[sr-dev] [kamailio/kamailio] topos module seems to break re-SUBSCRIBE routing to downstream destinations (#1724)

[George Diamantopoulos]

<!--
Kamailio Project uses GitHub Issues only for bugs in the code or feature requests. Please use this template only for bug reports.

If you have questions about using Kamailio or related to its configuration file, ask on sr-users mailing list:

  * http://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users

If you have questions about developing extensions to Kamailio or its existing C code, ask on sr-dev mailing list:

  * http://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-dev

Please try to fill this template as much as possible for any issue. It helps the developers to troubleshoot the issue.

If there is no content to be filled in a section, the entire section can be removed.

You can delete the comments from the template sections when filling.

You can delete next line and everything above before submitting (it is a comment).
-->

### Description
Kamailio seems to fail to properly route in-dialog SUBSCRIBE with the topos module enabled. In this configuration, SUBSCRIBEs are expected to be delivered to a downstream UAS, an asterisk instance in the internal network.

record_route() is executed for all initial requests, including SUBSCRIBEs. Routing is performed correctly with the topos module disabled, no other modifications were needed.
<!--
Explain what you did, what you expected to happen, and what actually happened.
-->

### Troubleshooting
I haven't been able to work around this issue in any other way other than disabling the topos module.
#### Reproduction
The configuration used is a heavily modified version of the example configuration file, but the handling of SUBSCRIBEs is generally simple. The initial SUBSCRIBE is subject to some tests, the R-URI is edited and dispatched to a farm of asterisk servers based on some criteria. Record Routing is enforced, so subsequent in-dialog re-SUBSCRIBEs are expected to be routed with loose_route(), which doesn't seem to handle things properly.
<!--
If the issue can be reproduced, describe how it can be done.
-->

#### Debugging Data
I'm attaching kamailio logs with debug=4, cfg_trace
<!--
If you got a core dump, use gdb to extract troubleshooting data - full backtrace,
local variables and the list of the code at the issue location.

  gdb /path/to/kamailio /path/to/corefile
  bt full
  info locals
  list

If you are familiar with gdb, feel free to attach more of what you consider to
be relevant.
-->


#### Log Messages
See attachments
<!--
Check the syslog file and if there are relevant log messages printed by Kamailio, add them next, or attach to issue, or provide a link to download them (e.g., to a pastebin site).
-->


#### SIP Traffic
Please see: https://www.cloudshark.org/captures/d2643aae7f2a
<!--
If the issue is exposed by processing specific SIP messages, grab them with ngrep or save in a pcap file, then add them next, or attach to issue, or provide a link to download them (e.g., to a pastebin site).
-->


### Possible Solutions

Using topoh instead for topos, but unfortunately this will break communication for other reasons (messages too large/UDP fragmentation for some peers).

### Additional Information
  * **Kamailio Version**
Tried with kamailio 5.1.6 and kamailio 5.3.0-dev0
deb.kamailio.org repositories were used to acquire binaries for both versions

* **Operating System**:
Debian Stretch
<!--
Details about the operating system, the type: Linux (e.g.,: Debian 8.4, Ubuntu 16.04, CentOS 7.1, ...), MacOS, xBSD, Solaris, ...;
Kernel details (output of `uname -a`)
-->
[resubscribe.log](https://github.com/kamailio/kamailio/files/2586440/resubscribe.log)





-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/kamailio/kamailio/issues/1724
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.kamailio.org/pipermail/sr-dev/attachments/20181115/0cbc6693/attachment.html>