## TURN

TURN — TURN Allocation Usage

## Stability Level

Stable, unless otherwise indicated

## Synopsis

    #include <stun/usages/turn.h>

    enum                StunUsageTurnCompatibility;
    enum                StunUsageTurnRequestPorts;
    enum                StunUsageTurnReturn;
    size_t              stun_usage_turn_create              (StunAgent *agent,
                                                             StunMessage *msg,
                                                             uint8_t *buffer,
                                                             size_t buffer_len,
                                                             StunMessage *previous_response,
                                                             StunUsageTurnRequestPorts request_ports,
                                                             int32_t bandwidth,
                                                             int32_t lifetime,
                                                             uint8_t *username,
                                                             size_t username_len,
                                                             uint8_t *password,
                                                             size_t password_len,
                                                             StunUsageTurnCompatibility compatibility);
    size_t              stun_usage_turn_create_refresh      (StunAgent *agent,
                                                             StunMessage *msg,
                                                             uint8_t *buffer,
                                                             size_t buffer_len,
                                                             StunMessage *previous_response,
                                                             int32_t lifetime,
                                                             uint8_t *username,
                                                             size_t username_len,
                                                             uint8_t *password,
                                                             size_t password_len,
                                                             StunUsageTurnCompatibility compatibility);
    StunUsageTurnReturn  stun_usage_turn_process            (StunMessage *msg,
                                                             struct sockaddr *relay_addr,
                                                             socklen_t *relay_addrlen,
                                                             struct sockaddr *addr,
                                                             socklen_t *addrlen,
                                                             struct sockaddr *alternate_server,
                                                             socklen_t *alternate_server_len,
                                                             uint32_t *bandwidth,
                                                             uint32_t *lifetime,
                                                             StunUsageTurnCompatibility compatibility);
    StunUsageTurnReturn  stun_usage_turn_refresh_process    (StunMessage *msg,
                                                             uint32_t *lifetime,
                                                             StunUsageTurnCompatibility compatibility);

## Description

The STUN TURN usage allows for easily creating and parsing STUN Allocate requests and responses used for TURN. The API allows you to create a new allocation or refresh an existing one as well as to parse a response to an allocate or refresh request.

## Details

### enum StunUsageTurnCompatibility

    typedef enum {
      STUN_USAGE_TURN_COMPATIBILITY_DRAFT9,
      STUN_USAGE_TURN_COMPATIBILITY_GOOGLE,
      STUN_USAGE_TURN_COMPATIBILITY_MSN,
    } StunUsageTurnCompatibility;

Specifies which TURN specification compatibility to use

`STUN_USAGE_TURN_COMPATIBILITY_DRAFT9` | Use the specification compatible with TURN Draft 09
`STUN_USAGE_TURN_COMPATIBILITY_GOOGLE` | Use the specification compatible with Google Talk's relay server
`STUN_USAGE_TURN_COMPATIBILITY_MSN` | Use the specification compatible with MSN TURN servers

### enum StunUsageTurnRequestPorts

    typedef enum {
      STUN_USAGE_TURN_REQUEST_PORT_NORMAL = 0,
      STUN_USAGE_TURN_REQUEST_PORT_EVEN = 1,
      STUN_USAGE_TURN_REQUEST_PORT_EVEN_AND_RESERVE = 2
    } StunUsageTurnRequestPorts;

This enum is used to specify which port configuration you want when creating a new Allocation

`STUN_USAGE_TURN_REQUEST_PORT_NORMAL` | Request a normal port
`STUN_USAGE_TURN_REQUEST_PORT_EVEN` | Request an even port
`STUN_USAGE_TURN_REQUEST_PORT_EVEN_AND_RESERVE` | Request an even port and reserve the next higher port

### enum StunUsageTurnReturn

    typedef enum {
      STUN_USAGE_TURN_RETURN_RELAY_SUCCESS,
      STUN_USAGE_TURN_RETURN_MAPPED_SUCCESS,
      STUN_USAGE_TURN_RETURN_ERROR,
      STUN_USAGE_TURN_RETURN_INVALID,
      STUN_USAGE_TURN_RETURN_ALTERNATE_SERVER,
    } StunUsageTurnReturn;

Return value of `stun_usage_turn_process()` and `stun_usage_turn_refresh_process()` which allows you to see what status the function call returned.

`STUN_USAGE_TURN_RETURN_RELAY_SUCCESS` | The response was successful and a relay address is provided
`STUN_USAGE_TURN_RETURN_MAPPED_SUCCESS` | The response was successful and a relay address as well as a mapped address are provided
`STUN_USAGE_TURN_RETURN_ERROR` | The response resulted in an error
`STUN_USAGE_TURN_RETURN_INVALID` | The response is not a valid response
`STUN_USAGE_TURN_RETURN_ALTERNATE_SERVER` | The server requests the message to be sent to an alternate server

### stun_usage_turn_create ()

    size_t              stun_usage_turn_create              (StunAgent *agent,
                                                             StunMessage *msg,
                                                             uint8_t *buffer,
                                                             size_t buffer_len,
                                                             StunMessage *previous_response,
                                                             StunUsageTurnRequestPorts request_ports,
                                                             int32_t bandwidth,
                                                             int32_t lifetime,
                                                             uint8_t *username,
                                                             size_t username_len,
                                                             uint8_t *password,
                                                             size_t password_len,
                                                             StunUsageTurnCompatibility compatibility);

Create a new TURN Allocation request

`agent` : | The StunAgent to use to build the request
`msg` : | The StunMessage to build
`buffer` : | The buffer to use for creating the StunMessage
`buffer_len` : | The size of the `buffer`

`previous_response` :

If this is the first request you are sending, set this argument to NULL, if it's a subsequent request you are building, then set this argument to the response you have received. This argument is used for building long term credentials (using the REALM and NONCE attributes) as well as for getting the RESERVATION-TOKEN attribute when you previously requested an allocation which reserved two ports

`request_ports` : | Specify how you want to request the allocated port(s). This is only used if the compatibility is set to STUN_USAGE_TURN_COMPATIBILITY_DRAFT9 See StunUsageTurnRequestPorts
`bandwidth` : | The bandwidth to request from the server for the allocation. If this value is negative, then no BANDWIDTH attribute is added to the request. This is only used if the compatibility is set to STUN_USAGE_TURN_COMPATIBILITY_DRAFT9
`lifetime` : | The lifetime of the allocation to request from the server. If this value is negative, then no LIFETIME attribute is added to the request. This is only used if the compatibility is set to STUN_USAGE_TURN_COMPATIBILITY_DRAFT9
`username` : | The username to use in the request
`username_len` : | The length of `username`
`password` : | The key to use for building the MESSAGE-INTEGRITY
`password_len` : | The length of `password`
`compatibility` : | The compatibility mode to use for building the Allocation request
Returns : | The length of the message to send

### stun_usage_turn_create_refresh ()

    size_t              stun_usage_turn_create_refresh      (StunAgent *agent,
                                                             StunMessage *msg,
                                                             uint8_t *buffer,
                                                             size_t buffer_len,
                                                             StunMessage *previous_response,
                                                             int32_t lifetime,
                                                             uint8_t *username,
                                                             size_t username_len,
                                                             uint8_t *password,
                                                             size_t password_len,
                                                             StunUsageTurnCompatibility compatibility);

Create a new TURN Refresh request

`agent` : | The StunAgent to use to build the request
`msg` : | The StunMessage to build
`buffer` : | The buffer to use for creating the StunMessage
`buffer_len` : | The size of the `buffer`
`previous_response` : | If this is the first request you are sending, set this argument to NULL, if it's a subsequent request you are building, then set this argument to the response you have received. This argument is used for building long term credentials (using the REALM and NONCE attributes)
`lifetime` : | The lifetime of the allocation to request from the server. If this value is negative, then no LIFETIME attribute is added to the request. This is only used if the compatibility is set to STUN_USAGE_TURN_COMPATIBILITY_DRAFT9
`username` : | The username to use in the request
`username_len` : | The length of `username`
`password` : | The key to use for building the MESSAGE-INTEGRITY
`password_len` : | The length of `password`
`compatibility` : | The compatibility mode to use for building the Allocation request
Returns : | The length of the message to send

### stun_usage_turn_process ()

    StunUsageTurnReturn  stun_usage_turn_process            (StunMessage *msg,
                                                             struct sockaddr *relay_addr,
                                                             socklen_t *relay_addrlen,
                                                             struct sockaddr *addr,
                                                             socklen_t *addrlen,
                                                             struct sockaddr *alternate_server,
                                                             socklen_t *alternate_server_len,
                                                             uint32_t *bandwidth,
                                                             uint32_t *lifetime,
                                                             StunUsageTurnCompatibility compatibility);

Process a TURN Allocate response and extract the necessary information from the message

`msg` : | The message containing the response
`relay_addr` : | A pointer to a sockaddr structure to fill with the relay address that the TURN server allocated for us
`relay_addrlen` : | The length of `relay_addr`
`addr` : | A pointer to a sockaddr structure to fill with the mapped address that the STUN response contains. This argument will only be filled if the return value of the function is STUN_USAGE_TURN_RETURN_MAPPED_SUCCESS
`addrlen` : | The length of `addr`
`alternate_server` : | A pointer to a sockaddr structure to fill with the address of an alternate server to which we should send our new STUN Allocate request, in case the currently used TURN server is requesting the use of an alternate server. This argument will only be filled if the return value of the function is STUN_USAGE_TURN_RETURN_ALTERNATE_SERVER
`alternate_server_len` : | The length of `alternate_server`
`bandwidth` : | A pointer to fill with the bandwidth the TURN server allocated us
`lifetime` : | A pointer to fill with the lifetime of the allocation
`compatibility` : | The compatibility mode to use for processing the Allocation response
Returns : | A StunUsageTurnReturn value

### stun_usage_turn_refresh_process ()

    StunUsageTurnReturn  stun_usage_turn_refresh_process    (StunMessage *msg,
                                                             uint32_t *lifetime,
                                                             StunUsageTurnCompatibility compatibility);

Process a TURN Refresh response and extract the necessary information from the message

`msg` : | The message containing the response
`lifetime` : | A pointer to fill with the lifetime of the allocation
`compatibility` : | The compatibility mode to use for processing the Refresh response
Returns : | A StunUsageTurnReturn value. A STUN_USAGE_TURN_RETURN_RELAY_SUCCESS means the Refresh was successful, but no relay address is given (kept the same as for the original allocation)