Attach a guest the way its own interface asks - #20
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A cell states a single attachment mode for every guest it runs. That is accurate while a cell runs one kind of guest, and wrong as soon as it runs two, because how a hypervisor learns about its device differs by guest. An interface that states its own attachment mode now decides for itself, and the cell-wide mode covers every interface that states none. The new HypervisorDeclared mode renders a tap attachment whose device is described to the hypervisor rather than discovered from the node, which the tap plugin reads from a single field in the attachment's CNI configuration. The field is omitted for every other attachment. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
scotwells
marked this pull request as ready for review
September 11, 2026 23:31
privateip
approved these changes
Sep 11, 2026
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A cell states one attachment mode for every guest it runs. That holds while a cell runs one kind of guest and breaks as soon as it runs two, because hypervisors differ in how they learn that their network device exists: some find it from the node, others have to be handed a description of it.
An interface that states its own attachment mode now decides how it is attached, and the cell-wide setting continues to cover every interface that states none. A guest asking to be handed its device gets a tap attachment whose description is written for its hypervisor to read; every other guest is attached exactly as before, byte for byte.
Nothing in any running cell changes until a workload asks for the new mode, and nothing asks for it yet. The cell-wide setting stays required and keeps working unchanged.
Depends on datum-cloud/network-services-operator#450, which defines the mode.
Testing
Unit suite and linters pass. The end-to-end suite could not run locally because the test cluster is unreachable from this machine, which reproduces on unmodified main.
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