1 /* Copyright (c) 2010-2023. 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 * Try to asynchronously get a new message from given mailbox. Return null if none available.
43 kademlia_message_t receive(node_t node, sg_mailbox_t mailbox)
45 if (node->receive_comm == NULL)
46 node->receive_comm = sg_mailbox_get_async(mailbox, &node->received_msg);
47 if (!sg_comm_test(node->receive_comm))
49 node->receive_comm = NULL;
50 return node->received_msg;
54 * @brief Tries to join the network
55 * @param node node data
56 * @param id_known id of the node I know in the network.
58 unsigned int join(node_t node, unsigned int id_known)
61 unsigned int got_answer = 0;
63 sg_mailbox_t mailbox = get_node_mailbox(node->id);
65 /* Add the guy we know to our routing table and ourselves. */
66 routing_table_update(node, node->id);
67 routing_table_update(node, id_known);
69 /* First step: Send a "FIND_NODE" request to the node we know */
70 send_find_node(node, id_known, node->id);
72 const kademlia_message_t msg = receive(node, mailbox);
74 XBT_DEBUG("Received an answer from the node I know.");
76 // retrieve the node list and ping them.
77 const s_answer_t* node_list = msg->answer;
78 if (node_list != NULL) {
79 node_contact_t contact;
80 xbt_dynar_foreach (node_list->nodes, i, contact)
81 routing_table_update(node, contact->id);
82 node->received_msg = NULL;
84 handle_find_node(node, msg);
88 sg_actor_sleep_for(1);
90 } while (got_answer == 0);
92 /* Second step: Send a FIND_NODE to a random node in buckets */
93 unsigned int bucket_id = routing_table_find_bucket(node->table, id_known)->id;
94 xbt_assert(bucket_id <= IDENTIFIER_SIZE);
95 for (i = 0; ((bucket_id > i) || (bucket_id + i) <= IDENTIFIER_SIZE) && i < JOIN_BUCKETS_QUERIES; i++) {
97 unsigned int id_in_bucket = get_id_in_prefix(node->id, bucket_id - i);
98 find_node(node, id_in_bucket, 0);
100 if (bucket_id + i <= IDENTIFIER_SIZE) {
101 unsigned int id_in_bucket = get_id_in_prefix(node->id, bucket_id + i);
102 find_node(node, id_in_bucket, 0);
108 /** @brief Send a "FIND_NODE" to a node
109 * @param node sender node data
110 * @param id node we are querying
111 * @param destination node we are trying to find.
113 void send_find_node(const_node_t node, unsigned int id, unsigned int destination)
115 /* Gets the mailbox to send to */
116 sg_mailbox_t mailbox = get_node_mailbox(id);
117 /* Build the message */
118 kademlia_message_t msg = new_message(node->id, destination, NULL, node->mailbox, sg_host_self_get_name());
119 sg_comm_t comm = sg_mailbox_put_init(mailbox, msg, COMM_SIZE);
120 sg_comm_detach(comm, free_message);
121 XBT_VERB("Asking %u for its closest nodes", id);
125 * Sends to the best "KADEMLIA_ALPHA" nodes in the "node_list" array a "FIND_NODE" request, to ask them for their best
128 unsigned int send_find_node_to_best(const_node_t node, const_answer_t node_list)
132 unsigned int destination = node_list->destination_id;
133 while (j < KADEMLIA_ALPHA && i < node_list->size) {
134 /* We need to have at most "KADEMLIA_ALPHA" requests each time, according to the protocol */
135 /* Gets the node we want to send the query to */
136 const s_node_contact_t* node_to_query = xbt_dynar_get_as(node_list->nodes, i, node_contact_t);
137 if (node_to_query->id != node->id) { /* No need to query ourselves */
138 send_find_node(node, node_to_query->id, destination);
146 /** @brief Updates/Puts the node id unsigned into our routing table
147 * @param node Our node data
148 * @param id The id of the node we need to add unsigned into our routing table
150 void routing_table_update(const_node_t node, unsigned int id)
152 const_routing_table_t table = node->table;
153 // retrieval of the bucket in which the should be
154 const_bucket_t bucket = routing_table_find_bucket(table, id);
156 // check if the id is already in the bucket.
157 unsigned int id_pos = bucket_find_id(bucket, id);
159 if (id_pos == (unsigned int)-1) {
160 /* We check if the bucket is full or not. If it is, we evict an old element */
161 if (xbt_dynar_length(bucket->nodes) >= BUCKET_SIZE)
162 xbt_dynar_pop(bucket->nodes, NULL);
164 xbt_dynar_unshift(bucket->nodes, &id);
165 XBT_VERB("I'm adding to my routing table %08x", id);
167 // We push to the front of the dynar the element.
168 unsigned int element = xbt_dynar_get_as(bucket->nodes, id_pos, unsigned int);
169 xbt_dynar_remove_at(bucket->nodes, id_pos, NULL);
170 xbt_dynar_unshift(bucket->nodes, &element);
171 XBT_VERB("I'm updating %08x", element);
175 /** @brief Finds the closest nodes to the node given.
176 * @param node : our node
177 * @param destination_id : the id of the guy we are trying to find
179 answer_t find_closest(const_node_t node, unsigned int destination_id)
181 answer_t answer = answer_init(destination_id);
182 /* We find the corresponding bucket for the id */
183 const_bucket_t bucket = routing_table_find_bucket(node->table, destination_id);
184 int bucket_id = bucket->id;
185 xbt_assert((bucket_id <= IDENTIFIER_SIZE), "Bucket found has a wrong identifier");
186 /* So, we copy the contents of the bucket unsigned into our result dynar */
187 answer_add_bucket(bucket, answer);
189 /* However, if we don't have enough elements in our bucket, we NEED to include at least "BUCKET_SIZE" elements
190 * (if, of course, we know at least "BUCKET_SIZE" elements. So we're going to look unsigned into the other buckets.
192 for (int i = 1; answer->size < BUCKET_SIZE && ((bucket_id - i > 0) || (bucket_id + i < IDENTIFIER_SIZE)); i++) {
193 /* We check the previous buckets */
194 if (bucket_id - i >= 0) {
195 const_bucket_t bucket_p = &node->table->buckets[bucket_id - i];
196 answer_add_bucket(bucket_p, answer);
198 /* We check the next buckets */
199 if (bucket_id + i <= IDENTIFIER_SIZE) {
200 const_bucket_t bucket_n = &node->table->buckets[bucket_id + i];
201 answer_add_bucket(bucket_n, answer);
204 /* We sort the array by XOR distance */
206 /* We trim the array to have only BUCKET_SIZE or less elements */
212 unsigned int find_node(node_t node, unsigned int id_to_find, unsigned int count_in_stats)
214 unsigned int queries;
215 unsigned int answers;
216 unsigned int destination_found = 0;
217 unsigned int nodes_added = 0;
218 double global_timeout = simgrid_get_clock() + FIND_NODE_GLOBAL_TIMEOUT;
219 unsigned int steps = 0;
221 /* First we build a list of who we already know */
222 answer_t node_list = find_closest(node, id_to_find);
223 xbt_assert((node_list != NULL), "node_list incorrect");
225 XBT_DEBUG("Doing a FIND_NODE on %08x", id_to_find);
227 /* Ask the nodes on our list if they have information about the node we are trying to find */
228 sg_mailbox_t mailbox = get_node_mailbox(node->id);
231 queries = send_find_node_to_best(node, node_list);
233 double timeout = simgrid_get_clock() + FIND_NODE_TIMEOUT;
235 double time_beginreceive = simgrid_get_clock();
238 const kademlia_message_t msg = receive(node, mailbox);
240 // Figure out if we received an answer or something else
241 // Check if what we have received is what we are looking for.
242 if (msg->answer != NULL && msg->answer->destination_id == id_to_find) {
244 routing_table_update(node, msg->sender_id);
245 node_contact_t contact;
247 xbt_dynar_foreach (node_list->nodes, i, contact)
248 routing_table_update(node, contact->id);
252 nodes_added = answer_merge(node_list, msg->answer);
253 XBT_DEBUG("Received an answer from %s (%s) with %lu nodes on it", sg_mailbox_get_name(msg->answer_to),
254 msg->issuer_host_name, xbt_dynar_length(msg->answer->nodes));
256 if (msg->answer != NULL) {
257 routing_table_update(node, msg->sender_id);
258 XBT_DEBUG("Received a wrong answer for a FIND_NODE");
260 handle_find_node(node, msg);
262 // Update the timeout if we didn't have our answer
263 timeout += simgrid_get_clock() - time_beginreceive;
264 time_beginreceive = simgrid_get_clock();
268 sg_actor_sleep_for(1);
270 } while (simgrid_get_clock() < timeout && answers < queries);
271 destination_found = answer_destination_found(node_list);
272 } while (!destination_found && (nodes_added > 0 || answers == 0) && simgrid_get_clock() < global_timeout &&
274 if (destination_found) {
276 node->find_node_success++;
278 XBT_VERB("FIND_NODE on %08x success in %u steps", id_to_find, steps);
279 routing_table_update(node, id_to_find);
281 if (count_in_stats) {
282 node->find_node_failed++;
283 XBT_VERB("%08x not found in %u steps", id_to_find, steps);
286 answer_free(node_list);
287 return destination_found;
290 /** @brief Does a pseudo-random lookup for someone in the system
291 * @param node caller node data
293 void random_lookup(node_t node)
295 unsigned int id_to_look = RANDOM_LOOKUP_NODE; // Totally random.
296 /* TODO: Use some pseudorandom generator. */
297 XBT_DEBUG("I'm doing a random lookup");
298 find_node(node, id_to_look, 1);
301 /** @brief Handles the answer to an incoming "find_node" message */
302 void handle_find_node(const_node_t node, const_kademlia_message_t msg)
304 routing_table_update(node, msg->sender_id);
305 XBT_VERB("Received a FIND_NODE from %s (%s), he's trying to find %08x", sg_mailbox_get_name(msg->answer_to),
306 msg->issuer_host_name, msg->destination_id);
307 // Building the msg to send
308 kademlia_message_t answer = new_message(node->id, msg->destination_id, find_closest(node, msg->destination_id),
309 node->mailbox, sg_host_self_get_name());
311 sg_comm_t comm = sg_mailbox_put_init(msg->answer_to, answer, COMM_SIZE);
312 sg_comm_detach(comm, &free_message);
315 /**@brief Returns an identifier which is in a specific bucket of a routing table
316 * @param id id of the routing table owner
317 * @param prefix id of the bucket where we want that identifier to be
319 unsigned int get_id_in_prefix(unsigned int id, unsigned int prefix)
324 return (1U << (prefix - 1)) ^ id;
328 /** @brief Returns the prefix of an identifier.
329 * The prefix is the id of the bucket in which the remote identifier xor our identifier should be stored.
330 * @param id : big unsigned int id to test
331 * @param nb_bits : key size
333 unsigned int get_node_prefix(unsigned int id, unsigned int nb_bits)
335 unsigned int size = sizeof(unsigned int) * 8;
336 for (unsigned int j = 0; j < size; j++) {
337 if (((id >> (size - 1 - j)) & 0x1) != 0) {
344 /** @brief Gets the mailbox name of a host given its identifier */
345 sg_mailbox_t get_node_mailbox(unsigned int id)
347 char mailbox_name[MAILBOX_NAME_SIZE];
348 snprintf(mailbox_name, MAILBOX_NAME_SIZE - 1, "%u", id);
349 return sg_mailbox_by_name(mailbox_name);
352 /** Constructor, build a new contact information. */
353 node_contact_t node_contact_new(unsigned int id, unsigned int distance)
355 node_contact_t contact = xbt_new(s_node_contact_t, 1);
358 contact->distance = distance;
363 /** Builds a contact information from a contact information */
364 node_contact_t node_contact_copy(const_node_contact_t node_contact)
366 node_contact_t contact = xbt_new(s_node_contact_t, 1);
368 contact->id = node_contact->id;
369 contact->distance = node_contact->distance;
375 void node_contact_free(node_contact_t contact)