PATH module
Admin Guide
Section titled “Admin Guide”Overview
Section titled “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.
Path insertion for registrations
Section titled “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.
Outbound routing to NAT’ed UACs
Section titled “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”.
Dependencies
Section titled “Dependencies”OpenSIPS Modules
Section titled “OpenSIPS Modules”The following modules must be loaded before this module:
- The “rr” module is needed for outbound routing according to the “received” parameter.
External Libraries or Applications
Section titled “External Libraries or Applications”The following libraries or applications must be installed before running OpenSIPS with this module loaded:
- None.
Exported Parameters
Section titled “Exported Parameters”use_received (int)
Section titled “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.
...modparam("path", "use_received", 1)...enable_double_path (integer)
Section titled “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).
...modparam("path", "enable_double_path", 0)...Exported Functions
Section titled “Exported Functions”add_path()
Section titled “add_path()”This function is used to insert a Path header in the form “Path: sip:1.2.3.4;lr”, where “1.2.3.4” is the address of the outgoing interface.
This function can be used from REQUEST_ROUTE.
...if (!add_path()) { sl_send_reply("503", "Internal Path Error"); ...};...add_path(user)
Section titled “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 - The username to be inserted as user part.
This function can be used from REQUEST_ROUTE.
...if (!add_path("loadbalancer")) { sl_send_reply("503", "Internal Path Error"); ...};...add_path_received()
Section titled “add_path_received()”This function adds a Path header in the form “Path: sip:1.2.3.4;received=sip:2.3.4.5:1234;lr”, setting it’s own outgoing address as domain-part, and the address the request has been received from as received-parameter.
This function can be used from REQUEST_ROUTE.
...if (!add_path_received()) { sl_send_reply("503", "Internal Path Error"); ...};...add_path_received(user)
Section titled “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.
This function can be used from REQUEST_ROUTE.
...if (!add_path_received("inbound")) { sl_send_reply("503", "Internal Path Error"); ...};...Contributors
Section titled “Contributors”By Commit Statistics
Section titled “By Commit Statistics”Top contributors by DevScore(1), authored commits(2) and lines added/removed(3)
| # | Name | DevScore | Commits | Lines++ | Lines— |
|---|---|---|---|---|---|
| 1. | Bogdan-Andrei Iancu (@bogdan-iancu) | 18 | 14 | 238 | 79 |
| 2. | Andreas Granig | 13 | 4 | 867 | 26 |
| 3. | Daniel-Constantin Mierla (@miconda) | 12 | 10 | 25 | 21 |
| 4. | Liviu Chircu (@liviuchircu) | 8 | 6 | 45 | 34 |
| 5. | Stefan Darius (@dariusstefan) | 8 | 4 | 259 | 45 |
| 6. | Razvan Crainea (@razvancrainea) | 7 | 5 | 9 | 9 |
| 7. | Henning Westerholt (@henningw) | 4 | 2 | 5 | 32 |
| 8. | Ancuta Onofrei | 3 | 1 | 12 | 12 |
| 9. | Konstantin Bokarius | 3 | 1 | 2 | 5 |
| 10. | Edson Gellert Schubert | 3 | 1 | 0 | 103 |
All remaining contributors: 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
(3) ignoring whitespace edits, renamed files and auto-generated files
By Commit Activity
Section titled “By Commit Activity”| # | Name | Commit Activity |
|---|---|---|
| 1. | Stefan Darius (@dariusstefan) | Jun 2026 - Jul 2026 |
| 2. | Razvan Crainea (@razvancrainea) | Aug 2010 - Jun 2026 |
| 3. | Liviu Chircu (@liviuchircu) | Mar 2014 - Mar 2015 |
| 4. | Bogdan-Andrei Iancu (@bogdan-iancu) | Oct 2006 - Oct 2014 |
| 5. | Daniel-Constantin Mierla (@miconda) | Nov 2006 - Mar 2008 |
| 6. | Konstantin Bokarius | Mar 2008 - Mar 2008 |
| 7. | Edson Gellert Schubert | Feb 2008 - Feb 2008 |
| 8. | Henning Westerholt (@henningw) | Apr 2007 - Dec 2007 |
| 9. | Ancuta Onofrei | Sep 2007 - Sep 2007 |
| 10. | Andreas Granig | Mar 2006 - Aug 2007 |
All remaining contributors: Elena-Ramona Modroiu.
(1) including any documentation-related commits, excluding merge commits
Documentation
Section titled “Documentation”Contributors
Section titled “Contributors”Last edited by: Razvan Crainea (@razvancrainea), Bogdan-Andrei Iancu (@bogdan-iancu), Daniel-Constantin Mierla (@miconda), Konstantin Bokarius, Edson Gellert Schubert, Elena-Ramona Modroiu, Andreas Granig.
License
Section titled “License”All documentation files (i.e. .md extension) are licensed under the Creative Common License 4.0