/* Copyright (C) 2010-2013 B.A.T.M.A.N. contributors:
 *
 * Andreas Langer
 *
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA
 */

#include "main.h"
#include "unicast.h"
#include "send.h"
#include "soft-interface.h"
#include "gateway_client.h"
#include "originator.h"
#include "hash.h"
#include "translation-table.h"
#include "routing.h"
#include "hard-interface.h"


static struct sk_buff *
batadv_frag_merge_packet(struct list_head *head,
                         struct batadv_frag_packet_list_entry *tfp,
                         struct sk_buff *skb)
{
        struct batadv_unicast_frag_packet *up;
        struct sk_buff *tmp_skb;
        struct batadv_unicast_packet *unicast_packet;
        int hdr_len = sizeof(*unicast_packet);
        int uni_diff = sizeof(*up) - hdr_len;
        uint8_t *packet_pos;

        up = (struct batadv_unicast_frag_packet *)skb->data;
        /* set skb to the first part and tmp_skb to the second part */
        if (up->flags & BATADV_UNI_FRAG_HEAD) {
                tmp_skb = tfp->skb;
        } else {
                tmp_skb = skb;
                skb = tfp->skb;
        }

        if (skb_linearize(skb) < 0 || skb_linearize(tmp_skb) < 0)
                goto err;

        skb_pull(tmp_skb, sizeof(*up));
        if (pskb_expand_head(skb, 0, tmp_skb->len, GFP_ATOMIC) < 0)
                goto err;

        /* move free entry to end */
        tfp->skb = NULL;
        tfp->seqno = 0;
        list_move_tail(&tfp->list, head);

        memcpy(skb_put(skb, tmp_skb->len), tmp_skb->data, tmp_skb->len);
        kfree_skb(tmp_skb);

        memmove(skb->data + uni_diff, skb->data, hdr_len);
        packet_pos = skb_pull(skb, uni_diff);
        unicast_packet = (struct batadv_unicast_packet *)packet_pos;
        unicast_packet->header.packet_type = BATADV_UNICAST;

        return skb;

err:
        /* free buffered skb, skb will be freed later */
        kfree_skb(tfp->skb);
        return NULL;
}

static void batadv_frag_create_entry(struct list_head *head,
                                     struct sk_buff *skb)
{
        struct batadv_frag_packet_list_entry *tfp;
        struct batadv_unicast_frag_packet *up;

        up = (struct batadv_unicast_frag_packet *)skb->data;

        /* free and oldest packets stand at the end */
        tfp = list_entry((head)->prev, typeof(*tfp), list);
        kfree_skb(tfp->skb);

        tfp->seqno = ntohs(up->seqno);
        tfp->skb = skb;
        list_move(&tfp->list, head);
        return;
}

static int batadv_frag_create_buffer(struct list_head *head)
{
        int i;
        struct batadv_frag_packet_list_entry *tfp;

        for (i = 0; i < BATADV_FRAG_BUFFER_SIZE; i++) {
                tfp = kmalloc(sizeof(*tfp), GFP_ATOMIC);
                if (!tfp) {
                        batadv_frag_list_free(head);
                        return -ENOMEM;
                }
                tfp->skb = NULL;
                tfp->seqno = 0;
                INIT_LIST_HEAD(&tfp->list);
                list_add(&tfp->list, head);
        }

        return 0;
}

static struct batadv_frag_packet_list_entry *
batadv_frag_search_packet(struct list_head *head,
                          const struct batadv_unicast_frag_packet *up)
{
        struct batadv_frag_packet_list_entry *tfp;
        struct batadv_unicast_frag_packet *tmp_up = NULL;
        bool is_head_tmp, is_head;
        uint16_t search_seqno;

        if (up->flags & BATADV_UNI_FRAG_HEAD)
                search_seqno = ntohs(up->seqno)+1;
        else
                search_seqno = ntohs(up->seqno)-1;

        is_head = up->flags & BATADV_UNI_FRAG_HEAD;

        list_for_each_entry(tfp, head, list) {
                if (!tfp->skb)
                        continue;

                if (tfp->seqno == ntohs(up->seqno))
                        goto mov_tail;

                tmp_up = (struct batadv_unicast_frag_packet *)tfp->skb->data;

                if (tfp->seqno == search_seqno) {
                        is_head_tmp = tmp_up->flags & BATADV_UNI_FRAG_HEAD;
                        if (is_head_tmp != is_head)
                                return tfp;
                        else
                                goto mov_tail;
                }
        }
        return NULL;

mov_tail:
        list_move_tail(&tfp->list, head);
        return NULL;
}

void batadv_frag_list_free(struct list_head *head)
{
        struct batadv_frag_packet_list_entry *pf, *tmp_pf;

        if (!list_empty(head)) {
                list_for_each_entry_safe(pf, tmp_pf, head, list) {
                        kfree_skb(pf->skb);
                        list_del(&pf->list);
                        kfree(pf);
                }
        }
        return;
}

/* frag_reassemble_skb():
 * returns NET_RX_DROP if the operation failed - skb is left intact
 * returns NET_RX_SUCCESS if the fragment was buffered (skb_new will be NULL)
 * or the skb could be reassembled (skb_new will point to the new packet and
 * skb was freed)
 */
int batadv_frag_reassemble_skb(struct sk_buff *skb,
                               struct batadv_priv *bat_priv,
                               struct sk_buff **new_skb)
{
        struct batadv_orig_node *orig_node;
        struct batadv_frag_packet_list_entry *tmp_frag_entry;
        int ret = NET_RX_DROP;
        struct batadv_unicast_frag_packet *unicast_packet;

        unicast_packet = (struct batadv_unicast_frag_packet *)skb->data;
        *new_skb = NULL;

        orig_node = batadv_orig_hash_find(bat_priv, unicast_packet->orig);
        if (!orig_node)
                goto out;

        orig_node->last_frag_packet = jiffies;

        if (list_empty(&orig_node->frag_list) &&
            batadv_frag_create_buffer(&orig_node->frag_list)) {
                pr_debug("couldn't create frag buffer\n");
                goto out;
        }

        tmp_frag_entry = batadv_frag_search_packet(&orig_node->frag_list,
                                                   unicast_packet);

        if (!tmp_frag_entry) {
                batadv_frag_create_entry(&orig_node->frag_list, skb);
                ret = NET_RX_SUCCESS;
                goto out;
        }

        *new_skb = batadv_frag_merge_packet(&orig_node->frag_list,
                                            tmp_frag_entry, skb);
        /* if not, merge failed */
        if (*new_skb)
                ret = NET_RX_SUCCESS;

out:
        if (orig_node)
                batadv_orig_node_free_ref(orig_node);
        return ret;
}

int batadv_frag_send_skb(struct sk_buff *skb, struct batadv_priv *bat_priv,
                         struct batadv_hard_iface *hard_iface,
                         const uint8_t dstaddr[])
{
        struct batadv_unicast_packet tmp_uc, *unicast_packet;
        struct batadv_hard_iface *primary_if;
        struct sk_buff *frag_skb;
        struct batadv_unicast_frag_packet *frag1, *frag2;
        int uc_hdr_len = sizeof(*unicast_packet);
        int ucf_hdr_len = sizeof(*frag1);
        int data_len = skb->len - uc_hdr_len;
        int large_tail = 0, ret = NET_RX_DROP;
        uint16_t seqno;

        primary_if = batadv_primary_if_get_selected(bat_priv);
        if (!primary_if)
                goto dropped;

        frag_skb = dev_alloc_skb(data_len - (data_len / 2) + ucf_hdr_len);
        if (!frag_skb)
                goto dropped;
        skb_reserve(frag_skb, ucf_hdr_len);

        unicast_packet = (struct batadv_unicast_packet *)skb->data;
        memcpy(&tmp_uc, unicast_packet, uc_hdr_len);
        skb_split(skb, frag_skb, data_len / 2 + uc_hdr_len);

        if (batadv_skb_head_push(skb, ucf_hdr_len - uc_hdr_len) < 0 ||
            batadv_skb_head_push(frag_skb, ucf_hdr_len) < 0)
                goto drop_frag;

        frag1 = (struct batadv_unicast_frag_packet *)skb->data;
        frag2 = (struct batadv_unicast_frag_packet *)frag_skb->data;

        memcpy(frag1, &tmp_uc, sizeof(tmp_uc));

        frag1->header.ttl--;
        frag1->header.version = BATADV_COMPAT_VERSION;
        frag1->header.packet_type = BATADV_UNICAST_FRAG;

        memcpy(frag1->orig, primary_if->net_dev->dev_addr, ETH_ALEN);
        memcpy(frag2, frag1, sizeof(*frag2));

        if (data_len & 1)
                large_tail = BATADV_UNI_FRAG_LARGETAIL;

        frag1->flags = BATADV_UNI_FRAG_HEAD | large_tail;
        frag2->flags = large_tail;

        seqno = atomic_add_return(2, &hard_iface->frag_seqno);
        frag1->seqno = htons(seqno - 1);
        frag2->seqno = htons(seqno);

        batadv_send_skb_packet(skb, hard_iface, dstaddr);
        batadv_send_skb_packet(frag_skb, hard_iface, dstaddr);
        ret = NET_RX_SUCCESS;
        goto out;

drop_frag:
        kfree_skb(frag_skb);
dropped:
        kfree_skb(skb);
out:
        if (primary_if)
                batadv_hardif_free_ref(primary_if);
        return ret;
}

/**
 * batadv_unicast_push_and_fill_skb - extends the buffer and initializes the
 * common fields for unicast packets
 * @skb: packet
 * @hdr_size: amount of bytes to push at the beginning of the skb
 * @orig_node: the destination node
 *
 * Returns false if the buffer extension was not possible or true otherwise
 */
static bool batadv_unicast_push_and_fill_skb(struct sk_buff *skb, int hdr_size,
                                             struct batadv_orig_node *orig_node)
{
        struct batadv_unicast_packet *unicast_packet;
        uint8_t ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);

        if (batadv_skb_head_push(skb, hdr_size) < 0)
                return false;

        unicast_packet = (struct batadv_unicast_packet *)skb->data;
        unicast_packet->header.version = BATADV_COMPAT_VERSION;
        /* batman packet type: unicast */
        unicast_packet->header.packet_type = BATADV_UNICAST;
        /* set unicast ttl */
        unicast_packet->header.ttl = BATADV_TTL;
        /* copy the destination for faster routing */
        memcpy(unicast_packet->dest, orig_node->orig, ETH_ALEN);
        /* set the destination tt version number */
        unicast_packet->ttvn = ttvn;

        return true;
}

/**
 * batadv_unicast_prepare_skb - encapsulate an skb with a unicast header
 * @skb: the skb containing the payload to encapsulate
 * @orig_node: the destination node
 *
 * Returns false if the payload could not be encapsulated or true otherwise
 */
static bool batadv_unicast_prepare_skb(struct sk_buff *skb,
                                       struct batadv_orig_node *orig_node)
{
        size_t uni_size = sizeof(struct batadv_unicast_packet);
        return batadv_unicast_push_and_fill_skb(skb, uni_size, orig_node);
}

/**
 * batadv_unicast_4addr_prepare_skb - encapsulate an skb with a unicast4addr
 * header
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: the skb containing the payload to encapsulate
 * @orig_node: the destination node
 * @packet_subtype: the batman 4addr packet subtype to use
 *
 * Returns false if the payload could not be encapsulated or true otherwise
 */
bool batadv_unicast_4addr_prepare_skb(struct batadv_priv *bat_priv,
                                      struct sk_buff *skb,
                                      struct batadv_orig_node *orig,
                                      int packet_subtype)
{
        struct batadv_hard_iface *primary_if;
        struct batadv_unicast_4addr_packet *unicast_4addr_packet;
        bool ret = false;

        primary_if = batadv_primary_if_get_selected(bat_priv);
        if (!primary_if)
                goto out;

        /* pull the header space and fill the unicast_packet substructure.
         * We can do that because the first member of the unicast_4addr_packet
         * is of type struct unicast_packet
         */
        if (!batadv_unicast_push_and_fill_skb(skb,
                                              sizeof(*unicast_4addr_packet),
                                              orig))
                goto out;

        unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;
        unicast_4addr_packet->u.header.packet_type = BATADV_UNICAST_4ADDR;
        memcpy(unicast_4addr_packet->src, primary_if->net_dev->dev_addr,
               ETH_ALEN);
        unicast_4addr_packet->subtype = packet_subtype;
        unicast_4addr_packet->reserved = 0;

        ret = true;
out:
        if (primary_if)
                batadv_hardif_free_ref(primary_if);
        return ret;
}

/**
 * batadv_unicast_generic_send_skb - send an skb as unicast
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: payload to send
 * @packet_type: the batman unicast packet type to use
 * @packet_subtype: the batman packet subtype. It is ignored if packet_type is
 *                  not BATADV_UNICAT_4ADDR
 *
 * Returns 1 in case of error or 0 otherwise
 */
int batadv_unicast_generic_send_skb(struct batadv_priv *bat_priv,
                                    struct sk_buff *skb, int packet_type,
                                    int packet_subtype)
{
        struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
        struct batadv_unicast_packet *unicast_packet;
        struct batadv_orig_node *orig_node;
        struct batadv_neigh_node *neigh_node;
        int data_len = skb->len;
        int ret = NET_RX_DROP;
        unsigned int dev_mtu;

        /* get routing information */
        if (is_multicast_ether_addr(ethhdr->h_dest)) {
                orig_node = batadv_gw_get_selected_orig(bat_priv);
                if (orig_node)
                        goto find_router;
        }

        /* check for tt host - increases orig_node refcount.
         * returns NULL in case of AP isolation
         */
        orig_node = batadv_transtable_search(bat_priv, ethhdr->h_source,
                                             ethhdr->h_dest);

find_router:
        /* find_router():
         *  - if orig_node is NULL it returns NULL
         *  - increases neigh_nodes refcount if found.
         */
        neigh_node = batadv_find_router(bat_priv, orig_node, NULL);

        if (!neigh_node)
                goto out;

        switch (packet_type) {
        case BATADV_UNICAST:
                batadv_unicast_prepare_skb(skb, orig_node);
                break;
        case BATADV_UNICAST_4ADDR:
                batadv_unicast_4addr_prepare_skb(bat_priv, skb, orig_node,
                                                 packet_subtype);
                break;
        default:
                /* this function supports UNICAST and UNICAST_4ADDR only. It
                 * should never be invoked with any other packet type
                 */
                goto out;
        }

        unicast_packet = (struct batadv_unicast_packet *)skb->data;

        /* inform the destination node that we are still missing a correct route
         * for this client. The destination will receive this packet and will
         * try to reroute it because the ttvn contained in the header is less
         * than the current one
         */
        if (batadv_tt_global_client_is_roaming(bat_priv, ethhdr->h_dest))
                unicast_packet->ttvn = unicast_packet->ttvn - 1;

        dev_mtu = neigh_node->if_incoming->net_dev->mtu;
        /* fragmentation mechanism only works for UNICAST (now) */
        if (packet_type == BATADV_UNICAST &&
            atomic_read(&bat_priv->fragmentation) &&
            data_len + sizeof(*unicast_packet) > dev_mtu) {
                /* send frag skb decreases ttl */
                unicast_packet->header.ttl++;
                ret = batadv_frag_send_skb(skb, bat_priv,
                                           neigh_node->if_incoming,
                                           neigh_node->addr);
                goto out;
        }

        if (batadv_send_skb_to_orig(skb, orig_node, NULL))
                ret = 0;

out:
        if (neigh_node)
                batadv_neigh_node_free_ref(neigh_node);
        if (orig_node)
                batadv_orig_node_free_ref(orig_node);
        if (ret == NET_RX_DROP)
                kfree_skb(skb);
        return ret;
}