LOST Module

Wolfgang Kampichler

Frequentis AG
DEC112 (funded by netidee)

Edited by

Wolfgang Kampichler


Table of Contents

1. Admin Guide
1. Overview
2. Dependencies
2.1. Kamailio Modules
2.2. External Libraries or Applications
3. Parameters
3.1. exact_type (int)
3.2. response_time (int)
3.3. location_type (string)
4. Functions
4.1. lost_held_query(con, [id,] pidf-lo, url, error)
4.2. lost_query(con, [pidf-lo, urn,] uri, name, error)
5. Counters
6. Remarks

List of Examples

1.1. Set exact_type parameter
1.2. Set response_time parameter
1.3. Set location_type parameter
1.4. lost_held_query() usage
1.5. lost() usage

Chapter 1. Admin Guide

1. Overview

SIP requests may be forwarded based on a location provided with the request or retrieved from a specific location server using an identity (HELD). This module implements the basic functionality to get or parse location information (civic and geodetic) and to query a mapping service (LOST) in order to get next hop based on location and service urn either specified or provided with the request.

This module implements protocol functions that use the http_client api to fetch data from external LOST and HELD servers. The module is using the http_client concept of "connections" to define properties of HTTP sessions. A connection has one or multiple servers and a set of settings that apply to the specific connection.

The function lost_held_query allows Kamailio to assemble a HELD locationRequest as defined in RFC6155 (https://tools.ietf.org/html/rfc6155) to query location information represented as PIDF-LO for a given identity (in most cases a SIP URI). The identity may be a specific parameter or taken from the P-Asserted-Identity or From header. The locationRequest response is parsed and represented as PIDF-LO and location URI to dereference location via HTTP(S).

The function lost_query allows Kamailio to assemble a LOST findService request as defined in RFC5222 (https://tools.ietf.org/html/rfc5255) to query routing information for a given (geodetic or civic) location and a service URN. Both, PIDF-LO and service URN may be provided as function parameter, or are taken from the request message if applicable. The findServiceResponse is parsed and represented as display name and SIP URI typically used as next hop in a Route header.

The http_client module use the CURL library setting up connections. The CURL library by default use the system configured DNS resolver, not the Kamailio resolver.

The module is limited to using HTTP and HTTPS protocols.

2. Dependencies

2.1. Kamailio Modules

The following modules must be loaded before this module:

  • HTTP_CLIENT - the http_client module should be loaded first in order to initialize connections properly.

  • TLS - if you use TLS connections (https) the tls module should be loaded first in order to initialize OpenSSL properly.

2.2. External Libraries or Applications

The following libraries or applications must be installed before running Kamailio with this module loaded:

3. Parameters

Besides parameters listed, this module uses http_client therefore according parameters may apply.

3.1. exact_type (int)

Indicates to the location server that the contents of the "location_type" parameter must be strictly followed. Values are 0 (false) or 1 (true).

Default: 0 (false)

Example 1.1. Set exact_type parameter

    ...
    modparam("lost", "exact_type", 1)
    ...

3.2. response_time (int)

A time value indicating to the location server how long the client is prepared to wait for a response.

The value is expressed as a non-negative integer in units of milliseconds. Note: The time value is indicative only.

Default: 0 (response time not set)

Example 1.2. Set response_time parameter

    ...
    modparam("lost", "response_time", 5000)
    ...

3.3. location_type (string)

The "locationType" element contains a list of types that are requested. Values are "any", "geodetic", "civic" or "locationURI" and combinations.

  • any - returns location information in all forms available

  • geodetic - returns a location by value in the form of a geodetic location

  • civic - returns a location by value in the form of a civic address

  • locationURI - returns a set of location URIs (location by reference)

Default: "geodetic locationURI".

Example 1.3. Set location_type parameter

    ...
    modparam("http_client", "location_type, "civic geodetic locationURI")
    ...

4. Functions

4.1.  lost_held_query(con, [id,] pidf-lo, url, error)

Sends a HELD locationRequest to a given connection. The device identity is either specified, or the P-A-I header value, or the From header value.

  • con - the name of an existing HTTP connection, defined by a httpcon modparam

  • id - the device id used in the HELD locationRequest

  • pidf-lo - the PIDF-LO returned in the HELD locationRequest response

  • url - the location reference returned in the HELD locationRequest response - this reference may be added as Geolocation header value and forwarded downstream. Note: to work properly, it is required to include "locationURI" in the location_type parameter.

  • error - any error code returned in the HELD locationRequest response

The return value is 200 on success, 400 if an internal error occured, or 500 if an error code is returned in the HELD locationRequest response.

This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, and BRANCH_ROUTE.

Example 1.4. lost_held_query() usage

...
modparam("http_client", "httpcon", "heldsrv=>http://service.org/api/held");
...
# HELD location request
$var(id) = "sip:alice@atlanta";
$var(res) = lost_held_query("heldsrv", "$var(id)" , "$var(pidf)", "$var(url)", "$var(err)");
xlog("L_INFO", "HELD locationRequest: Result code $var(res)\nUrl: $var(url)\n$var(pidf)");
...
$var(res) = lost_held_query("heldsrv", "$var(pidf)", "$var(url)"", "$var(err)");
xlog("L_INFO", "HELD locationRequest: Result code $var(res)\nUrl: $var(url)\n$var(pidf)\n");
...

4.2.  lost_query(con, [pidf-lo, urn,] uri, name, error)

Sends a LOST findService request to a given connection. PIDF-LO and URN are either specified, or, if omitted, parsed from the message body (PIDF-LO) and request line (URN). Either "pidf-lo" or "urn" can be set to an empty string in order to be ignored.

  • con - the name of an existing HTTP connection defined by a httpcon modparam

  • pidf-lo - the PIDF-LO used to create the LOST findService request

  • urn - the URN used to create the LOST findService request

  • uri - the SIP uri returned in the LOST findServiceResponse

  • name - the display name returned in the LOST findServiceResponse

  • error - any error code returned in the LOST findServiceResponse

The return value is 200 on success, 400 if an internal error occured, or 500 if an error code is returned in the LOST findServiceResponse.

This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, and BRANCH_ROUTE.

Example 1.5. lost() usage

...
modparam("http_client", "httpcon", "heldsrv=>http://service.org/api/held");
modparam("http_client", "httpcon", "lostsrv=>http://service.org/api/lost");
...
# HELD location request
$var(id) = "sip:alice@atlanta";
$var(res) = lost_held_query("heldsrv", "$var(id)" , "$var(pidf)", "$var(url)", "$var(err)");
...
# LOST findService request - pidf-lo and urn as parameter
$var(id) = "urn:service:sos";
$var(res) = lost_query("lostsrv", "$var(pidf)", "$var(urn)", "$var(uri)", "$var(name)", "$var(err)");
xlog("L_INFO", "LOST findService: Result code $var(res)\nUri: $var(uri)\nName: $var(name)\n");
...
# LOST findService request - pidf-lo as parameter, urn taken from request line
$var(res) = lost_query("lostsrv", "$var(pidf)", "", "$var(uri)", "$var(name)", "$var(err)");
xlog("L_INFO", "LOST findService: Result code $var(res)\nUri: $var(uri)\nName: $var(name)\n");
...
# LOST findService request - urn as parameter, pidf-lo taken from message body
$var(res) = lost_query("lostsrv", "", "$var(urn)", "$var(uri)", "$var(name)", "$var(err)");
xlog("L_INFO", "LOST findService: Result code $var(res)\nUri: $var(uri)\nName: $var(name\n");
...
# LOST findService request - pidf-lo and urn taken from message
$var(res) = lost_query("lostsrv", "$var(uri)", "$var(name)", "$var(err)");
xlog("L_INFO", "LOST findService: Result code $var(res)\nUri: $var(uri)\nName: $var(name)\n");
...

5. Counters

This module has no specific counters but uses http_client therefore according counters may apply.

6. Remarks

Note: libcurl leak in CentOS 6 - this module uses libcurl library (via http_client) and in case if you are using CentOS 6, be aware that standard libcurl-7.19.7-52 has a memory leak. To fix this memory, install libcurl from city-fan repository. More details at: https://www.digitalocean.com/community/questions/how-to-upgrade-curl-in-centos6.

Note: http_client_query exported by the http_client API returns by default the first line of the HTTP response, but the lost module requires the complete response message, otherwise dereferencing location via the HTTP URL provided with the Geolocation header causes an error. Therefore, to work properly, it is required to set the http_client module parameter query_result to 0. More details at: https://www.kamailio.org/docs/modules/devel/modules/http_client.html#http_client.p.query_result.

Note: to test the module with a mapping service (LOST), an API key may be requested under the following link (search for "GET ACCESS"): https://gridgears.at/.