feat(nomadnet): browse pages over Model B (NE-side fetch via IPC)

[torlando-tech]

What

NomadNet site browsing now works on the Swift / Model B build. Previously every "Browse Site" returned "request failed: not-started" even though transport was healthy.

Why

On the Swift build, BackendPreference.modelB is hardcoded on, so BackendFactory returns ProxyRnsBackend (the NE owns the lxmf node). But ProxyRnsBackend.fetchNomadNetPage was a hard .notStarted stub ("Model B: runs NE-side / not proxied yet") and the NE had no page-fetch handler at all. So NomadNet was simply unimplemented on this architecture — .notStarted was a misleading status (transport was fine; the fetch just never happened).

How

Wire the fetch across the existing app↔NE ProxyRequest/ProxyResponse IPC seam, reusing the fetch logic that already works in Model A:

• Sources/Shared/NomadNetFetch.swift (new, dual-target): the one-shot RNS-Link page fetch extracted verbatim from SwiftRNSBackend so both the foreground Swift backend (Model A) and the NE node (Model B) share one implementation. Foundation + ReticulumSwift only, so it compiles into the extension target.
• SwiftRNSBackend.fetchNomadNetPage now delegates to the shared helper (Model A behavior unchanged; 3 private statics moved out).
• ProxyIPC: new .nomadnetFetch request case + ProxyNomadNetOutcome reply DTO, mirroring the .lxmfSend / ProxySendOutcome pattern.
• NEReticulumNode.fetchNomadNetPageForIPC: runs the shared fetch with the NE's transport/identity/pathTable; never throws across the seam.
• PacketTunnelProvider: dispatches .nomadnetFetch to the NE handler.
• ProxyRnsBackend.fetchNomadNetPage: real round-trip + result mapping.

Safety fix (required)

roundTrip gains an optional bounded deadline (default nil → every existing caller byte-identical). The seam had no app-side timeout, so a dropped/jetsammed NE reply would hang the continuation forever. The NomadNet call passes timeout + 8s; the NE self-bounds every step (path 15s, link/request/response timeouts) and always replies, with the deadline as a backstop (degrades to .timeout).

Design note

Synchronous round-trip chosen over async/poll: browsing is an interactive request the user blocks on, and the seam already proves long-async-after-await replies (.start awaits node bring-up before replying). If the held ~30s sendProviderMessage had proven unreliable on-device, the fallback was an async Darwin-notification design — but on-device testing shows it works.

Verification

Builds clean for both targets (Columba-Swift, app + NE extension). Verified on a physical device: Background Transport up → Contacts → Network Announces → tap a nomadnetwork.node → Browse Site renders the page. Model A (SwiftRNSBackend) path unchanged by the extraction.

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

This PR wires NomadNet page browsing across the app↔NE IPC seam for Model B, replacing the hard .notStarted stub in ProxyRnsBackend with a real round-trip. A new shared NomadNetFetch.swift extracts the link/fetch algorithm from SwiftRNSBackend so both architectures share one implementation with no code duplication.

• NomadNetFetch.swift (new, dual-target): one-shot RNS Link fetch shared by SwiftRNSBackend (Model A) and NEReticulumNode (Model B); extracted verbatim with matching Status raw values so callers map across by rawValue without a lookup table.
• ProxyIPC: new .nomadnetFetch request case and ProxyNomadNetOutcome DTO follow the established .lxmfSend/ProxySendOutcome pattern; roundTrip gains an optional deadline parameter that activates sendWithDeadline — an unstructured-Task race through a ResumeOnce latch, intentionally chosen over withTaskGroup.
• ProxyRnsBackend.fetchNomadNetPage: ipcDeadline = 2 * timeout + 30 comfortably exceeds the NE's worst-case budget, providing a 13 s backstop against a truly wedged or jetsammed extension.

Confidence Score: 5/5

Safe to merge; IPC wiring is correct, ResumeOnce latch prevents double-resume, and NE failures degrade gracefully to .timeout on the app side.

The core fetch logic is a verbatim extraction of already-working code, the IPC serialization follows established patterns, and sendWithDeadline correctly prevents the continuation from hanging indefinitely. Both flagged observations are acknowledged design trade-offs documented in inline comments with no correctness bugs introduced.

No files require special attention; ProxyRnsBackend.swift has the most novel logic (sendWithDeadline + ResumeOnce) but it is well-commented and the design rationale is sound.

Important Files Changed

Filename	Overview
Sources/Shared/NomadNetFetch.swift	New shared helper extracted verbatim from SwiftRNSBackend; correct dual-target compilation, clean abstraction with matching Status rawValues
Sources/RNSBackendProxy/ProxyRnsBackend.swift	Implements real NomadNet round-trip via IPC; sendWithDeadline correctly races unstructured Tasks through ResumeOnce latch; abandoned send Task on timeout is intentional but accumulates if fetches repeatedly time out
Sources/ColumbaNetworkExtension/NEReticulumNode.swift	fetchNomadNetPageForIPC correctly delegates to NomadNetFetch and maps all errors to Foundation-only ProxyNomadNetOutcome without throwing across the IPC seam
Sources/ColumbaNetworkExtension/PacketTunnelProvider.swift	Cleanly dispatches the new .nomadnetFetch case to the NE handler, mirroring the existing .lxmfSend pattern
Sources/Shared/ProxyIPC.swift	New .nomadnetFetch case and ProxyNomadNetOutcome DTO correctly follow the established discriminated-union Codable pattern; CodingKeys are non-conflicting
Sources/RNSBackendSwift/SwiftRNSBackend.swift	fetchNomadNetPage cleanly delegates to NomadNetFetch.fetch; Model A behavior is unchanged by the extraction
Columba.xcodeproj/project.pbxproj	NomadNetFetch.swift correctly added to both app and NE extension targets (NMF1B, NMF2B) under the Shared group

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant UI as App UI
    participant PRB as ProxyRnsBackend
    participant IPC as ProxyIPC seam
    participant PTP as PacketTunnelProvider
    participant NERN as NEReticulumNode
    participant RNS as ReticulumSwift (NE)

    UI->>PRB: fetchNomadNetPage(destHashHex, path, timeout)
    PRB->>PRB: "ipcDeadline = 2*timeout + 30"
    PRB->>PRB: sendWithDeadline(wire, deadline)
    note over PRB: Race two unstructured Tasks through ResumeOnce<br/>to guarantee caller unblocks at deadline even if<br/>sendProviderMessage callback never fires
    PRB-->>IPC: .nomadnetFetch(destHashHex, path, timeoutSeconds, formFields)
    IPC-->>PTP: ProxyRequest decoded
    PTP->>NERN: fetchNomadNetPageForIPC(destHashHex, path, timeoutSeconds, formFields)
    NERN->>RNS: NomadNetFetch.fetch(transport, identity, pathTable, destHash, path, timeout)
    note over RNS: awaitPath(15s)<br/>initiateLink → awaitLinkEstablished(timeout)<br/>link.request → awaitResponse(timeout + 2s)
    RNS-->>NERN: NomadNetFetch.Result
    NERN-->>PTP: ProxyNomadNetOutcome (never throws)
    PTP-->>IPC: .ok(JSON payload)
    IPC-->>PRB: ProxyResponse.ok
    PRB-->>UI: NomadNetFetchResult(.ok, data, contentType)

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sequenceDiagram
    participant UI as App UI
    participant PRB as ProxyRnsBackend
    participant IPC as ProxyIPC seam
    participant PTP as PacketTunnelProvider
    participant NERN as NEReticulumNode
    participant RNS as ReticulumSwift (NE)

    UI->>PRB: fetchNomadNetPage(destHashHex, path, timeout)
    PRB->>PRB: "ipcDeadline = 2*timeout + 30"
    PRB->>PRB: sendWithDeadline(wire, deadline)
    note over PRB: Race two unstructured Tasks through ResumeOnce<br/>to guarantee caller unblocks at deadline even if<br/>sendProviderMessage callback never fires
    PRB-->>IPC: .nomadnetFetch(destHashHex, path, timeoutSeconds, formFields)
    IPC-->>PTP: ProxyRequest decoded
    PTP->>NERN: fetchNomadNetPageForIPC(destHashHex, path, timeoutSeconds, formFields)
    NERN->>RNS: NomadNetFetch.fetch(transport, identity, pathTable, destHash, path, timeout)
    note over RNS: awaitPath(15s)<br/>initiateLink → awaitLinkEstablished(timeout)<br/>link.request → awaitResponse(timeout + 2s)
    RNS-->>NERN: NomadNetFetch.Result
    NERN-->>PTP: ProxyNomadNetOutcome (never throws)
    PTP-->>IPC: .ok(JSON payload)
    IPC-->>PRB: ProxyResponse.ok
    PRB-->>UI: NomadNetFetchResult(.ok, data, contentType)

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_{Reviews (3): Last reviewed commit: "fix(nomadnet): widen IPC deadline past t..." | Re-trigger Greptile}

[codecov]

Codecov Report

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