1. Options Module

Nils Ohlmeier

FhG Fokus

1.1. Overview
1.2. Dependencies
1.3. Parameters
1.3.1. accept (string)
1.3.2. accept_encoding (string)
1.3.3. accept_language (string)
1.3.4. supported (string)
1.3.5. contact (string)
1.3.6. contact_param (string)
1.4. Functions
1.4.1. options_reply()

1.1. 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).

1.2. Dependencies

The following modules must be loaded before this module:

  • sl - Stateless replies.

1.3. Parameters

1.3.1. accept (string)

This parameter is the content of the Accept header field. 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 "*/*".

Example 1. Set accept parameter

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

1.3.2. accept_encoding (string)

This parameter is the content of the Accept-Encoding header field. Please do not change the default value because SER does not support any encodings yet.

Default value is "".

Example 2. Set accept_encoding parameter

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

1.3.3. accept_language (string)

This parameter is the content of the Accept-Language header field. 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".

Example 3. Set accept_language parameter

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

1.3.4. supported (string)

This parameter is the content of the Supported header field Here you can enter the extensions which are supported by your SER config. Normally you should only use values here which are registered with the IANA.

Default value is "".

Example 4. Set supported parameter

modparam("options", "supported", "100rel")

1.3.5. contact (string)

The content of this parameter will be inserted into the reply as the URI of the Contact header. If this parameter is empty (default case) then no Contact header in included in the reply. If this parameter is set to "dstip" the reply contains a Contact header with the IP, port and transport of the socket where the request was sent to. If this parameter is set to "ruri" the reply contains a Contact header with the same URI as the request URI of the original OPTIONS request.

Default value is "".

Example 5. Set contact parameter

modparam("options", "contact", "example.com")

1.3.6. contact_param (string)

This parameter is appended to the value of the Contact header is case it is set. If just this parameter is set but the contact module parameter not, then the contact parameter is automatically set to dstip.

Default value is "".

Example 6. Set contact_param parameter

modparam("options", "contact_param", "lr=on")

1.4. Functions

1.4.1.  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).

Example 7. options_reply usage

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