path: root/toxcore/TCP_connection.c

/* TCP_connection.c
 *
 * Handles TCP relay connections between two Tox clients.
 *
 *  Copyright (C) 2015 Tox project All Rights Reserved.
 *
 *  This file is part of Tox.
 *
 *  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/>.
 *
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "TCP_connection.h"

/* Set the size of the array to num.
 *
 *  return -1 if realloc fails.
 *  return 0 if it succeeds.
 */
#define realloc_tox_array(array, element_size, num, temp_pointer) (num ? (temp_pointer = realloc(array, ((num) * (element_size))), temp_pointer ? (array = temp_pointer, 0) : (-1) ) : (free(array), array = NULL, 0))


/* return 1 if the connections_number is not valid.
 * return 0 if the connections_number is valid.
 */
static _Bool connections_number_not_valid(const TCP_Connections *tcp_c, int connections_number)
{
    if ((unsigned int)connections_number >= tcp_c->connections_length)
        return 1;

    if (tcp_c->connections == NULL)
        return 1;

    if (tcp_c->connections[connections_number].status == TCP_CONN_NONE)
        return 1;

    return 0;
}

/* return 1 if the tcp_connections_number is not valid.
 * return 0 if the tcp_connections_number is valid.
 */
static _Bool tcp_connections_number_not_valid(const TCP_Connections *tcp_c, int tcp_connections_number)
{
    if ((unsigned int)tcp_connections_number >= tcp_c->tcp_connections_length)
        return 1;

    if (tcp_c->tcp_connections == NULL)
        return 1;

    if (tcp_c->tcp_connections[tcp_connections_number].status == TCP_CONN_NONE)
        return 1;

    return 0;
}

/* Create a new empty connection.
 *
 * return -1 on failure.
 * return connections_number on success.
 */
static int create_connection(TCP_Connections *tcp_c)
{
    uint32_t i;

    for (i = 0; i < tcp_c->connections_length; ++i) {
        if (tcp_c->connections[i].status == TCP_CONN_NONE)
            return i;
    }

    int id = -1;

    TCP_Connection_to *temp_pointer;

    if (realloc_tox_array(tcp_c->connections, sizeof(TCP_Connection_to), tcp_c->connections_length + 1,
                          temp_pointer) == 0) {
        id = tcp_c->connections_length;
        ++tcp_c->connections_length;
        memset(&(tcp_c->connections[id]), 0, sizeof(TCP_Connection_to));
    }

    return id;
}

/* Create a new empty tcp connection.
 *
 * return -1 on failure.
 * return tcp_connections_number on success.
 */
static int create_tcp_connection(TCP_Connections *tcp_c)
{
    uint32_t i;

    for (i = 0; i < tcp_c->tcp_connections_length; ++i) {
        if (tcp_c->tcp_connections[i].status == TCP_CONN_NONE)
            return i;
    }

    int id = -1;

    TCP_con *temp_pointer;

    if (realloc_tox_array(tcp_c->tcp_connections, sizeof(TCP_con), tcp_c->tcp_connections_length + 1, temp_pointer) == 0) {
        id = tcp_c->tcp_connections_length;
        ++tcp_c->tcp_connections_length;
        memset(&(tcp_c->tcp_connections[id]), 0, sizeof(TCP_con));
    }

    return id;
}

/* Wipe a connection.
 *
 * return -1 on failure.
 * return 0 on success.
 */
static int wipe_connection(TCP_Connections *tcp_c, int connections_number)
{
    if (connections_number_not_valid(tcp_c, connections_number))
        return -1;

    uint32_t i;
    memset(&(tcp_c->connections[connections_number]), 0 , sizeof(TCP_Connection_to));

    for (i = tcp_c->connections_length; i != 0; --i) {
        if (tcp_c->connections[i - 1].status != TCP_CONN_NONE)
            break;
    }

    if (tcp_c->connections_length != i) {
        tcp_c->connections_length = i;
        TCP_Connection_to *temp_pointer;
        realloc_tox_array(tcp_c->connections, sizeof(TCP_Connection_to), tcp_c->connections_length, temp_pointer);
    }

    return 0;
}

/* Wipe a connection.
 *
 * return -1 on failure.
 * return 0 on success.
 */
static int wipe_tcp_connection(TCP_Connections *tcp_c, int tcp_connections_number)
{
    if (tcp_connections_number_not_valid(tcp_c, tcp_connections_number))
        return -1;

    uint32_t i;
    memset(&(tcp_c->tcp_connections[tcp_connections_number]), 0 , sizeof(TCP_con));

    for (i = tcp_c->tcp_connections_length; i != 0; --i) {
        if (tcp_c->tcp_connections[i - 1].status != TCP_CONN_NONE)
            break;
    }

    if (tcp_c->tcp_connections_length != i) {
        tcp_c->tcp_connections_length = i;
        TCP_con *temp_pointer;
        realloc_tox_array(tcp_c->tcp_connections, sizeof(TCP_con), tcp_c->tcp_connections_length, temp_pointer);
    }

    return 0;
}

static TCP_Connection_to *get_connection(const TCP_Connections *tcp_c, int connections_number)
{
    if (connections_number_not_valid(tcp_c, connections_number))
        return 0;

    return &tcp_c->connections[connections_number];
}

static TCP_con *get_tcp_connection(const TCP_Connections *tcp_c, int tcp_connections_number)
{
    if (tcp_connections_number_not_valid(tcp_c, tcp_connections_number))
        return 0;

    return &tcp_c->tcp_connections[tcp_connections_number];
}

/* Send a packet to the TCP connection.
 *
 * return -1 on failure.
 * return 0 on success.
 */
int send_packet_tcp_connection(TCP_Connections *tcp_c, int connections_number, const uint8_t *packet, uint16_t length)
{
    TCP_Connection_to *con_to = get_connection(tcp_c, connections_number);

    if (!con_to) {
        return -1;
    }

    //TODO: detect and kill bad relays.
    //TODO: thread safety?
    unsigned int i;
    int ret = -1;

    for (i = 0; i < MAX_FRIEND_TCP_CONNECTIONS; ++i) {
        uint32_t tcp_con_num = con_to->connections[i].tcp_connection;
        uint8_t status = con_to->connections[i].status;
        uint8_t connection_id = con_to->connections[i].connection_id;

        if (tcp_con_num && status == TCP_CONNECTIONS_STATUS_ONLINE) {
            tcp_con_num -= 1;
            TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_con_num);

            if (!tcp_con) {
                continue;
            }

            ret = send_data(tcp_con->connection, connection_id, packet, length);

            if (ret == 1) {
                break;
            }
        }
    }

    if (ret == 1) {
        return 0;
    } else {
        for (i = 0; i < MAX_FRIEND_TCP_CONNECTIONS; ++i) {
            uint32_t tcp_con_num = con_to->connections[i].tcp_connection;
            uint8_t status = con_to->connections[i].status;
            uint8_t connection_id = con_to->connections[i].connection_id;

            if (tcp_con_num && status == TCP_CONNECTIONS_STATUS_REGISTERED) {
                tcp_con_num -= 1;
                TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_con_num);

                if (!tcp_con) {
                    continue;
                }

                ret = send_oob_packet(tcp_con->connection, con_to->public_key, packet, length);

                if (ret == 1) {
                    break;
                }
            }
        }

        if (ret == 1) {
            return 0;
        } else {
            return -1;
        }
    }
}

/* Return a random TCP connection number for use in send_tcp_onion_request.
 *
 * TODO: This number is just the index of an array that the elements can
 * change without warning.
 *
 * return TCP connection number on success.
 * return -1 on failure.
 */
int get_random_tcp_conn_number(TCP_Connections *tcp_c)
{
    unsigned int i, r = rand();

    for (i = 0; i < tcp_c->tcp_connections_length; ++i) {
        if (tcp_c->tcp_connections[(i + r) % tcp_c->tcp_connections_length].status == TCP_CONN_CONNECTED) {
            return ((i + r) % tcp_c->tcp_connections_length);
        }
    }

    return -1;
}

/* Send an onion packet via the TCP relay corresponding to tcp_connections_number.
 *
 * return 0 on success.
 * return -1 on failure.
 */
int tcp_send_onion_request(TCP_Connections *tcp_c, unsigned int tcp_connections_number, const uint8_t *data,
                           uint16_t length)
{
    if (tcp_connections_number >= tcp_c->tcp_connections_length) {
        return -1;
    }

    if (tcp_c->tcp_connections[tcp_connections_number].status == TCP_CONN_CONNECTED) {
        int ret = send_onion_request(tcp_c->tcp_connections[tcp_connections_number].connection, data, length);

        if (ret == 1)
            return 0;
    }

    return -1;
}

/* Send an oob packet via the TCP relay corresponding to tcp_connections_number.
 *
 * return 0 on success.
 * return -1 on failure.
 */
int tcp_send_oob_packet(TCP_Connections *tcp_c, unsigned int tcp_connections_number, const uint8_t *public_key,
                        const uint8_t *packet, uint16_t length)
{
    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

    if (!tcp_con)
        return -1;

    int ret = send_oob_packet(tcp_con->connection, public_key, packet, length);

    if (ret == 1)
        return 0;

    return -1;
}

/* Set the callback for TCP data packets.
 */
void set_packet_tcp_connection_callback(TCP_Connections *tcp_c, int (*tcp_data_callback)(void *object, int id,
                                        const uint8_t *data, uint16_t length), void *object)
{
    tcp_c->tcp_data_callback = tcp_data_callback;
    tcp_c->tcp_data_callback_object = object;
}

/* Set the callback for TCP onion packets.
 */
void set_oob_packet_tcp_connection_callback(TCP_Connections *tcp_c, int (*tcp_oob_callback)(void *object,
        const uint8_t *public_key, unsigned int tcp_connections_number, const uint8_t *data, uint16_t length), void *object)
{
    tcp_c->tcp_oob_callback = tcp_oob_callback;
    tcp_c->tcp_oob_callback_object = object;
}

/* Set the callback for TCP oob data packets.
 */
void set_onion_packet_tcp_connection_callback(TCP_Connections *tcp_c, int (*tcp_onion_callback)(void *object,
        const uint8_t *data, uint16_t length), void *object)
{
    tcp_c->tcp_onion_callback = tcp_onion_callback;
    tcp_c->tcp_onion_callback_object = object;
}


/* Find the TCP connection with public_key.
 *
 * return connections_number on success.
 * return -1 on failure.
 */
static int find_tcp_connection_to(TCP_Connections *tcp_c, const uint8_t *public_key)
{
    unsigned int i;

    for (i = 0; i < tcp_c->connections_length; ++i) {
        TCP_Connection_to *con_to = get_connection(tcp_c, i);

        if (con_to) {
            if (memcmp(con_to->public_key, public_key, crypto_box_PUBLICKEYBYTES) == 0) {
                return i;
            }
        }
    }

    return -1;
}

/* Find the TCP connection to a relay with relay_pk.
 *
 * return connections_number on success.
 * return -1 on failure.
 */
static int find_tcp_connection_relay(TCP_Connections *tcp_c, const uint8_t *relay_pk)
{
    unsigned int i;

    for (i = 0; i < tcp_c->tcp_connections_length; ++i) {
        TCP_con *tcp_con = get_tcp_connection(tcp_c, i);

        if (tcp_con) {
            if (memcmp(tcp_con->connection->public_key, relay_pk, crypto_box_PUBLICKEYBYTES) == 0) {
                return i;
            }
        }
    }

    return -1;
}

/* Create a new TCP connection to public_key.
 *
 * id is the id in the callbacks for that connection.
 *
 * return connections_number on success.
 * return -1 on failure.
 */
int new_tcp_connection_to(TCP_Connections *tcp_c, const uint8_t *public_key, int id)
{
    if (find_tcp_connection_to(tcp_c, public_key) != -1)
        return -1;

    int connections_number = create_connection(tcp_c);

    if (connections_number == -1)
        return -1;

    TCP_Connection_to *con_to = &tcp_c->connections[connections_number];

    con_to->status = TCP_CONN_VALID;
    memcpy(con_to->public_key, public_key, crypto_box_PUBLICKEYBYTES);
    con_to->id = id;

    return connections_number;
}

/* return 0 on success.
 * return -1 on failure.
 */
int kill_tcp_connection_to(TCP_Connections *tcp_c, int connections_number)
{
    TCP_Connection_to *con_to = get_connection(tcp_c, connections_number);

    if (!con_to)
        return -1;

    unsigned int i;

    for (i = 0; i < MAX_FRIEND_TCP_CONNECTIONS; ++i) {
        if (con_to->connections[i].tcp_connection) {
            unsigned int tcp_connections_number = con_to->connections[i].tcp_connection - 1;
            TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

            if (!tcp_con)
                continue;

            if (tcp_con->status == TCP_CONN_CONNECTED) {
                send_disconnect_request(tcp_con->connection, con_to->connections[i].connection_id);
            }

            --tcp_con->lock_count;
        }
    }

    return wipe_connection(tcp_c, connections_number);
}

static _Bool tcp_connection_in_conn(TCP_Connection_to *con_to, int tcp_connections_number)
{
    unsigned int i;

    for (i = 0; i < MAX_FRIEND_TCP_CONNECTIONS; ++i) {
        if (con_to->connections[i].tcp_connection == (tcp_connections_number + 1)) {
            return 1;
        }
    }

    return 0;
}

/* return index on success.
 * return -1 on failure.
 */
static int add_tcp_connection_to_conn(TCP_Connection_to *con_to, int tcp_connections_number)
{
    unsigned int i;

    if (tcp_connection_in_conn(con_to, tcp_connections_number))
        return -1;

    for (i = 0; i < MAX_FRIEND_TCP_CONNECTIONS; ++i) {
        if (con_to->connections[i].tcp_connection == 0) {
            con_to->connections[i].tcp_connection = tcp_connections_number + 1;
            con_to->connections[i].status = TCP_CONNECTIONS_STATUS_NONE;
            con_to->connections[i].connection_id = 0;
            return i;
        }
    }

    return -1;
}

/* return index on success.
 * return -1 on failure.
 */
static int rm_tcp_connection_from_conn(TCP_Connection_to *con_to, int tcp_connections_number)
{
    unsigned int i;

    for (i = 0; i < MAX_FRIEND_TCP_CONNECTIONS; ++i) {
        if (con_to->connections[i].tcp_connection == (tcp_connections_number + 1)) {
            con_to->connections[i].tcp_connection = 0;
            con_to->connections[i].status = TCP_CONNECTIONS_STATUS_NONE;
            con_to->connections[i].connection_id = 0;
            return i;
        }
    }

    return -1;
}

/* return index on success.
 * return -1 on failure.
 */
static int set_tcp_connection_status(TCP_Connection_to *con_to, int tcp_connections_number, unsigned int status,
                                     uint8_t connection_id)
{
    unsigned int i;

    for (i = 0; i < MAX_FRIEND_TCP_CONNECTIONS; ++i) {
        if (con_to->connections[i].tcp_connection == (tcp_connections_number + 1)) {
            con_to->connections[i].status = status;
            con_to->connections[i].connection_id = connection_id;
            return i;
        }
    }

    return -1;
}

/* Kill a TCP relay connection.
 *
 * return 0 on success.
 * return -1 on failure.
 */
static int kill_tcp_relay_connection(TCP_Connections *tcp_c, int tcp_connections_number)
{
    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

    if (!tcp_con)
        return -1;

    unsigned int i;

    for (i = 0; i < tcp_c->connections_length; ++i) {
        TCP_Connection_to *con_to = get_connection(tcp_c, i);

        if (con_to) {
            rm_tcp_connection_from_conn(con_to, tcp_connections_number);
        }
    }

    kill_TCP_connection(tcp_con->connection);

    return wipe_tcp_connection(tcp_c, tcp_connections_number);
}

/* Send a TCP routing request.
 *
 * return 0 on success.
 * return -1 on failure.
 */
static int send_tcp_relay_routing_request(TCP_Connections *tcp_c, int tcp_connections_number, uint8_t *public_key)
{
    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

    if (!tcp_con)
        return -1;

    if (send_routing_request(tcp_con->connection, public_key) != 1)
        return -1;

    return 0;
}

static int tcp_response_callback(void *object, uint8_t connection_id, const uint8_t *public_key)
{
    TCP_Client_Connection *TCP_client_con = object;
    TCP_Connections *tcp_c = TCP_client_con->custom_object;

    unsigned int tcp_connections_number = TCP_client_con->custom_uint;
    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

    if (!tcp_con)
        return -1;

    int connections_number = find_tcp_connection_to(tcp_c, public_key);

    if (connections_number == -1)
        return -1;

    set_tcp_connection_number(tcp_con->connection, connection_id, connections_number);

    TCP_Connection_to *con_to = get_connection(tcp_c, connections_number);

    if (con_to == NULL)
        return -1;

    if (set_tcp_connection_status(con_to, tcp_connections_number, TCP_CONNECTIONS_STATUS_REGISTERED, connection_id) == -1)
        return -1;

    return 0;
}

static int tcp_status_callback(void *object, uint32_t number, uint8_t connection_id, uint8_t status)
{
    TCP_Client_Connection *TCP_client_con = object;
    TCP_Connections *tcp_c = TCP_client_con->custom_object;

    unsigned int tcp_connections_number = TCP_client_con->custom_uint;
    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);
    TCP_Connection_to *con_to = get_connection(tcp_c, number);

    if (!con_to || !tcp_con)
        return -1;

    if (status == 1) {
        if (set_tcp_connection_status(con_to, tcp_connections_number, TCP_CONNECTIONS_STATUS_REGISTERED, connection_id) == -1)
            return -1;

    } else if (status == 2) {
        if (set_tcp_connection_status(con_to, tcp_connections_number, TCP_CONNECTIONS_STATUS_ONLINE, connection_id) == -1)
            return -1;

    }

    return 0;
}

static int tcp_data_callback(void *object, uint32_t number, uint8_t connection_id, const uint8_t *data, uint16_t length)
{

    if (length == 0)
        return -1;

    TCP_Client_Connection *TCP_client_con = object;
    TCP_Connections *tcp_c = TCP_client_con->custom_object;

    unsigned int tcp_connections_number = TCP_client_con->custom_uint;
    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

    if (!tcp_con)
        return -1;

    TCP_Connection_to *con_to = get_connection(tcp_c, number);

    if (!con_to)
        return -1;

    if (tcp_c->tcp_data_callback)
        tcp_c->tcp_data_callback(tcp_c->tcp_data_callback_object, con_to->id, data, length);

    return 0;
}

static int tcp_oob_callback(void *object, const uint8_t *public_key, const uint8_t *data, uint16_t length)
{
    if (length == 0)
        return -1;

    TCP_Client_Connection *TCP_client_con = object;
    TCP_Connections *tcp_c = TCP_client_con->custom_object;

    unsigned int tcp_connections_number = TCP_client_con->custom_uint;
    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

    if (!tcp_con)
        return -1;

    uint8_t relay_pk[crypto_box_PUBLICKEYBYTES];
    memcpy(relay_pk, tcp_con->connection->public_key, crypto_box_PUBLICKEYBYTES);

    if (tcp_c->tcp_oob_callback)
        tcp_c->tcp_oob_callback(tcp_c->tcp_oob_callback_object, public_key, tcp_connections_number, data, length);

    return 0;
}

static int tcp_onion_callback(void *object, const uint8_t *data, uint16_t length)
{
    TCP_Connections *tcp_c = object;

    if (tcp_c->tcp_onion_callback)
        tcp_c->tcp_onion_callback(tcp_c->tcp_onion_callback_object, data, length);

    return 0;
}

/* Set callbacks for the TCP relay connection.
 *
 * return 0 on success.
 * return -1 on failure.
 */
static int tcp_relay_set_callbacks(TCP_Connections *tcp_c, int tcp_connections_number)
{
    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

    if (!tcp_con)
        return -1;

    TCP_Client_Connection *con = tcp_con->connection;

    con->custom_object = tcp_c;
    con->custom_uint = tcp_connections_number;
    onion_response_handler(con, &tcp_onion_callback, tcp_c);
    routing_response_handler(con, &tcp_response_callback, con);
    routing_status_handler(con, &tcp_status_callback, con);
    routing_data_handler(con, &tcp_data_callback, con);
    oob_data_handler(con, &tcp_oob_callback, con);

    return 0;
}

static int tcp_relay_on_online(TCP_Connections *tcp_c, int tcp_connections_number)
{
    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

    if (!tcp_con)
        return -1;

    unsigned int i;

    for (i = 0; i < tcp_c->connections_length; ++i) {
        TCP_Connection_to *con_to = get_connection(tcp_c, i);

        if (con_to) {
            if (tcp_connection_in_conn(con_to, tcp_connections_number)) {
                send_tcp_relay_routing_request(tcp_c, tcp_connections_number, con_to->public_key);
            }
        }
    }

    tcp_relay_set_callbacks(tcp_c, tcp_connections_number);
    tcp_con->status = TCP_CONN_CONNECTED;
    return 0;
}

static int add_tcp_relay(TCP_Connections *tcp_c, IP_Port ip_port, const uint8_t *relay_pk)
{
    if (ip_port.ip.family == TCP_INET) {
        ip_port.ip.family = AF_INET;
    } else if (ip_port.ip.family == TCP_INET6) {
        ip_port.ip.family = AF_INET6;
    }

    if (ip_port.ip.family != AF_INET && ip_port.ip.family != AF_INET6)
        return -1;

    int tcp_connections_number = create_tcp_connection(tcp_c);

    if (tcp_connections_number == -1)
        return -1;

    TCP_con *tcp_con = &tcp_c->tcp_connections[tcp_connections_number];


    tcp_con->connection = new_TCP_connection(ip_port, relay_pk, tcp_c->dht->self_public_key, tcp_c->dht->self_secret_key,
                          &tcp_c->proxy_info);

    if (!tcp_con->connection)
        return -1;

    tcp_con->status = TCP_CONN_VALID;

    return tcp_connections_number;
}

/* Add a TCP relay to the instance.
 *
 * return 0 on success.
 * return -1 on failure.
 */
int add_tcp_relay_global(TCP_Connections *tcp_c, IP_Port ip_port, const uint8_t *relay_pk)
{
    int tcp_connections_number = find_tcp_connection_relay(tcp_c, relay_pk);

    if (tcp_connections_number != -1)
        return -1;

    if (add_tcp_relay(tcp_c, ip_port, relay_pk) == -1)
        return -1;

    return 0;
}

/* Add a TCP relay tied to a connection.
 *
 * return 0 on success.
 * return -1 on failure.
 */
int add_tcp_number_relay_connection(TCP_Connections *tcp_c, int connections_number, unsigned int tcp_connections_number)
{
    TCP_Connection_to *con_to = get_connection(tcp_c, connections_number);

    if (!con_to)
        return -1;

    TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

    if (!tcp_con)
        return -1;

    if (add_tcp_connection_to_conn(con_to, tcp_connections_number) == -1)
        return -1;

    ++tcp_con->lock_count;

    if (tcp_con->status == TCP_CONN_CONNECTED) {
        send_tcp_relay_routing_request(tcp_c, tcp_connections_number, con_to->public_key);
    }

    return 0;
}

/* Add a TCP relay tied to a connection.
 *
 * return 0 on success.
 * return -1 on failure.
 */
int add_tcp_relay_connection(TCP_Connections *tcp_c, int connections_number, IP_Port ip_port, const uint8_t *relay_pk)
{
    TCP_Connection_to *con_to = get_connection(tcp_c, connections_number);

    if (!con_to)
        return -1;

    int tcp_connections_number = find_tcp_connection_relay(tcp_c, relay_pk);

    if (tcp_connections_number != -1) {
        return add_tcp_number_relay_connection(tcp_c, connections_number, tcp_connections_number);
    } else {
        int tcp_connections_number = add_tcp_relay(tcp_c, ip_port, relay_pk);

        if (add_tcp_connection_to_conn(con_to, tcp_connections_number) == -1) {
            return -1;
        }

        TCP_con *tcp_con = get_tcp_connection(tcp_c, tcp_connections_number);

        if (!tcp_con)
            return -1;

        ++tcp_con->lock_count;
        return 0;
    }
}

/* Copy a maximum of max_num TCP relays we are connected to to tcp_relays.
 * NOTE that the family of the copied ip ports will be set to TCP_INET or TCP_INET6.
 *
 * return number of relays copied to tcp_relays on success.
 * return 0 on failure.
 */
unsigned int tcp_copy_connected_relays(TCP_Connections *tcp_c, Node_format *tcp_relays, uint16_t max_num)
{
    unsigned int i, copied = 0;

    for (i = 0; (i < tcp_c->tcp_connections_length) && (copied < max_num); ++i) {
        TCP_con *tcp_con = get_tcp_connection(tcp_c, i);

        if (!tcp_con) {
            continue;
        }

        if (tcp_con->status == TCP_CONN_CONNECTED) {
            memcpy(tcp_relays[copied].public_key, tcp_con->connection->public_key, crypto_box_PUBLICKEYBYTES);
            tcp_relays[copied].ip_port = tcp_con->connection->ip_port;

            if (tcp_relays[copied].ip_port.ip.family == AF_INET) {
                tcp_relays[copied].ip_port.ip.family = TCP_INET;
            } else if (tcp_relays[copied].ip_port.ip.family == AF_INET6) {
                tcp_relays[copied].ip_port.ip.family = TCP_INET6;
            }

            ++copied;
        }
    }

    return copied;
}

TCP_Connections *new_tcp_connections(DHT *dht)
{
    if (dht == NULL)
        return NULL;

    TCP_Connections *temp = calloc(1, sizeof(TCP_Connections));

    if (temp == NULL)
        return NULL;

    temp->dht = dht;
    return temp;
}

static void do_tcp_conns(TCP_Connections *tcp_c)
{
    unsigned int i;

    for (i = 0; i < tcp_c->tcp_connections_length; ++i) {
        TCP_con *tcp_con = get_tcp_connection(tcp_c, i);

        if (tcp_con) {
            do_TCP_connection(tcp_con->connection);

            /* callbacks can change TCP connection address. */
            tcp_con = get_tcp_connection(tcp_c, i);

            if (tcp_con->connection->status == TCP_CLIENT_DISCONNECTED) {
                kill_tcp_relay_connection(tcp_c, i);
                continue;
            }

            if (tcp_con->status == TCP_CONN_VALID && tcp_con->connection->status == TCP_CLIENT_CONFIRMED) {
                tcp_relay_on_online(tcp_c, i);
            }
        }
    }
}

static void kill_nonused_tcp(TCP_Connections *tcp_c)
{
    unsigned int i, num_online = 0;

    for (i = 0; i < tcp_c->tcp_connections_length; ++i) {
        TCP_con *tcp_con = get_tcp_connection(tcp_c, i);

        if (tcp_con) {
            if (tcp_con->status == TCP_CONN_CONNECTED) {
                if (!tcp_con->lock_count && num_online >= MAX_FRIEND_TCP_CONNECTIONS) {
                    kill_tcp_relay_connection(tcp_c, i);
                    continue;
                }

                ++num_online;
            }
        }
    }
}

void do_tcp_connections(TCP_Connections *tcp_c)
{
    //TODO reconnect to TCP relays if disconnects happen.
    do_tcp_conns(tcp_c);
    kill_nonused_tcp(tcp_c);
}

void kill_tcp_connections(TCP_Connections *tcp_c)
{
    unsigned int i;

    for (i = 0; i < tcp_c->tcp_connections_length; ++i) {
        kill_TCP_connection(tcp_c->tcp_connections[i].connection);
    }

    free(tcp_c->tcp_connections);
    free(tcp_c->connections);
    free(tcp_c);
}