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#### Description <!-- Describe your changes in detail --> This PR fixes an issue regarding KEMI framework for onsend_route.

KSR.set_drop() in [ksr_onsend_route](https://www.kamailio.org/wikidocs/cookbooks/5.7.x/core/#onsend_route) does not make kamailio dropping the message when using kemi (python3) (probably holds true for other engines too):

This is exactly the example from [documentation](https://kamailio.org/docs/tutorials/devel/kamailio-kemi-framework/kemimods/#...): ``` def ksr_onsend_route(self, msg): KSR.set_drop() exit() ```

The issue arises because we are not setting `ret = 0` when the drop flag is set, but instead check if it's not set to return `ret=1` (The case for native that returns `0` but no `DROP_R_F` was set).

**Note**: KEMI Case: `ret = 1` always See [app_python3/apy_kemi.c](https://github.com/kamailio/kamailio/blob/79697b4d565665b696ee39021e27d82e71...) Native case: `ret` can be `0` for drop, or `1` for success You can view, comment on, or merge this pull request online at:

https://github.com/kamailio/kamailio/pull/3718

-- Commit Summary --

* core: Fix check to also work for KEMI framework

-- File Changes --

M src/core/onsend.c (13)

-- Patch Links --

https://github.com/kamailio/kamailio/pull/3718.patch https://github.com/kamailio/kamailio/pull/3718.diff