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+/*
+ * An implementation of the DHT as seen in docs/updates/DHT.md
+ */
+
+/*
+ * Copyright © 2016-2017 The TokTok team.
+ * Copyright © 2013 Tox project.
+ *
+ * This file is part of Tox, the free peer to peer instant messenger.
+ *
+ * Tox is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Tox 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 Tox. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef DHT_H
+#define DHT_H
+
+#include "crypto_core.h"
+#include "logger.h"
+#include "network.h"
+#include "ping_array.h"
+
+#include <stdbool.h>
+
+/* Maximum number of clients stored per friend. */
+#define MAX_FRIEND_CLIENTS 8
+
+#define LCLIENT_NODES (MAX_FRIEND_CLIENTS)
+#define LCLIENT_LENGTH 128
+
+/* A list of the clients mathematically closest to ours. */
+#define LCLIENT_LIST (LCLIENT_LENGTH * LCLIENT_NODES)
+
+#define MAX_CLOSE_TO_BOOTSTRAP_NODES 8
+
+/* The max number of nodes to send with send nodes. */
+#define MAX_SENT_NODES 4
+
+/* Ping timeout in seconds */
+#define PING_TIMEOUT 5
+
+/* size of DHT ping arrays. */
+#define DHT_PING_ARRAY_SIZE 512
+
+/* Ping interval in seconds for each node in our lists. */
+#define PING_INTERVAL 60
+
+/* The number of seconds for a non responsive node to become bad. */
+#define PINGS_MISSED_NODE_GOES_BAD 1
+#define PING_ROUNDTRIP 2
+#define BAD_NODE_TIMEOUT (PING_INTERVAL + PINGS_MISSED_NODE_GOES_BAD * (PING_INTERVAL + PING_ROUNDTRIP))
+
+/* The number of "fake" friends to add (for optimization purposes and so our paths for the onion part are more random) */
+#define DHT_FAKE_FRIEND_NUMBER 2
+
+#define MAX_CRYPTO_REQUEST_SIZE 1024
+
+#define CRYPTO_PACKET_FRIEND_REQ 32 /* Friend request crypto packet ID. */
+#define CRYPTO_PACKET_HARDENING 48 /* Hardening crypto packet ID. */
+#define CRYPTO_PACKET_DHTPK 156
+#define CRYPTO_PACKET_NAT_PING 254 /* NAT ping crypto packet ID. */
+
+/* Create a request to peer.
+ * send_public_key and send_secret_key are the pub/secret keys of the sender.
+ * recv_public_key is public key of receiver.
+ * packet must be an array of MAX_CRYPTO_REQUEST_SIZE big.
+ * Data represents the data we send with the request with length being the length of the data.
+ * request_id is the id of the request (32 = friend request, 254 = ping request).
+ *
+ * return -1 on failure.
+ * return the length of the created packet on success.
+ */
+int create_request(const uint8_t *send_public_key, const uint8_t *send_secret_key, uint8_t *packet,
+ const uint8_t *recv_public_key, const uint8_t *data, uint32_t length, uint8_t request_id);
+
+/* puts the senders public key in the request in public_key, the data from the request
+ in data if a friend or ping request was sent to us and returns the length of the data.
+ packet is the request packet and length is its length
+ return -1 if not valid request. */
+int handle_request(const uint8_t *self_public_key, const uint8_t *self_secret_key, uint8_t *public_key, uint8_t *data,
+ uint8_t *request_id, const uint8_t *packet, uint16_t length);
+
+typedef struct {
+ IP_Port ip_port;
+ uint64_t timestamp;
+} IPPTs;
+
+typedef struct {
+ /* Node routes request correctly (true (1) or false/didn't check (0)) */
+ uint8_t routes_requests_ok;
+ /* Time which we last checked this.*/
+ uint64_t routes_requests_timestamp;
+ uint8_t routes_requests_pingedid[CRYPTO_PUBLIC_KEY_SIZE];
+ /* Node sends correct send_node (true (1) or false/didn't check (0)) */
+ uint8_t send_nodes_ok;
+ /* Time which we last checked this.*/
+ uint64_t send_nodes_timestamp;
+ uint8_t send_nodes_pingedid[CRYPTO_PUBLIC_KEY_SIZE];
+ /* Node can be used to test other nodes (true (1) or false/didn't check (0)) */
+ uint8_t testing_requests;
+ /* Time which we last checked this.*/
+ uint64_t testing_timestamp;
+ uint8_t testing_pingedid[CRYPTO_PUBLIC_KEY_SIZE];
+} Hardening;
+
+typedef struct {
+ IP_Port ip_port;
+ uint64_t timestamp;
+ uint64_t last_pinged;
+
+ Hardening hardening;
+ /* Returned by this node. Either our friend or us. */
+ IP_Port ret_ip_port;
+ uint64_t ret_timestamp;
+} IPPTsPng;
+
+typedef struct {
+ uint8_t public_key[CRYPTO_PUBLIC_KEY_SIZE];
+ IPPTsPng assoc4;
+ IPPTsPng assoc6;
+} Client_data;
+
+/*----------------------------------------------------------------------------------*/
+
+typedef struct {
+ /* 1 if currently hole punching, otherwise 0 */
+ uint8_t hole_punching;
+ uint32_t punching_index;
+ uint32_t tries;
+ uint32_t punching_index2;
+
+ uint64_t punching_timestamp;
+ uint64_t recvNATping_timestamp;
+ uint64_t NATping_id;
+ uint64_t NATping_timestamp;
+} NAT;
+
+#define DHT_FRIEND_MAX_LOCKS 32
+
+typedef struct {
+ uint8_t public_key[CRYPTO_PUBLIC_KEY_SIZE];
+ IP_Port ip_port;
+}
+Node_format;
+
+typedef struct {
+ uint8_t public_key[CRYPTO_PUBLIC_KEY_SIZE];
+ Client_data client_list[MAX_FRIEND_CLIENTS];
+
+ /* Time at which the last get_nodes request was sent. */
+ uint64_t lastgetnode;
+ /* number of times get_node packets were sent. */
+ uint32_t bootstrap_times;
+
+ /* Symetric NAT hole punching stuff. */
+ NAT nat;
+
+ uint16_t lock_count;
+ struct {
+ void (*ip_callback)(void *, int32_t, IP_Port);
+ void *data;
+ int32_t number;
+ } callbacks[DHT_FRIEND_MAX_LOCKS];
+
+ Node_format to_bootstrap[MAX_SENT_NODES];
+ unsigned int num_to_bootstrap;
+} DHT_Friend;
+
+/* Return packet size of packed node with ip_family on success.
+ * Return -1 on failure.
+ */
+int packed_node_size(uint8_t ip_family);
+
+/* Pack number of nodes into data of maxlength length.
+ *
+ * return length of packed nodes on success.
+ * return -1 on failure.
+ */
+int pack_nodes(uint8_t *data, uint16_t length, const Node_format *nodes, uint16_t number);
+
+/* Unpack data of length into nodes of size max_num_nodes.
+ * Put the length of the data processed in processed_data_len.
+ * tcp_enabled sets if TCP nodes are expected (true) or not (false).
+ *
+ * return number of unpacked nodes on success.
+ * return -1 on failure.
+ */
+int unpack_nodes(Node_format *nodes, uint16_t max_num_nodes, uint16_t *processed_data_len, const uint8_t *data,
+ uint16_t length, uint8_t tcp_enabled);
+
+
+/*----------------------------------------------------------------------------------*/
+/* struct to store some shared keys so we don't have to regenerate them for each request. */
+#define MAX_KEYS_PER_SLOT 4
+#define KEYS_TIMEOUT 600
+
+typedef struct {
+ uint8_t public_key[CRYPTO_PUBLIC_KEY_SIZE];
+ uint8_t shared_key[CRYPTO_SHARED_KEY_SIZE];
+ uint32_t times_requested;
+ uint8_t stored; /* 0 if not, 1 if is */
+ uint64_t time_last_requested;
+} Shared_Key;
+
+typedef struct {
+ Shared_Key keys[256 * MAX_KEYS_PER_SLOT];
+} Shared_Keys;
+
+/*----------------------------------------------------------------------------------*/
+
+typedef int (*cryptopacket_handler_callback)(void *object, IP_Port ip_port, const uint8_t *source_pubkey,
+ const uint8_t *data, uint16_t len, void *userdata);
+
+typedef struct {
+ cryptopacket_handler_callback function;
+ void *object;
+} Cryptopacket_Handles;
+
+typedef struct {
+ Logger *log;
+ Networking_Core *net;
+
+ bool hole_punching_enabled;
+
+ Client_data close_clientlist[LCLIENT_LIST];
+ uint64_t close_lastgetnodes;
+ uint32_t close_bootstrap_times;
+
+ /* Note: this key should not be/is not used to transmit any sensitive materials */
+ uint8_t secret_symmetric_key[CRYPTO_SYMMETRIC_KEY_SIZE];
+ /* DHT keypair */
+ uint8_t self_public_key[CRYPTO_PUBLIC_KEY_SIZE];
+ uint8_t self_secret_key[CRYPTO_SECRET_KEY_SIZE];
+
+ DHT_Friend *friends_list;
+ uint16_t num_friends;
+
+ Node_format *loaded_nodes_list;
+ uint32_t loaded_num_nodes;
+ unsigned int loaded_nodes_index;
+
+ Shared_Keys shared_keys_recv;
+ Shared_Keys shared_keys_sent;
+
+ struct PING *ping;
+ Ping_Array dht_ping_array;
+ Ping_Array dht_harden_ping_array;
+ uint64_t last_run;
+
+ Cryptopacket_Handles cryptopackethandlers[256];
+
+ Node_format to_bootstrap[MAX_CLOSE_TO_BOOTSTRAP_NODES];
+ unsigned int num_to_bootstrap;
+} DHT;
+/*----------------------------------------------------------------------------------*/
+
+/* Shared key generations are costly, it is therefor smart to store commonly used
+ * ones so that they can re used later without being computed again.
+ *
+ * If shared key is already in shared_keys, copy it to shared_key.
+ * else generate it into shared_key and copy it to shared_keys
+ */
+void get_shared_key(Shared_Keys *shared_keys, uint8_t *shared_key, const uint8_t *secret_key,
+ const uint8_t *public_key);
+
+/* Copy shared_key to encrypt/decrypt DHT packet from public_key into shared_key
+ * for packets that we receive.
+ */
+void DHT_get_shared_key_recv(DHT *dht, uint8_t *shared_key, const uint8_t *public_key);
+
+/* Copy shared_key to encrypt/decrypt DHT packet from public_key into shared_key
+ * for packets that we send.
+ */
+void DHT_get_shared_key_sent(DHT *dht, uint8_t *shared_key, const uint8_t *public_key);
+
+void DHT_getnodes(DHT *dht, const IP_Port *from_ipp, const uint8_t *from_id, const uint8_t *which_id);
+
+/* Add a new friend to the friends list.
+ * public_key must be CRYPTO_PUBLIC_KEY_SIZE bytes long.
+ *
+ * ip_callback is the callback of a function that will be called when the ip address
+ * is found along with arguments data and number.
+ *
+ * lock_count will be set to a non zero number that must be passed to DHT_delfriend()
+ * to properly remove the callback.
+ *
+ * return 0 if success.
+ * return -1 if failure (friends list is full).
+ */
+int DHT_addfriend(DHT *dht, const uint8_t *public_key, void (*ip_callback)(void *data, int32_t number, IP_Port),
+ void *data, int32_t number, uint16_t *lock_count);
+
+/* Delete a friend from the friends list.
+ * public_key must be CRYPTO_PUBLIC_KEY_SIZE bytes long.
+ *
+ * return 0 if success.
+ * return -1 if failure (public_key not in friends list).
+ */
+int DHT_delfriend(DHT *dht, const uint8_t *public_key, uint16_t lock_count);
+
+/* Get ip of friend.
+ * public_key must be CRYPTO_PUBLIC_KEY_SIZE bytes long.
+ * ip must be 4 bytes long.
+ * port must be 2 bytes long.
+ *
+ * int DHT_getfriendip(DHT *dht, uint8_t *public_key, IP_Port *ip_port);
+ *
+ * return -1, -- if public_key does NOT refer to a friend
+ * return 0, -- if public_key refers to a friend and we failed to find the friend (yet)
+ * return 1, ip if public_key refers to a friend and we found him
+ */
+int DHT_getfriendip(const DHT *dht, const uint8_t *public_key, IP_Port *ip_port);
+
+/* Compares pk1 and pk2 with pk.
+ *
+ * return 0 if both are same distance.
+ * return 1 if pk1 is closer.
+ * return 2 if pk2 is closer.
+ */
+int id_closest(const uint8_t *pk, const uint8_t *pk1, const uint8_t *pk2);
+
+/* Add node to the node list making sure only the nodes closest to cmp_pk are in the list.
+ */
+bool add_to_list(Node_format *nodes_list, unsigned int length, const uint8_t *pk, IP_Port ip_port,
+ const uint8_t *cmp_pk);
+
+/* Return 1 if node can be added to close list, 0 if it can't.
+ */
+bool node_addable_to_close_list(DHT *dht, const uint8_t *public_key, IP_Port ip_port);
+
+/* Get the (maximum MAX_SENT_NODES) closest nodes to public_key we know
+ * and put them in nodes_list (must be MAX_SENT_NODES big).
+ *
+ * sa_family = family (IPv4 or IPv6) (0 if we don't care)?
+ * is_LAN = return some LAN ips (true or false)
+ * want_good = do we want tested nodes or not? (TODO(irungentoo))
+ *
+ * return the number of nodes returned.
+ *
+ */
+int get_close_nodes(const DHT *dht, const uint8_t *public_key, Node_format *nodes_list, Family sa_family,
+ uint8_t is_LAN, uint8_t want_good);
+
+
+/* Put up to max_num nodes in nodes from the random friends.
+ *
+ * return the number of nodes.
+ */
+uint16_t randfriends_nodes(DHT *dht, Node_format *nodes, uint16_t max_num);
+
+/* Put up to max_num nodes in nodes from the closelist.
+ *
+ * return the number of nodes.
+ */
+uint16_t closelist_nodes(DHT *dht, Node_format *nodes, uint16_t max_num);
+
+/* Run this function at least a couple times per second (It's the main loop). */
+void do_DHT(DHT *dht);
+
+/*
+ * Use these two functions to bootstrap the client.
+ */
+/* Sends a "get nodes" request to the given node with ip, port and public_key
+ * to setup connections
+ */
+void DHT_bootstrap(DHT *dht, IP_Port ip_port, const uint8_t *public_key);
+/* Resolves address into an IP address. If successful, sends a "get nodes"
+ * request to the given node with ip, port and public_key to setup connections
+ *
+ * address can be a hostname or an IP address (IPv4 or IPv6).
+ * if ipv6enabled is 0 (zero), the resolving sticks STRICTLY to IPv4 addresses
+ * if ipv6enabled is not 0 (zero), the resolving looks for IPv6 addresses first,
+ * then IPv4 addresses.
+ *
+ * returns 1 if the address could be converted into an IP address
+ * returns 0 otherwise
+ */
+int DHT_bootstrap_from_address(DHT *dht, const char *address, uint8_t ipv6enabled,
+ uint16_t port, const uint8_t *public_key);
+
+/* Start sending packets after DHT loaded_friends_list and loaded_clients_list are set.
+ *
+ * returns 0 if successful
+ * returns -1 otherwise
+ */
+int DHT_connect_after_load(DHT *dht);
+
+/* ROUTING FUNCTIONS */
+
+/* Send the given packet to node with public_key.
+ *
+ * return -1 if failure.
+ */
+int route_packet(const DHT *dht, const uint8_t *public_key, const uint8_t *packet, uint16_t length);
+
+/* Send the following packet to everyone who tells us they are connected to friend_id.
+ *
+ * return number of nodes it sent the packet to.
+ */
+int route_tofriend(const DHT *dht, const uint8_t *friend_id, const uint8_t *packet, uint16_t length);
+
+/* Function to handle crypto packets.
+ */
+void cryptopacket_registerhandler(DHT *dht, uint8_t byte, cryptopacket_handler_callback cb, void *object);
+
+/* SAVE/LOAD functions */
+
+/* Get the size of the DHT (for saving). */
+uint32_t DHT_size(const DHT *dht);
+
+/* Save the DHT in data where data is an array of size DHT_size(). */
+void DHT_save(DHT *dht, uint8_t *data);
+
+/* Load the DHT from data of size size.
+ *
+ * return -1 if failure.
+ * return 0 if success.
+ */
+int DHT_load(DHT *dht, const uint8_t *data, uint32_t length);
+
+/* Initialize DHT. */
+DHT *new_DHT(Logger *log, Networking_Core *net, bool holepunching_enabled);
+
+void kill_DHT(DHT *dht);
+
+/* return 0 if we are not connected to the DHT.
+ * return 1 if we are.
+ */
+int DHT_isconnected(const DHT *dht);
+
+/* return 0 if we are not connected or only connected to lan peers with the DHT.
+ * return 1 if we are.
+ */
+int DHT_non_lan_connected(const DHT *dht);
+
+
+uint32_t addto_lists(DHT *dht, IP_Port ip_port, const uint8_t *public_key);
+
+#endif
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