docs: clarify host-level firewall requirements#5860
Merged
JamesC1305 merged 3 commits intoMay 6, 2026
Conversation
Clarify threat model to emphasise that outbound traffic from the guest should be treated as untrusted, and that host-level filtering should be implemented. Add a section to the MMDS design docs to emphasise that the MMDS network stack should not be relied on to filter guest egress. Add an entry to prod host setup suggesting firewall rules should be setup for guest VM outbound traffic. Also add a comment to write_to_mmds_or_tap to clarify that Firecracker is not responsible for packet filtering, and therefore we will not fix a TOCTOU allowing guests to race and avoid MMDS packet detouring. Signed-off-by: James Curtis <jxcurtis@amazon.co.uk>
JamesC1305
added
the
Status: Awaiting review
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #5860 +/- ##
==========================================
+ Coverage 82.62% 82.80% +0.18%
==========================================
Files 275 277 +2
Lines 29750 29895 +145
==========================================
+ Hits 24581 24756 +175
+ Misses 5169 5139 -30
Flags with carried forward coverage won't be shown. Click here to find out more. ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
|
Manciukic
approved these changes
Apr 29, 2026
zulinx86
approved these changes
May 5, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Clarify threat model to emphasise that outbound traffic from the guest should be treated as untrusted, and that host-level filtering should be implemented.
Add a section to the MMDS design docs to emphasise that the MMDS network stack should not be relied on to filter guest egress.
Add an entry to prod host setup suggesting firewall rules should be setup for guest VM outbound traffic.
Also add a comment to write_to_mmds_or_tap to clarify that Firecracker is not responsible for packet filtering, and therefore we will not fix a TOCTOU allowing guests to race and avoid MMDS packet detouring.
Changes
...
Reason
...
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.Runbook for Firecracker API changes.
integration tests.
TODO.rust-vmm.