/* Copyright (C) 2009-2016  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 "gateway_common.h"
#include "main.h"

#include <linux/atomic.h>
#include <linux/byteorder/generic.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/netdevice.h>
#include <linux/stddef.h>
#include <linux/string.h>

#include "gateway_client.h"
#include "log.h"
#include "packet.h"
#include "tvlv.h"

/**
 * batadv_parse_throughput - parse supplied string buffer to extract throughput
 *  information
 * @net_dev: the soft interface net device
 * @buff: string buffer to parse
 * @description: text shown when throughput string cannot be parsed
 * @throughput: pointer holding the returned throughput information
 *
 * Return: false on parse error and true otherwise.
 */
bool batadv_parse_throughput(struct net_device *net_dev, char *buff,
                             const char *description, u32 *throughput)
{
        enum batadv_bandwidth_units bw_unit_type = BATADV_BW_UNIT_KBIT;
        u64 lthroughput;
        char *tmp_ptr;
        int ret;

        if (strlen(buff) > 4) {
                tmp_ptr = buff + strlen(buff) - 4;

                if (strncasecmp(tmp_ptr, "mbit", 4) == 0)
                        bw_unit_type = BATADV_BW_UNIT_MBIT;

                if ((strncasecmp(tmp_ptr, "kbit", 4) == 0) ||
                    (bw_unit_type == BATADV_BW_UNIT_MBIT))
                        *tmp_ptr = '\0';
        }

        ret = kstrtou64(buff, 10, &lthroughput);
        if (ret) {
                batadv_err(net_dev,
                           "Invalid throughput speed for %s: %s\n",
                           description, buff);
                return false;
        }

        switch (bw_unit_type) {
        case BATADV_BW_UNIT_MBIT:
                /* prevent overflow */
                if (U64_MAX / 10 < lthroughput) {
                        batadv_err(net_dev,
                                   "Throughput speed for %s too large: %s\n",
                                   description, buff);
                        return false;
                }

                lthroughput *= 10;
                break;
        case BATADV_BW_UNIT_KBIT:
        default:
                lthroughput = div_u64(lthroughput, 100);
                break;
        }

        if (lthroughput > U32_MAX) {
                batadv_err(net_dev,
                           "Throughput speed for %s too large: %s\n",
                           description, buff);
                return false;
        }

        *throughput = lthroughput;

        return true;
}

/**
 * batadv_parse_gw_bandwidth - parse supplied string buffer to extract download
 *  and upload bandwidth information
 * @net_dev: the soft interface net device
 * @buff: string buffer to parse
 * @down: pointer holding the returned download bandwidth information
 * @up: pointer holding the returned upload bandwidth information
 *
 * Return: false on parse error and true otherwise.
 */
static bool batadv_parse_gw_bandwidth(struct net_device *net_dev, char *buff,
                                      u32 *down, u32 *up)
{
        char *slash_ptr;
        bool ret;

        slash_ptr = strchr(buff, '/');
        if (slash_ptr)
                *slash_ptr = 0;

        ret = batadv_parse_throughput(net_dev, buff, "download gateway speed",
                                      down);
        if (!ret)
                return false;

        /* we also got some upload info */
        if (slash_ptr) {
                ret = batadv_parse_throughput(net_dev, slash_ptr + 1,
                                              "upload gateway speed", up);
                if (!ret)
                        return false;
        }

        return true;
}

/**
 * batadv_gw_tvlv_container_update - update the gw tvlv container after gateway
 *  setting change
 * @bat_priv: the bat priv with all the soft interface information
 */
void batadv_gw_tvlv_container_update(struct batadv_priv *bat_priv)
{
        struct batadv_tvlv_gateway_data gw;
        u32 down, up;
        char gw_mode;

        gw_mode = atomic_read(&bat_priv->gw.mode);

        switch (gw_mode) {
        case BATADV_GW_MODE_OFF:
        case BATADV_GW_MODE_CLIENT:
                batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_GW, 1);
                break;
        case BATADV_GW_MODE_SERVER:
                down = atomic_read(&bat_priv->gw.bandwidth_down);
                up = atomic_read(&bat_priv->gw.bandwidth_up);
                gw.bandwidth_down = htonl(down);
                gw.bandwidth_up = htonl(up);
                batadv_tvlv_container_register(bat_priv, BATADV_TVLV_GW, 1,
                                               &gw, sizeof(gw));
                break;
        }
}

ssize_t batadv_gw_bandwidth_set(struct net_device *net_dev, char *buff,
                                size_t count)
{
        struct batadv_priv *bat_priv = netdev_priv(net_dev);
        u32 down_curr;
        u32 up_curr;
        u32 down_new = 0;
        u32 up_new = 0;
        bool ret;

        down_curr = (unsigned int)atomic_read(&bat_priv->gw.bandwidth_down);
        up_curr = (unsigned int)atomic_read(&bat_priv->gw.bandwidth_up);

        ret = batadv_parse_gw_bandwidth(net_dev, buff, &down_new, &up_new);
        if (!ret)
                return -EINVAL;

        if (!down_new)
                down_new = 1;

        if (!up_new)
                up_new = down_new / 5;

        if (!up_new)
                up_new = 1;

        if ((down_curr == down_new) && (up_curr == up_new))
                return count;

        batadv_gw_reselect(bat_priv);
        batadv_info(net_dev,
                    "Changing gateway bandwidth from: '%u.%u/%u.%u MBit' to: '%u.%u/%u.%u MBit'\n",
                    down_curr / 10, down_curr % 10, up_curr / 10, up_curr % 10,
                    down_new / 10, down_new % 10, up_new / 10, up_new % 10);

        atomic_set(&bat_priv->gw.bandwidth_down, down_new);
        atomic_set(&bat_priv->gw.bandwidth_up, up_new);
        batadv_gw_tvlv_container_update(bat_priv);

        return count;
}

/**
 * batadv_gw_tvlv_ogm_handler_v1 - process incoming gateway tvlv container
 * @bat_priv: the bat priv with all the soft interface information
 * @orig: the orig_node of the ogm
 * @flags: flags indicating the tvlv state (see batadv_tvlv_handler_flags)
 * @tvlv_value: tvlv buffer containing the gateway data
 * @tvlv_value_len: tvlv buffer length
 */
static void batadv_gw_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
                                          struct batadv_orig_node *orig,
                                          u8 flags,
                                          void *tvlv_value, u16 tvlv_value_len)
{
        struct batadv_tvlv_gateway_data gateway, *gateway_ptr;

        /* only fetch the tvlv value if the handler wasn't called via the
         * CIFNOTFND flag and if there is data to fetch
         */
        if ((flags & BATADV_TVLV_HANDLER_OGM_CIFNOTFND) ||
            (tvlv_value_len < sizeof(gateway))) {
                gateway.bandwidth_down = 0;
                gateway.bandwidth_up = 0;
        } else {
                gateway_ptr = tvlv_value;
                gateway.bandwidth_down = gateway_ptr->bandwidth_down;
                gateway.bandwidth_up = gateway_ptr->bandwidth_up;
                if ((gateway.bandwidth_down == 0) ||
                    (gateway.bandwidth_up == 0)) {
                        gateway.bandwidth_down = 0;
                        gateway.bandwidth_up = 0;
                }
        }

        batadv_gw_node_update(bat_priv, orig, &gateway);

        /* restart gateway selection if fast or late switching was enabled */
        if ((gateway.bandwidth_down != 0) &&
            (atomic_read(&bat_priv->gw.mode) == BATADV_GW_MODE_CLIENT) &&
            (atomic_read(&bat_priv->gw.sel_class) > 2))
                batadv_gw_check_election(bat_priv, orig);
}

/**
 * batadv_gw_init - initialise the gateway handling internals
 * @bat_priv: the bat priv with all the soft interface information
 */
void batadv_gw_init(struct batadv_priv *bat_priv)
{
        batadv_tvlv_handler_register(bat_priv, batadv_gw_tvlv_ogm_handler_v1,
                                     NULL, BATADV_TVLV_GW, 1,
                                     BATADV_TVLV_HANDLER_OGM_CIFNOTFND);
}

/**
 * batadv_gw_free - free the gateway handling internals
 * @bat_priv: the bat priv with all the soft interface information
 */
void batadv_gw_free(struct batadv_priv *bat_priv)
{
        batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_GW, 1);
        batadv_tvlv_handler_unregister(bat_priv, BATADV_TVLV_GW, 1);
}