// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2010-2011 EIA Electronics,
//                         Pieter Beyens <pieter.beyens@eia.be>
// Copyright (c) 2010-2011 EIA Electronics,
//                         Kurt Van Dijck <kurt.van.dijck@eia.be>
// Copyright (c) 2018 Protonic,
//                         Robin van der Gracht <robin@protonic.nl>
// Copyright (c) 2017-2019 Pengutronix,
//                         Marc Kleine-Budde <kernel@pengutronix.de>
// Copyright (c) 2017-2019 Pengutronix,
//                         Oleksij Rempel <kernel@pengutronix.de>

/* Core of can-j1939 that links j1939 to CAN. */

#include <linux/can/can-ml.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/if_arp.h>
#include <linux/module.h>

#include "j1939-priv.h"

MODULE_DESCRIPTION("PF_CAN SAE J1939");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("EIA Electronics (Kurt Van Dijck & Pieter Beyens)");
MODULE_ALIAS("can-proto-" __stringify(CAN_J1939));

/* LOWLEVEL CAN interface */

/* CAN_HDR: #bytes before can_frame data part */
#define J1939_CAN_HDR (offsetof(struct can_frame, data))

/* CAN_FTR: #bytes beyond data part */
#define J1939_CAN_FTR (sizeof(struct can_frame) - J1939_CAN_HDR - \
                 sizeof(((struct can_frame *)0)->data))

/* lowest layer */
static void j1939_can_recv(struct sk_buff *iskb, void *data)
{
        struct j1939_priv *priv = data;
        struct sk_buff *skb;
        struct j1939_sk_buff_cb *skcb, *iskcb;
        struct can_frame *cf;

        /* create a copy of the skb
         * j1939 only delivers the real data bytes,
         * the header goes into sockaddr.
         * j1939 may not touch the incoming skb in such way
         */
        skb = skb_clone(iskb, GFP_ATOMIC);
        if (!skb)
                return;

        j1939_priv_get(priv);
        can_skb_set_owner(skb, iskb->sk);

        /* get a pointer to the header of the skb
         * the skb payload (pointer) is moved, so that the next skb_data
         * returns the actual payload
         */
        cf = (void *)skb->data;
        skb_pull(skb, J1939_CAN_HDR);

        /* fix length, set to dlc, with 8 maximum */
        skb_trim(skb, min_t(uint8_t, cf->len, 8));

        /* set addr */
        skcb = j1939_skb_to_cb(skb);
        memset(skcb, 0, sizeof(*skcb));

        iskcb = j1939_skb_to_cb(iskb);
        skcb->tskey = iskcb->tskey;
        skcb->priority = (cf->can_id >> 26) & 0x7;
        skcb->addr.sa = cf->can_id;
        skcb->addr.pgn = (cf->can_id >> 8) & J1939_PGN_MAX;
        /* set default message type */
        skcb->addr.type = J1939_TP;
        if (j1939_pgn_is_pdu1(skcb->addr.pgn)) {
                /* Type 1: with destination address */
                skcb->addr.da = skcb->addr.pgn;
                /* normalize pgn: strip dst address */
                skcb->addr.pgn &= 0x3ff00;
        } else {
                /* set broadcast address */
                skcb->addr.da = J1939_NO_ADDR;
        }

        /* update localflags */
        read_lock_bh(&priv->lock);
        if (j1939_address_is_unicast(skcb->addr.sa) &&
            priv->ents[skcb->addr.sa].nusers)
                skcb->flags |= J1939_ECU_LOCAL_SRC;
        if (j1939_address_is_unicast(skcb->addr.da) &&
            priv->ents[skcb->addr.da].nusers)
                skcb->flags |= J1939_ECU_LOCAL_DST;
        read_unlock_bh(&priv->lock);

        /* deliver into the j1939 stack ... */
        j1939_ac_recv(priv, skb);

        if (j1939_tp_recv(priv, skb))
                /* this means the transport layer processed the message */
                goto done;

        j1939_simple_recv(priv, skb);
        j1939_sk_recv(priv, skb);
 done:
        j1939_priv_put(priv);
        kfree_skb(skb);
}

/* NETDEV MANAGEMENT */

/* values for can_rx_(un)register */
#define J1939_CAN_ID CAN_EFF_FLAG
#define J1939_CAN_MASK (CAN_EFF_FLAG | CAN_RTR_FLAG)

static DEFINE_SPINLOCK(j1939_netdev_lock);

static struct j1939_priv *j1939_priv_create(struct net_device *ndev)
{
        struct j1939_priv *priv;

        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return NULL;

        rwlock_init(&priv->lock);
        INIT_LIST_HEAD(&priv->ecus);
        priv->ndev = ndev;
        kref_init(&priv->kref);
        kref_init(&priv->rx_kref);
        dev_hold(ndev);

        netdev_dbg(priv->ndev, "%s : 0x%p\n", __func__, priv);

        return priv;
}

static inline void j1939_priv_set(struct net_device *ndev,
                                  struct j1939_priv *priv)
{
        struct can_ml_priv *can_ml = can_get_ml_priv(ndev);

        can_ml->j1939_priv = priv;
}

static void __j1939_priv_release(struct kref *kref)
{
        struct j1939_priv *priv = container_of(kref, struct j1939_priv, kref);
        struct net_device *ndev = priv->ndev;

        netdev_dbg(priv->ndev, "%s: 0x%p\n", __func__, priv);

        WARN_ON_ONCE(!list_empty(&priv->active_session_list));
        WARN_ON_ONCE(!list_empty(&priv->ecus));
        WARN_ON_ONCE(!list_empty(&priv->j1939_socks));

        dev_put(ndev);
        kfree(priv);
}

void j1939_priv_put(struct j1939_priv *priv)
{
        kref_put(&priv->kref, __j1939_priv_release);
}

void j1939_priv_get(struct j1939_priv *priv)
{
        kref_get(&priv->kref);
}

static int j1939_can_rx_register(struct j1939_priv *priv)
{
        struct net_device *ndev = priv->ndev;
        int ret;

        j1939_priv_get(priv);
        ret = can_rx_register(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
                              j1939_can_recv, priv, "j1939", NULL);
        if (ret < 0) {
                j1939_priv_put(priv);
                return ret;
        }

        return 0;
}

static void j1939_can_rx_unregister(struct j1939_priv *priv)
{
        struct net_device *ndev = priv->ndev;

        can_rx_unregister(dev_net(ndev), ndev, J1939_CAN_ID, J1939_CAN_MASK,
                          j1939_can_recv, priv);

        /* The last reference of priv is dropped by the RCU deferred
         * j1939_sk_sock_destruct() of the last socket, so we can
         * safely drop this reference here.
         */
        j1939_priv_put(priv);
}

static void __j1939_rx_release(struct kref *kref)
        __releases(&j1939_netdev_lock)
{
        struct j1939_priv *priv = container_of(kref, struct j1939_priv,
                                               rx_kref);

        j1939_can_rx_unregister(priv);
        j1939_ecu_unmap_all(priv);
        j1939_priv_set(priv->ndev, NULL);
        spin_unlock(&j1939_netdev_lock);
}

/* get pointer to priv without increasing ref counter */
static inline struct j1939_priv *j1939_ndev_to_priv(struct net_device *ndev)
{
        struct can_ml_priv *can_ml = can_get_ml_priv(ndev);

        return can_ml->j1939_priv;
}

static struct j1939_priv *j1939_priv_get_by_ndev_locked(struct net_device *ndev)
{
        struct j1939_priv *priv;

        lockdep_assert_held(&j1939_netdev_lock);

        priv = j1939_ndev_to_priv(ndev);
        if (priv)
                j1939_priv_get(priv);

        return priv;
}

static struct j1939_priv *j1939_priv_get_by_ndev(struct net_device *ndev)
{
        struct j1939_priv *priv;

        spin_lock(&j1939_netdev_lock);
        priv = j1939_priv_get_by_ndev_locked(ndev);
        spin_unlock(&j1939_netdev_lock);

        return priv;
}

struct j1939_priv *j1939_netdev_start(struct net_device *ndev)
{
        struct j1939_priv *priv, *priv_new;
        int ret;

        priv = j1939_priv_get_by_ndev(ndev);
        if (priv) {
                kref_get(&priv->rx_kref);
                return priv;
        }

        priv = j1939_priv_create(ndev);
        if (!priv)
                return ERR_PTR(-ENOMEM);

        j1939_tp_init(priv);
        spin_lock_init(&priv->j1939_socks_lock);
        INIT_LIST_HEAD(&priv->j1939_socks);

        spin_lock(&j1939_netdev_lock);
        priv_new = j1939_priv_get_by_ndev_locked(ndev);
        if (priv_new) {
                /* Someone was faster than us, use their priv and roll
                 * back our's.
                 */
                spin_unlock(&j1939_netdev_lock);
                dev_put(ndev);
                kfree(priv);
                kref_get(&priv_new->rx_kref);
                return priv_new;
        }
        j1939_priv_set(ndev, priv);
        spin_unlock(&j1939_netdev_lock);

        ret = j1939_can_rx_register(priv);
        if (ret < 0)
                goto out_priv_put;

        return priv;

 out_priv_put:
        j1939_priv_set(ndev, NULL);
        dev_put(ndev);
        kfree(priv);

        return ERR_PTR(ret);
}

void j1939_netdev_stop(struct j1939_priv *priv)
{
        kref_put_lock(&priv->rx_kref, __j1939_rx_release, &j1939_netdev_lock);
        j1939_priv_put(priv);
}

int j1939_send_one(struct j1939_priv *priv, struct sk_buff *skb)
{
        int ret, dlc;
        canid_t canid;
        struct j1939_sk_buff_cb *skcb = j1939_skb_to_cb(skb);
        struct can_frame *cf;

        /* apply sanity checks */
        if (j1939_pgn_is_pdu1(skcb->addr.pgn))
                skcb->addr.pgn &= J1939_PGN_PDU1_MAX;
        else
                skcb->addr.pgn &= J1939_PGN_MAX;

        if (skcb->priority > 7)
                skcb->priority = 6;

        ret = j1939_ac_fixup(priv, skb);
        if (unlikely(ret))
                goto failed;
        dlc = skb->len;

        /* re-claim the CAN_HDR from the SKB */
        cf = skb_push(skb, J1939_CAN_HDR);

        /* make it a full can frame again */
        skb_put(skb, J1939_CAN_FTR + (8 - dlc));

        canid = CAN_EFF_FLAG |
                (skcb->priority << 26) |
                (skcb->addr.pgn << 8) |
                skcb->addr.sa;
        if (j1939_pgn_is_pdu1(skcb->addr.pgn))
                canid |= skcb->addr.da << 8;

        cf->can_id = canid;
        cf->len = dlc;

        return can_send(skb, 1);

 failed:
        kfree_skb(skb);
        return ret;
}

static int j1939_netdev_notify(struct notifier_block *nb,
                               unsigned long msg, void *data)
{
        struct net_device *ndev = netdev_notifier_info_to_dev(data);
        struct can_ml_priv *can_ml = can_get_ml_priv(ndev);
        struct j1939_priv *priv;

        if (!can_ml)
                goto notify_done;

        priv = j1939_priv_get_by_ndev(ndev);
        if (!priv)
                goto notify_done;

        switch (msg) {
        case NETDEV_DOWN:
                j1939_cancel_active_session(priv, NULL);
                j1939_sk_netdev_event_netdown(priv);
                j1939_ecu_unmap_all(priv);
                break;
        }

        j1939_priv_put(priv);

notify_done:
        return NOTIFY_DONE;
}

static struct notifier_block j1939_netdev_notifier = {
        .notifier_call = j1939_netdev_notify,
};

/* MODULE interface */
static __init int j1939_module_init(void)
{
        int ret;

        pr_info("can: SAE J1939\n");

        ret = register_netdevice_notifier(&j1939_netdev_notifier);
        if (ret)
                goto fail_notifier;

        ret = can_proto_register(&j1939_can_proto);
        if (ret < 0) {
                pr_err("can: registration of j1939 protocol failed\n");
                goto fail_sk;
        }

        return 0;

 fail_sk:
        unregister_netdevice_notifier(&j1939_netdev_notifier);
 fail_notifier:
        return ret;
}

static __exit void j1939_module_exit(void)
{
        can_proto_unregister(&j1939_can_proto);

        unregister_netdevice_notifier(&j1939_netdev_notifier);
}

module_init(j1939_module_init);
module_exit(j1939_module_exit);