When upgrading from stretch to buster the kamailio packages aren't upgraded because the 5.3.1+stretch version is greater than 5.3.1+buster: ``` $ dpkg --compare-versions 5.3.1+stretch gt 5.3.1+buster ; echo $? 0 ```
The package version should include the release version instead of its codename, e.g. 5.3.1+deb9u1 & 5.3.1+deb10u1 like done for [stable updates](https://www.debian.org/doc/manuals/developers-reference/pkgs.en.html#upload-...): ``` $ dpkg --compare-versions 5.3.1+deb10u1 gt 5.3.1+deb9u1 ; echo $? 0 ```