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test(minvmd): vsock stub and bridge end-to-end test - #350

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test(minvmd): vsock stub and bridge end-to-end test#350
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Closes #328

Summary

Implements the vsock stub and bridge end-to-end tests for the minvmd host daemon (R3.3, R3.4, R3.5, R2.4 READY round-trip).

Changes

crates/minvmd/tests/bridge_e2e.rs (new)

Bridge end-to-end test (R3.3, R3.4):

  • Gated on MINVMD_E2E=1, #[ignore], macOS-only.
  • Boots the VM via minvmd boot --foreground, waits up to 15 s for vm-up.
  • Opens 5 concurrent host UDS connections to $XDG_RUNTIME_DIR/minimal/minimald.sock.
  • Each writes a distinct payload (BRIDGE_PAYLOAD_0..4\n) and reads it back through the libkrun UDS↔vsock bridge.
  • All 5 must succeed — demonstrates libkrun-multiplexed bidirectional bridging.
  • Isolated per run via tempfile::TempDir as XDG_RUNTIME_DIR.

crates/minvmd/src/vm.rs (modified)

Adds a comment near the krun_add_vsock_port2 call documenting the TSI ~62-concurrent-connection cap (R3.5).

Proof Artifacts

Proof 1 — Bridge concurrent round-trip (R3.3, R3.4)

MINVMD_E2E=1 cargo test -p minvmd --test bridge_e2e -- --include-ignored

Boots a VM, opens 5 concurrent host UDS connections, each writes a distinct payload and reads it back — all 5 succeed.

Proof 2 — Boot→READY round-trip (R2.4)

MINVMD_E2E=1 cargo test -p minvmd --test boot_e2e -- --include-ignored

The pre-existing tests/boot_e2e.rs asserts the full READY marker round-trip: the guest stub writes READY\n to vsock port 7350 (VSOCK_MARKER_PORT) and the host parent receives vm-up on stdout.

Proof 3 — TSI cap comment (R3.5)

crates/minvmd/src/vm.rs now contains a comment near krun_add_vsock_port2 documenting the TSI ~62-concurrent-connection cap.

Guest-side vsock stub (R3.4)

The guest stub source is already embedded in scripts/build-rootfs.sh as /sbin/minvmd-stub-init:

  1. Connects to host vsock CID 2 port 7350 and writes READY\n (R2.4 marker).
  2. Execs socat VSOCK-LISTEN:2222,fork EXEC:cat — listens on vsock 2222 and echoes per connection (R3.3, R3.4).

Merging this pull request closes task sub-issue #328. Once every task sub-issue under tracking issue #311 is closed, the pipeline advances to sdd:done for final human review and close.

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Generated by sdd-execute (sonnet tier) for issue #328 · ● 32.4M ·

Summary by CodeRabbit

  • Tests

    • Added a macOS end-to-end bridge test (ignored by default) that runs concurrent host↔guest connection workers with retries and byte-for-byte echo validation.
  • Documentation

    • Clarified macOS notes about the connection‑capacity cap and the resulting queuing behavior on the host bridge.
  • Chores

    • macOS CI updated to build and run the new bridge E2E alongside existing boot tests using the codesigned binaries.

…R3.5)

Closes #328

- Add tests/bridge_e2e.rs: boots a VM via minvmd boot --foreground, waits
  for vm-up, then opens 5 concurrent host UDS connections to the minimald
  bridge socket; each writes a distinct payload and reads it back through
  the libkrun UDS↔vsock bridge — all 5 must succeed (R3.3, R3.4).
  XDG_RUNTIME_DIR is isolated per run via tempfile::TempDir.
- Add TSI ~62-concurrent-connection cap comment to vm.rs near the
  krun_add_vsock_port2 call (R3.5).

The boot→READY round-trip (R2.4) is verified by the pre-existing
tests/boot_e2e.rs, which was moved from #326. The guest-side vsock stub
(/sbin/minvmd-stub-init) source is already embedded in
scripts/build-rootfs.sh: it sends READY\n to vsock port 7350 and then
exec-s socat VSOCK-LISTEN:2222,fork EXEC:cat for the bridge (R3.4).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Review Change Stack

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info
⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ce5ebe2c-26b9-44f5-9f40-b2d067a7b9d3

📥 Commits

Reviewing files that changed from the base of the PR and between d5955be and 9feebda.

📒 Files selected for processing (1)
  • crates/minvmd/tests/bridge_e2e.rs

📝 Walkthrough

Walkthrough

Adds a macOS-only end-to-end test that boots minvmd boot --foreground, waits for the guest vm-up marker, then performs 5 concurrent host UDS↔vsock round-trips; documents the TSI ~62 concurrent-connection cap in VmConfig::apply and updates macOS CI to build and run the new test binary.

Changes

Bridge E2E Test and TSI Documentation

Layer / File(s) Summary
TSI connection limit documentation
crates/minvmd/src/vm.rs
Inline comments in VmConfig::apply (macOS) document the TSI ~62 concurrent connection limit and resulting connection-queueing behavior on the host transport/bridge port.
macOS CI build and run
.github/workflows/ci-macos.yml (lines 96–129)
Pre-codesign build changed to build both boot_e2e and bridge_e2e (--no-run) and added a Bridge E2E step that finds the bridge_e2e binary, sets E2E env vars, and executes it with --include-ignored --nocapture.
Bridge E2E test structure and setup
crates/minvmd/tests/bridge_e2e.rs (lines 1–88)
New macOS-gated, ignored-by-default test file with env-var gating (MINVMD_E2E, kernel/rootfs), compile-time constants, isolated XDG_RUNTIME_DIR/XDG_STATE_HOME, spawns minvmd boot --foreground, and waits up to 15s for vm-up with cleanup on timeout.
Concurrent bridge round-trip validation and cleanup
crates/minvmd/tests/bridge_e2e.rs (lines 90–173)
Five concurrent threads connect to the bridge UDS socket, write distinct payloads, half-close the write side, read echoed responses with read_exact, validate payload equality, collect results, then kill/wait for the minvmd child and assert all round-trips succeeded.

Sequence Diagram(s)

sequenceDiagram
  participant TestBinary
  participant minvmd
  participant HostUDS
  participant GuestVsock
  TestBinary->>minvmd: spawn `minvmd boot --foreground`
  minvmd->>GuestVsock: configure vsock bridge port
  loop 5 concurrent threads
    TestBinary->>HostUDS: connect and write payload
    HostUDS->>GuestVsock: libkrun forwards payload via vsock
    GuestVsock-->>HostUDS: echo payload back
    HostUDS-->>TestBinary: return echoed payload
  end
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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related issues

  • #311: The added macOS bridge E2E test, MINVMD_E2E gating, and TSI doc implement the host UDS ↔ guest vsock bridging and test objectives referenced by this issue.

Possibly related PRs

Suggested reviewers

  • norrietaylor
  • evanspearman

Poem

🐰 Five threads hop across the bridge at dawn,

Each byte a carrot, quickly drawn.
The TSI gate hums with sixty-two lights,
Echoes bound back in playful flights.
🥕✨

🚥 Pre-merge checks | ✅ 5
✅ Passed checks (5 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title accurately summarizes the main changes: adding vsock stub and bridge end-to-end tests for minvmd.
Linked Issues check ✅ Passed All coding requirements from #328 are met: bridge_e2e test with concurrent connections, TSI cap documentation, and boot_e2e READY round-trip validation.
Out of Scope Changes check ✅ Passed All changes (bridge_e2e test, vm.rs comment, CI workflow) directly support the linked #328 objectives; no extraneous modifications detected.
Docstring Coverage ✅ Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.

✨ Finishing Touches
📝 Generate docstrings
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  • Commit on current branch

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🧹 Nitpick comments (1)
crates/minvmd/tests/bridge_e2e.rs (1)

90-92: 💤 Low value

Fixed sleep introduces minor race condition.

The 200ms sleep assumes the guest's socat listener will be ready within that window. While the subsequent retry logic (lines 103-122) mitigates failures, consider documenting that the retry loop handles race conditions if the sleep is insufficient.

📝 Optional: clarify retry safety in comment
-    // The guest stub sends READY before exec-ing the vsock 2222 listener;
-    // give socat a moment to start accepting.
+    // The guest stub sends READY before exec-ing the vsock 2222 listener.
+    // Brief sleep to reduce initial connection failures; the per-connection
+    // retry loop (lines 103-122) handles races if socat is not yet listening.
     std::thread::sleep(Duration::from_millis(200));
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@crates/minvmd/tests/bridge_e2e.rs` around lines 90 - 92, The fixed 200ms
sleep (std::thread::sleep(Duration::from_millis(200))) can still race with the
guest socat listener; update the inline comment above that sleep to explicitly
state that the subsequent connect retry loop handles any remaining race (the
retry logic that attempts to connect to vsock/2222 and retries on failure), so
future readers know the sleep is a best-effort delay and the retry loop provides
correctness; optionally mention alternatives (increase sleep or poll for socket)
as notes for future change.
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@crates/minvmd/tests/bridge_e2e.rs`:
- Around line 90-92: The fixed 200ms sleep
(std::thread::sleep(Duration::from_millis(200))) can still race with the guest
socat listener; update the inline comment above that sleep to explicitly state
that the subsequent connect retry loop handles any remaining race (the retry
logic that attempts to connect to vsock/2222 and retries on failure), so future
readers know the sleep is a best-effort delay and the retry loop provides
correctness; optionally mention alternatives (increase sleep or poll for socket)
as notes for future change.

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Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 1204aea8-852c-471b-9158-9812f9cf8dca

📥 Commits

Reviewing files that changed from the base of the PR and between 9dddd76 and 6d4ee58.

📒 Files selected for processing (2)
  • crates/minvmd/src/vm.rs
  • crates/minvmd/tests/bridge_e2e.rs

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@gominimal-aw-bot gominimal-aw-bot Bot added the needs-human An agent handed off; a human must act, then clear this label. label Jun 4, 2026
@gominimal-aw-bot gominimal-aw-bot Bot mentioned this pull request Jun 4, 2026
bridge_e2e was added by #350 but wired into no CI job, so the
self-hosted Apple Silicon runner compiled it (via `cargo test -p
minvmd`) yet never executed its `#[ignore]` body. The new test ran
nowhere despite the macOS e2e infrastructure existing.

Build the bridge_e2e harness alongside boot_e2e before the single
codesign, then run its binary directly with the cache-pulled kernel and
staged rootfs — mirroring the boot_e2e gating step so the codesigned
minvmd keeps its hypervisor entitlement.

Refs: #328
@norrietaylor norrietaylor removed the needs-human An agent handed off; a human must act, then clear this label. label Jun 5, 2026
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@gominimal-aw-bot gominimal-aw-bot Bot added the needs-human An agent handed off; a human must act, then clear this label. label Jun 5, 2026
The 200ms sleep is best-effort; update the comment to explicitly state
that the per-connection retry loop handles races if socat is not yet
listening, so future readers understand the correctness guarantee.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Commit pushed: d5955be

Generated by sdd-execute (sonnet tier) · ● 5.1M

@norrietaylor norrietaylor removed the needs-human An agent handed off; a human must act, then clear this label. label Jun 5, 2026
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/revise pull the latest branch and fix the failing test

Relying on write-side shutdown propagation through the libkrun
UDS\u2194vsock bridge caused read_to_string to block until the 5-second
IO timeout: the bridge does not reliably translate a UDS half-close
into a vsock EOF that socat's cat sees.

Switch to read_exact(payload.len()), which reads back exactly the
bytes we sent without waiting for EOF. cat echoes data as it arrives,
so this is sufficient and never blocks.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Commit pushed: 9feebda

Generated by sdd-execute (sonnet tier) · ● 47.4M

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Commit pushed: 64d1f90

Fix: replaced shutdown(Write) + read_to_string with read_exact(payload.len()) in bridge_e2e_concurrent_round_trip.

The original approach relied on write-side half-close propagating through libkrun's UDS↔vsock bridge so the guest's cat would see EOF and close the connection. If the bridge doesn't translate that half-close correctly, read_to_string blocks for the full 5-second IO_TIMEOUT and the test fails.

read_exact reads back exactly as many bytes as were written. cat echoes data as it arrives, so this always terminates without needing EOF and doesn't depend on bridge half-close semantics.

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Generated by sdd-execute (sonnet tier) for issue #350 · ● 47.4M ·

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Generated by sdd-review for issue #350 · ● 19.6M

Comment on lines +126 to +129
MINVMD_E2E=1 \
MINVMD_KERNEL_PATH="$RUNNER_TEMP/kernel/vmlinuz" \
MINVMD_ROOTFS_PATH="$(scripts/build-rootfs.sh --print-path)" \
"$testbin" --include-ignored --nocapture

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LOW · correctness — Missing MINVMD_BOOT_LOG capture.

The adjacent boot E2E step (line 115) sets MINVMD_BOOT_LOG="$RUNNER_TEMP/boot.log" so the hvc0 console output is captured and uploaded on failure. This step boots its own VM but omits the env var, so if this boot fails there is no console log to debug it — the upload step only has the boot_e2e log.

Consider adding e.g. MINVMD_BOOT_LOG="$RUNNER_TEMP/bridge-boot.log" and a matching upload step (or adjusting the existing upload to glob both).

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sdd-validate · Implementation boundary

Boundary: Implementation (no spec or architecture files changed).
Task: #328 (Vsock stub and bridge end-to-end test)
Feature: #311 (full-path; already at sdd:review)
Gates applied: Proof artifacts · Changed files · No credentials

Findings

# Gate Severity Finding
1 Proof artifacts Info Bridge E2E test (Proof 1) deferred to consumer CI
2 Proof artifacts Info Boot E2E test (Proof 2) deferred to consumer CI
3 Proof artifacts ✅ Pass TSI cap comment (Proof 3) verified in source
4 Changed files Blocker .github/workflows/ci-macos.yml is a protected path
5 Changed files Warning crates/minvmd/src/vm.rs is outside files-in-scope
6 No credentials ✅ Pass No credentials found in diff

Details

Finding 1 — Info · Proof 1 deferred to consumer CI.
MINVMD_E2E=1 cargo test -p minvmd --test bridge_e2e -- --include-ignored requires macOS, libkrun, a kernel image, and an Alpine rootfs. This agent runs on Linux in a network-restricted container — infrastructure limit, not a code defect. Consumer CI covers this: .github/workflows/ci-macos.yml step "Bridge E2E (concurrent UDS↔vsock round-trip)" runs the identical binary with --include-ignored. Check-run status on the head SHA is unreadable (403); coverage identified from the workflow file content in the diff.

Finding 2 — Info · Proof 2 deferred to consumer CI.
MINVMD_E2E=1 cargo test -p minvmd --test boot_e2e -- --include-ignored has the same macOS + libkrun infrastructure requirement. Consumer CI covers this: .github/workflows/ci-macos.yml step "Boot E2E (READY round-trip)" runs the pre-existing boot_e2e binary. Same 403 limitation on check-run status.

Finding 3 — Pass · TSI cap comment verified.
crates/minvmd/src/vm.rs:64-67 contains the R3.5 comment documenting the TSI ~62-concurrent-connection cap directly above ctx.add_vsock_port2(...). Matches proof artifact 3.

Finding 4 — Blocker · Protected path change outside task scope.
.github/workflows/ci-macos.yml is under the protected .github/ path and is not listed in the task's files in scope: block. The change adds the new bridge_e2e test to the macOS CI pipeline (build step and run step) — it is additive and does not alter existing behavior, but the gate requires human verification of any protected-path modification.

Finding 5 — Warning · vm.rs outside files-in-scope.
crates/minvmd/src/vm.rs is not in the task's files in scope: block. However, proof artifact 3 explicitly requires this change ("A comment near the krun_add_vsock_port2 call in vm.rs"), indicating the task definition's scope list is incomplete rather than the change being unauthorized. The modification is a 4-line documentation comment only.

Finding 6 — Pass · No credentials.
The diff introduces no secrets, tokens, keys, or credentials.


Action required: Finding 4 is a Blocker — needs-human applied. A human must verify the .github/workflows/ci-macos.yml change is acceptable. The CI change adds the bridge E2E test alongside the existing boot E2E test in the macOS CI pipeline; no security-sensitive modifications were observed.

Lifecycle: Feature #311 already carries sdd:review — no lifecycle move needed.

Generated by sdd-validate for issue #350 · ● 15.8M ·

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Proofs have been validated in CI

@norrietaylor norrietaylor removed the needs-human An agent handed off; a human must act, then clear this label. label Jun 5, 2026
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Unresolved review comment — protected path edit required

The unresolved thread from sdd-review (discussion_r3360022935) identifies a missing MINVMD_BOOT_LOG capture in the Bridge E2E step of .github/workflows/ci-macos.yml. The concern is valid: if the bridge test's VM boot fails, there is no console log available for debugging (the upload step only captures boot.log from the Boot E2E step).

Addressing this requires editing .github/workflows/ci-macos.yml, which is a protected path. This agent cannot make that edit.

Required change (.github/workflows/ci-macos.yml, Bridge E2E step, around line 126–129):

  MINVMD_E2E=1 \
  MINVMD_KERNEL_PATH="$RUNNER_TEMP/kernel/vmlinuz" \
  MINVMD_ROOTFS_PATH="$(scripts/build-rootfs.sh --print-path)" \
+  MINVMD_BOOT_LOG="$RUNNER_TEMP/bridge-boot.log" \
    "$testbin" --include-ignored --nocapture

And update the upload step (around line 130–138) to capture both log files, e.g. by globbing:

  with:
    name: minvmd-boot-log
-   path: ${{ runner.temp }}/boot.log
+   path: ${{ runner.temp }}/*-boot.log
    if-no-files-found: ignore

Note on the CodeRabbit nitpick (bridge_e2e.rs lines 90–92): already addressed in the current code — the comment now reads "retry loop below handles races if socat is not yet listening", which captures the intent of the suggestion. No further change needed there.

Please make the .github/ change and clear the needs-human label to resume.

Generated by sdd-execute (sonnet tier) for issue #350 · ● 4.7M ·

@norrietaylor
norrietaylor merged commit c332b4c into main Jun 5, 2026
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norrietaylor deleted the sdd/328-vsock-stub-bridge-e2e-52cae33ae75383f5 branch June 5, 2026 03:05
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Vsock stub and bridge end-to-end test

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