// SPDX-License-Identifier: GPL-2.0-only
/*
 * Generic HDLC support routines for Linux
 * Cisco HDLC support
 *
 * Copyright (C) 2000 - 2006 Krzysztof Halasa <khc@pm.waw.pl>
 */

#include <linux/errno.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>

#undef DEBUG_HARD_HEADER

#define CISCO_MULTICAST         0x8F    /* Cisco multicast address */
#define CISCO_UNICAST           0x0F    /* Cisco unicast address */
#define CISCO_KEEPALIVE         0x8035  /* Cisco keepalive protocol */
#define CISCO_SYS_INFO          0x2000  /* Cisco interface/system info */
#define CISCO_ADDR_REQ          0       /* Cisco address request */
#define CISCO_ADDR_REPLY        1       /* Cisco address reply */
#define CISCO_KEEPALIVE_REQ     2       /* Cisco keepalive request */

struct hdlc_header {
        u8 address;
        u8 control;
        __be16 protocol;
} __packed;

struct cisco_packet {
        __be32 type;            /* code */
        __be32 par1;
        __be32 par2;
        __be16 rel;             /* reliability */
        __be32 time;
} __packed;
#define CISCO_PACKET_LEN        18
#define CISCO_BIG_PACKET_LEN    20

struct cisco_state {
        cisco_proto settings;

        struct timer_list timer;
        struct net_device *dev;
        spinlock_t lock;
        unsigned long last_poll;
        int up;
        u32 txseq; /* TX sequence number, 0 = none */
        u32 rxseq; /* RX sequence number */
};

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

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

static int cisco_hard_header(struct sk_buff *skb, struct net_device *dev,
                             u16 type, const void *daddr, const void *saddr,
                             unsigned int len)
{
        struct hdlc_header *data;
#ifdef DEBUG_HARD_HEADER
        netdev_dbg(dev, "%s called\n", __func__);
#endif

        skb_push(skb, sizeof(struct hdlc_header));
        data = (struct hdlc_header *)skb->data;
        if (type == CISCO_KEEPALIVE)
                data->address = CISCO_MULTICAST;
        else
                data->address = CISCO_UNICAST;
        data->control = 0;
        data->protocol = htons(type);

        return sizeof(struct hdlc_header);
}

static void cisco_keepalive_send(struct net_device *dev, u32 type,
                                 __be32 par1, __be32 par2)
{
        struct sk_buff *skb;
        struct cisco_packet *data;

        skb = dev_alloc_skb(sizeof(struct hdlc_header) +
                            sizeof(struct cisco_packet));
        if (!skb)
                return;

        skb_reserve(skb, 4);
        cisco_hard_header(skb, dev, CISCO_KEEPALIVE, NULL, NULL, 0);
        data = (struct cisco_packet *)(skb->data + 4);

        data->type = htonl(type);
        data->par1 = par1;
        data->par2 = par2;
        data->rel = cpu_to_be16(0xFFFF);
        /* we will need do_div here if 1000 % HZ != 0 */
        data->time = htonl((jiffies - INITIAL_JIFFIES) * (1000 / HZ));

        skb_put(skb, sizeof(struct cisco_packet));
        skb->priority = TC_PRIO_CONTROL;
        skb->dev = dev;
        skb->protocol = htons(ETH_P_HDLC);
        skb_reset_network_header(skb);

        dev_queue_xmit(skb);
}

static __be16 cisco_type_trans(struct sk_buff *skb, struct net_device *dev)
{
        struct hdlc_header *data = (struct hdlc_header *)skb->data;

        if (skb->len < sizeof(struct hdlc_header))
                return cpu_to_be16(ETH_P_HDLC);

        if (data->address != CISCO_MULTICAST &&
            data->address != CISCO_UNICAST)
                return cpu_to_be16(ETH_P_HDLC);

        switch (data->protocol) {
        case cpu_to_be16(ETH_P_IP):
        case cpu_to_be16(ETH_P_IPX):
        case cpu_to_be16(ETH_P_IPV6):
                skb_pull(skb, sizeof(struct hdlc_header));
                return data->protocol;
        default:
                return cpu_to_be16(ETH_P_HDLC);
        }
}

static int cisco_rx(struct sk_buff *skb)
{
        struct net_device *dev = skb->dev;
        hdlc_device *hdlc = dev_to_hdlc(dev);
        struct cisco_state *st = state(hdlc);
        struct hdlc_header *data = (struct hdlc_header *)skb->data;
        struct cisco_packet *cisco_data;
        struct in_device *in_dev;
        __be32 addr, mask;
        u32 ack;

        if (skb->len < sizeof(struct hdlc_header))
                goto rx_error;

        if (data->address != CISCO_MULTICAST &&
            data->address != CISCO_UNICAST)
                goto rx_error;

        switch (ntohs(data->protocol)) {
        case CISCO_SYS_INFO:
                /* Packet is not needed, drop it. */
                dev_kfree_skb_any(skb);
                return NET_RX_SUCCESS;

        case CISCO_KEEPALIVE:
                if ((skb->len != sizeof(struct hdlc_header) +
                     CISCO_PACKET_LEN) &&
                    (skb->len != sizeof(struct hdlc_header) +
                     CISCO_BIG_PACKET_LEN)) {
                        netdev_info(dev, "Invalid length of Cisco control packet (%d bytes)\n",
                                    skb->len);
                        goto rx_error;
                }

                cisco_data = (struct cisco_packet *)(skb->data + sizeof
                                                    (struct hdlc_header));

                switch (ntohl(cisco_data->type)) {
                case CISCO_ADDR_REQ: /* Stolen from syncppp.c :-) */
                        rcu_read_lock();
                        in_dev = __in_dev_get_rcu(dev);
                        addr = 0;
                        mask = ~cpu_to_be32(0); /* is the mask correct? */

                        if (in_dev != NULL) {
                                const struct in_ifaddr *ifa;

                                in_dev_for_each_ifa_rcu(ifa, in_dev) {
                                        if (strcmp(dev->name,
                                                   ifa->ifa_label) == 0) {
                                                addr = ifa->ifa_local;
                                                mask = ifa->ifa_mask;
                                                break;
                                        }
                                }

                                cisco_keepalive_send(dev, CISCO_ADDR_REPLY,
                                                     addr, mask);
                        }
                        rcu_read_unlock();
                        dev_kfree_skb_any(skb);
                        return NET_RX_SUCCESS;

                case CISCO_ADDR_REPLY:
                        netdev_info(dev, "Unexpected Cisco IP address reply\n");
                        goto rx_error;

                case CISCO_KEEPALIVE_REQ:
                        spin_lock(&st->lock);
                        st->rxseq = ntohl(cisco_data->par1);
                        ack = ntohl(cisco_data->par2);
                        if (ack && (ack == st->txseq ||
                                    /* our current REQ may be in transit */
                                    ack == st->txseq - 1)) {
                                st->last_poll = jiffies;
                                if (!st->up) {
                                        u32 sec, min, hrs, days;

                                        sec = ntohl(cisco_data->time) / 1000;
                                        min = sec / 60; sec -= min * 60;
                                        hrs = min / 60; min -= hrs * 60;
                                        days = hrs / 24; hrs -= days * 24;
                                        netdev_info(dev, "Link up (peer uptime %ud%uh%um%us)\n",
                                                    days, hrs, min, sec);
                                        netif_dormant_off(dev);
                                        st->up = 1;
                                }
                        }
                        spin_unlock(&st->lock);

                        dev_kfree_skb_any(skb);
                        return NET_RX_SUCCESS;
                } /* switch (keepalive type) */
        } /* switch (protocol) */

        netdev_info(dev, "Unsupported protocol %x\n", ntohs(data->protocol));
        dev_kfree_skb_any(skb);
        return NET_RX_DROP;

rx_error:
        dev->stats.rx_errors++; /* Mark error */
        dev_kfree_skb_any(skb);
        return NET_RX_DROP;
}

static void cisco_timer(struct timer_list *t)
{
        struct cisco_state *st = timer_container_of(st, t, timer);
        struct net_device *dev = st->dev;

        spin_lock(&st->lock);
        if (st->up &&
            time_after(jiffies, st->last_poll + st->settings.timeout * HZ)) {
                st->up = 0;
                netdev_info(dev, "Link down\n");
                netif_dormant_on(dev);
        }

        cisco_keepalive_send(dev, CISCO_KEEPALIVE_REQ, htonl(++st->txseq),
                             htonl(st->rxseq));
        spin_unlock(&st->lock);

        st->timer.expires = jiffies + st->settings.interval * HZ;
        add_timer(&st->timer);
}

static void cisco_start(struct net_device *dev)
{
        hdlc_device *hdlc = dev_to_hdlc(dev);
        struct cisco_state *st = state(hdlc);
        unsigned long flags;

        spin_lock_irqsave(&st->lock, flags);
        st->up = st->txseq = st->rxseq = 0;
        spin_unlock_irqrestore(&st->lock, flags);

        st->dev = dev;
        timer_setup(&st->timer, cisco_timer, 0);
        st->timer.expires = jiffies + HZ; /* First poll after 1 s */
        add_timer(&st->timer);
}

static void cisco_stop(struct net_device *dev)
{
        hdlc_device *hdlc = dev_to_hdlc(dev);
        struct cisco_state *st = state(hdlc);
        unsigned long flags;

        timer_delete_sync(&st->timer);

        spin_lock_irqsave(&st->lock, flags);
        netif_dormant_on(dev);
        st->up = st->txseq = 0;
        spin_unlock_irqrestore(&st->lock, flags);
}

static struct hdlc_proto proto = {
        .start          = cisco_start,
        .stop           = cisco_stop,
        .type_trans     = cisco_type_trans,
        .ioctl          = cisco_ioctl,
        .netif_rx       = cisco_rx,
        .module         = THIS_MODULE,
};

static const struct header_ops cisco_header_ops = {
        .create = cisco_hard_header,
};

static int cisco_ioctl(struct net_device *dev, struct if_settings *ifs)
{
        cisco_proto __user *cisco_s = ifs->ifs_ifsu.cisco;
        const size_t size = sizeof(cisco_proto);
        cisco_proto new_settings;
        hdlc_device *hdlc = dev_to_hdlc(dev);
        int result;

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

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

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

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

                if (new_settings.interval < 1 ||
                    new_settings.timeout < 2)
                        return -EINVAL;

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

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

                memcpy(&state(hdlc)->settings, &new_settings, size);
                spin_lock_init(&state(hdlc)->lock);
                dev->header_ops = &cisco_header_ops;
                dev->hard_header_len = sizeof(struct hdlc_header);
                dev->type = ARPHRD_CISCO;
                call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
                netif_dormant_on(dev);
                return 0;
        }

        return -EINVAL;
}

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

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

module_init(hdlc_cisco_init);
module_exit(hdlc_cisco_exit);

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