ifindex = ifidx;
		e->hash = hash;
		e->lport = lport;
		e->v6 = addr_len == 16;
		atomic_set(&e->refcnt, 1);
		neigh_replace(e, neigh);
		e->vlan = vlan;
		e->next = d->l2tab[hash].first;
		d->l2tab[hash].first = e;
		spin_unlock(&e->lock);
	}
done:
	write_unlock_bh(&d->lock);
	return e;
}
EXPORT_SYMBOL(cxgb4_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 packet is sent to the device.
 *
 * XXX: maybe we should abandon the latter behavior and just require a failure
 * handler.
 */
static void handle_failed_resolution(struct adapter *adap, struct sk_buff *arpq)
{
	while (arpq) {
		struct sk_buff *skb = arpq;
		const struct l2t_skb_cb *cb = L2T_SKB_CB(skb);

		arpq = skb->next;
		skb->next = NULL;
		if (cb->arp_err_handler)
			cb->arp_err_handler(cb->handle, skb);
		else
			t4_ofld_send(adap, skb);
	}
}

/*
 * Called when the host's neighbor layer makes a change to some entry that is
 * loaded into the HW L2 table.
 */
void t4_l2t_update(struct adapter *adap, struct neighbour *neigh)
{
	struct l2t_entry *e;
	struct sk_buff *arpq = NULL;
	struct l2t_data *d = adap->l2t;
	int addr_len = neigh->tbl->key_len;
	u32 *addr = (u32 *) neigh->primary_key;
	int ifidx = neigh->dev->ifindex;
	int hash = addr_hash(addr, addr_len, ifidx);

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

 found:
	read_unlock(&d->lock);

	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)) &&
			   e->arpq_head) {
			write_l2e(adap, e, 1);
		}
	} else {
		e->state = neigh->nud_state & NUD_CONNECTED ?
			L2T_STATE_VALID : L2T_STATE_STALE;
		if (memcmp(e->dmac, neigh->ha, sizeof(e->dmac)))
			write_l2e(adap, e, 0);
	}

	spin_unlock_bh(&e->lock);

	if (arpq)
		handle_failed_resolution(adap, arpq);
}

/*
 * Allocate an L2T entry for use by a switching rule.  Such need to be
 * explicitly freed and while busy they are not on any hash chain, so normal
 * address resolution updates do not see them.
 */
struct l2t_entry *t4_l2t_alloc_switching(struct l2t_data *d)
{
	struct l2t_entry *e;

	write_lock_bh(&d->lock);
	e = alloc_l2e(d);
	if (e) {
		spin_lock(&e->lock);          /* avoid race with t4_l2t_free */
		e->state = L2T_STATE_SWITCHING;
		atomic_set(&e->refcnt, 1);
		spin_unlock(&e->lock);
	}
	write_unlock_bh(&d->lock);
	return e;
}

/*
 * Sets/updates the contents of a switching L2T entry that has been allocated
 * with an earlier call to @t4_l2t_alloc_switching.
 */
int t4_l2t_set_switching(struct adapter *adap, struct l2t_entry *e, u16 vlan,
			 u8 port, u8 *eth_addr)
{
	e->vlan = vlan;
	e->lport = port;
	memcpy(e->dmac, eth_addr, ETH_ALEN);
	return write_l2e(adap, e, 0);
}

struct l2t_data *t4_init_l2t(void)
{
	int i;
	struct l2t_data *d;

	d = t4_alloc_mem(sizeof(*d));
	if (!d)
		return NULL;

	d->rover = d->l2tab;
	atomic_set(&d->nfree, L2T_SIZE);
	rwlock_init(&d->lock);

	for (i = 0; i < L2T_SIZE; ++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);
	}
	return 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_entry *l2tab = seq->private;

	return pos >= L2T_SIZE ? NULL : &l2tab[pos];
}

static void *l2t_seq_start(struct seq_file *seq, loff_t *pos)
{
	return *pos ? l2t_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
}

static void *l2t_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	v = l2t_get_idx(seq, *pos);
	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_SYNC_WRITE: return 'W';
	case L2T_STATE_RESOLVING: return e->arpq_head ? 'A' : 'R';
	case L2T_STATE_SWITCHING: return 'X';
	default:
		return 'U';
	}
}

static int l2t_seq_show(struct seq_file *seq, void *v)
{
	if (v == SEQ_START_TOKEN)
		seq_puts(seq, " Idx IP address      Ethernet address  VLAN/P "
			 "LP State Users Port\n");
	else {
		char ip[60];
		struct l2t_entry *e = v;

		spin_lock_bh(&e->lock);
		if (e->state == L2T_STATE_SWITCHING)
			ip[0] = '\0';
		else if (!e->v6)
			sprintf(ip, NIPQUAD_FMT, NIPQUAD(e->addr[0]));
		else
			ip[0] = '\0';  // XXX IPv6 is too long, hmm
		seq_printf(seq, "%4u %-15s %02x:%02x:%02x:%02x:%02x:%02x %4d"
			   " %u %2u   %c   %5u %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), e->lport,
			   l2e_state(e), atomic_read(&e->refcnt),
			   e->neigh ? e->neigh->dev->name : "");
		spin_unlock_bh(&e->lock);
	}
	return 0;
}

static const 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 adapter *adap = PDE(inode)->data;
		struct seq_file *seq = file->private_data;

		seq->private = adap->l2t->l2tab;
	}
	return rc;
}

const struct file_operations t4_l2t_proc_fops = {
	.owner = THIS_MODULE,
	.open = l2t_seq_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = seq_release,
};
#endif