path Module
     __________________________________________________________

   Table of Contents

   1. Admin Guide

        1.1. Overview

              1.1.1. Path insertion for registrations
              1.1.2. Outbound routing to NAT'ed UACs

        1.2. Dependencies

              1.2.1. OpenSIPS Modules
              1.2.2. External Libraries or Applications

        1.3. Exported Parameters

              1.3.1. use_received (int)
              1.3.2. enable_double_path (integer)

        1.4. Exported Functions

              1.4.1. add_path([user])
              1.4.2. add_path_received([user])

   2. Contributors

        2.1. By Commit Statistics
        2.2. By Commit Activity

   3. Documentation

        3.1. Contributors

   List of Tables

   2.1. Top contributors by DevScore^(1), authored commits^(2) and
          lines added/removed^(3)

   2.2. Most recently active contributors^(1) to this module

   List of Examples

   1.1. Set use_received parameter
   1.2. Set enable_double_path parameter
   1.3. add_path(user) usage
   1.4. add_path_received(user) usage

Chapter 1. Admin Guide

1.1. Overview

   This module is designed to be used at intermediate sip proxies
   like loadbalancers in front of registrars and proxies. It
   provides functions for inserting a Path header including a
   parameter for passing forward the received-URI of a
   registration to the next hop. It also provides a mechanism for
   evaluating this parameter in subsequent requests and to set the
   destination URI according to it.

1.1.1. Path insertion for registrations

   For registrations in a scenario like “[UAC] -> [P1] -> [REG]”,
   the "path" module can be used at the intermediate proxy P1 to
   insert a Path header into the message before forwarding it to
   the registrar REG. Two functions can be used to achieve this:
     * add_path(...) adds a Path header in the form of “Path:
       <sip:1.2.3.4;lr>” to the message using the address of the
       outgoing interface. A port is only added if it's not the
       default port 5060.
       If a username is passed to the function, it is also
       included in the Path URI, like “Path:
       <sip:username@1.2.3.4;lr>”.
     * add_path_received(...) also add a Path header in the same
       form as above, but also adds a parameter indicating the
       received-URI of the message, like “Path:
       <sip:1.2.3.4;received=sip:2.3.4.5:1234;lr>”. This is
       especially useful if the proxy does NAT detection and wants
       to pass the NAT'ed address to the registrar.
       If the function is called with a username, it's included in
       the Path URI too.

1.1.2. Outbound routing to NAT'ed UACs

   If the NAT'ed address of an UAC is passed to the registrar, the
   registrar routes back subsequent requests using the Path header
   of the registration as Route header of the current request. If
   the intermediate proxy had inserted a Path header including the
   “received” parameter during the registration, this parameter
   will show up in the Route header of the new request as well,
   allowing the intermediate proxy to route to this address
   instead of the one propagated in the Route URI for tunneling
   through NAT. This behaviour can be activated by setting the
   module parameter “use_received”.

1.2. Dependencies

1.2.1. OpenSIPS Modules

   The following modules must be loaded before this module:
     * The "rr" module is needed for outbound routing according to
       the “received” parameter.

1.2.2. External Libraries or Applications

   The following libraries or applications must be installed
   before running OpenSIPS with this module loaded:
     * None.

1.3. Exported Parameters

1.3.1. use_received (int)

   If set to 1, the “received” parameter of the first Route URI is
   evaluated and used as destination-URI if present.

   Default value is 0.

   Example 1.1. Set use_received parameter
...
modparam("path", "use_received", 1)
...

1.3.2. enable_double_path (integer)

   There are some situations when the server needs to insert two
   Path header fields instead of one. For example when using two
   disconnected networks or doing cross-protocol forwarding from
   UDP->TCP. This parameter enables inserting of 2 Paths.

   Default value is 1 (yes).

   Example 1.2. Set enable_double_path parameter
...
modparam("path", "enable_double_path", 0)
...

1.4. Exported Functions

1.4.1.  add_path([user])

   This function adds a Path header in the form “Path:
   <sip:user@1.2.3.4;lr>”.

   Meaning of the parameters is as follows:
     * user (string, optional) - The username to be inserted as
       user part.

   This function can be used from REQUEST_ROUTE.

   Example 1.3. add_path(user) usage
...
if (!add_path("loadbalancer")) {
        sl_send_reply(503, "Internal Path Error");
        ...
};
...

1.4.2.  add_path_received([user])

   This function adds a Path header in the form “Path:
   <sip:user@1.2.3.4;received=sip:2.3.4.5:1234;lr>”, setting
   'user' as username part of address, it's own outgoing address
   as domain-part, and the address the request has been received
   from as received-parameter.

   Meaning of the parameters is as follows:
     * user (string, optional) - The username to be inserted as
       user part.

   This function can be used from REQUEST_ROUTE.

   Example 1.4. add_path_received(user) usage
...
if (!add_path_received("inbound")) {
        sl_send_reply(503, "Internal Path Error");
        ...
};
...

Chapter 2. Contributors

2.1. By Commit Statistics

   Table 2.1. Top contributors by DevScore^(1), authored
   commits^(2) and lines added/removed^(3)
     Name DevScore Commits Lines ++ Lines --
   1. Bogdan-Andrei Iancu (@bogdan-iancu) 20 16 239 79
   2. Liviu Chircu (@liviuchircu) 17 11 96 265
   3. Andreas Granig 13 4 863 22
   4. Daniel-Constantin Mierla (@miconda) 12 10 25 21
   5. Razvan Crainea (@razvancrainea) 9 7 10 8
   6. Vlad Patrascu (@rvlad-patrascu) 6 3 35 104
   7. Henning Westerholt (@henningw) 4 2 5 32
   8. Ancuta Onofrei 3 1 12 12
   9. Konstantin Bokarius 3 1 2 5
   10. Peter Lemenkov (@lemenkov) 3 1 1 1

   All remaining contributors: Edson Gellert Schubert,
   Elena-Ramona Modroiu.

   (1) DevScore = author_commits + author_lines_added /
   (project_lines_added / project_commits) + author_lines_deleted
   / (project_lines_deleted / project_commits)

   (2) including any documentation-related commits, excluding
   merge commits. Regarding imported patches/code, we do our best
   to count the work on behalf of the proper owner, as per the
   "fix_authors" and "mod_renames" arrays in
   opensips/doc/build-contrib.sh. If you identify any
   patches/commits which do not get properly attributed to you,
   please submit a pull request which extends "fix_authors" and/or
   "mod_renames".

   (3) ignoring whitespace edits, renamed files and auto-generated
   files

2.2. By Commit Activity

   Table 2.2. Most recently active contributors^(1) to this module
                      Name                   Commit Activity
   1.  Razvan Crainea (@razvancrainea)     Aug 2010 - Sep 2019
   2.  Bogdan-Andrei Iancu (@bogdan-iancu) Oct 2006 - Jul 2019
   3.  Vlad Patrascu (@rvlad-patrascu)     May 2017 - Apr 2019
   4.  Peter Lemenkov (@lemenkov)          Jun 2018 - Jun 2018
   5.  Liviu Chircu (@liviuchircu)         Mar 2014 - Jun 2018
   6.  Daniel-Constantin Mierla (@miconda) Nov 2006 - Mar 2008
   7.  Konstantin Bokarius                 Mar 2008 - Mar 2008
   8.  Edson Gellert Schubert              Feb 2008 - Feb 2008
   9.  Henning Westerholt (@henningw)      Apr 2007 - Dec 2007
   10. Ancuta Onofrei                      Sep 2007 - Sep 2007

   All remaining contributors: Andreas Granig, Elena-Ramona
   Modroiu.

   (1) including any documentation-related commits, excluding
   merge commits

Chapter 3. Documentation

3.1. Contributors

   Last edited by: Vlad Patrascu (@rvlad-patrascu), Peter Lemenkov
   (@lemenkov), Liviu Chircu (@liviuchircu), Bogdan-Andrei Iancu
   (@bogdan-iancu), Daniel-Constantin Mierla (@miconda),
   Konstantin Bokarius, Edson Gellert Schubert, Elena-Ramona
   Modroiu, Andreas Granig.

   Documentation Copyrights:

   Copyright © 2006 Inode GmbH
