/*
 * Copyright (c) 2003-2008 Chelsio, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * 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/skbuff.h>
#include <linux/netdevice.h>
#include <linux/if.h>
#include <linux/if_vlan.h>
#include <linux/jhash.h>
#include <linux/slab.h>
#include <linux/export.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;
}

/*
 * 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)
{
        struct cpl_l2t_write_req *req;
        struct sk_buff *tmp;

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

        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)));
        memcpy(e->dmac, e->neigh->ha, sizeof(e->dmac));
        memcpy(req->dst_mac, e->dmac, sizeof(req->dst_mac));
        skb->priority = CPL_PRIORITY_CONTROL;
        cxgb3_ofld_send(dev, skb);

        skb_queue_walk_safe(&e->arpq, skb, tmp) {
                __skb_unlink(skb, &e->arpq);
                cxgb3_ofld_send(dev, skb);
        }
        e->state = L2T_STATE_VALID;

        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_queue_tail(&e->arpq, 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);
                fallthrough;
        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 (!skb_queue_empty(&e->arpq))
                                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);

/*
 * 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 dst_entry *dst,
                             struct net_device *dev, const void *daddr)
{
        struct l2t_entry *e = NULL;
        struct neighbour *neigh;
        struct port_info *p;
        struct l2t_data *d;
        int hash;
        u32 addr;
        int ifidx;
        int smt_idx;

        rcu_read_lock();
        neigh = dst_neigh_lookup(dst, daddr);
        if (!neigh)
                goto done_rcu;

        addr = *(u32 *) neigh->primary_key;
        ifidx = neigh->dev->ifindex;

        if (!dev)
                dev = neigh->dev;
        p = netdev_priv(dev);
        smt_idx = p->port_id;

        d = L2DATA(cdev);
        if (!d)
                goto done_rcu;

        hash = arp_hash(addr, ifidx, d);

        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_unlock;
                }

        /* 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;
                atomic_set(&e->refcnt, 1);
                neigh_replace(e, neigh);
                if (is_vlan_dev(neigh->dev))
                        e->vlan = vlan_dev_vlan_id(neigh->dev);
                else
                        e->vlan = VLAN_NONE;
                spin_unlock(&e->lock);
        }
done_unlock:
        write_unlock_bh(&d->lock);
done_rcu:
        if (neigh)
                neigh_release(neigh);
        rcu_read_unlock();
        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_head *arpq)
{
        struct sk_buff *skb, *tmp;

        skb_queue_walk_safe(arpq, skb, tmp) {
                struct l2t_skb_cb *cb = L2T_SKB_CB(skb);

                __skb_unlink(skb, arpq);
                if (cb->arp_failure_handler)
                        cb->arp_failure_handler(dev, skb);
                else
                        cxgb3_ofld_send(dev, skb);
        }
}

/*
 * 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 sk_buff_head arpq;
        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_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:
        __skb_queue_head_init(&arpq);

        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) {
                                skb_queue_splice_init(&e->arpq, &arpq);
                        } 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 (!ether_addr_equal(e->dmac, neigh->ha))
                                setup_l2e_send_pending(dev, NULL, e);
                }
        }
        spin_unlock_bh(&e->lock);

        if (!skb_queue_empty(&arpq))
                handle_failed_resolution(dev, &arpq);
}

struct l2t_data *t3_init_l2t(unsigned int l2t_capacity)
{
        struct l2t_data *d;
        int i;

        d = kvzalloc_flex(*d, l2tab, l2t_capacity);
        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;
                __skb_queue_head_init(&d->l2tab[i].arpq);
                spin_lock_init(&d->l2tab[i].lock);
                atomic_set(&d->l2tab[i].refcnt, 0);
        }
        return d;
}