// SPDX-License-Identifier: GPL-2.0-only
/*
 * Generic HDLC support routines for Linux
 * X.25 support
 *
 * Copyright (C) 1999 - 2006 Krzysztof Halasa <khc@pm.waw.pl>
 */

#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/hdlc.h>
#include <linux/if_arp.h>
#include <linux/inetdevice.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/lapb.h>
#include <linux/module.h>
#include <linux/pkt_sched.h>
#include <linux/poll.h>
#include <linux/rtnetlink.h>
#include <linux/skbuff.h>
#include <net/x25device.h>

struct x25_state {
        x25_hdlc_proto settings;
        bool up;
        spinlock_t up_lock; /* Protects "up" */
        struct sk_buff_head rx_queue;
        struct tasklet_struct rx_tasklet;
};

static int x25_ioctl(struct net_device *dev, struct if_settings *ifs);

static struct x25_state *state(hdlc_device *hdlc)
{
        return hdlc->state;
}

static void x25_rx_queue_kick(struct tasklet_struct *t)
{
        struct x25_state *x25st = from_tasklet(x25st, t, rx_tasklet);
        struct sk_buff *skb = skb_dequeue(&x25st->rx_queue);

        while (skb) {
                netif_receive_skb_core(skb);
                skb = skb_dequeue(&x25st->rx_queue);
        }
}

/* These functions are callbacks called by LAPB layer */

static void x25_connect_disconnect(struct net_device *dev, int reason, int code)
{
        struct x25_state *x25st = state(dev_to_hdlc(dev));
        struct sk_buff *skb;
        unsigned char *ptr;

        skb = __dev_alloc_skb(1, GFP_ATOMIC | __GFP_NOMEMALLOC);
        if (!skb)
                return;

        ptr = skb_put(skb, 1);
        *ptr = code;

        skb->protocol = x25_type_trans(skb, dev);

        skb_queue_tail(&x25st->rx_queue, skb);
        tasklet_schedule(&x25st->rx_tasklet);
}

static void x25_connected(struct net_device *dev, int reason)
{
        x25_connect_disconnect(dev, reason, X25_IFACE_CONNECT);
}

static void x25_disconnected(struct net_device *dev, int reason)
{
        x25_connect_disconnect(dev, reason, X25_IFACE_DISCONNECT);
}

static int x25_data_indication(struct net_device *dev, struct sk_buff *skb)
{
        struct x25_state *x25st = state(dev_to_hdlc(dev));
        unsigned char *ptr;

        if (skb_cow(skb, 1)) {
                kfree_skb(skb);
                return NET_RX_DROP;
        }

        skb_push(skb, 1);

        ptr  = skb->data;
        *ptr = X25_IFACE_DATA;

        skb->protocol = x25_type_trans(skb, dev);

        skb_queue_tail(&x25st->rx_queue, skb);
        tasklet_schedule(&x25st->rx_tasklet);
        return NET_RX_SUCCESS;
}

static void x25_data_transmit(struct net_device *dev, struct sk_buff *skb)
{
        hdlc_device *hdlc = dev_to_hdlc(dev);

        skb_reset_network_header(skb);
        skb->protocol = hdlc_type_trans(skb, dev);

        if (dev_nit_active(dev))
                dev_queue_xmit_nit(skb, dev);

        hdlc->xmit(skb, dev); /* Ignore return value :-( */
}

static netdev_tx_t x25_xmit(struct sk_buff *skb, struct net_device *dev)
{
        hdlc_device *hdlc = dev_to_hdlc(dev);
        struct x25_state *x25st = state(hdlc);
        int result;

        /* There should be a pseudo header of 1 byte added by upper layers.
         * Check to make sure it is there before reading it.
         */
        if (skb->len < 1) {
                kfree_skb(skb);
                return NETDEV_TX_OK;
        }

        spin_lock_bh(&x25st->up_lock);
        if (!x25st->up) {
                spin_unlock_bh(&x25st->up_lock);
                kfree_skb(skb);
                return NETDEV_TX_OK;
        }

        switch (skb->data[0]) {
        case X25_IFACE_DATA:    /* Data to be transmitted */
                skb_pull(skb, 1);
                result = lapb_data_request(dev, skb);
                if (result != LAPB_OK)
                        dev_kfree_skb(skb);
                spin_unlock_bh(&x25st->up_lock);
                return NETDEV_TX_OK;

        case X25_IFACE_CONNECT:
                result = lapb_connect_request(dev);
                if (result != LAPB_OK) {
                        if (result == LAPB_CONNECTED)
                                /* Send connect confirm. msg to level 3 */
                                x25_connected(dev, 0);
                        else
                                netdev_err(dev, "LAPB connect request failed, error code = %i\n",
                                           result);
                }
                break;

        case X25_IFACE_DISCONNECT:
                result = lapb_disconnect_request(dev);
                if (result != LAPB_OK) {
                        if (result == LAPB_NOTCONNECTED)
                                /* Send disconnect confirm. msg to level 3 */
                                x25_disconnected(dev, 0);
                        else
                                netdev_err(dev, "LAPB disconnect request failed, error code = %i\n",
                                           result);
                }
                break;

        default:                /* to be defined */
                break;
        }

        spin_unlock_bh(&x25st->up_lock);
        dev_kfree_skb(skb);
        return NETDEV_TX_OK;
}

static int x25_open(struct net_device *dev)
{
        static const struct lapb_register_struct cb = {
                .connect_confirmation = x25_connected,
                .connect_indication = x25_connected,
                .disconnect_confirmation = x25_disconnected,
                .disconnect_indication = x25_disconnected,
                .data_indication = x25_data_indication,
                .data_transmit = x25_data_transmit,
        };
        hdlc_device *hdlc = dev_to_hdlc(dev);
        struct x25_state *x25st = state(hdlc);
        struct lapb_parms_struct params;
        int result;

        result = lapb_register(dev, &cb);
        if (result != LAPB_OK)
                return -ENOMEM;

        result = lapb_getparms(dev, &params);
        if (result != LAPB_OK)
                return -EINVAL;

        if (state(hdlc)->settings.dce)
                params.mode = params.mode | LAPB_DCE;

        if (state(hdlc)->settings.modulo == 128)
                params.mode = params.mode | LAPB_EXTENDED;

        params.window = state(hdlc)->settings.window;
        params.t1 = state(hdlc)->settings.t1;
        params.t2 = state(hdlc)->settings.t2;
        params.n2 = state(hdlc)->settings.n2;

        result = lapb_setparms(dev, &params);
        if (result != LAPB_OK)
                return -EINVAL;

        spin_lock_bh(&x25st->up_lock);
        x25st->up = true;
        spin_unlock_bh(&x25st->up_lock);

        return 0;
}

static void x25_close(struct net_device *dev)
{
        hdlc_device *hdlc = dev_to_hdlc(dev);
        struct x25_state *x25st = state(hdlc);

        spin_lock_bh(&x25st->up_lock);
        x25st->up = false;
        spin_unlock_bh(&x25st->up_lock);

        lapb_unregister(dev);
        tasklet_kill(&x25st->rx_tasklet);
}

static int x25_rx(struct sk_buff *skb)
{
        struct net_device *dev = skb->dev;
        hdlc_device *hdlc = dev_to_hdlc(dev);
        struct x25_state *x25st = state(hdlc);

        skb = skb_share_check(skb, GFP_ATOMIC);
        if (!skb) {
                dev->stats.rx_dropped++;
                return NET_RX_DROP;
        }

        spin_lock_bh(&x25st->up_lock);
        if (!x25st->up) {
                spin_unlock_bh(&x25st->up_lock);
                kfree_skb(skb);
                dev->stats.rx_dropped++;
                return NET_RX_DROP;
        }

        if (lapb_data_received(dev, skb) == LAPB_OK) {
                spin_unlock_bh(&x25st->up_lock);
                return NET_RX_SUCCESS;
        }

        spin_unlock_bh(&x25st->up_lock);
        dev->stats.rx_errors++;
        dev_kfree_skb_any(skb);
        return NET_RX_DROP;
}

static struct hdlc_proto proto = {
        .open           = x25_open,
        .close          = x25_close,
        .ioctl          = x25_ioctl,
        .netif_rx       = x25_rx,
        .xmit           = x25_xmit,
        .module         = THIS_MODULE,
};

static int x25_ioctl(struct net_device *dev, struct if_settings *ifs)
{
        x25_hdlc_proto __user *x25_s = ifs->ifs_ifsu.x25;
        const size_t size = sizeof(x25_hdlc_proto);
        hdlc_device *hdlc = dev_to_hdlc(dev);
        x25_hdlc_proto new_settings;
        int result;

        switch (ifs->type) {
        case IF_GET_PROTO:
                if (dev_to_hdlc(dev)->proto != &proto)
                        return -EINVAL;
                ifs->type = IF_PROTO_X25;
                if (ifs->size < size) {
                        ifs->size = size; /* data size wanted */
                        return -ENOBUFS;
                }
                if (copy_to_user(x25_s, &state(hdlc)->settings, size))
                        return -EFAULT;
                return 0;

        case IF_PROTO_X25:
                if (!capable(CAP_NET_ADMIN))
                        return -EPERM;

                if (dev->flags & IFF_UP)
                        return -EBUSY;

                /* backward compatibility */
                if (ifs->size == 0) {
                        new_settings.dce = 0;
                        new_settings.modulo = 8;
                        new_settings.window = 7;
                        new_settings.t1 = 3;
                        new_settings.t2 = 1;
                        new_settings.n2 = 10;
                } else {
                        if (copy_from_user(&new_settings, x25_s, size))
                                return -EFAULT;

                        if ((new_settings.dce != 0 &&
                             new_settings.dce != 1) ||
                            (new_settings.modulo != 8 &&
                             new_settings.modulo != 128) ||
                            new_settings.window < 1 ||
                            (new_settings.modulo == 8 &&
                             new_settings.window > 7) ||
                            (new_settings.modulo == 128 &&
                             new_settings.window > 127) ||
                            new_settings.t1 < 1 ||
                            new_settings.t1 > 255 ||
                            new_settings.t2 < 1 ||
                            new_settings.t2 > 255 ||
                            new_settings.n2 < 1 ||
                            new_settings.n2 > 255)
                                return -EINVAL;
                }

                result = hdlc->attach(dev, ENCODING_NRZ,
                                      PARITY_CRC16_PR1_CCITT);
                if (result)
                        return result;

                result = attach_hdlc_protocol(dev, &proto,
                                              sizeof(struct x25_state));
                if (result)
                        return result;

                memcpy(&state(hdlc)->settings, &new_settings, size);
                state(hdlc)->up = false;
                spin_lock_init(&state(hdlc)->up_lock);
                skb_queue_head_init(&state(hdlc)->rx_queue);
                tasklet_setup(&state(hdlc)->rx_tasklet, x25_rx_queue_kick);

                /* There's no header_ops so hard_header_len should be 0. */
                dev->hard_header_len = 0;
                /* When transmitting data:
                 * first we'll remove a pseudo header of 1 byte,
                 * then we'll prepend an LAPB header of at most 3 bytes.
                 */
                dev->needed_headroom = 3 - 1;

                dev->type = ARPHRD_X25;
                call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
                netif_dormant_off(dev);
                return 0;
        }

        return -EINVAL;
}

static int __init hdlc_x25_init(void)
{
        register_hdlc_protocol(&proto);
        return 0;
}

static void __exit hdlc_x25_exit(void)
{
        unregister_hdlc_protocol(&proto);
}

module_init(hdlc_x25_init);
module_exit(hdlc_x25_exit);

MODULE_AUTHOR("Krzysztof Halasa <khc@pm.waw.pl>");
MODULE_DESCRIPTION("X.25 protocol support for generic HDLC");
MODULE_LICENSE("GPL v2");