Function isc_match_filter() got a new local variable firstflag in order to handle the case where a FAILURE_ROUTE callback is received before the first AS has been contacted. The firstflag is also forwarded to function isc_forward() as parameter.

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#### Pre-Submission Checklist <!-- Go over all points below, and after creating the PR, tick all the checkboxes that apply --> <!-- All points should be verified, otherwise, read the CONTRIBUTING guidelines from above--> <!-- If you're unsure about any of these, don't hesitate to ask on sr-dev mailing list --> - [x] Commit message has the format required by CONTRIBUTING guide - [x] Commits are split per component (core, individual modules, libs, utils, ...) - [x] Each component has a single commit (if not, squash them into one commit) - [x] No commits to README files for modules (changes must be done to docbook files in `doc/` subfolder, the README file is autogenerated)

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#### Checklist: <!-- Go over all points below, and after creating the PR, tick the checkboxes that apply --> - [x] PR should be backported to stable branches - [x] Tested changes locally against Version 5.1.0 - [x] Related to issue #1168 (replace XXXX with an open issue number)

#### Description <!-- Describe your changes in detail --> This is the 5.1 pull request, which was created by cherry-pick from the master pull request You can view, comment on, or merge this pull request online at:

https://github.com/kamailio/kamailio/pull/1553

-- Commit Summary --

* ims_isc: initial fix of issue #1168

-- File Changes --

M src/modules/ims_isc/ims_isc_mod.c (9) M src/modules/ims_isc/isc.c (4) M src/modules/ims_isc/isc.h (2)

-- Patch Links --

https://github.com/kamailio/kamailio/pull/1553.patch https://github.com/kamailio/kamailio/pull/1553.diff