64 lines
3.6 KiB
Markdown
64 lines
3.6 KiB
Markdown
# E-1608 network scan -- design
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Date: 2026-11-02. Status: approved in conversation, awaiting written-spec review.
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## Goal
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The E-1608 connection form gets a "Scan network" row that finds boards and fills the address or the
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MAC from a click. Today a user must already know the address, or give a MAC and rely on a lookup.
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## Finding (tested on a real board, 2026-11-02)
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The board was at 169.254.88.75 on `net0`; the default route is `wlan0`. A `D` probe sent to
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255.255.255.255 with no binding found nothing (it left through `wlan0`). The same probe sent with
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`SO_BINDTODEVICE net0`, or bound to the interface address, or sent to a directed broadcast, or by
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unicast, was answered (64 bytes, first byte `D`). So a single limited broadcast is not enough on a
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host with several interfaces; the existing "find by MAC" lookup has the same flaw.
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## Discovery layer (`e1608_link.{hpp,cpp}`)
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- `class Scan` (non-blocking, one instance per scan): `Scan(port)` enumerates up, non-loopback IPv4
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interfaces with `IFF_BROADCAST` (`getifaddrs`), opens one UDP socket per interface bound to it
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(`SO_BINDTODEVICE`, falling back to binding the interface address if the call is refused), enables
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`SO_BROADCAST`, and sends `D` to 255.255.255.255 on each. `poll()` drains every socket without
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blocking and returns the devices found so far (E-1608 product id only, one entry per MAC, the same
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reply parsing as `discover`). The caller owns the clock.
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- `discover()` keeps its signature. A new overload or helper `discover_broadcast(port, wait_ms)` is
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`Scan` plus a blocking wait. `E1608Source`'s lookup uses it when the subnet is empty; a given
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subnet still uses `sweep_targets` + `discover` as today.
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- An interface that cannot be opened or sent on is skipped, never an error; no interfaces is an empty
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result.
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## Form (`e1608_kind.cpp`)
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- At the top of the Connection expander, an `AdwActionRow` "Scan network" with a text suffix button
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"Scan" (widget name `e1608-scan`). The row subtitle reads "Scanning...", "N boards found" or
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"No board found". No theme icons.
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- A scan starts a `Scan` on the port in the Port field and a 50 ms `g_timeout_add` poll for about
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1.5 s. There is no thread: the project has exactly two. The timer is removed when the form is
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destroyed (`Form::alive` guard plus the destroy hook) and when a new scan starts.
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- Each device found becomes an `AdwActionRow` in the Connection expander right after the scan row,
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replacing the previous results. Title: IP. Subtitle: MAC. Activating the row fills Address and
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clears MAC and Subnet. A suffix text button "Use MAC" (`e1608-use-mac`) fills MAC and clears
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Address and Subnet. Fill is done under the form's `updating` guard, then `changed` fires once.
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- Result rows are not read or written by the session: only the filled fields persist.
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- The description line mentions the scan.
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## Verification
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- A scan probe (env var in the existing pattern): starts against `tools/mock_e1608.py` on a
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loopback-reachable port, presses the scan button, and prints `[e1608] scan: found=N ip=... mac=...
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fill_addr=1 fill_mac=1 ok=1`, covering both fills and that the results are replaced on a rescan.
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If the sandbox refuses the broadcast, the line says so and the limitation is documented, not claimed.
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- A manual run of the scan against the real board, recorded in the README.
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- Baselines unchanged: 3 warnings clean, `gtk warnings: 0`, no `Gtk-CRITICAL`.
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## Docs
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`README.md` (E-1608 paragraph), `docs/claude/{build-and-run,verification,probe-readings,architecture}.md`.
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## Out of scope
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Remembering scan results across runs; scanning other subnets than the host's interfaces (the
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`subnet` sweep field remains for that); a worker thread.
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