caif_dev.c

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/*
 * CAIF Interface registration.
 * Copyright (C) ST-Ericsson AB 2010
 * Author:  Sjur Brendeland/[email protected]
 * License terms: GNU General Public License (GPL) version 2
 *
 * Borrowed heavily from file: pn_dev.c. Thanks to Remi Denis-Courmont
 *  and Sakari Ailus <[email protected]>
 */

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

#include <linux/kernel.h>
#include <linux/if_arp.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <net/netns/generic.h>
#include <net/net_namespace.h>
#include <net/pkt_sched.h>
#include <net/caif/caif_device.h>
#include <net/caif/caif_layer.h>
#include <net/caif/cfpkt.h>
#include <net/caif/cfcnfg.h>
#include <net/caif/cfserl.h>

MODULE_LICENSE("GPL");

/* Used for local tracking of the CAIF net devices */
struct caif_device_entry {
    struct cflayer layer;
    struct list_head list;
    struct net_device *netdev;
    int __percpu *pcpu_refcnt;
    spinlock_t flow_lock;
    struct sk_buff *xoff_skb;
    void (*xoff_skb_dtor)(struct sk_buff *skb);
    bool xoff;
};

struct caif_device_entry_list {
    struct list_head list;
    /* Protects simulanous deletes in list */
    struct mutex lock;
};

struct caif_net {
    struct cfcnfg *cfg;
    struct caif_device_entry_list caifdevs;
};

static int caif_net_id;
static int q_high = 50; /* Percent */

struct cfcnfg *get_cfcnfg(struct net *net)
{
    struct caif_net *caifn;
    caifn = net_generic(net, caif_net_id);
    return caifn->cfg;
}
EXPORT_SYMBOL(get_cfcnfg);

static struct caif_device_entry_list *caif_device_list(struct net *net)
{
    struct caif_net *caifn;
    caifn = net_generic(net, caif_net_id);
    return &caifn->caifdevs;
}

static void caifd_put(struct caif_device_entry *e)
{
    this_cpu_dec(*e->pcpu_refcnt);
}

static void caifd_hold(struct caif_device_entry *e)
{
    this_cpu_inc(*e->pcpu_refcnt);
}

static int caifd_refcnt_read(struct caif_device_entry *e)
{
    int i, refcnt = 0;
    for_each_possible_cpu(i)
        refcnt += *per_cpu_ptr(e->pcpu_refcnt, i);
    return refcnt;
}

/* Allocate new CAIF device. */
static struct caif_device_entry *caif_device_alloc(struct net_device *dev)
{
    struct caif_device_entry *caifd;

    caifd = kzalloc(sizeof(*caifd), GFP_KERNEL);
    if (!caifd)
        return NULL;
    caifd->pcpu_refcnt = alloc_percpu(int);
    if (!caifd->pcpu_refcnt) {
        kfree(caifd);
        return NULL;
    }
    caifd->netdev = dev;
    dev_hold(dev);
    return caifd;
}

static struct caif_device_entry *caif_get(struct net_device *dev)
{
    struct caif_device_entry_list *caifdevs =
        caif_device_list(dev_net(dev));
    struct caif_device_entry *caifd;

    list_for_each_entry_rcu(caifd, &caifdevs->list, list) {
        if (caifd->netdev == dev)
            return caifd;
    }
    return NULL;
}

void caif_flow_cb(struct sk_buff *skb)
{
    struct caif_device_entry *caifd;
    void (*dtor)(struct sk_buff *skb) = NULL;
    bool send_xoff;

    WARN_ON(skb->dev == NULL);

    rcu_read_lock();
    caifd = caif_get(skb->dev);

    WARN_ON(caifd == NULL);
    if (caifd == NULL)
        return;

    caifd_hold(caifd);
    rcu_read_unlock();

    spin_lock_bh(&caifd->flow_lock);
    send_xoff = caifd->xoff;
    caifd->xoff = 0;
    dtor = caifd->xoff_skb_dtor;

    if (WARN_ON(caifd->xoff_skb != skb))
        skb = NULL;

    caifd->xoff_skb = NULL;
    caifd->xoff_skb_dtor = NULL;

    spin_unlock_bh(&caifd->flow_lock);

    if (dtor && skb)
        dtor(skb);

    if (send_xoff)
        caifd->layer.up->
            ctrlcmd(caifd->layer.up,
                _CAIF_CTRLCMD_PHYIF_FLOW_ON_IND,
                caifd->layer.id);
    caifd_put(caifd);
}

static int transmit(struct cflayer *layer, struct cfpkt *pkt)
{
    int err, high = 0, qlen = 0;
    struct caif_device_entry *caifd =
        container_of(layer, struct caif_device_entry, layer);
    struct sk_buff *skb;
    struct netdev_queue *txq;

    rcu_read_lock_bh();

    skb = cfpkt_tonative(pkt);
    skb->dev = caifd->netdev;
    skb_reset_network_header(skb);
    skb->protocol = htons(ETH_P_CAIF);

    /* Check if we need to handle xoff */
    if (likely(caifd->netdev->tx_queue_len == 0))
        goto noxoff;

    if (unlikely(caifd->xoff))
        goto noxoff;

    if (likely(!netif_queue_stopped(caifd->netdev))) {
        /* If we run with a TX queue, check if the queue is too long*/
        txq = netdev_get_tx_queue(skb->dev, 0);
        qlen = qdisc_qlen(rcu_dereference_bh(txq->qdisc));

        if (likely(qlen == 0))
            goto noxoff;

        high = (caifd->netdev->tx_queue_len * q_high) / 100;
        if (likely(qlen < high))
            goto noxoff;
    }

    /* Hold lock while accessing xoff */
    spin_lock_bh(&caifd->flow_lock);
    if (caifd->xoff) {
        spin_unlock_bh(&caifd->flow_lock);
        goto noxoff;
    }

    /*
     * Handle flow off, we do this by temporary hi-jacking this
     * skb's destructor function, and replace it with our own
     * flow-on callback. The callback will set flow-on and call
     * the original destructor.
     */

    pr_debug("queue has stopped(%d) or is full (%d > %d)\n",
            netif_queue_stopped(caifd->netdev),
            qlen, high);
    caifd->xoff = 1;
    caifd->xoff_skb = skb;
    caifd->xoff_skb_dtor = skb->destructor;
    skb->destructor = caif_flow_cb;
    spin_unlock_bh(&caifd->flow_lock);

    caifd->layer.up->ctrlcmd(caifd->layer.up,
                    _CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
                    caifd->layer.id);
noxoff:
    rcu_read_unlock_bh();

    err = dev_queue_xmit(skb);
    if (err > 0)
        err = -EIO;

    return err;
}

/*
 * Stuff received packets into the CAIF stack.
 * On error, returns non-zero and releases the skb.
 */
static int receive(struct sk_buff *skb, struct net_device *dev,
           struct packet_type *pkttype, struct net_device *orig_dev)
{
    struct cfpkt *pkt;
    struct caif_device_entry *caifd;
    int err;

    pkt = cfpkt_fromnative(CAIF_DIR_IN, skb);

    rcu_read_lock();
    caifd = caif_get(dev);

    if (!caifd || !caifd->layer.up || !caifd->layer.up->receive ||
            !netif_oper_up(caifd->netdev)) {
        rcu_read_unlock();
        kfree_skb(skb);
        return NET_RX_DROP;
    }

    /* Hold reference to netdevice while using CAIF stack */
    caifd_hold(caifd);
    rcu_read_unlock();

    err = caifd->layer.up->receive(caifd->layer.up, pkt);

    /* For -EILSEQ the packet is not freed so so it now */
    if (err == -EILSEQ)
        cfpkt_destroy(pkt);

    /* Release reference to stack upwards */
    caifd_put(caifd);

    if (err != 0)
        err = NET_RX_DROP;
    return err;
}

static struct packet_type caif_packet_type __read_mostly = {
    .type = cpu_to_be16(ETH_P_CAIF),
    .func = receive,
};

static void dev_flowctrl(struct net_device *dev, int on)
{
    struct caif_device_entry *caifd;

    rcu_read_lock();

    caifd = caif_get(dev);
    if (!caifd || !caifd->layer.up || !caifd->layer.up->ctrlcmd) {
        rcu_read_unlock();
        return;
    }

    caifd_hold(caifd);
    rcu_read_unlock();

    caifd->layer.up->ctrlcmd(caifd->layer.up,
                 on ?
                 _CAIF_CTRLCMD_PHYIF_FLOW_ON_IND :
                 _CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
                 caifd->layer.id);
    caifd_put(caifd);
}

void caif_enroll_dev(struct net_device *dev, struct caif_dev_common *caifdev,
            struct cflayer *link_support, int head_room,
            struct cflayer **layer, int (**rcv_func)(
                struct sk_buff *, struct net_device *,
                struct packet_type *, struct net_device *))
{
    struct caif_device_entry *caifd;
    enum cfcnfg_phy_preference pref;
    struct cfcnfg *cfg = get_cfcnfg(dev_net(dev));
    struct caif_device_entry_list *caifdevs;

    caifdevs = caif_device_list(dev_net(dev));
    caifd = caif_device_alloc(dev);
    if (!caifd)
        return;
    *layer = &caifd->layer;
    spin_lock_init(&caifd->flow_lock);

    switch (caifdev->link_select) {
    case CAIF_LINK_HIGH_BANDW:
        pref = CFPHYPREF_HIGH_BW;
        break;
    case CAIF_LINK_LOW_LATENCY:
        pref = CFPHYPREF_LOW_LAT;
        break;
    default:
        pref = CFPHYPREF_HIGH_BW;
        break;
    }
    mutex_lock(&caifdevs->lock);
    list_add_rcu(&caifd->list, &caifdevs->list);

    strncpy(caifd->layer.name, dev->name,
        sizeof(caifd->layer.name) - 1);
    caifd->layer.name[sizeof(caifd->layer.name) - 1] = 0;
    caifd->layer.transmit = transmit;
    cfcnfg_add_phy_layer(cfg,
                dev,
                &caifd->layer,
                pref,
                link_support,
                caifdev->use_fcs,
                head_room);
    mutex_unlock(&caifdevs->lock);
    if (rcv_func)
        *rcv_func = receive;
}
EXPORT_SYMBOL(caif_enroll_dev);

/* notify Caif of device events */
static int caif_device_notify(struct notifier_block *me, unsigned long what,
                  void *arg)
{
    struct net_device *dev = arg;
    struct caif_device_entry *caifd = NULL;
    struct caif_dev_common *caifdev;
    struct cfcnfg *cfg;
    struct cflayer *layer, *link_support;
    int head_room = 0;
    struct caif_device_entry_list *caifdevs;

    cfg = get_cfcnfg(dev_net(dev));
    caifdevs = caif_device_list(dev_net(dev));

    caifd = caif_get(dev);
    if (caifd == NULL && dev->type != ARPHRD_CAIF)
        return 0;

    switch (what) {
    case NETDEV_REGISTER:
        if (caifd != NULL)
            break;

        caifdev = netdev_priv(dev);

        link_support = NULL;
        if (caifdev->use_frag) {
            head_room = 1;
            link_support = cfserl_create(dev->ifindex,
                            caifdev->use_stx);
            if (!link_support) {
                pr_warn("Out of memory\n");
                break;
            }
        }
        caif_enroll_dev(dev, caifdev, link_support, head_room,
                &layer, NULL);
        caifdev->flowctrl = dev_flowctrl;
        break;

    case NETDEV_UP:
        rcu_read_lock();

        caifd = caif_get(dev);
        if (caifd == NULL) {
            rcu_read_unlock();
            break;
        }

        caifd->xoff = 0;
        cfcnfg_set_phy_state(cfg, &caifd->layer, true);
        rcu_read_unlock();

        break;

    case NETDEV_DOWN:
        rcu_read_lock();

        caifd = caif_get(dev);
        if (!caifd || !caifd->layer.up || !caifd->layer.up->ctrlcmd) {
            rcu_read_unlock();
            return -EINVAL;
        }

        cfcnfg_set_phy_state(cfg, &caifd->layer, false);
        caifd_hold(caifd);
        rcu_read_unlock();

        caifd->layer.up->ctrlcmd(caifd->layer.up,
                     _CAIF_CTRLCMD_PHYIF_DOWN_IND,
                     caifd->layer.id);

        spin_lock_bh(&caifd->flow_lock);

        /*
         * Replace our xoff-destructor with original destructor.
         * We trust that skb->destructor *always* is called before
         * the skb reference is invalid. The hijacked SKB destructor
         * takes the flow_lock so manipulating the skb->destructor here
         * should be safe.
        */
        if (caifd->xoff_skb_dtor != NULL && caifd->xoff_skb != NULL)
            caifd->xoff_skb->destructor = caifd->xoff_skb_dtor;

        caifd->xoff = 0;
        caifd->xoff_skb_dtor = NULL;
        caifd->xoff_skb = NULL;

        spin_unlock_bh(&caifd->flow_lock);
        caifd_put(caifd);
        break;

    case NETDEV_UNREGISTER:
        mutex_lock(&caifdevs->lock);

        caifd = caif_get(dev);
        if (caifd == NULL) {
            mutex_unlock(&caifdevs->lock);
            break;
        }
        list_del_rcu(&caifd->list);

        /*
         * NETDEV_UNREGISTER is called repeatedly until all reference
         * counts for the net-device are released. If references to
         * caifd is taken, simply ignore NETDEV_UNREGISTER and wait for
         * the next call to NETDEV_UNREGISTER.
         *
         * If any packets are in flight down the CAIF Stack,
         * cfcnfg_del_phy_layer will return nonzero.
         * If no packets are in flight, the CAIF Stack associated
         * with the net-device un-registering is freed.
         */

        if (caifd_refcnt_read(caifd) != 0 ||
            cfcnfg_del_phy_layer(cfg, &caifd->layer) != 0) {

            pr_info("Wait for device inuse\n");
            /* Enrole device if CAIF Stack is still in use */
            list_add_rcu(&caifd->list, &caifdevs->list);
            mutex_unlock(&caifdevs->lock);
            break;
        }

        synchronize_rcu();
        dev_put(caifd->netdev);
        free_percpu(caifd->pcpu_refcnt);
        kfree(caifd);

        mutex_unlock(&caifdevs->lock);
        break;
    }
    return 0;
}

static struct notifier_block caif_device_notifier = {
    .notifier_call = caif_device_notify,
    .priority = 0,
};

/* Per-namespace Caif devices handling */
static int caif_init_net(struct net *net)
{
    struct caif_net *caifn = net_generic(net, caif_net_id);
    INIT_LIST_HEAD(&caifn->caifdevs.list);
    mutex_init(&caifn->caifdevs.lock);

    caifn->cfg = cfcnfg_create();
    if (!caifn->cfg)
        return -ENOMEM;

    return 0;
}

static void caif_exit_net(struct net *net)
{
    struct caif_device_entry *caifd, *tmp;
    struct caif_device_entry_list *caifdevs =
        caif_device_list(net);
    struct cfcnfg *cfg =  get_cfcnfg(net);

    rtnl_lock();
    mutex_lock(&caifdevs->lock);

    list_for_each_entry_safe(caifd, tmp, &caifdevs->list, list) {
        int i = 0;
        list_del_rcu(&caifd->list);
        cfcnfg_set_phy_state(cfg, &caifd->layer, false);

        while (i < 10 &&
            (caifd_refcnt_read(caifd) != 0 ||
            cfcnfg_del_phy_layer(cfg, &caifd->layer) != 0)) {

            pr_info("Wait for device inuse\n");
            msleep(250);
            i++;
        }
        synchronize_rcu();
        dev_put(caifd->netdev);
        free_percpu(caifd->pcpu_refcnt);
        kfree(caifd);
    }
    cfcnfg_remove(cfg);

    mutex_unlock(&caifdevs->lock);
    rtnl_unlock();
}

static struct pernet_operations caif_net_ops = {
    .init = caif_init_net,
    .exit = caif_exit_net,
    .id   = &caif_net_id,
    .size = sizeof(struct caif_net),
};

/* Initialize Caif devices list */
static int __init caif_device_init(void)
{
    int result;

    result = register_pernet_subsys(&caif_net_ops);

    if (result)
        return result;

    register_netdevice_notifier(&caif_device_notifier);
    dev_add_pack(&caif_packet_type);

    return result;
}

static void __exit caif_device_exit(void)
{
    unregister_netdevice_notifier(&caif_device_notifier);
    dev_remove_pack(&caif_packet_type);
    unregister_pernet_subsys(&caif_net_ops);
}

module_init(caif_device_init);
module_exit(caif_device_exit);