in_forward: Fix of handshaking on forward protocol [Backport to 4.0]

[cosmo0920]

Backporting of #11026 and #11028.

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Testing
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Documentation

• Documentation required for this feature

Backporting

• Backport to latest stable release.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch in_forward-protocol-fix-4.0

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