// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      X.25 Packet Layer release 002
 *
 *      This is ALPHA test software. This code may break your machine,
 *      randomly fail to work with new releases, misbehave and/or generally
 *      screw up. It might even work.
 *
 *      This code REQUIRES 2.1.15 or higher
 *
 *      History
 *      X.25 001        Jonathan Naylor   Started coding.
 *      X.25 002        Jonathan Naylor   New timer architecture.
 *      mar/20/00       Daniela Squassoni Disabling/enabling of facilities
 *                                        negotiation.
 *      2000-09-04      Henner Eisen      dev_hold() / dev_put() for x25_neigh.
 */

#define pr_fmt(fmt) "X25: " fmt

#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/timer.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/uaccess.h>
#include <linux/init.h>
#include <net/x25.h>

LIST_HEAD(x25_neigh_list);
DEFINE_RWLOCK(x25_neigh_list_lock);

static void x25_t20timer_expiry(struct timer_list *);

static void x25_transmit_restart_confirmation(struct x25_neigh *nb);
static void x25_transmit_restart_request(struct x25_neigh *nb);

/*
 *      Linux set/reset timer routines
 */
static inline void x25_start_t20timer(struct x25_neigh *nb)
{
        mod_timer(&nb->t20timer, jiffies + nb->t20);
}

static void x25_t20timer_expiry(struct timer_list *t)
{
        struct x25_neigh *nb = timer_container_of(nb, t, t20timer);

        x25_transmit_restart_request(nb);

        x25_start_t20timer(nb);
}

static inline void x25_stop_t20timer(struct x25_neigh *nb)
{
        timer_delete(&nb->t20timer);
}

/*
 *      This handles all restart and diagnostic frames.
 */
void x25_link_control(struct sk_buff *skb, struct x25_neigh *nb,
                      unsigned short frametype)
{
        struct sk_buff *skbn;

        switch (frametype) {
        case X25_RESTART_REQUEST:
                switch (nb->state) {
                case X25_LINK_STATE_0:
                        /* This can happen when the x25 module just gets loaded
                         * and doesn't know layer 2 has already connected
                         */
                        nb->state = X25_LINK_STATE_3;
                        x25_transmit_restart_confirmation(nb);
                        break;
                case X25_LINK_STATE_2:
                        x25_stop_t20timer(nb);
                        nb->state = X25_LINK_STATE_3;
                        break;
                case X25_LINK_STATE_3:
                        /* clear existing virtual calls */
                        x25_kill_by_neigh(nb);

                        x25_transmit_restart_confirmation(nb);
                        break;
                }
                break;

        case X25_RESTART_CONFIRMATION:
                switch (nb->state) {
                case X25_LINK_STATE_2:
                        x25_stop_t20timer(nb);
                        nb->state = X25_LINK_STATE_3;
                        break;
                case X25_LINK_STATE_3:
                        /* clear existing virtual calls */
                        x25_kill_by_neigh(nb);

                        x25_transmit_restart_request(nb);
                        nb->state = X25_LINK_STATE_2;
                        x25_start_t20timer(nb);
                        break;
                }
                break;

        case X25_DIAGNOSTIC:
                if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 4))
                        break;

                pr_warn("diagnostic #%d - %02X %02X %02X\n",
                       skb->data[3], skb->data[4],
                       skb->data[5], skb->data[6]);
                break;

        default:
                pr_warn("received unknown %02X with LCI 000\n",
                       frametype);
                break;
        }

        if (nb->state == X25_LINK_STATE_3)
                while ((skbn = skb_dequeue(&nb->queue)) != NULL)
                        x25_send_frame(skbn, nb);
}

/*
 *      This routine is called when a Restart Request is needed
 */
static void x25_transmit_restart_request(struct x25_neigh *nb)
{
        unsigned char *dptr;
        int len = X25_MAX_L2_LEN + X25_STD_MIN_LEN + 2;
        struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);

        if (!skb)
                return;

        skb_reserve(skb, X25_MAX_L2_LEN);

        dptr = skb_put(skb, X25_STD_MIN_LEN + 2);

        *dptr++ = nb->extended ? X25_GFI_EXTSEQ : X25_GFI_STDSEQ;
        *dptr++ = 0x00;
        *dptr++ = X25_RESTART_REQUEST;
        *dptr++ = 0x00;
        *dptr++ = 0;

        skb->sk = NULL;

        x25_send_frame(skb, nb);
}

/*
 * This routine is called when a Restart Confirmation is needed
 */
static void x25_transmit_restart_confirmation(struct x25_neigh *nb)
{
        unsigned char *dptr;
        int len = X25_MAX_L2_LEN + X25_STD_MIN_LEN;
        struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);

        if (!skb)
                return;

        skb_reserve(skb, X25_MAX_L2_LEN);

        dptr = skb_put(skb, X25_STD_MIN_LEN);

        *dptr++ = nb->extended ? X25_GFI_EXTSEQ : X25_GFI_STDSEQ;
        *dptr++ = 0x00;
        *dptr++ = X25_RESTART_CONFIRMATION;

        skb->sk = NULL;

        x25_send_frame(skb, nb);
}

/*
 *      This routine is called when a Clear Request is needed outside of the context
 *      of a connected socket.
 */
void x25_transmit_clear_request(struct x25_neigh *nb, unsigned int lci,
                                unsigned char cause)
{
        unsigned char *dptr;
        int len = X25_MAX_L2_LEN + X25_STD_MIN_LEN + 2;
        struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);

        if (!skb)
                return;

        skb_reserve(skb, X25_MAX_L2_LEN);

        dptr = skb_put(skb, X25_STD_MIN_LEN + 2);

        *dptr++ = ((lci >> 8) & 0x0F) | (nb->extended ?
                                         X25_GFI_EXTSEQ :
                                         X25_GFI_STDSEQ);
        *dptr++ = (lci >> 0) & 0xFF;
        *dptr++ = X25_CLEAR_REQUEST;
        *dptr++ = cause;
        *dptr++ = 0x00;

        skb->sk = NULL;

        x25_send_frame(skb, nb);
}

void x25_transmit_link(struct sk_buff *skb, struct x25_neigh *nb)
{
        switch (nb->state) {
        case X25_LINK_STATE_0:
                skb_queue_tail(&nb->queue, skb);
                nb->state = X25_LINK_STATE_1;
                x25_establish_link(nb);
                break;
        case X25_LINK_STATE_1:
        case X25_LINK_STATE_2:
                skb_queue_tail(&nb->queue, skb);
                break;
        case X25_LINK_STATE_3:
                x25_send_frame(skb, nb);
                break;
        }
}

/*
 *      Called when the link layer has become established.
 */
void x25_link_established(struct x25_neigh *nb)
{
        switch (nb->state) {
        case X25_LINK_STATE_0:
        case X25_LINK_STATE_1:
                x25_transmit_restart_request(nb);
                nb->state = X25_LINK_STATE_2;
                x25_start_t20timer(nb);
                break;
        }
}

/*
 *      Called when the link layer has terminated, or an establishment
 *      request has failed.
 */

void x25_link_terminated(struct x25_neigh *nb)
{
        nb->state = X25_LINK_STATE_0;
        skb_queue_purge(&nb->queue);
        x25_stop_t20timer(nb);

        /* Out of order: clear existing virtual calls (X.25 03/93 4.6.3) */
        x25_kill_by_neigh(nb);
}

/*
 *      Add a new device.
 */
void x25_link_device_up(struct net_device *dev)
{
        struct x25_neigh *nb = kmalloc_obj(*nb, GFP_ATOMIC);

        if (!nb)
                return;

        skb_queue_head_init(&nb->queue);
        timer_setup(&nb->t20timer, x25_t20timer_expiry, 0);

        dev_hold(dev);
        nb->dev      = dev;
        nb->state    = X25_LINK_STATE_0;
        nb->extended = 0;
        /*
         * Enables negotiation
         */
        nb->global_facil_mask = X25_MASK_REVERSE |
                                       X25_MASK_THROUGHPUT |
                                       X25_MASK_PACKET_SIZE |
                                       X25_MASK_WINDOW_SIZE;
        nb->t20      = sysctl_x25_restart_request_timeout;
        refcount_set(&nb->refcnt, 1);

        write_lock_bh(&x25_neigh_list_lock);
        list_add(&nb->node, &x25_neigh_list);
        write_unlock_bh(&x25_neigh_list_lock);
}

/**
 *      __x25_remove_neigh - remove neighbour from x25_neigh_list
 *      @nb: - neigh to remove
 *
 *      Remove neighbour from x25_neigh_list. If it was there.
 *      Caller must hold x25_neigh_list_lock.
 */
static void __x25_remove_neigh(struct x25_neigh *nb)
{
        if (nb->node.next) {
                list_del(&nb->node);
                x25_neigh_put(nb);
        }
}

/*
 *      A device has been removed, remove its links.
 */
void x25_link_device_down(struct net_device *dev)
{
        struct x25_neigh *nb;
        struct list_head *entry, *tmp;

        write_lock_bh(&x25_neigh_list_lock);

        list_for_each_safe(entry, tmp, &x25_neigh_list) {
                nb = list_entry(entry, struct x25_neigh, node);

                if (nb->dev == dev) {
                        __x25_remove_neigh(nb);
                        dev_put(dev);
                }
        }

        write_unlock_bh(&x25_neigh_list_lock);
}

/*
 *      Given a device, return the neighbour address.
 */
struct x25_neigh *x25_get_neigh(struct net_device *dev)
{
        struct x25_neigh *nb, *use = NULL;

        read_lock_bh(&x25_neigh_list_lock);
        list_for_each_entry(nb, &x25_neigh_list, node) {
                if (nb->dev == dev) {
                        use = nb;
                        break;
                }
        }

        if (use)
                x25_neigh_hold(use);
        read_unlock_bh(&x25_neigh_list_lock);
        return use;
}

/*
 *      Handle the ioctls that control the subscription functions.
 */
int x25_subscr_ioctl(unsigned int cmd, void __user *arg)
{
        struct x25_subscrip_struct x25_subscr;
        struct x25_neigh *nb;
        struct net_device *dev;
        int rc = -EINVAL;

        if (cmd != SIOCX25GSUBSCRIP && cmd != SIOCX25SSUBSCRIP)
                goto out;

        rc = -EFAULT;
        if (copy_from_user(&x25_subscr, arg, sizeof(x25_subscr)))
                goto out;

        rc = -EINVAL;
        if ((dev = x25_dev_get(x25_subscr.device)) == NULL)
                goto out;

        if ((nb = x25_get_neigh(dev)) == NULL)
                goto out_dev_put;

        dev_put(dev);

        if (cmd == SIOCX25GSUBSCRIP) {
                read_lock_bh(&x25_neigh_list_lock);
                x25_subscr.extended          = nb->extended;
                x25_subscr.global_facil_mask = nb->global_facil_mask;
                read_unlock_bh(&x25_neigh_list_lock);
                rc = copy_to_user(arg, &x25_subscr,
                                  sizeof(x25_subscr)) ? -EFAULT : 0;
        } else {
                rc = -EINVAL;
                if (!(x25_subscr.extended && x25_subscr.extended != 1)) {
                        rc = 0;
                        write_lock_bh(&x25_neigh_list_lock);
                        nb->extended         = x25_subscr.extended;
                        nb->global_facil_mask = x25_subscr.global_facil_mask;
                        write_unlock_bh(&x25_neigh_list_lock);
                }
        }
        x25_neigh_put(nb);
out:
        return rc;
out_dev_put:
        dev_put(dev);
        goto out;
}


/*
 *      Release all memory associated with X.25 neighbour structures.
 */
void __exit x25_link_free(void)
{
        struct x25_neigh *nb;
        struct list_head *entry, *tmp;

        write_lock_bh(&x25_neigh_list_lock);

        list_for_each_safe(entry, tmp, &x25_neigh_list) {
                struct net_device *dev;

                nb = list_entry(entry, struct x25_neigh, node);
                dev = nb->dev;
                __x25_remove_neigh(nb);
                dev_put(dev);
        }
        write_unlock_bh(&x25_neigh_list_lock);
}