# &adminguide;

## Overview

This module provides a function to answer OPTIONS requests which are directed to the server itself. This means an OPTIONS request which has the address of the server in the request URI, and no username in the URI. The request will be answered with a 200 OK which the capabilities of the server.

To answer OPTIONS request directed to your server is the easiest way for is-alive-tests on the SIP (application) layer from remote (similar to ICMP echo requests, also known as ping, on the network layer).

## Dependencies

### &osips; Modules

The following modules must be loaded before this module:

- sl -- Stateless replies.

- signaling -- Stateless replies.

### External Libraries or Applications

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

- None.

## Exported Parameters

### `accept` (string)

This parameter is the content of the Accept header field. If , the header is not added in the reply. Note: it is not clearly written in RFC3261 if a proxy should accept any content (the default */*) because it does not care about content. Or if it does not accept any content, which is .

Default value is */*.

#### Set `accept` parameter

    ...
    modparam("options", "accept", "application/*")
    ...

### `accept_encoding` (string)

This parameter is the content of the Accept-Encoding header field. If , the header is not added in the reply. Please do not change the default value because &osips; does not support any encodings yet.

Default value is .

#### Set `accept_encoding` parameter

    ...
    modparam("options", "accept_encoding", "gzip")
    ...

### `accept_language` (string)

This parameter is the content of the Accept-Language header field. If , the header is not added in the reply. You can set any language code which you prefer for error descriptions from other devices, but presumably there are not much devices around which support other languages then the default English.

Default value is en.

#### Set `accept_language` parameter

    ...
    modparam("options", "accept_language", "de")
    ...

### `support` (string)

This parameter is the content of the Support header field. If , the header is not added in the reply. Please do not change the default value, because &osips; currently does not support any of the SIP extensions registered at the IANA.

Default value is .

#### Set `support` parameter

    ...
    modparam("options", "support", "100rel")
    ...

## Exported Functions

### `options_reply()`

This function checks if the request method is OPTIONS and if the request URI does not contain an username. If both is true the request will be answered stateless with 200 OK and the capabilities from the modules parameters.

It sends 500 Server Internal Error for some errors and returns false if it is called for a wrong request.

The check for the request method and the missing username is optional because it is also done by the function itself. But you should not call this function outside the myself check because in this case the function could answer OPTIONS requests which are sent to you as outbound proxy but with an other destination then your proxy (this check is currently missing in the function).

This function can be used from REQUEST_ROUTE.

#### `options_reply` usage

    ...
    if (uri==myself) {
    	if ((method==OPTIONS) && (! uri=~"sip:.*[@]+.*")) {
    		options_reply();
    	}
    }
    ...