/*
 * Equalizer Load-balancer for serial network interfaces.
 *
 * (c) Copyright 1995 Simon "Guru Aleph-Null" Janes
 * NCM: Network and Communications Management, Inc.
 *
 * (c) Copyright 2002 David S. Miller (davem@redhat.com)
 *
 *      This software may be used and distributed according to the terms
 *      of the GNU General Public License, incorporated herein by reference.
 *
 * The author may be reached as simon@ncm.com, or C/O
 *    NCM
 *    Attn: Simon Janes
 *    6803 Whittier Ave
 *    McLean VA 22101
 *    Phone: 1-703-847-0040 ext 103
 */

/*
 * Sources:
 *   skeleton.c by Donald Becker.
 * Inspirations:
 *   The Harried and Overworked Alan Cox
 * Conspiracies:
 *   The Alan Cox and Mike McLagan plot to get someone else to do the code,
 *   which turned out to be me.
 */

/*
 * $Log: eql.c,v $
 * Revision 1.2  1996/04/11 17:51:52  guru
 * Added one-line eql_remove_slave patch.
 *
 * Revision 1.1  1996/04/11 17:44:17  guru
 * Initial revision
 *
 * Revision 3.13  1996/01/21  15:17:18  alan
 * tx_queue_len changes.
 * reformatted.
 *
 * Revision 3.12  1995/03/22  21:07:51  anarchy
 * Added capable() checks on configuration.
 * Moved header file.
 *
 * Revision 3.11  1995/01/19  23:14:31  guru
 *                    slave_load = (ULONG_MAX - (ULONG_MAX / 2)) -
 *                      (priority_Bps) + bytes_queued * 8;
 *
 * Revision 3.10  1995/01/19  23:07:53  guru
 * back to
 *                    slave_load = (ULONG_MAX - (ULONG_MAX / 2)) -
 *                      (priority_Bps) + bytes_queued;
 *
 * Revision 3.9  1995/01/19  22:38:20  guru
 *                    slave_load = (ULONG_MAX - (ULONG_MAX / 2)) -
 *                      (priority_Bps) + bytes_queued * 4;
 *
 * Revision 3.8  1995/01/19  22:30:55  guru
 *       slave_load = (ULONG_MAX - (ULONG_MAX / 2)) -
 *                      (priority_Bps) + bytes_queued * 2;
 *
 * Revision 3.7  1995/01/19  21:52:35  guru
 * printk's trimmed out.
 *
 * Revision 3.6  1995/01/19  21:49:56  guru
 * This is working pretty well. I gained 1 K/s in speed.. now it's just
 * robustness and printk's to be diked out.
 *
 * Revision 3.5  1995/01/18  22:29:59  guru
 * still crashes the kernel when the lock_wait thing is woken up.
 *
 * Revision 3.4  1995/01/18  21:59:47  guru
 * Broken set-bit locking snapshot
 *
 * Revision 3.3  1995/01/17  22:09:18  guru
 * infinite sleep in a lock somewhere..
 *
 * Revision 3.2  1995/01/15  16:46:06  guru
 * Log trimmed of non-pertinent 1.x branch messages
 *
 * Revision 3.1  1995/01/15  14:41:45  guru
 * New Scheduler and timer stuff...
 *
 * Revision 1.15  1995/01/15  14:29:02  guru
 * Will make 1.14 (now 1.15) the 3.0 branch, and the 1.12 the 2.0 branch, the one
 * with the dumber scheduler
 *
 * Revision 1.14  1995/01/15  02:37:08  guru
 * shock.. the kept-new-versions could have zonked working
 * stuff.. shudder
 *
 * Revision 1.13  1995/01/15  02:36:31  guru
 * big changes
 *
 *      scheduler was torn out and replaced with something smarter
 *
 *      global names not prefixed with eql_ were renamed to protect
 *      against namespace collisions
 *
 *      a few more abstract interfaces were added to facilitate any
 *      potential change of datastructure.  the driver is still using
 *      a linked list of slaves.  going to a heap would be a bit of
 *      an overkill.
 *
 *      this compiles fine with no warnings.
 *
 *      the locking mechanism and timer stuff must be written however,
 *      this version will not work otherwise
 *
 * Sorry, I had to rewrite most of this for 2.5.x -DaveM
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/compat.h>
#include <linux/capability.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/netdevice.h>
#include <net/net_namespace.h>

#include <linux/if.h>
#include <linux/if_arp.h>
#include <linux/if_eql.h>
#include <linux/pkt_sched.h>

#include <linux/uaccess.h>

static int eql_open(struct net_device *dev);
static int eql_close(struct net_device *dev);
static int eql_siocdevprivate(struct net_device *dev, struct ifreq *ifr,
                              void __user *data, int cmd);
static netdev_tx_t eql_slave_xmit(struct sk_buff *skb, struct net_device *dev);

#define eql_is_slave(dev)       ((dev->flags & IFF_SLAVE) == IFF_SLAVE)
#define eql_is_master(dev)      ((dev->flags & IFF_MASTER) == IFF_MASTER)

static void eql_kill_one_slave(slave_queue_t *queue, slave_t *slave);

static void eql_timer(struct timer_list *t)
{
        equalizer_t *eql = timer_container_of(eql, t, timer);
        struct list_head *this, *tmp, *head;

        spin_lock(&eql->queue.lock);
        head = &eql->queue.all_slaves;
        list_for_each_safe(this, tmp, head) {
                slave_t *slave = list_entry(this, slave_t, list);

                if ((slave->dev->flags & IFF_UP) == IFF_UP) {
                        slave->bytes_queued -= slave->priority_Bps;
                        if (slave->bytes_queued < 0)
                                slave->bytes_queued = 0;
                } else {
                        eql_kill_one_slave(&eql->queue, slave);
                }

        }
        spin_unlock(&eql->queue.lock);

        eql->timer.expires = jiffies + EQL_DEFAULT_RESCHED_IVAL;
        add_timer(&eql->timer);
}

static const char version[] __initconst =
        "Equalizer2002: Simon Janes (simon@ncm.com) and David S. Miller (davem@redhat.com)";

static const struct net_device_ops eql_netdev_ops = {
        .ndo_open       = eql_open,
        .ndo_stop       = eql_close,
        .ndo_siocdevprivate = eql_siocdevprivate,
        .ndo_start_xmit = eql_slave_xmit,
};

static void __init eql_setup(struct net_device *dev)
{
        equalizer_t *eql = netdev_priv(dev);

        timer_setup(&eql->timer, eql_timer, 0);
        eql->timer.expires      = jiffies + EQL_DEFAULT_RESCHED_IVAL;

        spin_lock_init(&eql->queue.lock);
        INIT_LIST_HEAD(&eql->queue.all_slaves);
        eql->queue.master_dev   = dev;

        dev->netdev_ops         = &eql_netdev_ops;

        /*
         *      Now we undo some of the things that eth_setup does
         *      that we don't like
         */

        dev->mtu                = EQL_DEFAULT_MTU;      /* set to 576 in if_eql.h */
        dev->flags              = IFF_MASTER;

        dev->type               = ARPHRD_SLIP;
        dev->tx_queue_len       = 5;            /* Hands them off fast */
        netif_keep_dst(dev);
}

static int eql_open(struct net_device *dev)
{
        equalizer_t *eql = netdev_priv(dev);

        /* XXX We should force this off automatically for the user. */
        netdev_info(dev,
                    "remember to turn off Van-Jacobson compression on your slave devices\n");

        BUG_ON(!list_empty(&eql->queue.all_slaves));

        eql->min_slaves = 1;
        eql->max_slaves = EQL_DEFAULT_MAX_SLAVES; /* 4 usually... */

        add_timer(&eql->timer);

        return 0;
}

static void eql_kill_one_slave(slave_queue_t *queue, slave_t *slave)
{
        list_del(&slave->list);
        queue->num_slaves--;
        slave->dev->flags &= ~IFF_SLAVE;
        netdev_put(slave->dev, &slave->dev_tracker);
        kfree(slave);
}

static void eql_kill_slave_queue(slave_queue_t *queue)
{
        struct list_head *head, *tmp, *this;

        spin_lock_bh(&queue->lock);

        head = &queue->all_slaves;
        list_for_each_safe(this, tmp, head) {
                slave_t *s = list_entry(this, slave_t, list);

                eql_kill_one_slave(queue, s);
        }

        spin_unlock_bh(&queue->lock);
}

static int eql_close(struct net_device *dev)
{
        equalizer_t *eql = netdev_priv(dev);

        /*
         *      The timer has to be stopped first before we start hacking away
         *      at the data structure it scans every so often...
         */

        timer_delete_sync(&eql->timer);

        eql_kill_slave_queue(&eql->queue);

        return 0;
}

static int eql_enslave(struct net_device *dev,  slaving_request_t __user *srq);
static int eql_emancipate(struct net_device *dev, slaving_request_t __user *srq);

static int eql_g_slave_cfg(struct net_device *dev, slave_config_t __user *sc);
static int eql_s_slave_cfg(struct net_device *dev, slave_config_t __user *sc);

static int eql_g_master_cfg(struct net_device *dev, master_config_t __user *mc);
static int eql_s_master_cfg(struct net_device *dev, master_config_t __user *mc);

static int eql_siocdevprivate(struct net_device *dev, struct ifreq *ifr,
                              void __user *data, int cmd)
{
        if (cmd != EQL_GETMASTRCFG && cmd != EQL_GETSLAVECFG &&
            !capable(CAP_NET_ADMIN))
                return -EPERM;

        if (in_compat_syscall()) /* to be implemented */
                return -EOPNOTSUPP;

        switch (cmd) {
                case EQL_ENSLAVE:
                        return eql_enslave(dev, data);
                case EQL_EMANCIPATE:
                        return eql_emancipate(dev, data);
                case EQL_GETSLAVECFG:
                        return eql_g_slave_cfg(dev, data);
                case EQL_SETSLAVECFG:
                        return eql_s_slave_cfg(dev, data);
                case EQL_GETMASTRCFG:
                        return eql_g_master_cfg(dev, data);
                case EQL_SETMASTRCFG:
                        return eql_s_master_cfg(dev, data);
                default:
                        return -EOPNOTSUPP;
        }
}

/* queue->lock must be held */
static slave_t *__eql_schedule_slaves(slave_queue_t *queue)
{
        unsigned long best_load = ~0UL;
        struct list_head *this, *tmp, *head;
        slave_t *best_slave;

        best_slave = NULL;

        /* Make a pass to set the best slave. */
        head = &queue->all_slaves;
        list_for_each_safe(this, tmp, head) {
                slave_t *slave = list_entry(this, slave_t, list);
                unsigned long slave_load, bytes_queued, priority_Bps;

                /* Go through the slave list once, updating best_slave
                 * whenever a new best_load is found.
                 */
                bytes_queued = slave->bytes_queued;
                priority_Bps = slave->priority_Bps;
                if ((slave->dev->flags & IFF_UP) == IFF_UP) {
                        slave_load = (~0UL - (~0UL / 2)) -
                                (priority_Bps) + bytes_queued * 8;

                        if (slave_load < best_load) {
                                best_load = slave_load;
                                best_slave = slave;
                        }
                } else {
                        /* We found a dead slave, kill it. */
                        eql_kill_one_slave(queue, slave);
                }
        }
        return best_slave;
}

static netdev_tx_t eql_slave_xmit(struct sk_buff *skb, struct net_device *dev)
{
        equalizer_t *eql = netdev_priv(dev);
        slave_t *slave;

        spin_lock(&eql->queue.lock);

        slave = __eql_schedule_slaves(&eql->queue);
        if (slave) {
                struct net_device *slave_dev = slave->dev;

                skb->dev = slave_dev;
                skb->priority = TC_PRIO_FILLER;
                slave->bytes_queued += skb->len;
                dev_queue_xmit(skb);
                dev->stats.tx_packets++;
        } else {
                dev->stats.tx_dropped++;
                dev_kfree_skb(skb);
        }

        spin_unlock(&eql->queue.lock);

        return NETDEV_TX_OK;
}

/*
 *      Private ioctl functions
 */

/* queue->lock must be held */
static slave_t *__eql_find_slave_dev(slave_queue_t *queue, struct net_device *dev)
{
        struct list_head *this, *head;

        head = &queue->all_slaves;
        list_for_each(this, head) {
                slave_t *slave = list_entry(this, slave_t, list);

                if (slave->dev == dev)
                        return slave;
        }

        return NULL;
}

static inline int eql_is_full(slave_queue_t *queue)
{
        equalizer_t *eql = netdev_priv(queue->master_dev);

        if (queue->num_slaves >= eql->max_slaves)
                return 1;
        return 0;
}

/* queue->lock must be held */
static int __eql_insert_slave(slave_queue_t *queue, slave_t *slave)
{
        if (!eql_is_full(queue)) {
                slave_t *duplicate_slave = NULL;

                duplicate_slave = __eql_find_slave_dev(queue, slave->dev);
                if (duplicate_slave)
                        eql_kill_one_slave(queue, duplicate_slave);

                netdev_hold(slave->dev, &slave->dev_tracker, GFP_ATOMIC);
                list_add(&slave->list, &queue->all_slaves);
                queue->num_slaves++;
                slave->dev->flags |= IFF_SLAVE;

                return 0;
        }

        return -ENOSPC;
}

static int eql_enslave(struct net_device *master_dev, slaving_request_t __user *srqp)
{
        struct net_device *slave_dev;
        slaving_request_t srq;

        if (copy_from_user(&srq, srqp, sizeof (slaving_request_t)))
                return -EFAULT;

        slave_dev = __dev_get_by_name(&init_net, srq.slave_name);
        if (!slave_dev)
                return -ENODEV;

        if ((master_dev->flags & IFF_UP) == IFF_UP) {
                /* slave is not a master & not already a slave: */
                if (!eql_is_master(slave_dev) && !eql_is_slave(slave_dev)) {
                        slave_t *s = kzalloc_obj(*s);
                        equalizer_t *eql = netdev_priv(master_dev);
                        int ret;

                        if (!s)
                                return -ENOMEM;

                        s->dev = slave_dev;
                        s->priority = srq.priority;
                        s->priority_bps = srq.priority;
                        s->priority_Bps = srq.priority / 8;

                        spin_lock_bh(&eql->queue.lock);
                        ret = __eql_insert_slave(&eql->queue, s);
                        if (ret)
                                kfree(s);

                        spin_unlock_bh(&eql->queue.lock);

                        return ret;
                }
        }

        return -EINVAL;
}

static int eql_emancipate(struct net_device *master_dev, slaving_request_t __user *srqp)
{
        equalizer_t *eql = netdev_priv(master_dev);
        struct net_device *slave_dev;
        slaving_request_t srq;
        int ret;

        if (copy_from_user(&srq, srqp, sizeof (slaving_request_t)))
                return -EFAULT;

        slave_dev = __dev_get_by_name(&init_net, srq.slave_name);
        if (!slave_dev)
                return -ENODEV;

        ret = -EINVAL;
        spin_lock_bh(&eql->queue.lock);
        if (eql_is_slave(slave_dev)) {
                slave_t *slave = __eql_find_slave_dev(&eql->queue, slave_dev);
                if (slave) {
                        eql_kill_one_slave(&eql->queue, slave);
                        ret = 0;
                }
        }
        spin_unlock_bh(&eql->queue.lock);

        return ret;
}

static int eql_g_slave_cfg(struct net_device *dev, slave_config_t __user *scp)
{
        equalizer_t *eql = netdev_priv(dev);
        slave_t *slave;
        struct net_device *slave_dev;
        slave_config_t sc;
        int ret;

        if (copy_from_user(&sc, scp, sizeof (slave_config_t)))
                return -EFAULT;

        slave_dev = __dev_get_by_name(&init_net, sc.slave_name);
        if (!slave_dev)
                return -ENODEV;

        ret = -EINVAL;

        spin_lock_bh(&eql->queue.lock);
        if (eql_is_slave(slave_dev)) {
                slave = __eql_find_slave_dev(&eql->queue, slave_dev);
                if (slave) {
                        sc.priority = slave->priority;
                        ret = 0;
                }
        }
        spin_unlock_bh(&eql->queue.lock);

        if (!ret && copy_to_user(scp, &sc, sizeof (slave_config_t)))
                ret = -EFAULT;

        return ret;
}

static int eql_s_slave_cfg(struct net_device *dev, slave_config_t __user *scp)
{
        slave_t *slave;
        equalizer_t *eql;
        struct net_device *slave_dev;
        slave_config_t sc;
        int ret;

        if (copy_from_user(&sc, scp, sizeof (slave_config_t)))
                return -EFAULT;

        slave_dev = __dev_get_by_name(&init_net, sc.slave_name);
        if (!slave_dev)
                return -ENODEV;

        ret = -EINVAL;

        eql = netdev_priv(dev);
        spin_lock_bh(&eql->queue.lock);
        if (eql_is_slave(slave_dev)) {
                slave = __eql_find_slave_dev(&eql->queue, slave_dev);
                if (slave) {
                        slave->priority = sc.priority;
                        slave->priority_bps = sc.priority;
                        slave->priority_Bps = sc.priority / 8;
                        ret = 0;
                }
        }
        spin_unlock_bh(&eql->queue.lock);

        return ret;
}

static int eql_g_master_cfg(struct net_device *dev, master_config_t __user *mcp)
{
        equalizer_t *eql;
        master_config_t mc;

        memset(&mc, 0, sizeof(master_config_t));

        if (eql_is_master(dev)) {
                eql = netdev_priv(dev);
                mc.max_slaves = eql->max_slaves;
                mc.min_slaves = eql->min_slaves;
                if (copy_to_user(mcp, &mc, sizeof (master_config_t)))
                        return -EFAULT;
                return 0;
        }
        return -EINVAL;
}

static int eql_s_master_cfg(struct net_device *dev, master_config_t __user *mcp)
{
        equalizer_t *eql;
        master_config_t mc;

        if (copy_from_user(&mc, mcp, sizeof (master_config_t)))
                return -EFAULT;

        if (eql_is_master(dev)) {
                eql = netdev_priv(dev);
                eql->max_slaves = mc.max_slaves;
                eql->min_slaves = mc.min_slaves;
                return 0;
        }
        return -EINVAL;
}

static struct net_device *dev_eql;

static int __init eql_init_module(void)
{
        int err;

        pr_info("%s\n", version);

        dev_eql = alloc_netdev(sizeof(equalizer_t), "eql", NET_NAME_UNKNOWN,
                               eql_setup);
        if (!dev_eql)
                return -ENOMEM;

        err = register_netdev(dev_eql);
        if (err)
                free_netdev(dev_eql);
        return err;
}

static void __exit eql_cleanup_module(void)
{
        unregister_netdev(dev_eql);
        free_netdev(dev_eql);
}

module_init(eql_init_module);
module_exit(eql_cleanup_module);
MODULE_DESCRIPTION("Equalizer Load-balancer for serial network interfaces");
MODULE_LICENSE("GPL");