# &adminguide;

## 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 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 () 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 () to query routing information for a given (geodetic) 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 asdisplay 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 resolvers, not the Kamailio resolver.

The module is limited to using HTTP and HTTPS protocols.

## Dependencies

### &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.

### External Libraries or Applications

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

- &libcurl;

- libxml2

## Parameters

This module has no specific paramater but uses http_client therfore according parameters may apply.

## Functions

### `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, definied 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

- 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.

#### `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");
    ...

### `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 definied 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.

#### `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(uri)\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(uri)\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(uri)\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(uri)\n");
    ...

## Counters

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

## 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 (query_params.oneline = 1), but the lost module requires the complete response message, which requires query_params.oneline set to 0. In the case lost_query is used with the default http_client API, dereferencing location via HTTP provided with the Geolocation header causes an error. Therefore, to work properlu=y, it requires to set http_client module parameter query_result to 0.