# &adminguide;

## Overview

This is a module that enables media streams to be relayed via pylrkproxy engine that exist in: https://github.com/mojtabaesfandiari/pylrkproxy It does relaying audio streams between peers in PREROUTING netfilter-hooking section in kernel-space linux. The LRKProxy architecture is composed of two different layers. These layers are independent of each other. For more information about LRKProxy architecture, please visit our paper in ieeexplore: https://ieeexplore.ieee.org/document/9303608

## LRKProxy Architecture

### LRKP_Controlling Layer (LRKP_CL)

The first layer is developed as User-Space application that allows User-Space to directly access and manipulate cache data buffer and packet buffer in Kernel-Space. This layer gets all information about creating new sessions, active sessions and teardown sessions which is gotten from SDP body during signaling plan and relay them to the LRKP-Transport Stateful Layer (LRKP- TSL).

### LRKP_Transport Stateful Layer (LRKP_TSL)

The second layer is developed in Kernel-Space as a main decision point for RTP admission controller and Quickpath selector to where a received packet should be forwarded with power of packet mangling framework in the network stack.

The LRKP_CL and LRKP-TSL could be run as independence functions on different machines. We could have one LRKP_CL with multiple LRKP-TSL on different machines. The LRKP_CL could works with all LRKP-TSL with different strategies(lrkp_alg parameter).

## Multiple LRKProxy usage

The LRKP_CL Layer can support multiple LRKP_TSL Layer for balancing/distribution and control/selection purposes.

The module allows definition of several sets of LRKP_TSL. Load-balancing will be performed over predefine algorithm by setting lrkp_alg parameter.

IMPORTANT: This module does not support balancing inside a set like as is done RTPProxy module based on the weight of each rtpproxy from the set. The balancing would be run on different machine

## Dependencies

### &kamailio; Modules

The following modules must be loaded before this module:

- tm module - (optional) if you want to have lrkproxy_manage() fully functional

### External Libraries or Applications

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

- None.

### Parameters

#### `lrkproxy_sock` (string)

Used to define the list of LRKP_TSL instances to connect to. These can be UNIX sockets or IPv4/IPv6 UDP sockets. Each modparam entry will insert sockets into a single set with default value set ID '0'. To define multiple LRKP_TSL, just add the instances in each modparam.

Default value is NONE (disabled).

##### Set `lrkproxy_sock` parameter

    						...
    						# single lrkproxy
    						modparam("lrkproxy", "lrkproxy_sock", "udp:192.168.122.108:8080")

    						# multiple lrkproxies for LB in different machine
    						modparam("lrkproxy", "lrkproxy_sock", "udp:192.168.122.108:8080")
    						modparam("lrkproxy", "lrkproxy_sock", "udp:192.168.122.109:8080")

    						...

#### `lrkproxy_disable_tout` (integer)

Once LRKP_TSL was found unreachable and marked as disabled, the LRKP_CL module will not attempt to establish communication to LRKP_TSL for lrkproxy_disable_tout seconds.

Default value is 60.

##### Set `lrkproxy_disable_tout` parameter

    						...
    						modparam("lrkproxy", "lrkproxy_disable_tout", 20)
    						...

#### `lrkproxy_tout` (integer)

Timeout value in waiting for reply from LRKP_TSL.

Default value is 1.

##### Set `lrkproxy_tout` parameter

    						...
    						modparam("lrkproxy", "lrkproxy_tout", 2)
    						...

#### `lrkproxy_retr` (integer)

How many times the LRKP_CL should retry to send and receive after timeout was generated.

Default value is 5.

##### Set `lrkproxy_retr` parameter

    						...
    						modparam("lrkproxy", "lrkproxy_retr", 2)
    						...

#### `lrkp_alg` (integer)

This parameter set the algorithm of LRKP_TSL selection. lrk_LINER=0, lrk_RR=1

Default value is 0.

##### Set `lrkp_alg` parameter

    						...
    						modparam("lrkproxy", "lrkp_alg", 1)
    						...

#### `hash_table_tout` (integer)

Number of seconds after an lrkproxy hash table entry is marked for deletion. By default, this parameter is set to 3600 (seconds).

To maintain information about a selected rtp machine node, for a given call, entries are added in a hashtable of (callid, viabranch) pairs. When command comes, lookup callid, viabranch pairs. If found, return chosen node. If not found, choose a new node, insert it in the hastable and return the chosen node.

NOTE: In the current implementation, the actual deletion happens on the fly, while insert/remove/lookup the hastable, only for the entries in the insert/remove/lookup path.

NOTE: When configuring this parameter, one should consider maximum call time VS shared memory for unfinished calls.

Default value is 3600.

##### Set `hash_table_tout` parameter

    						...
    						modparam("lrkproxy", "hash_table_tout", "3600")
    						...

#### `hash_table_size` (integer)

Size of the hash table. Default value is 128.

Default value is 128.

##### Set `hash_table_size` parameter

    						...
    						modparam("lrkproxy", "hash_table_size", 256)
    						...

#### `custom_sdp_ip_avp` (string)

This option useful for solving STUN and help UDP packets make it across NAT devices safe and sound. In this way, it should be set by clients' IP public manually.

Default value is NULL.

##### Set `custom_sdp_ip_avp` parameter

    						...
    						modparam("lrkproxy", "custom_sdp_ip_avp", "$avp(RR_CUSTOM_SDP_IP_AVP)")
    						...

#### `gt` (integer)

This option useful for optimization in allocation port resource in lrkproxy service.

Default value is 0.

##### Set `gt` parameter

    						...
    						modparam("lrkproxy", "gt", "1")
    						...

#### `behind_nat` (integer)

The behind_nat is used when the LRKProxy is behind NAT firewall and the external IP should be as Advertised IP. It could be set 0:disable or 1:enable. If you use AWS for LRKProxy, you might should set behind_nat option.

Default value is 0.

##### Set `behind_nat` parameter

    						...
    						modparam("lrkproxy", "behind_nat", "1")
    						...

#### `start_port` (integer)

This option use for local rang port for working with LRKProxy engine. Default value is based on LRKProxy engine option. For example if the range of ports in LRKProxy is set from 20000 to 30000, You could use this option to set a subset of the LRKProxy range.

##### Set `start_port` parameter

    						...
    						modparam("lrkproxy", "start_port", "25000")
    						...

#### `end_port` (integer)

This option use for local rang port for working with LRKProxy engine. Default value is based on LRKProxy engine option. For example if the range of ports in LRKProxy is set from 20000 to 30000, You could use this option to set a subset of the LRKProxy range.

##### Set `start_port` parameter

    						...
    						modparam("lrkproxy", "end_port", "28000")
    						...

### Functions

#### `set_lrkproxy_set(setid)`

Sets the Id of the lrkproxy set to be used for the next lrkproxy_manage() command. The parameter can be an integer or a config variable holding an integer.

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

##### `set_lrkproxy_set` usage

    						...
    						set_lrkproxy_set("0");
    						lrkproxy_manage();
    						...

#### `lrkproxy_manage([flags [, ip_address]])`

Manage the LRKProxy session - it combines the functionality of lrkproxy_offer(), lrkproxy_answer() and unforce_lrkproxy(), detecting internally based on message type and method which one to execute.

IMPORTANT:The LRKProxy just has one function relating rtp packets. It does not support combination of functionality of lrkproxy_offer(), lrkproxy_answer() and unforce_lrkproxy() and other etc. So you have to just use lrkproxy_manage.

Meaning of the parameters is as follows:

- flags - flags to turn on some features.

  - internal,external - The shorthand of this flag is "ie". This can be used to relay media sessions between two different NIC from internal to external path.

  - external,internal - The shorthand of this flag is "ei". This can be used to relay media sessions between two different NIC from external to internal path.

- ip_address - new SDP IP address. This optional parameter is under development.

This function can be used from ANY_ROUTE.

##### `lrkproxy_manage` usage

    						...
    						lrkproxy_manage();
    						//or
    						lrkproxy_manage("ie");
    						//or
    						lrkproxy_manage("ei");

    						...