[21065] Bugfix: correct liveliness state in a multiple reader - one writer scenario (backport #4822)

[mergify]

Description

This PR corrects a misbehavior given in a single writer - multiple readers scenario. When the writer is destroyed, the WriterProxy is removed from readers. When it is removed from the first one, the LivelinessManager::remove_writer() returns false as --writer.count is 1, hence the liveliness_changed callback is not triggered (callback_ within LivelinessManager is not invoked). When the WriterProxy is deleted from the second reader, the LivelinessManager::remove_writer() correctly removes the writer and fires the callback. The problem in this case is that, later, in WLP::sub_liveliness_changed() the update_liveliness_changed_status() is only called for this later reader, since the first one is not matched anymore and reader->matched_writer_is_matched() returns false, corrupting its liveliness state. In this situation, if the writer wakes up again, the first reader is going to return an alive_count of 2 instead of 1.

The fix proposes that every time we unpair a WriterProxy from a reader, we should also update the liveliness state for that particular reader. The solution tries to avoid defining extra collections for tracking readers/writers.

@Mergifyio backport 2.14.x 2.13.x 2.10.x 2.6.x

Fixes #4610

Contributor Checklist

• Commit messages follow the project guidelines.

• The code follows the style guidelines of this project.

• Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally

• Any new/modified methods have been properly documented using Doxygen.

• NO Any new configuration API has an equivalent XML API (with the corresponding XSD extension)

• Changes are backport compatible: they do NOT break ABI nor change library core behavior.

• Changes are API compatible.

• NO New feature has been added to the versions.md file (if applicable).

• NO New feature has been documented/Current behavior is correctly described in the documentation.

• Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

---

This is an automatic backport of pull request #4822 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of df90943 has failed:

On branch mergify/bp/2.13.x/pr-4822
Your branch is up to date with 'origin/2.13.x'.

You are currently cherry-picking commit df909438f.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   src/cpp/rtps/builtin/liveliness/WLP.cpp
	modified:   src/cpp/rtps/reader/StatefulReader.cpp
	modified:   src/cpp/rtps/reader/StatelessReader.cpp
	modified:   test/blackbox/common/BlackboxTestsLivelinessQos.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   include/fastdds/rtps/writer/LivelinessManager.h
	both modified:   src/cpp/rtps/writer/LivelinessManager.cpp
	both modified:   test/unittest/rtps/writer/LivelinessManagerTests.cpp

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[JesusPoderoso]

@richiprosima please test this

[JesusPoderoso]

LGTM