Wi-Fi bulk transport: AWDL data plane for large media with BLE fallback

BLE stays the control plane: a sender with a queued file > 64 KiB to a
directly connected peer advertising the wifiBulk capability sends a
bulkTransferOffer (0x04) inside the established Noise session — transferID,
file size, payload SHA-256, a fresh 32-byte token, and a random per-transfer
Bonjour instance name. The receiver answers bulkTransferResponse (0x05) with
its own token half, then both sides meet on a per-transfer
_bitchat-bulk._tcp channel over peer-to-peer Wi-Fi (AWDL).

The TCP stream is secured independently of TLS: both tokens traveled inside
Noise, so only the two peers can derive the ChaChaPoly channel key
(HKDF-SHA256, domain "bitchat-bulk-v1", transferID as salt). Frames are
length-prefixed sealed boxes with structured direction+counter nonces; the
first frame must prove knowledge of the key or the client is disconnected,
and the final hash is verified against the offer before delivery.

Decline, timeout, or any mid-transfer error falls back to BLE fragmentation
exactly once, driving the same TransferProgressManager stream so the UI is
unchanged. Wi-Fi-negotiated transfers may carry up to 8 MiB (new
FileTransferLimits.maxWifiBulkPayloadBytes, enforced by the receiver from
the accepted offer); the BLE path keeps its existing caps.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bitchatTests/WifiBulk/WifiBulkLoopbackTests.swift

@@ -0,0 +1,246 @@
+//
+// WifiBulkLoopbackTests.swift
+// bitchatTests
+//
+// This is free and unencumbered software released into the public domain.
+// For more information, see <https://unlicense.org>
+//
+
+import CryptoKit
+import BitFoundation
+import Foundation
+import Network
+import Testing
+@testable import bitchat
+
+/// End-to-end integration over real Network.framework sockets on localhost:
+/// two `WifiBulkTransferService` instances negotiate through an in-process
+/// "Noise" pipe, then move the payload over a genuine TCP connection using
+/// the production listener/browser-free test hooks (peer-to-peer and Bonjour
+/// are disabled — unit-test hosts have no AWDL or mDNS access).
+@Suite("WifiBulk loopback integration", .serialized)
+struct WifiBulkLoopbackTests {
+    private static let senderPeer = PeerID(str: "00112233aabbccdd")
+    private static let receiverPeer = PeerID(str: "ddccbbaa33221100")
+
+    private func makeConfig() -> WifiBulkTransferServiceConfig {
+        var config = WifiBulkTransferServiceConfig()
+        config.usePeerToPeer = false
+        config.publishBonjourService = false
+        config.offerTimeout = 5.0
+        config.transferWindow = 10.0
+        return config
+    }
+
+    @Test("Payload crosses a real TCP loopback channel and lands verified")
+    func loopbackTransferSucceeds() async throws {
+        let payload = Data((0..<300_000).map { UInt8($0 % 249) })
+
+        let delivered = WifiBulkTestBox<Data>()
+        let progress = WifiBulkTestBox<String>()
+        let fallbacks = WifiBulkTestBox<Bool>()
+        let ports = WifiBulkTestBox<(Data, UInt16)>()
+        let offers = WifiBulkTestBox<Data>()
+
+        var senderService: WifiBulkTransferService?
+        var receiverService: WifiBulkTransferService?
+
+        // Once the receiver has accepted AND the listener port is known,
+        // connect the receiver straight to 127.0.0.1 (Bonjour stand-in).
+        let accepted = WifiBulkTestBox<Data>()
+        let connectIfReady: () -> Void = {
+            guard let (transferID, port) = ports.values.first,
+                  accepted.values.contains(transferID),
+                  let nwPort = NWEndpoint.Port(rawValue: port) else { return }
+            receiverService?._test_connectIncoming(
+                transferID: transferID,
+                to: NWEndpoint.hostPort(host: "127.0.0.1", port: nwPort)
+            )
+        }
+
+        let senderEnv = WifiBulkTransferServiceEnvironment(
+            sendNoisePayload: { typed, _ in
+                // Sender → receiver control plane (offer).
+                guard typed.first == NoisePayloadType.bulkTransferOffer.rawValue else { return true }
+                offers.append(Data(typed.dropFirst()))
+                receiverService?.handleOfferPayload(Data(typed.dropFirst()), from: Self.senderPeer)
+                return true
+            },
+            isPeerConnected: { _ in true },
+            deliverReceivedFile: { _, _, _ in },
+            progressStart: { id, total in progress.append("start:\(id):\(total)") },
+            progressChunkSent: { id in progress.append("chunk:\(id)") },
+            progressReset: { id in progress.append("reset:\(id)") },
+            progressCancel: { id in progress.append("cancel:\(id)") }
+        )
+        let receiverEnv = WifiBulkTransferServiceEnvironment(
+            sendNoisePayload: { typed, _ in
+                // Receiver → sender control plane (response).
+                guard typed.first == NoisePayloadType.bulkTransferResponse.rawValue else { return true }
+                let body = Data(typed.dropFirst())
+                if let response = WifiBulkResponse.decode(body), response.accepted {
+                    accepted.append(response.transferID)
+                }
+                senderService?.handleResponsePayload(body, from: Self.receiverPeer)
+                connectIfReady()
+                return true
+            },
+            isPeerConnected: { _ in true },
+            deliverReceivedFile: { data, peer, limit in
+                #expect(peer == Self.senderPeer)
+                #expect(limit == FileTransferLimits.maxWifiBulkPayloadBytes)
+                delivered.append(data)
+            },
+            progressStart: { _, _ in },
+            progressChunkSent: { _ in },
+            progressReset: { _ in },
+            progressCancel: { _ in }
+        )
+
+        let sender = WifiBulkTransferService(environment: senderEnv, config: makeConfig())
+        sender._test_onListenerReady = { transferID, port in
+            ports.append((transferID, port))
+            connectIfReady()
+        }
+        let receiver = WifiBulkTransferService(environment: receiverEnv, config: makeConfig())
+        senderService = sender
+        receiverService = receiver
+
+        sender.sendFile(payload: payload, to: Self.receiverPeer, transferId: "t-loopback") {
+            fallbacks.append(true)
+        }
+
+        #expect(await wifiBulkWait(timeout: 10.0) { delivered.count == 1 })
+        #expect(delivered.values.first == payload)
+        #expect(fallbacks.count == 0)
+
+        // Deterministic teardown: both sides drop all transfer state.
+        #expect(await wifiBulkWait { sender._test_activeOutgoingCount == 0 })
+        #expect(await wifiBulkWait { receiver._test_activeIncomingCount == 0 })
+
+        // Progress mirrored the BLE contract: start with the chunk total,
+        // then exactly `total` chunk ticks (the last one gated on the receipt).
+        let totalChunks = (payload.count + TransportConfig.wifiBulkChunkBytes - 1) / TransportConfig.wifiBulkChunkBytes
+        #expect(await wifiBulkWait { progress.values.filter { $0 == "chunk:t-loopback" }.count == totalChunks })
+        #expect(progress.values.first == "start:t-loopback:\(totalChunks)")
+        #expect(!progress.values.contains("reset:t-loopback"))
+    }
+
+    @Test("A gatecrasher without the channel key is disconnected and the real peer still succeeds")
+    func gatecrasherIsRejected() async throws {
+        let payload = Data((0..<150_000).map { UInt8($0 % 241) })
+
+        let delivered = WifiBulkTestBox<Data>()
+        let fallbacks = WifiBulkTestBox<Bool>()
+        let ports = WifiBulkTestBox<(Data, UInt16)>()
+        let accepted = WifiBulkTestBox<Data>()
+
+        var senderService: WifiBulkTransferService?
+        var receiverService: WifiBulkTransferService?
+
+        let gatecrashed = WifiBulkTestBox<Bool>()
+        let connectIfReady: () -> Void = {
+            guard let (transferID, port) = ports.values.first,
+                  accepted.values.contains(transferID),
+                  gatecrashed.count > 0,
+                  let nwPort = NWEndpoint.Port(rawValue: port) else { return }
+            receiverService?._test_connectIncoming(
+                transferID: transferID,
+                to: NWEndpoint.hostPort(host: "127.0.0.1", port: nwPort)
+            )
+        }
+
+        let senderEnv = WifiBulkTransferServiceEnvironment(
+            sendNoisePayload: { typed, _ in
+                guard typed.first == NoisePayloadType.bulkTransferOffer.rawValue else { return true }
+                receiverService?.handleOfferPayload(Data(typed.dropFirst()), from: Self.senderPeer)
+                return true
+            },
+            isPeerConnected: { _ in true },
+            deliverReceivedFile: { _, _, _ in },
+            progressStart: { _, _ in },
+            progressChunkSent: { _ in },
+            progressReset: { _ in },
+            progressCancel: { _ in }
+        )
+        let receiverEnv = WifiBulkTransferServiceEnvironment(
+            sendNoisePayload: { typed, _ in
+                guard typed.first == NoisePayloadType.bulkTransferResponse.rawValue else { return true }
+                let body = Data(typed.dropFirst())
+                if let response = WifiBulkResponse.decode(body), response.accepted {
+                    accepted.append(response.transferID)
+                }
+                senderService?.handleResponsePayload(body, from: Self.receiverPeer)
+                connectIfReady()
+                return true
+            },
+            isPeerConnected: { _ in true },
+            deliverReceivedFile: { data, _, _ in delivered.append(data) },
+            progressStart: { _, _ in },
+            progressChunkSent: { _ in },
+            progressReset: { _ in },
+            progressCancel: { _ in }
+        )
+
+        let sender = WifiBulkTransferService(environment: senderEnv, config: makeConfig())
+        let gateQueue = DispatchQueue(label: "test.gatecrasher")
+        sender._test_onListenerReady = { transferID, port in
+            ports.append((transferID, port))
+            guard let nwPort = NWEndpoint.Port(rawValue: port) else { return }
+            // A stranger who saw the Bonjour advertisement connects first and
+            // sends garbage that cannot carry a valid MAC.
+            let crasher = NWConnection(
+                to: NWEndpoint.hostPort(host: "127.0.0.1", port: nwPort),
+                using: .tcp
+            )
+            crasher.stateUpdateHandler = { state in
+                if case .ready = state {
+                    let junkBody = Data(repeating: 0xAA, count: 60)
+                    crasher.send(
+                        content: WifiBulkCrypto.frameData(body: junkBody),
+                        completion: .contentProcessed { _ in
+                            gatecrashed.append(true)
+                            connectIfReady()
+                        }
+                    )
+                }
+            }
+            crasher.start(queue: gateQueue)
+        }
+        let receiver = WifiBulkTransferService(environment: receiverEnv, config: makeConfig())
+        senderService = sender
+        receiverService = receiver
+
+        sender.sendFile(payload: payload, to: Self.receiverPeer, transferId: "t-gatecrash") {
+            fallbacks.append(true)
+        }
+
+        #expect(await wifiBulkWait(timeout: 10.0) { delivered.count == 1 })
+        #expect(delivered.values.first == payload)
+        #expect(fallbacks.count == 0)
+        #expect(await wifiBulkWait { sender._test_activeOutgoingCount == 0 })
+    }
+
+    @Test("Receiver vanishing mid-negotiation leaves the sender to time out into BLE")
+    func vanishedReceiverFallsBack() async {
+        var config = makeConfig()
+        config.offerTimeout = 0.3
+
+        let fallbacks = WifiBulkTestBox<Bool>()
+        let environment = WifiBulkTransferServiceEnvironment(
+            sendNoisePayload: { _, _ in true }, // offer sent, receiver never answers
+            isPeerConnected: { _ in true },
+            deliverReceivedFile: { _, _, _ in },
+            progressStart: { _, _ in },
+            progressChunkSent: { _ in },
+            progressReset: { _ in },
+            progressCancel: { _ in }
+        )
+        let sender = WifiBulkTransferService(environment: environment, config: config)
+        sender.sendFile(payload: Data(repeating: 1, count: 100_000), to: Self.receiverPeer, transferId: "t-vanish") {
+            fallbacks.append(true)
+        }
+        #expect(await wifiBulkWait { fallbacks.count == 1 })
+        #expect(sender._test_activeOutgoingCount == 0)
+    }
+}