1 /* Copyright (c) 2010-2021. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
7 #include "routing_table.h"
8 #include "simgrid/comm.h"
10 #include <stdio.h> /* snprintf */
12 XBT_LOG_NEW_DEFAULT_CATEGORY(dht_kademlia_node, "Messages specific for this example");
14 /** @brief Initialization of a node
15 * @param node_id the id of the node
16 * @return the node created
18 node_t node_init(unsigned int node_id)
20 node_t node = xbt_new(s_node_t, 1);
22 node->table = routing_table_init(node_id);
23 node->mailbox = get_node_mailbox(node_id);
24 node->find_node_failed = 0;
25 node->find_node_success = 0;
27 node->received_msg = NULL;
28 node->receive_comm = NULL;
33 /* @brief Node destructor */
34 void node_free(node_t node)
36 routing_table_free(node->table);
41 * @brief Tries to join the network
42 * @param node node data
43 * @param id_known id of the node I know in the network.
45 unsigned int join(node_t node, unsigned int id_known)
48 unsigned int got_answer = 0;
50 sg_mailbox_t mailbox = get_node_mailbox(node->id);
52 /* Add the guy we know to our routing table and ourselves. */
53 routing_table_update(node, node->id);
54 routing_table_update(node, id_known);
56 /* First step: Send a "FIND_NODE" request to the node we know */
57 send_find_node(node, id_known, node->id);
59 if (node->receive_comm == NULL)
60 node->receive_comm = sg_mailbox_get_async(mailbox, &node->received_msg);
62 if (sg_comm_test(node->receive_comm)) {
63 XBT_DEBUG("Received an answer from the node I know.");
65 // retrieve the node list and ping them.
66 const kademlia_message_t msg = (kademlia_message_t)(node->received_msg);
67 const s_answer_t* node_list = msg->answer;
68 if (node_list != NULL) {
69 node_contact_t contact;
70 xbt_dynar_foreach (node_list->nodes, i, contact)
71 routing_table_update(node, contact->id);
72 node->received_msg = NULL;
74 handle_find_node(node, msg);
76 answer_free(msg->answer);
78 node->receive_comm = NULL;
80 sg_actor_sleep_for(1);
82 } while (got_answer == 0);
84 /* Second step: Send a FIND_NODE to a random node in buckets */
85 unsigned int bucket_id = routing_table_find_bucket(node->table, id_known)->id;
86 xbt_assert(bucket_id <= IDENTIFIER_SIZE);
87 for (i = 0; ((bucket_id > i) || (bucket_id + i) <= IDENTIFIER_SIZE) && i < JOIN_BUCKETS_QUERIES; i++) {
89 unsigned int id_in_bucket = get_id_in_prefix(node->id, bucket_id - i);
90 find_node(node, id_in_bucket, 0);
92 if (bucket_id + i <= IDENTIFIER_SIZE) {
93 unsigned int id_in_bucket = get_id_in_prefix(node->id, bucket_id + i);
94 find_node(node, id_in_bucket, 0);
100 /** @brief Send a "FIND_NODE" to a node
101 * @param node sender node data
102 * @param id node we are querying
103 * @param destination node we are trying to find.
105 void send_find_node(const_node_t node, unsigned int id, unsigned int destination)
107 /* Gets the mailbox to send to */
108 sg_mailbox_t mailbox = get_node_mailbox(id);
109 /* Build the message */
110 kademlia_message_t msg = new_message(node->id, destination, NULL, node->mailbox, sg_host_self_get_name());
111 sg_comm_t comm = sg_mailbox_put_init(mailbox, msg, COMM_SIZE);
112 sg_comm_detach(comm, free_message);
113 XBT_VERB("Asking %u for its closest nodes", id);
117 * Sends to the best "KADEMLIA_ALPHA" nodes in the "node_list" array a "FIND_NODE" request, to ask them for their best
120 unsigned int send_find_node_to_best(const_node_t node, const_answer_t node_list)
124 unsigned int destination = node_list->destination_id;
125 while (j < KADEMLIA_ALPHA && i < node_list->size) {
126 /* We need to have at most "KADEMLIA_ALPHA" requests each time, according to the protocol */
127 /* Gets the node we want to send the query to */
128 const s_node_contact_t* node_to_query = xbt_dynar_get_as(node_list->nodes, i, node_contact_t);
129 if (node_to_query->id != node->id) { /* No need to query ourselves */
130 send_find_node(node, node_to_query->id, destination);
138 /** @brief Updates/Puts the node id unsigned into our routing table
139 * @param node Our node data
140 * @param id The id of the node we need to add unsigned into our routing table
142 void routing_table_update(const_node_t node, unsigned int id)
144 const_routing_table_t table = node->table;
145 // retrieval of the bucket in which the should be
146 const_bucket_t bucket = routing_table_find_bucket(table, id);
148 // check if the id is already in the bucket.
149 unsigned int id_pos = bucket_find_id(bucket, id);
152 /* We check if the bucket is full or not. If it is, we evict an old element */
153 if (xbt_dynar_length(bucket->nodes) >= BUCKET_SIZE)
154 xbt_dynar_pop(bucket->nodes, NULL);
156 xbt_dynar_unshift(bucket->nodes, &id);
157 XBT_VERB("I'm adding to my routing table %08x", id);
159 // We push to the front of the dynar the element.
160 unsigned int element = xbt_dynar_get_as(bucket->nodes, id_pos, unsigned int);
161 xbt_dynar_remove_at(bucket->nodes, id_pos, NULL);
162 xbt_dynar_unshift(bucket->nodes, &element);
163 XBT_VERB("I'm updating %08x", element);
167 /** @brief Finds the closest nodes to the node given.
168 * @param node : our node
169 * @param destination_id : the id of the guy we are trying to find
171 answer_t find_closest(const_node_t node, unsigned int destination_id)
173 answer_t answer = answer_init(destination_id);
174 /* We find the corresponding bucket for the id */
175 const_bucket_t bucket = routing_table_find_bucket(node->table, destination_id);
176 int bucket_id = bucket->id;
177 xbt_assert((bucket_id <= IDENTIFIER_SIZE), "Bucket found has a wrong identifier");
178 /* So, we copy the contents of the bucket unsigned into our result dynar */
179 answer_add_bucket(bucket, answer);
181 /* However, if we don't have enough elements in our bucket, we NEED to include at least "BUCKET_SIZE" elements
182 * (if, of course, we know at least "BUCKET_SIZE" elements. So we're going to look unsigned into the other buckets.
184 for (int i = 1; answer->size < BUCKET_SIZE && ((bucket_id - i > 0) || (bucket_id + i < IDENTIFIER_SIZE)); i++) {
185 /* We check the previous buckets */
186 if (bucket_id - i >= 0) {
187 const_bucket_t bucket_p = &node->table->buckets[bucket_id - i];
188 answer_add_bucket(bucket_p, answer);
190 /* We check the next buckets */
191 if (bucket_id + i <= IDENTIFIER_SIZE) {
192 const_bucket_t bucket_n = &node->table->buckets[bucket_id + i];
193 answer_add_bucket(bucket_n, answer);
196 /* We sort the array by XOR distance */
198 /* We trim the array to have only BUCKET_SIZE or less elements */
204 unsigned int find_node(node_t node, unsigned int id_to_find, unsigned int count_in_stats)
207 unsigned int queries;
208 unsigned int answers;
209 unsigned int destination_found = 0;
210 unsigned int nodes_added = 0;
211 double global_timeout = simgrid_get_clock() + FIND_NODE_GLOBAL_TIMEOUT;
212 unsigned int steps = 0;
214 /* First we build a list of who we already know */
215 answer_t node_list = find_closest(node, id_to_find);
216 xbt_assert((node_list != NULL), "node_list incorrect");
218 XBT_DEBUG("Doing a FIND_NODE on %08x", id_to_find);
220 /* Ask the nodes on our list if they have information about the node we are trying to find */
221 sg_mailbox_t mailbox = get_node_mailbox(node->id);
224 queries = send_find_node_to_best(node, node_list);
226 double timeout = simgrid_get_clock() + FIND_NODE_TIMEOUT;
228 double time_beginreceive = simgrid_get_clock();
231 if (node->receive_comm == NULL)
232 node->receive_comm = sg_mailbox_get_async(mailbox, &node->received_msg);
234 if (sg_comm_test(node->receive_comm)) {
235 // Figure out if we received an answer or something else
236 const kademlia_message_t msg = (kademlia_message_t)(node->received_msg);
238 // Check if what we have received is what we are looking for.
239 if (msg->answer != NULL && msg->answer->destination_id == id_to_find) {
241 routing_table_update(node, msg->sender_id);
242 node_contact_t contact;
243 xbt_dynar_foreach (node_list->nodes, i, contact)
244 routing_table_update(node, contact->id);
248 nodes_added = answer_merge(node_list, msg->answer);
249 XBT_DEBUG("Received an answer from %s (%s) with %lu nodes on it", sg_mailbox_get_name(msg->answer_to),
250 msg->issuer_host_name, xbt_dynar_length(msg->answer->nodes));
252 if (msg->answer != NULL) {
253 routing_table_update(node, msg->sender_id);
254 XBT_DEBUG("Received a wrong answer for a FIND_NODE");
256 handle_find_node(node, msg);
258 // Update the timeout if we didn't have our answer
259 timeout += simgrid_get_clock() - time_beginreceive;
260 time_beginreceive = simgrid_get_clock();
262 answer_free(msg->answer);
264 node->receive_comm = NULL;
266 sg_actor_sleep_for(1);
268 } while (simgrid_get_clock() < timeout && answers < queries);
269 destination_found = answer_destination_found(node_list);
270 } while (!destination_found && (nodes_added > 0 || answers == 0) && simgrid_get_clock() < global_timeout &&
272 if (destination_found) {
274 node->find_node_success++;
276 XBT_VERB("FIND_NODE on %08x success in %u steps", id_to_find, steps);
277 routing_table_update(node, id_to_find);
279 if (count_in_stats) {
280 node->find_node_failed++;
281 XBT_VERB("%08x not found in %u steps", id_to_find, steps);
284 answer_free(node_list);
285 return destination_found;
288 /** @brief Does a pseudo-random lookup for someone in the system
289 * @param node caller node data
291 void random_lookup(node_t node)
293 unsigned int id_to_look = RANDOM_LOOKUP_NODE; // Totally random.
294 /* TODO: Use some pseudorandom generator. */
295 XBT_DEBUG("I'm doing a random lookup");
296 find_node(node, id_to_look, 1);
299 /** @brief Handles the answer to an incoming "find_node" message */
300 void handle_find_node(const_node_t node, const_kademlia_message_t msg)
302 routing_table_update(node, msg->sender_id);
303 XBT_VERB("Received a FIND_NODE from %s (%s), he's trying to find %08x", sg_mailbox_get_name(msg->answer_to),
304 msg->issuer_host_name, msg->destination_id);
305 // Building the msg to send
306 kademlia_message_t answer = new_message(node->id, msg->destination_id, find_closest(node, msg->destination_id),
307 node->mailbox, sg_host_self_get_name());
309 sg_comm_t comm = sg_mailbox_put_init(msg->answer_to, answer, COMM_SIZE);
310 sg_comm_detach(comm, &free_message);
313 /**@brief Returns an identifier which is in a specific bucket of a routing table
314 * @param id id of the routing table owner
315 * @param prefix id of the bucket where we want that identifier to be
317 unsigned int get_id_in_prefix(unsigned int id, unsigned int prefix)
322 return (1U << (prefix - 1)) ^ id;
326 /** @brief Returns the prefix of an identifier.
327 * The prefix is the id of the bucket in which the remote identifier xor our identifier should be stored.
328 * @param id : big unsigned int id to test
329 * @param nb_bits : key size
331 unsigned int get_node_prefix(unsigned int id, unsigned int nb_bits)
333 unsigned int size = sizeof(unsigned int) * 8;
334 for (unsigned int j = 0; j < size; j++) {
335 if (((id >> (size - 1 - j)) & 0x1) != 0) {
336 return nb_bits - (j);
342 /** @brief Gets the mailbox name of a host given its identifier */
343 sg_mailbox_t get_node_mailbox(unsigned int id)
345 char mailbox_name[MAILBOX_NAME_SIZE];
346 snprintf(mailbox_name, MAILBOX_NAME_SIZE - 1, "%u", id);
347 return sg_mailbox_by_name(mailbox_name);
350 /** Constructor, build a new contact information. */
351 node_contact_t node_contact_new(unsigned int id, unsigned int distance)
353 node_contact_t contact = xbt_new(s_node_contact_t, 1);
356 contact->distance = distance;
361 /** Builds a contact information from a contact information */
362 node_contact_t node_contact_copy(const_node_contact_t node_contact)
364 node_contact_t contact = xbt_new(s_node_contact_t, 1);
366 contact->id = node_contact->id;
367 contact->distance = node_contact->distance;
373 void node_contact_free(node_contact_t contact)