// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
 */
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/spinlock.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>

static DEFINE_SPINLOCK(ax25_frag_lock);

ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, ax25_address *src, ax25_address *dest, ax25_digi *digi, struct net_device *dev)
{
        ax25_dev *ax25_dev;
        ax25_cb *ax25;

        /*
         * Take the default packet length for the device if zero is
         * specified.
         */
        if (paclen == 0) {
                if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
                        return NULL;

                paclen = ax25_dev->values[AX25_VALUES_PACLEN];
        }

        /*
         * Look for an existing connection.
         */
        if ((ax25 = ax25_find_cb(src, dest, digi, dev)) != NULL) {
                ax25_output(ax25, paclen, skb);
                return ax25;            /* It already existed */
        }

        if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
                return NULL;

        if ((ax25 = ax25_create_cb()) == NULL)
                return NULL;

        ax25_fillin_cb(ax25, ax25_dev);

        ax25->source_addr = *src;
        ax25->dest_addr   = *dest;

        if (digi != NULL) {
                ax25->digipeat = kmemdup(digi, sizeof(*digi), GFP_ATOMIC);
                if (ax25->digipeat == NULL) {
                        ax25_cb_put(ax25);
                        return NULL;
                }
        }

        switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
        case AX25_PROTO_STD_SIMPLEX:
        case AX25_PROTO_STD_DUPLEX:
                ax25_std_establish_data_link(ax25);
                break;

#ifdef CONFIG_AX25_DAMA_SLAVE
        case AX25_PROTO_DAMA_SLAVE:
                if (ax25_dev->dama.slave)
                        ax25_ds_establish_data_link(ax25);
                else
                        ax25_std_establish_data_link(ax25);
                break;
#endif
        }

        /*
         * There is one ref for the state machine; a caller needs
         * one more to put it back, just like with the existing one.
         */
        ax25_cb_hold(ax25);

        ax25_cb_add(ax25);

        ax25->state = AX25_STATE_1;

        ax25_start_heartbeat(ax25);

        ax25_output(ax25, paclen, skb);

        return ax25;                    /* We had to create it */
}

EXPORT_SYMBOL(ax25_send_frame);

/*
 *      All outgoing AX.25 I frames pass via this routine. Therefore this is
 *      where the fragmentation of frames takes place. If fragment is set to
 *      zero then we are not allowed to do fragmentation, even if the frame
 *      is too large.
 */
void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
{
        struct sk_buff *skbn;
        unsigned char *p;
        int frontlen, len, fragno, ka9qfrag, first = 1;

        if (paclen < 16) {
                WARN_ON_ONCE(1);
                kfree_skb(skb);
                return;
        }

        if ((skb->len - 1) > paclen) {
                if (*skb->data == AX25_P_TEXT) {
                        skb_pull(skb, 1); /* skip PID */
                        ka9qfrag = 0;
                } else {
                        paclen -= 2;    /* Allow for fragment control info */
                        ka9qfrag = 1;
                }

                fragno = skb->len / paclen;
                if (skb->len % paclen == 0) fragno--;

                frontlen = skb_headroom(skb);   /* Address space + CTRL */

                while (skb->len > 0) {
                        spin_lock_bh(&ax25_frag_lock);
                        if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
                                spin_unlock_bh(&ax25_frag_lock);
                                printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
                                return;
                        }

                        if (skb->sk != NULL)
                                skb_set_owner_w(skbn, skb->sk);

                        spin_unlock_bh(&ax25_frag_lock);

                        len = (paclen > skb->len) ? skb->len : paclen;

                        if (ka9qfrag == 1) {
                                skb_reserve(skbn, frontlen + 2);
                                skb_set_network_header(skbn,
                                                      skb_network_offset(skb));
                                skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
                                p = skb_push(skbn, 2);

                                *p++ = AX25_P_SEGMENT;

                                *p = fragno--;
                                if (first) {
                                        *p |= AX25_SEG_FIRST;
                                        first = 0;
                                }
                        } else {
                                skb_reserve(skbn, frontlen + 1);
                                skb_set_network_header(skbn,
                                                      skb_network_offset(skb));
                                skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
                                p = skb_push(skbn, 1);
                                *p = AX25_P_TEXT;
                        }

                        skb_pull(skb, len);
                        skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
                }

                kfree_skb(skb);
        } else {
                skb_queue_tail(&ax25->write_queue, skb);          /* Throw it on the queue */
        }

        switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
        case AX25_PROTO_STD_SIMPLEX:
        case AX25_PROTO_STD_DUPLEX:
                ax25_kick(ax25);
                break;

#ifdef CONFIG_AX25_DAMA_SLAVE
        /*
         * A DAMA slave is _required_ to work as normal AX.25L2V2
         * if no DAMA master is available.
         */
        case AX25_PROTO_DAMA_SLAVE:
                if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
                break;
#endif
        }
}

/*
 *  This procedure is passed a buffer descriptor for an iframe. It builds
 *  the rest of the control part of the frame and then writes it out.
 */
static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
{
        unsigned char *frame;

        if (skb == NULL)
                return;

        skb_reset_network_header(skb);

        if (ax25->modulus == AX25_MODULUS) {
                frame = skb_push(skb, 1);

                *frame = AX25_I;
                *frame |= (poll_bit) ? AX25_PF : 0;
                *frame |= (ax25->vr << 5);
                *frame |= (ax25->vs << 1);
        } else {
                frame = skb_push(skb, 2);

                frame[0] = AX25_I;
                frame[0] |= (ax25->vs << 1);
                frame[1] = (poll_bit) ? AX25_EPF : 0;
                frame[1] |= (ax25->vr << 1);
        }

        ax25_start_idletimer(ax25);

        ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
}

void ax25_kick(ax25_cb *ax25)
{
        struct sk_buff *skb, *skbn;
        int last = 1;
        unsigned short start, end, next;

        if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
                return;

        if (ax25->condition & AX25_COND_PEER_RX_BUSY)
                return;

        if (skb_peek(&ax25->write_queue) == NULL)
                return;

        start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
        end   = (ax25->va + ax25->window) % ax25->modulus;

        if (start == end)
                return;

        /*
         * Transmit data until either we're out of data to send or
         * the window is full. Send a poll on the final I frame if
         * the window is filled.
         */

        /*
         * Dequeue the frame and copy it.
         * Check for race with ax25_clear_queues().
         */
        skb  = skb_dequeue(&ax25->write_queue);
        if (!skb)
                return;

        ax25->vs = start;

        do {
                if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
                        skb_queue_head(&ax25->write_queue, skb);
                        break;
                }

                if (skb->sk != NULL)
                        skb_set_owner_w(skbn, skb->sk);

                next = (ax25->vs + 1) % ax25->modulus;
                last = (next == end);

                /*
                 * Transmit the frame copy.
                 * bke 960114: do not set the Poll bit on the last frame
                 * in DAMA mode.
                 */
                switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
                case AX25_PROTO_STD_SIMPLEX:
                case AX25_PROTO_STD_DUPLEX:
                        ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
                        break;

#ifdef CONFIG_AX25_DAMA_SLAVE
                case AX25_PROTO_DAMA_SLAVE:
                        ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
                        break;
#endif
                }

                ax25->vs = next;

                /*
                 * Requeue the original data frame.
                 */
                skb_queue_tail(&ax25->ack_queue, skb);

        } while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);

        ax25->condition &= ~AX25_COND_ACK_PENDING;

        if (!ax25_t1timer_running(ax25)) {
                ax25_stop_t3timer(ax25);
                ax25_calculate_t1(ax25);
                ax25_start_t1timer(ax25);
        }
}

void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
{
        unsigned char *ptr;
        int headroom;

        if (ax25->ax25_dev == NULL) {
                ax25_disconnect(ax25, ENETUNREACH);
                return;
        }

        headroom = ax25_addr_size(ax25->digipeat);

        if (unlikely(skb_headroom(skb) < headroom)) {
                skb = skb_expand_head(skb, headroom);
                if (!skb) {
                        printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
                        return;
                }
        }

        ptr = skb_push(skb, headroom);

        ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);

        ax25_queue_xmit(skb, ax25->ax25_dev->dev);
}

/*
 *      A small shim to dev_queue_xmit to add the KISS control byte, and do
 *      any packet forwarding in operation.
 */
void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
{
        unsigned char *ptr;

        skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));

        ptr  = skb_push(skb, 1);
        *ptr = 0x00;                    /* KISS */

        dev_queue_xmit(skb);
}

int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
{
        if (ax25->vs == nr) {
                ax25_frames_acked(ax25, nr);
                ax25_calculate_rtt(ax25);
                ax25_stop_t1timer(ax25);
                ax25_start_t3timer(ax25);
                return 1;
        } else {
                if (ax25->va != nr) {
                        ax25_frames_acked(ax25, nr);
                        ax25_calculate_t1(ax25);
                        ax25_start_t1timer(ax25);
                        return 1;
                }
        }
        return 0;
}