// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2007-2018  B.A.T.M.A.N. contributors:
 *
 * Marek Lindner
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include "icmp_socket.h"
#include "main.h"

#include <linux/atomic.h>
#include <linux/compiler.h>
#include <linux/debugfs.h>
#include <linux/errno.h>
#include <linux/etherdevice.h>
#include <linux/eventpoll.h>
#include <linux/export.h>
#include <linux/fcntl.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/if_ether.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/pkt_sched.h>
#include <linux/poll.h>
#include <linux/printk.h>
#include <linux/sched.h> /* for linux/wait.h */
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/stddef.h>
#include <linux/string.h>
#include <linux/uaccess.h>
#include <linux/wait.h>
#include <uapi/linux/batadv_packet.h>

#include "hard-interface.h"
#include "log.h"
#include "originator.h"
#include "send.h"

static struct batadv_socket_client *batadv_socket_client_hash[256];

static void batadv_socket_add_packet(struct batadv_socket_client *socket_client,
                                     struct batadv_icmp_header *icmph,
                                     size_t icmp_len);

/**
 * batadv_socket_init() - Initialize soft interface independent socket data
 */
void batadv_socket_init(void)
{
        memset(batadv_socket_client_hash, 0, sizeof(batadv_socket_client_hash));
}

static int batadv_socket_open(struct inode *inode, struct file *file)
{
        unsigned int i;
        struct batadv_socket_client *socket_client;

        if (!try_module_get(THIS_MODULE))
                return -EBUSY;

        nonseekable_open(inode, file);

        socket_client = kmalloc(sizeof(*socket_client), GFP_KERNEL);
        if (!socket_client) {
                module_put(THIS_MODULE);
                return -ENOMEM;
        }

        for (i = 0; i < ARRAY_SIZE(batadv_socket_client_hash); i++) {
                if (!batadv_socket_client_hash[i]) {
                        batadv_socket_client_hash[i] = socket_client;
                        break;
                }
        }

        if (i == ARRAY_SIZE(batadv_socket_client_hash)) {
                pr_err("Error - can't add another packet client: maximum number of clients reached\n");
                kfree(socket_client);
                module_put(THIS_MODULE);
                return -EXFULL;
        }

        INIT_LIST_HEAD(&socket_client->queue_list);
        socket_client->queue_len = 0;
        socket_client->index = i;
        socket_client->bat_priv = inode->i_private;
        spin_lock_init(&socket_client->lock);
        init_waitqueue_head(&socket_client->queue_wait);

        file->private_data = socket_client;

        return 0;
}

static int batadv_socket_release(struct inode *inode, struct file *file)
{
        struct batadv_socket_client *client = file->private_data;
        struct batadv_socket_packet *packet, *tmp;

        spin_lock_bh(&client->lock);

        /* for all packets in the queue ... */
        list_for_each_entry_safe(packet, tmp, &client->queue_list, list) {
                list_del(&packet->list);
                kfree(packet);
        }

        batadv_socket_client_hash[client->index] = NULL;
        spin_unlock_bh(&client->lock);

        kfree(client);
        module_put(THIS_MODULE);

        return 0;
}

static ssize_t batadv_socket_read(struct file *file, char __user *buf,
                                  size_t count, loff_t *ppos)
{
        struct batadv_socket_client *socket_client = file->private_data;
        struct batadv_socket_packet *socket_packet;
        size_t packet_len;
        int error;

        if ((file->f_flags & O_NONBLOCK) && socket_client->queue_len == 0)
                return -EAGAIN;

        if (!buf || count < sizeof(struct batadv_icmp_packet))
                return -EINVAL;

        if (!access_ok(VERIFY_WRITE, buf, count))
                return -EFAULT;

        error = wait_event_interruptible(socket_client->queue_wait,
                                         socket_client->queue_len);

        if (error)
                return error;

        spin_lock_bh(&socket_client->lock);

        socket_packet = list_first_entry(&socket_client->queue_list,
                                         struct batadv_socket_packet, list);
        list_del(&socket_packet->list);
        socket_client->queue_len--;

        spin_unlock_bh(&socket_client->lock);

        packet_len = min(count, socket_packet->icmp_len);
        error = copy_to_user(buf, &socket_packet->icmp_packet, packet_len);

        kfree(socket_packet);

        if (error)
                return -EFAULT;

        return packet_len;
}

static ssize_t batadv_socket_write(struct file *file, const char __user *buff,
                                   size_t len, loff_t *off)
{
        struct batadv_socket_client *socket_client = file->private_data;
        struct batadv_priv *bat_priv = socket_client->bat_priv;
        struct batadv_hard_iface *primary_if = NULL;
        struct sk_buff *skb;
        struct batadv_icmp_packet_rr *icmp_packet_rr;
        struct batadv_icmp_header *icmp_header;
        struct batadv_orig_node *orig_node = NULL;
        struct batadv_neigh_node *neigh_node = NULL;
        size_t packet_len = sizeof(struct batadv_icmp_packet);
        u8 *addr;

        if (len < sizeof(struct batadv_icmp_header)) {
                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                           "Error - can't send packet from char device: invalid packet size\n");
                return -EINVAL;
        }

        primary_if = batadv_primary_if_get_selected(bat_priv);

        if (!primary_if) {
                len = -EFAULT;
                goto out;
        }

        if (len >= BATADV_ICMP_MAX_PACKET_SIZE)
                packet_len = BATADV_ICMP_MAX_PACKET_SIZE;
        else
                packet_len = len;

        skb = netdev_alloc_skb_ip_align(NULL, packet_len + ETH_HLEN);
        if (!skb) {
                len = -ENOMEM;
                goto out;
        }

        skb->priority = TC_PRIO_CONTROL;
        skb_reserve(skb, ETH_HLEN);
        icmp_header = skb_put(skb, packet_len);

        if (copy_from_user(icmp_header, buff, packet_len)) {
                len = -EFAULT;
                goto free_skb;
        }

        if (icmp_header->packet_type != BATADV_ICMP) {
                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                           "Error - can't send packet from char device: got bogus packet type (expected: BAT_ICMP)\n");
                len = -EINVAL;
                goto free_skb;
        }

        switch (icmp_header->msg_type) {
        case BATADV_ECHO_REQUEST:
                if (len < sizeof(struct batadv_icmp_packet)) {
                        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                                   "Error - can't send packet from char device: invalid packet size\n");
                        len = -EINVAL;
                        goto free_skb;
                }

                if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
                        goto dst_unreach;

                orig_node = batadv_orig_hash_find(bat_priv, icmp_header->dst);
                if (!orig_node)
                        goto dst_unreach;

                neigh_node = batadv_orig_router_get(orig_node,
                                                    BATADV_IF_DEFAULT);
                if (!neigh_node)
                        goto dst_unreach;

                if (!neigh_node->if_incoming)
                        goto dst_unreach;

                if (neigh_node->if_incoming->if_status != BATADV_IF_ACTIVE)
                        goto dst_unreach;

                icmp_packet_rr = (struct batadv_icmp_packet_rr *)icmp_header;
                if (packet_len == sizeof(*icmp_packet_rr)) {
                        addr = neigh_node->if_incoming->net_dev->dev_addr;
                        ether_addr_copy(icmp_packet_rr->rr[0], addr);
                }

                break;
        default:
                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                           "Error - can't send packet from char device: got unknown message type\n");
                len = -EINVAL;
                goto free_skb;
        }

        icmp_header->uid = socket_client->index;

        if (icmp_header->version != BATADV_COMPAT_VERSION) {
                icmp_header->msg_type = BATADV_PARAMETER_PROBLEM;
                icmp_header->version = BATADV_COMPAT_VERSION;
                batadv_socket_add_packet(socket_client, icmp_header,
                                         packet_len);
                goto free_skb;
        }

        ether_addr_copy(icmp_header->orig, primary_if->net_dev->dev_addr);

        batadv_send_unicast_skb(skb, neigh_node);
        goto out;

dst_unreach:
        icmp_header->msg_type = BATADV_DESTINATION_UNREACHABLE;
        batadv_socket_add_packet(socket_client, icmp_header, packet_len);
free_skb:
        kfree_skb(skb);
out:
        if (primary_if)
                batadv_hardif_put(primary_if);
        if (neigh_node)
                batadv_neigh_node_put(neigh_node);
        if (orig_node)
                batadv_orig_node_put(orig_node);
        return len;
}

static __poll_t batadv_socket_poll(struct file *file, poll_table *wait)
{
        struct batadv_socket_client *socket_client = file->private_data;

        poll_wait(file, &socket_client->queue_wait, wait);

        if (socket_client->queue_len > 0)
                return EPOLLIN | EPOLLRDNORM;

        return 0;
}

static const struct file_operations batadv_fops = {
        .owner = THIS_MODULE,
        .open = batadv_socket_open,
        .release = batadv_socket_release,
        .read = batadv_socket_read,
        .write = batadv_socket_write,
        .poll = batadv_socket_poll,
        .llseek = no_llseek,
};

/**
 * batadv_socket_setup() - Create debugfs "socket" file
 * @bat_priv: the bat priv with all the soft interface information
 *
 * Return: 0 on success or negative error number in case of failure
 */
int batadv_socket_setup(struct batadv_priv *bat_priv)
{
        struct dentry *d;

        if (!bat_priv->debug_dir)
                goto err;

        d = debugfs_create_file(BATADV_ICMP_SOCKET, 0600, bat_priv->debug_dir,
                                bat_priv, &batadv_fops);
        if (!d)
                goto err;

        return 0;

err:
        return -ENOMEM;
}

/**
 * batadv_socket_add_packet() - schedule an icmp packet to be sent to
 *  userspace on an icmp socket.
 * @socket_client: the socket this packet belongs to
 * @icmph: pointer to the header of the icmp packet
 * @icmp_len: total length of the icmp packet
 */
static void batadv_socket_add_packet(struct batadv_socket_client *socket_client,
                                     struct batadv_icmp_header *icmph,
                                     size_t icmp_len)
{
        struct batadv_socket_packet *socket_packet;
        size_t len;

        socket_packet = kmalloc(sizeof(*socket_packet), GFP_ATOMIC);

        if (!socket_packet)
                return;

        len = icmp_len;
        /* check the maximum length before filling the buffer */
        if (len > sizeof(socket_packet->icmp_packet))
                len = sizeof(socket_packet->icmp_packet);

        INIT_LIST_HEAD(&socket_packet->list);
        memcpy(&socket_packet->icmp_packet, icmph, len);
        socket_packet->icmp_len = len;

        spin_lock_bh(&socket_client->lock);

        /* while waiting for the lock the socket_client could have been
         * deleted
         */
        if (!batadv_socket_client_hash[icmph->uid]) {
                spin_unlock_bh(&socket_client->lock);
                kfree(socket_packet);
                return;
        }

        list_add_tail(&socket_packet->list, &socket_client->queue_list);
        socket_client->queue_len++;

        if (socket_client->queue_len > 100) {
                socket_packet = list_first_entry(&socket_client->queue_list,
                                                 struct batadv_socket_packet,
                                                 list);

                list_del(&socket_packet->list);
                kfree(socket_packet);
                socket_client->queue_len--;
        }

        spin_unlock_bh(&socket_client->lock);

        wake_up(&socket_client->queue_wait);
}

/**
 * batadv_socket_receive_packet() - schedule an icmp packet to be received
 *  locally and sent to userspace.
 * @icmph: pointer to the header of the icmp packet
 * @icmp_len: total length of the icmp packet
 */
void batadv_socket_receive_packet(struct batadv_icmp_header *icmph,
                                  size_t icmp_len)
{
        struct batadv_socket_client *hash;

        hash = batadv_socket_client_hash[icmph->uid];
        if (hash)
                batadv_socket_add_packet(hash, icmph, icmp_len);
}