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author | Antonio Quartulli <ordex@autistici.org> | 2011-11-23 11:35:44 +0100 |
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committer | Antonio Quartulli <ordex@autistici.org> | 2012-11-07 20:00:19 +0100 |
commit | 785ea1144182c341b8b85b0f8180291839d176a8 (patch) | |
tree | 218d58e56db4e2a2ef49c6ab0d889cdb6e1df309 /net/batman-adv/distributed-arp-table.c | |
parent | 0e861a3c4ffef56822e1d51c355e5020deaeaf5a (diff) | |
download | linux-785ea1144182c341b8b85b0f8180291839d176a8.tar.gz linux-785ea1144182c341b8b85b0f8180291839d176a8.tar.bz2 linux-785ea1144182c341b8b85b0f8180291839d176a8.zip |
batman-adv: Distributed ARP Table - create DHT helper functions
Add all the relevant functions in order to manage a Distributed Hash Table over
the B.A.T.M.A.N.-adv network. It will later be used to store several ARP entries
and implement DAT (Distributed ARP Table)
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Diffstat (limited to 'net/batman-adv/distributed-arp-table.c')
-rw-r--r-- | net/batman-adv/distributed-arp-table.c | 270 |
1 files changed, 270 insertions, 0 deletions
diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c new file mode 100644 index 000000000000..ce39e8a5be38 --- /dev/null +++ b/net/batman-adv/distributed-arp-table.c @@ -0,0 +1,270 @@ +/* Copyright (C) 2011-2012 B.A.T.M.A.N. contributors: + * + * Antonio Quartulli + * + * 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 <linux/if_ether.h> +#include <linux/if_arp.h> + +#include "main.h" +#include "distributed-arp-table.h" +#include "hard-interface.h" +#include "originator.h" +#include "send.h" +#include "types.h" +#include "unicast.h" + +/** + * batadv_hash_dat - compute the hash value for an IP address + * @data: data to hash + * @size: size of the hash table + * + * Returns the selected index in the hash table for the given data + */ +static uint32_t batadv_hash_dat(const void *data, uint32_t size) +{ + const unsigned char *key = data; + uint32_t hash = 0; + size_t i; + + for (i = 0; i < 4; i++) { + hash += key[i]; + hash += (hash << 10); + hash ^= (hash >> 6); + } + + hash += (hash << 3); + hash ^= (hash >> 11); + hash += (hash << 15); + + return hash % size; +} + +/** + * batadv_is_orig_node_eligible - check whether a node can be a DHT candidate + * @res: the array with the already selected candidates + * @select: number of already selected candidates + * @tmp_max: address of the currently evaluated node + * @max: current round max address + * @last_max: address of the last selected candidate + * @candidate: orig_node under evaluation + * @max_orig_node: last selected candidate + * + * Returns true if the node has been elected as next candidate or false othrwise + */ +static bool batadv_is_orig_node_eligible(struct batadv_dat_candidate *res, + int select, batadv_dat_addr_t tmp_max, + batadv_dat_addr_t max, + batadv_dat_addr_t last_max, + struct batadv_orig_node *candidate, + struct batadv_orig_node *max_orig_node) +{ + bool ret = false; + int j; + + /* Check if this node has already been selected... */ + for (j = 0; j < select; j++) + if (res[j].orig_node == candidate) + break; + /* ..and possibly skip it */ + if (j < select) + goto out; + /* sanity check: has it already been selected? This should not happen */ + if (tmp_max > last_max) + goto out; + /* check if during this iteration an originator with a closer dht + * address has already been found + */ + if (tmp_max < max) + goto out; + /* this is an hash collision with the temporary selected node. Choose + * the one with the lowest address + */ + if ((tmp_max == max) && + (batadv_compare_eth(candidate->orig, max_orig_node->orig) > 0)) + goto out; + + ret = true; +out: + return ret; +} + +/** + * batadv_choose_next_candidate - select the next DHT candidate + * @bat_priv: the bat priv with all the soft interface information + * @cands: candidates array + * @select: number of candidates already present in the array + * @ip_key: key to look up in the DHT + * @last_max: pointer where the address of the selected candidate will be saved + */ +static void batadv_choose_next_candidate(struct batadv_priv *bat_priv, + struct batadv_dat_candidate *cands, + int select, batadv_dat_addr_t ip_key, + batadv_dat_addr_t *last_max) +{ + batadv_dat_addr_t max = 0, tmp_max = 0; + struct batadv_orig_node *orig_node, *max_orig_node = NULL; + struct batadv_hashtable *hash = bat_priv->orig_hash; + struct hlist_node *node; + struct hlist_head *head; + int i; + + /* if no node is eligible as candidate, leave the candidate type as + * NOT_FOUND + */ + cands[select].type = BATADV_DAT_CANDIDATE_NOT_FOUND; + + /* iterate over the originator list and find the node with closest + * dat_address which has not been selected yet + */ + for (i = 0; i < hash->size; i++) { + head = &hash->table[i]; + + rcu_read_lock(); + hlist_for_each_entry_rcu(orig_node, node, head, hash_entry) { + /* the dht space is a ring and addresses are unsigned */ + tmp_max = BATADV_DAT_ADDR_MAX - orig_node->dat_addr + + ip_key; + + if (!batadv_is_orig_node_eligible(cands, select, + tmp_max, max, + *last_max, orig_node, + max_orig_node)) + continue; + + if (!atomic_inc_not_zero(&orig_node->refcount)) + continue; + + max = tmp_max; + if (max_orig_node) + batadv_orig_node_free_ref(max_orig_node); + max_orig_node = orig_node; + } + rcu_read_unlock(); + } + if (max_orig_node) { + cands[select].type = BATADV_DAT_CANDIDATE_ORIG; + cands[select].orig_node = max_orig_node; + batadv_dbg(BATADV_DBG_DAT, bat_priv, + "dat_select_candidates() %d: selected %pM addr=%u dist=%u\n", + select, max_orig_node->orig, max_orig_node->dat_addr, + max); + } + *last_max = max; +} + +/** + * batadv_dat_select_candidates - selects the nodes which the DHT message has to + * be sent to + * @bat_priv: the bat priv with all the soft interface information + * @ip_dst: ipv4 to look up in the DHT + * + * An originator O is selected if and only if its DHT_ID value is one of three + * closest values (from the LEFT, with wrap around if needed) then the hash + * value of the key. ip_dst is the key. + * + * Returns the candidate array of size BATADV_DAT_CANDIDATE_NUM + */ +static struct batadv_dat_candidate * +batadv_dat_select_candidates(struct batadv_priv *bat_priv, __be32 ip_dst) +{ + int select; + batadv_dat_addr_t last_max = BATADV_DAT_ADDR_MAX, ip_key; + struct batadv_dat_candidate *res; + + if (!bat_priv->orig_hash) + return NULL; + + res = kmalloc(BATADV_DAT_CANDIDATES_NUM * sizeof(*res), GFP_ATOMIC); + if (!res) + return NULL; + + ip_key = (batadv_dat_addr_t)batadv_hash_dat(&ip_dst, + BATADV_DAT_ADDR_MAX); + + batadv_dbg(BATADV_DBG_DAT, bat_priv, + "dat_select_candidates(): IP=%pI4 hash(IP)=%u\n", &ip_dst, + ip_key); + + for (select = 0; select < BATADV_DAT_CANDIDATES_NUM; select++) + batadv_choose_next_candidate(bat_priv, res, select, ip_key, + &last_max); + + return res; +} + +/** + * batadv_dat_send_data - send a payload to the selected candidates + * @bat_priv: the bat priv with all the soft interface information + * @skb: payload to send + * @ip: the DHT key + * @packet_subtype: unicast4addr packet subtype to use + * + * In this function the skb is copied by means of pskb_copy() and is sent as + * unicast packet to each of the selected candidates + * + * Returns true if the packet is sent to at least one candidate, false otherwise + */ +static bool batadv_dat_send_data(struct batadv_priv *bat_priv, + struct sk_buff *skb, __be32 ip, + int packet_subtype) +{ + int i; + bool ret = false; + int send_status; + struct batadv_neigh_node *neigh_node = NULL; + struct sk_buff *tmp_skb; + struct batadv_dat_candidate *cand; + + cand = batadv_dat_select_candidates(bat_priv, ip); + if (!cand) + goto out; + + batadv_dbg(BATADV_DBG_DAT, bat_priv, "DHT_SEND for %pI4\n", &ip); + + for (i = 0; i < BATADV_DAT_CANDIDATES_NUM; i++) { + if (cand[i].type == BATADV_DAT_CANDIDATE_NOT_FOUND) + continue; + + neigh_node = batadv_orig_node_get_router(cand[i].orig_node); + if (!neigh_node) + goto free_orig; + + tmp_skb = pskb_copy(skb, GFP_ATOMIC); + if (!batadv_unicast_4addr_prepare_skb(bat_priv, tmp_skb, + cand[i].orig_node, + packet_subtype)) { + kfree_skb(tmp_skb); + goto free_neigh; + } + + send_status = batadv_send_skb_packet(tmp_skb, + neigh_node->if_incoming, + neigh_node->addr); + if (send_status == NET_XMIT_SUCCESS) + /* packet sent to a candidate: return true */ + ret = true; +free_neigh: + batadv_neigh_node_free_ref(neigh_node); +free_orig: + batadv_orig_node_free_ref(cand[i].orig_node); + } + +out: + kfree(cand); + return ret; +} |