feat(mmds): Add flag for making MMDS operate like EC2 IMDS #5310
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The snapshot versioning follows the semantic versioning (i.e. snapshot restore is allowed only if the restore major version is same as the snapshot major version and the restore minor version is greater than or equal to the snapshot minor version). We already bumped the major version up multiple times since we added `mmds_version` state. That means snapshots taken when `mmds_version` didn't exist are not able to be restored in the current version. The code to restore such snapshots is no longer needed. Signed-off-by: Takahiro Itazuri <[email protected]>
Currently the only MMDS-related state saved in the snapshot is the version info. To enable persisting more MMDS-related state, generalize the struct for MMDS state. Bumped up the snapshot major version since it is a breaking change. Signed-off-by: Takahiro Itazuri <[email protected]>
The method sets not only the version but also the AAD. Signed-off-by: Takahiro Itazuri <[email protected]>
roypat
previously approved these changes
Jul 22, 2025
Manciukic
previously approved these changes
Jul 22, 2025
While EC2 IMDS only supports text/plain and ignores Accept header, Firecracker MMDS supports not only text/plain but also application/json. If users don't have the control of libraries that set "Accept: application/json" but expect MMDS to behave like EC2 IMDS, the above difference becomes a problem. Not to break existing workloads, add a new flag `imds_compat` (default to false) to PUT /mmds/config API. Signed-off-by: Takahiro Itazuri <[email protected]>
Manciukic
previously approved these changes
Jul 23, 2025
`_validate_mmds_snapshot()` is used only once. Signed-off-by: Takahiro Itazuri <[email protected]>
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@Manciukic Sorry, I needed to fix a style error (unused import)... |
Manciukic
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Jul 23, 2025
roypat
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Jul 24, 2025
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Changes
Added an optional
imds_compatfield (default to false if not provided) to PUT requests to/mmds/configto enforce MMDS to always respond plain text contents in the IMDS format regardless of theAcceptheader in requests.Reason
While EC2 IMDS only supports
text/plaincontent type and ignoresAcceptheader, Firecracker MMDS supports not onlytext/plainbut alsoapplication/json. If users don't have the control of libraries that set "Accept: application/json" but expect MMDS to behave like EC2 IMDS, the above difference becomes a problem.License Acceptance
By submitting this pull request, I confirm that my contribution is made under
the terms of the Apache 2.0 license. For more information on following Developer
Certificate of Origin and signing off your commits, please check
CONTRIBUTING.md.PR Checklist
tools/devtool checkbuild --allto verify that the PR passesbuild checks on all supported architectures.
tools/devtool checkstyleto verify that the PR passes theautomated style checks.
how they are solving the problem in a clear and encompassing way.
in the PR.
CHANGELOG.md.[ ] If a specific issue led to this PR, this PR closes the issue.Runbook for Firecracker API changes.
integration tests.
[ ] I have linked an issue to every newTODO.rust-vmm.