unicast.c

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/* Copyright (C) 2010-2012 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;
    int 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;
}

int batadv_unicast_send_skb(struct sk_buff *skb, struct batadv_priv *bat_priv)
{
    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 = 1;
    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;

    if (batadv_skb_head_push(skb, sizeof(*unicast_packet)) < 0)
        goto out;

    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 = (uint8_t)atomic_read(&orig_node->last_ttvn);

    /* 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;
    if (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;
    }

    batadv_send_skb_packet(skb, neigh_node->if_incoming, neigh_node->addr);
    ret = 0;
    goto out;

out:
    if (neigh_node)
        batadv_neigh_node_free_ref(neigh_node);
    if (orig_node)
        batadv_orig_node_free_ref(orig_node);
    if (ret == 1)
        kfree_skb(skb);
    return ret;
}