# &adminguide;

## Overview

### The idea

A stun server working with the same port as SIP (5060) in order to gain accurate information. The benefit would be an exact external address in the case of NATs translating differently when given different destination ports. The server may also advertise different network addresses than the ones it is actually listening on.

### Basic Operation

The stun server will use 4 sockets:

- socket1 = ip1 : port1
- socket2 = ip1 : port2
- socket3 = ip2 : port1
- socket4 = ip2 : port2

The sockets come from existing SIP sockets or are created.

Socket1 must allways be a SIP UDP listener from OpenSIPS.

The server will create a separate process. This process will listen for data on created sockets. The server will register a callback function to SIP. This function is called when a specific (stun)header is found.

### Supported STUN Attributes

This stun implements RFC3489 (and XOR_MAPPED_ADDRESS from RFC5389)

- MAPPED_ADDRESS
- RESPONSE_ADDRESS
- CHANGE_REQUEST
- SOURCE_ADDRESS
- CHANGED_ADDRESS
- ERROR_CODE
- UNKNOWN_ATTRIBUTES
- REFLECTED_FROM
- XOR_MAPPED_ADDRESS

Not supported attributes:

- USERNAME
- PASSWORD
- MESSAGE_INTEGRITY

and associated ERROR_CODEs

## Dependencies

### &osips; Modules

The following modules must be loaded before this module:

None.

### External Libraries or Applications

The following libraries or applications must be installed before running &osips; with this module loaded:

- None.

## Exported Parameters

### `primary_ip` (str)

The IP of an interface which is configured as an UDP SIP listener in &osips;. This is a mandatory parameter.

Syntax: "ip [/ advertised_ip]

By default, the primary_ip and the advertised primary_ip will be identical. This may be changed with an optional "/ xxx.xxx.xxx.xxx" string.

#### Set `primary_ip` parameter

    ...
    modparam("stun", "primary_ip", "192.168.0.100")

    # Example of a STUN server within OpenSIPS which is behind NAT
    modparam("stun", "primary_ip", "192.168.0.100 / 64.50.46.78")
    ...

### `primary_port` (str)

The port configured (together with the primary_ip) as an UDP SIP listener in &osips;. The default value is 5060.

Syntax: "port [/ advertised_port]

By default, the primary_port and the advertised primary_port will be identical. This may be changed with an optional "/ adv_port" string.

#### Set `primary_port` parameter

    ...
    modparam("stun", "primary_port", "5060")

    # Listening on a primary port, but advertising a different one
    modparam("stun", "primary_port", "5060 / 5062")
    ...

### `alternate_ip` (str)

Another IP from another interface. This is a mandatory parameter.

Syntax: "ip [/ advertised_ip]

By default, the alternate_ip and the advertised alternate_ip will be identical. This may be changed with an optional "/ xxx.xxx.xxx.xxx" string.

#### Set `alternate_ip` parameter

    ...
    modparam("stun","alternate_ip","11.22.33.44")

    # Example of a STUN server within OpenSIPS which is behind NAT
    modparam("stun", "alternate_ip", "192.168.0.100 / 64.78.46.50")
    ...

### `alternate_port` (str)

The port used by the STUN server for the second interface. The default value is 3478 (default STUN port).

Syntax: "port [/ advertised_port]

By default, the alternate_port and the advertised alternate_port will be identical. This may be changed with an optional "/ adv_port" string.

#### Set `alternate_port` parameter

    ...
    modparam("stun","alternate_port","3479")

    # Listening on an alternate port, but advertising a different one
    modparam("stun", "alternate_port", "5060 / 5062")
    ...

## Exported MI Functions