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Set the carrier of a tap according to the Link state of a port.
Otherwise, taps are always seen as up, meaning that:
FRR believes they are up when they may not.
No link events are recorded and we lose the ability to diagnose link flaps
they always show as up in the CLI, which lies.
Fix this by adding a method to set the carrier state of a tap and spawning a task in the cpbridge per bridgeport to set the carrier according to the bridgeport link state.
The generation of events is "restored" because when the tap carrier changes, the interface monitor gets a netlink event and propagates it.
Add method to set the carrier state of a tap device.
We will use this to "synchronize" the state of a tap (seen by FRR)
with the operational state of the interface/port that it represents.
Signed-off-by: Fredi Raspall <[email protected]>
Spawn a task to change the carrier of a tap according to the
Link status of a port so that the components that rely on the
taps (FRR) see the actual/similar state of ports.
Without this change, the status seen by the routing crate and FRR
would always be up since the tap devices are always up.
Signed-off-by: Fredi Raspall <[email protected]>
The tap device now exposes carrier control through TUNSETCARRIER. The bridge synchronizes tap carrier with port link state. Monitor tests check events after tap link and carrier changes.
Changes: Tap Carrier Synchronization
Layer / File(s)
Summary
Tap carrier control API interface-manager/src/interface/tap.rs
TapDevice::set_carrier applies TUNSETCARRIER to the tap descriptor and returns ioctl errors. A test checks the reported carrier after toggling it.
Bridge link synchronization dataplane/src/drivers/cpbridge.rs
A per-tap sync_tap task sets carrier according to port link state and exits when the link watch closes or cancellation occurs. The ARP bridge test reports Link::Up.
Tap link and carrier monitor tests interface-manager/src/monitor/mod.rs
Tests use TAP devices and rtnetlink to change link and carrier state, then check interface events and monitor cancellation.
Merge Risk: Minimal · up to e3276
The tap carrier and monitor changes are mergeable after normal checks; no concrete blocking issue remains.
Pre-merge checks: 5
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Status
Explanation
Title check
The title clearly describes the main change: aligning tap carrier state with port link state.
Description check
The description explains the tap carrier synchronization and its effect on link events.
Docstring Coverage
Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…
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Check skipped because no linked issues were found for this pull request.
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Full details: Docstring Coverage
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Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 6 functions across 3 files.
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🟡 Changes recommended
The bridge tests do not verify carrier transitions, leaving permanently enabled TAP carrier undetected without regression coverage of kernel carrier states and netlink notifications.
The test does not await _monitor, so it cannot detect a monitor that fails to stop.
Suggested fix
- let _monitor = tokio::spawn(InterfaceMonitor::run(ifmonitor));+ let monitor = tokio::spawn(InterfaceMonitor::run(ifmonitor));
+ assert!(!monitor.is_finished(), "monitor stopped before cancellation");
ct.cancel();
+ timeout(Duration::from_secs(5), monitor)+ .await+ .expect("monitor did not stop after cancellation")+ .expect("monitor task failed")+ .expect("monitor returned an error");
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Review comment at @interface-manager/src/monitor/mod.rs at line 363:
Update the cancellation test around InterfaceMonitor::run to retain the spawned
task’s JoinHandle instead of discarding it. Assert the monitor is still running
before cancellation, then await its completion with a bounded timeout and verify
both the task join and monitor result succeed.
Fix comments: Fix CodeRabbit comments on this PR
Prompt to fix all issues
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Inline comments:
Review comments at @interface-manager/src/monitor/mod.rs:
- Around line 345-346: Update the event-count condition in the test loop around
events_seen so it waits for and verifies the third event from bring_down_tap,
while preserving the existing event checks.
---
Nitpick comments:
Review comments at @interface-manager/src/monitor/mod.rs:
- Line 363: Update the cancellation test around InterfaceMonitor::run to retain
the spawned task’s JoinHandle instead of discarding it. Assert the monitor is
still running before cancellation, then await its completion with a bounded
timeout and verify both the task join and monitor result succeed.
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Actionable comments posted: 1
Fix comments: Fix CodeRabbit comments on this PR
Prompt to fix all issues
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Inline comments:
Review comments at @interface-manager/src/monitor/mod.rs:
- Line 333: Replace the fixed 200 ms sleep in both tests with a bounded
readiness signal or bounded polling of observable monitor state, and create the
TAP only after InterfaceMonitor::run is ready to observe its creation event.
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nl -ba interface-manager/src/interface/tap.rs | sed -n '235,350p'
Repository: githedgehog/dataplane
Length of output: 5937
Wait for monitor readiness before creating the TAP.
Both tests use a 200 ms sleep to wait for InterfaceMonitor::run. If the monitor starts late, it can miss the creation event and the test can time out.
Use a bounded readiness signal or bounded polling of observable monitor state before creating the TAP.
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Review comment at @interface-manager/src/monitor/mod.rs at line 333:
Replace the fixed 200 ms sleep in both tests with a bounded readiness signal or
bounded polling of observable monitor state, and create the TAP only after
InterfaceMonitor::run is ready to observe its creation event.
After applying the fix, consider running `coderabbit review --agent` for local
review. Visit https://docs.coderabbit.ai/cli?utm_source=ghpr
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Additional comments: 1
interface-manager/src/monitor/mod.rs: 1
433-433: Trivial · Maintainability & Code Quality · Low value
Unverified finding
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Await the monitor task after cancellation.
test_tap_carrier_is_seen_in_events calls ct.cancel() but discards the _monitor join handle. The test ends without confirming that the monitor stopped. A monitor error or panic goes unnoticed. test_interface_monitor already awaits the handle with a timeout. Apply the same check here.
Proposed fix
- let _monitor = tokio::spawn(InterfaceMonitor::run(ifmonitor));+ let monitor = tokio::spawn(InterfaceMonitor::run(ifmonitor));
ct.cancel();
++ timeout(Duration::from_secs(5), monitor)+ .await+ .expect("monitor did not stop after cancellation")+ .expect("monitor task failed")+ .expect("monitor returned an error");
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interface-manager/src/monitor/mod.rs
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1) Add test test_set_carrier() that checks if the set_carrier
method actually changes the carrier value, by pulling the link
from the kernel.
2) restore test_interface_monitor()
The test was disabled while the n_vm was not in place.
The prior test created a dummy interface. The n_vm does not
include support for dummy interfaces. Re-write the test
using a tap. No elevated caps are needed when run in n_vm.
3) add test for tap set_carrier() in interface monitor
Add a test that checks if by changing the carrier of a tap device
a netlink event is generated and the interface monitor generates
an EthEvent for it.
Signed-off-by: Fredi Raspall <[email protected]>
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Additional comments: 3
interface-manager/src/monitor/mod.rs: 3
375-375: Trivial · Maintainability & Code Quality · Low value
Unverified finding
Verification ran but could not confirm this finding. It is shown for review, not as a verified issue.
Fix the typo "foir" in the timeout messages.
Both expect messages read "no event foir the tap was heard". Change "foir" to "for".
Also applies to: 443-443
394-394: Trivial · Maintainability & Code Quality · Low value
Unverified finding
Verification ran but could not confirm this finding. It is shown for review, not as a verified issue.
Await the monitor task after cancellation in test_tap_carrier_is_seen_in_events.
The test cancels ct but drops the join handle. A monitor error or panic goes unnoticed. The first test already awaits the task. Apply the same check here for consistency.
Unverified finding
Verification ran but could not confirm this finding. It is shown for review, not as a verified issue.
Check the TAP events with an exact sequence guard.
The test matches events only by name. A repeated event with the same ifup value, for example from the kernel emitting two link messages for one change, can break the strict events_seen ordering. The assertions would then fail intermittently. The carrier test has the same risk: a link event whose ifup and carrier values do not change would fail the next assertion.
Consider skipping events whose state matches the previous event. This keeps the test tolerant of duplicate netlink messages.
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interface-manager/src/monitor/mod.rs
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bugSomething isn't workingci:+merge-readyRun all checks which will be run in the merge queue regardless of label statusci:+vlabEnable VLAB tests
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Set the carrier of a tap according to the Link state of a port.
Otherwise, taps are always seen as up, meaning that:
Fix this by adding a method to set the carrier state of a tap and spawning a task in the cpbridge per bridgeport to set the carrier according to the bridgeport link state.
The generation of events is "restored" because when the tap carrier changes, the interface monitor gets a netlink event and propagates it.