/*

   * Copyright (C) 2010-2011 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 *frag_merge_packet(struct list_head *head,
  					 struct frag_packet_list_entry *tfp,
  					 struct sk_buff *skb)
  {
  	struct unicast_frag_packet *up =
  		(struct unicast_frag_packet *)skb->data;
  	struct sk_buff *tmp_skb;
  	struct unicast_packet *unicast_packet;

  	int hdr_len = sizeof(*unicast_packet);
  	int uni_diff = sizeof(*up) - hdr_len;

  
  	/* set skb to the first part and tmp_skb to the second part */
  	if (up->flags & 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);
  	unicast_packet = (struct unicast_packet *) skb_pull(skb, uni_diff);
  	unicast_packet->packet_type = BAT_UNICAST;
  
  	return skb;

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

  }
  
  static void frag_create_entry(struct list_head *head, struct sk_buff *skb)
  {
  	struct frag_packet_list_entry *tfp;
  	struct unicast_frag_packet *up =
  		(struct 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 frag_create_buffer(struct list_head *head)
  {
  	int i;
  	struct frag_packet_list_entry *tfp;
  
  	for (i = 0; i < FRAG_BUFFER_SIZE; i++) {

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

  		if (!tfp) {
  			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 frag_packet_list_entry *frag_search_packet(struct list_head *head,

  					   const struct unicast_frag_packet *up)

  {
  	struct frag_packet_list_entry *tfp;
  	struct unicast_frag_packet *tmp_up = NULL;
  	uint16_t search_seqno;
  
  	if (up->flags & UNI_FRAG_HEAD)
  		search_seqno = ntohs(up->seqno)+1;
  	else
  		search_seqno = ntohs(up->seqno)-1;
  
  	list_for_each_entry(tfp, head, list) {
  
  		if (!tfp->skb)
  			continue;
  
  		if (tfp->seqno == ntohs(up->seqno))
  			goto mov_tail;
  
  		tmp_up = (struct unicast_frag_packet *)tfp->skb->data;
  
  		if (tfp->seqno == search_seqno) {
  
  			if ((tmp_up->flags & UNI_FRAG_HEAD) !=
  			    (up->flags & UNI_FRAG_HEAD))
  				return tfp;
  			else
  				goto mov_tail;
  		}
  	}
  	return NULL;
  
  mov_tail:
  	list_move_tail(&tfp->list, head);
  	return NULL;
  }
  
  void frag_list_free(struct list_head *head)
  {
  	struct 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 frag_reassemble_skb(struct sk_buff *skb, struct bat_priv *bat_priv,
  			struct sk_buff **new_skb)
  {
  	struct orig_node *orig_node;
  	struct frag_packet_list_entry *tmp_frag_entry;
  	int ret = NET_RX_DROP;
  	struct unicast_frag_packet *unicast_packet =
  		(struct unicast_frag_packet *)skb->data;
  
  	*new_skb = NULL;

  	orig_node = 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) &&
  	    frag_create_buffer(&orig_node->frag_list)) {
  		pr_debug("couldn't create frag buffer
  ");
  		goto out;
  	}
  
  	tmp_frag_entry = frag_search_packet(&orig_node->frag_list,
  					    unicast_packet);
  
  	if (!tmp_frag_entry) {
  		frag_create_entry(&orig_node->frag_list, skb);
  		ret = NET_RX_SUCCESS;
  		goto out;
  	}
  
  	*new_skb = 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)

  		orig_node_free_ref(orig_node);

  	return ret;
  }
  
  int frag_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv,

  		  struct hard_iface *hard_iface, const uint8_t dstaddr[])

  {
  	struct unicast_packet tmp_uc, *unicast_packet;

  	struct hard_iface *primary_if;

  	struct sk_buff *frag_skb;
  	struct 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 = 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 unicast_packet *) skb->data;

  	memcpy(&tmp_uc, unicast_packet, uc_hdr_len);

  	skb_split(skb, frag_skb, data_len / 2 + uc_hdr_len);

  
  	if (my_skb_head_push(skb, ucf_hdr_len - uc_hdr_len) < 0 ||
  	    my_skb_head_push(frag_skb, ucf_hdr_len) < 0)
  		goto drop_frag;
  
  	frag1 = (struct unicast_frag_packet *)skb->data;
  	frag2 = (struct unicast_frag_packet *)frag_skb->data;

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

  
  	frag1->ttl--;
  	frag1->version = COMPAT_VERSION;
  	frag1->packet_type = BAT_UNICAST_FRAG;

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

  	memcpy(frag2, frag1, sizeof(*frag2));

  	if (data_len & 1)
  		large_tail = UNI_FRAG_LARGETAIL;
  
  	frag1->flags = 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);

  	send_skb_packet(skb, hard_iface, dstaddr);
  	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)
  		hardif_free_ref(primary_if);
  	return ret;

  }
  
  int unicast_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv)
  {
  	struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
  	struct unicast_packet *unicast_packet;

  	struct orig_node *orig_node;

  	struct neigh_node *neigh_node;

  	int data_len = skb->len;

  	int ret = 1;

  
  	/* get routing information */

  	if (is_multicast_ether_addr(ethhdr->h_dest)) {

  		orig_node = 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 = 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 = find_router(bat_priv, orig_node, NULL);

  	if (!neigh_node)

  		goto out;

  	if (my_skb_head_push(skb, sizeof(*unicast_packet)) < 0)

  		goto out;

  
  	unicast_packet = (struct unicast_packet *)skb->data;
  
  	unicast_packet->version = COMPAT_VERSION;
  	/* batman packet type: unicast */
  	unicast_packet->packet_type = BAT_UNICAST;
  	/* set unicast ttl */
  	unicast_packet->ttl = 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);

  
  	if (atomic_read(&bat_priv->fragmentation) &&

  	    data_len + sizeof(*unicast_packet) >

  				neigh_node->if_incoming->net_dev->mtu) {

  		/* send frag skb decreases ttl */
  		unicast_packet->ttl++;

  		ret = frag_send_skb(skb, bat_priv,
  				    neigh_node->if_incoming, neigh_node->addr);

  		goto out;

  	}

  	send_skb_packet(skb, neigh_node->if_incoming, neigh_node->addr);

  	ret = 0;
  	goto out;

  out:
  	if (neigh_node)
  		neigh_node_free_ref(neigh_node);
  	if (orig_node)

  		orig_node_free_ref(orig_node);

  	if (ret == 1)
  		kfree_skb(skb);
  	return ret;

  }