// SPDX-License-Identifier: GPL-2.0-only
/*
 * Generic HDLC support routines for Linux
 * HDLC Ethernet emulation support
 *
 * Copyright (C) 2002-2006 Krzysztof Halasa <khc@pm.waw.pl>
 */

#include <linux/errno.h>
#include <linux/etherdevice.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/module.h>
#include <linux/pkt_sched.h>
#include <linux/poll.h>
#include <linux/rtnetlink.h>
#include <linux/skbuff.h>

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

static netdev_tx_t eth_tx(struct sk_buff *skb, struct net_device *dev)
{
        int pad = ETH_ZLEN - skb->len;
        if (pad > 0) {          /* Pad the frame with zeros */
                int len = skb->len;
                if (skb_tailroom(skb) < pad)
                        if (pskb_expand_head(skb, 0, pad, GFP_ATOMIC)) {
                                dev->stats.tx_dropped++;
                                dev_kfree_skb(skb);
                                return 0;
                        }
                skb_put(skb, pad);
                memset(skb->data + len, 0, pad);
        }
        return dev_to_hdlc(dev)->xmit(skb, dev);
}


static struct hdlc_proto proto = {
        .type_trans     = eth_type_trans,
        .xmit           = eth_tx,
        .ioctl          = raw_eth_ioctl,
        .module         = THIS_MODULE,
};


static int raw_eth_ioctl(struct net_device *dev, struct if_settings *ifs)
{
        raw_hdlc_proto __user *raw_s = ifs->ifs_ifsu.raw_hdlc;
        const size_t size = sizeof(raw_hdlc_proto);
        raw_hdlc_proto new_settings;
        hdlc_device *hdlc = dev_to_hdlc(dev);
        unsigned int old_qlen;
        int result;

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

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

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

                if (copy_from_user(&new_settings, raw_s, size))
                        return -EFAULT;

                if (new_settings.encoding == ENCODING_DEFAULT)
                        new_settings.encoding = ENCODING_NRZ;

                if (new_settings.parity == PARITY_DEFAULT)
                        new_settings.parity = PARITY_CRC16_PR1_CCITT;

                result = hdlc->attach(dev, new_settings.encoding,
                                      new_settings.parity);
                if (result)
                        return result;

                result = attach_hdlc_protocol(dev, &proto,
                                              sizeof(raw_hdlc_proto));
                if (result)
                        return result;
                memcpy(hdlc->state, &new_settings, size);
                old_qlen = dev->tx_queue_len;
                ether_setup(dev);
                dev->tx_queue_len = old_qlen;
                dev->priv_flags &= ~IFF_TX_SKB_SHARING;
                eth_hw_addr_random(dev);
                call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
                netif_dormant_off(dev);
                return 0;
        }

        return -EINVAL;
}


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



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


module_init(hdlc_eth_init);
module_exit(hdlc_eth_exit);

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