Refactor slow activities from nm-dispatcher script into separate listener service#680
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lmagyar wants to merge 4 commits into
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Refactor slow activities from nm-dispatcher script into separate listener service#680lmagyar wants to merge 4 commits into
lmagyar wants to merge 4 commits into
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WalkthroughThe dispatcher script refactors from direct synchronous subnet protection to queue-based enqueuing. New s6-overlay services ( ChangesSubnet Protection Async Queue Architecture
Sequence DiagramsequenceDiagram
participant NM as NetworkManager
participant Disp as Dispatcher Script
participant Queue as FIFO Queue
participant Listener as nm-dispatcher-listener
participant Routes as Route Protection
rect rgb(0, 100, 200, 0.5)
Note over NM,Routes: Old Flow (Synchronous, Blocking)
NM->>Disp: Interface up/down event
Disp->>Routes: protect-subnet-routes (blocks)
Routes->>Listener: Wait for Supervisor API
Listener-->>Routes: Timeout/Delay
Routes-->>Disp: Complete (slow)
Disp-->>NM: Dispatcher done (10+ min delay)
end
rect rgb(0, 150, 100, 0.5)
Note over NM,Routes: New Flow (Asynchronous, Non-blocking)
NM->>Disp: Interface up/down event
Disp->>Queue: Enqueue action (fast return)
Disp-->>NM: Dispatcher done (immediate)
Queue->>Listener: Read action from queue
Listener->>Routes: protect-subnet-routes (async)
Routes-->>Listener: Complete
Listener->>Listener: Update exit status
end
Estimated code review effort🎯 4 (Complex) | ⏱️ ~45 minutes Possibly related PRs
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This was referenced May 3, 2026
lmagyar
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Actionable comments posted: 2
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.
Inline comments:
In `@tailscale/rootfs/etc/NetworkManager/dispatcher.d/protect-subnets`:
- Around line 17-21: Before writing to the listener queue, verify
NM_DISPATCHER_LISTENER_QUEUE exists and is a FIFO (use [ -p
"$NM_DISPATCHER_LISTENER_QUEUE" ]) and wait with a short timeout (e.g., loop up
to a few seconds) for it to appear as a FIFO; if it never becomes a FIFO, log
fatal and exit (same behavior as current error path). Do not create a regular
file by redirecting into a non-existent path; instead fail fast when the FIFO is
absent or wrong type. Use the existing variables DEVICE_IP_IFACE and
NM_DISPATCHER_ACTION for the payload and preserve the current exit behavior that
writes to /run/s6-linux-init-container-results/exitcode and calls halt if the
check/write fails.
In `@tailscale/rootfs/etc/s6-overlay/s6-rc.d/nm-dispatcher-listener/run`:
- Around line 22-25: The script must fail fast if mkfifo fails or the path is
not a FIFO: before executing "exec 4<>\"${NM_DISPATCHER_LISTENER_QUEUE}\"",
attempt to create the FIFO with mkfifo and then validate the path is a FIFO
using a POSIX test (e.g., [ -p "$NM_DISPATCHER_LISTENER_QUEUE" ]); if mkfifo
fails and the path is absent or exists but is not a FIFO, write an error and
exit non‑zero so the listener doesn't proceed to "exec 4<>" on a regular file.
Update the run script around the mkfifo/exec 4<> sequence to perform this
validation and early exit when the queue is not a proper FIFO.
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📒 Files selected for processing (19)
tailscale/rootfs/etc/NetworkManager/dispatcher.d/protect-subnetstailscale/rootfs/etc/s6-overlay/s6-rc.d/init-protect-subnets/dependencies.d/local-networktailscale/rootfs/etc/s6-overlay/s6-rc.d/init-protect-subnets/downtailscale/rootfs/etc/s6-overlay/s6-rc.d/init-protect-subnets/finishtailscale/rootfs/etc/s6-overlay/s6-rc.d/init-protect-subnets/runtailscale/rootfs/etc/s6-overlay/s6-rc.d/init-protect-subnets/typetailscale/rootfs/etc/s6-overlay/s6-rc.d/init-protect-subnets/uptailscale/rootfs/etc/s6-overlay/s6-rc.d/nm-dispatcher-listener/dependencies.d/init-protect-subnetstailscale/rootfs/etc/s6-overlay/s6-rc.d/nm-dispatcher-listener/finishtailscale/rootfs/etc/s6-overlay/s6-rc.d/nm-dispatcher-listener/runtailscale/rootfs/etc/s6-overlay/s6-rc.d/nm-dispatcher-listener/typetailscale/rootfs/etc/s6-overlay/s6-rc.d/nm-dispatcher/dependencies.d/nm-dispatcher-listenertailscale/rootfs/etc/s6-overlay/s6-rc.d/nm-dispatcher/finishtailscale/rootfs/etc/s6-overlay/s6-rc.d/nm-dispatcher/runtailscale/rootfs/etc/s6-overlay/s6-rc.d/nm-dispatcher/typetailscale/rootfs/etc/s6-overlay/s6-rc.d/protect-subnets/contents.d/init-protect-subnetstailscale/rootfs/etc/s6-overlay/s6-rc.d/protect-subnets/contents.d/nm-dispatchertailscale/rootfs/etc/s6-overlay/s6-rc.d/protect-subnets/contents.d/nm-dispatcher-listenertailscale/rootfs/etc/s6-overlay/s6-rc.d/protect-subnets/type
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Looks quite neat, and I've tested it on my end, Tailscale no longer blocks Supervisor restart with this change (even with ✔️ LGTM! |
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Thank you for the feedback! |
lmagyar
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bugfix
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Proposed Changes
There is a plain linux pipe between the 2 services, each nm-dispatcher action is 1 line in it, then all the slow thing happen in the listener service sequentially - as currently, but returning to nm-dispatcher quickly.
Related Issues
fixes #678
closes #679
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