// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
 */
#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/net.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/termios.h>      /* For TIOCINQ/OUTQ */
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/notifier.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/sysctl.h>
#include <net/ip.h>
#include <net/arp.h>

/*
 *      IP over AX.25 encapsulation.
 */

/*
 *      Shove an AX.25 UI header on an IP packet and handle ARP
 */

#ifdef CONFIG_INET

static int ax25_hard_header(struct sk_buff *skb, struct net_device *dev,
                            unsigned short type, const void *daddr,
                            const void *saddr, unsigned int len)
{
        unsigned char *buff;

        /* they sometimes come back to us... */
        if (type == ETH_P_AX25)
                return 0;

        /* header is an AX.25 UI frame from us to them */
        buff = skb_push(skb, AX25_HEADER_LEN);
        *buff++ = 0x00; /* KISS DATA */

        if (daddr != NULL)
                memcpy(buff, daddr, dev->addr_len);     /* Address specified */

        buff[6] &= ~AX25_CBIT;
        buff[6] &= ~AX25_EBIT;
        buff[6] |= AX25_SSSID_SPARE;
        buff    += AX25_ADDR_LEN;

        if (saddr != NULL)
                memcpy(buff, saddr, dev->addr_len);
        else
                memcpy(buff, dev->dev_addr, dev->addr_len);

        buff[6] &= ~AX25_CBIT;
        buff[6] |= AX25_EBIT;
        buff[6] |= AX25_SSSID_SPARE;
        buff    += AX25_ADDR_LEN;

        *buff++  = AX25_UI;     /* UI */

        /* Append a suitable AX.25 PID */
        switch (type) {
        case ETH_P_IP:
                *buff++ = AX25_P_IP;
                break;
        case ETH_P_ARP:
                *buff++ = AX25_P_ARP;
                break;
        default:
                printk(KERN_ERR "AX.25: ax25_hard_header - wrong protocol type 0x%2.2x\n", type);
                *buff++ = 0;
                break;
        }

        if (daddr != NULL)
                return AX25_HEADER_LEN;

        return -AX25_HEADER_LEN;        /* Unfinished header */
}

netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
{
        struct sk_buff *ourskb;
        unsigned char *bp  = skb->data;
        ax25_route *route;
        struct net_device *dev = NULL;
        ax25_address *src, *dst;
        ax25_digi *digipeat = NULL;
        ax25_dev *ax25_dev;
        ax25_cb *ax25;
        char ip_mode = ' ';

        dst = (ax25_address *)(bp + 1);
        src = (ax25_address *)(bp + 8);

        ax25_route_lock_use();
        route = ax25_get_route(dst, NULL);
        if (route) {
                digipeat = route->digipeat;
                dev = route->dev;
                ip_mode = route->ip_mode;
        }

        if (dev == NULL)
                dev = skb->dev;

        if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) {
                kfree_skb(skb);
                goto put;
        }

        if (bp[16] == AX25_P_IP) {
                if (ip_mode == 'V' || (ip_mode == ' ' && ax25_dev->values[AX25_VALUES_IPDEFMODE])) {
                        /*
                         *      We copy the buffer and release the original thereby
                         *      keeping it straight
                         *
                         *      Note: we report 1 back so the caller will
                         *      not feed the frame direct to the physical device
                         *      We don't want that to happen. (It won't be upset
                         *      as we have pulled the frame from the queue by
                         *      freeing it).
                         *
                         *      NB: TCP modifies buffers that are still
                         *      on a device queue, thus we use skb_copy()
                         *      instead of using skb_clone() unless this
                         *      gets fixed.
                         */

                        ax25_address src_c;
                        ax25_address dst_c;

                        if ((ourskb = skb_copy(skb, GFP_ATOMIC)) == NULL) {
                                kfree_skb(skb);
                                goto put;
                        }

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

                        kfree_skb(skb);
                        /* dl9sau: bugfix
                         * after kfree_skb(), dst and src which were pointer
                         * to bp which is part of skb->data would not be valid
                         * anymore hope that after skb_pull(ourskb, ..) our
                         * dsc_c and src_c will not become invalid
                         */
                        bp  = ourskb->data;
                        dst_c = *(ax25_address *)(bp + 1);
                        src_c = *(ax25_address *)(bp + 8);

                        skb_pull(ourskb, AX25_HEADER_LEN - 1);  /* Keep PID */
                        skb_reset_network_header(ourskb);

                        ax25=ax25_send_frame(
                            ourskb,
                            ax25_dev->values[AX25_VALUES_PACLEN],
                            &src_c,
                            &dst_c, digipeat, dev);
                        if (ax25) {
                                ax25_cb_put(ax25);
                        }
                        goto put;
                }
        }

        bp[7]  &= ~AX25_CBIT;
        bp[7]  &= ~AX25_EBIT;
        bp[7]  |= AX25_SSSID_SPARE;

        bp[14] &= ~AX25_CBIT;
        bp[14] |= AX25_EBIT;
        bp[14] |= AX25_SSSID_SPARE;

        skb_pull(skb, AX25_KISS_HEADER_LEN);

        if (digipeat != NULL) {
                if ((ourskb = ax25_rt_build_path(skb, src, dst, route->digipeat)) == NULL) {
                        kfree_skb(skb);
                        goto put;
                }

                skb = ourskb;
        }

        ax25_queue_xmit(skb, dev);

put:

        ax25_route_lock_unuse();
        return NETDEV_TX_OK;
}

#else   /* INET */

static int ax25_hard_header(struct sk_buff *skb, struct net_device *dev,
                            unsigned short type, const void *daddr,
                            const void *saddr, unsigned int len)
{
        return -AX25_HEADER_LEN;
}

netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
{
        kfree_skb(skb);
        return NETDEV_TX_OK;
}
#endif

static bool ax25_validate_header(const char *header, unsigned int len)
{
        ax25_digi digi;

        if (!len)
                return false;

        if (header[0])
                return true;

        return ax25_addr_parse(header + 1, len - 1, NULL, NULL, &digi, NULL,
                               NULL);
}

const struct header_ops ax25_header_ops = {
        .create = ax25_hard_header,
        .validate = ax25_validate_header,
};

EXPORT_SYMBOL(ax25_header_ops);
EXPORT_SYMBOL(ax25_ip_xmit);