feat: S08.11 switching_transport BDD scenario (UDP↔TCP) on QEMU

Bdd/Targets/FreeRtos/README.md

@@ -6,13 +6,17 @@ QEMU's stdio UART.
 
 SolidSyslog runs here with the portable `SolidSyslogCircularBuffer` +
 `SolidSyslogFreeRtosMutex` drained by a dedicated FreeRTOS Service task,
-UdpSender over FreeRTOS-Plus-TCP, the `SolidSyslogFreeRtosStaticResolver`
-pinned to the QEMU slirp gateway (`10.0.2.2`), and the
-`Bdd/Targets/Common/BddTargetInteractive` runner. Drive identity /
-endpoint / PRIVAL fields over the UART command channel with
-`set NAME VALUE`, emit N RFC 5424 datagrams with `send N`, exit cleanly
-with `quit`. See [`Bdd/README.md`](../../Bdd/README.md) for how Behave
-pipes these commands through `qemu-system-arm`'s stdio UART.
+a `SolidSyslogSwitchingSender` wrapping a UDP sender (over
+`SolidSyslogFreeRtosDatagram`) and a TCP sender (over
+`SolidSyslogFreeRtosTcpStream` + `SolidSyslogStreamSender`), the
+`SolidSyslogFreeRtosStaticResolver` pinned to the QEMU slirp gateway
+(`10.0.2.2`), and the `Bdd/Targets/Common/BddTargetInteractive` runner.
+Drive identity / endpoint / PRIVAL fields over the UART command channel
+with `set NAME VALUE`, flip the active transport at runtime with
+`switch udp` / `switch tcp` (routed through `BddTargetSwitchConfig`),
+emit N RFC 5424 messages with `send N`, exit cleanly with `quit`. See
+[`Bdd/README.md`](../../Bdd/README.md) for how Behave pipes these
+commands through `qemu-system-arm`'s stdio UART.
 
 `Common/` carries the shared infrastructure (CMSDK UART driver, newlib
 syscalls, mps2-an385 linker script, startup) and `cmake/` the
@@ -122,9 +126,11 @@ polled `_read` / `_write` via newlib retargeting
 static IPv4 of `10.0.2.15` on the QEMU slirp network, and starts the
 scheduler. On link-up the IP-task event hook spawns the interactive task
 (running `BddTargetInteractive_Run`) and the Service task (draining the
-`SolidSyslogCircularBuffer` and pushing through the UDP sender). Each
-`send N` line over the UART emits N RFC 5424 datagrams to
-`{10.0.2.2, port=g_port}`.
+`SolidSyslogCircularBuffer` and pushing through the
+`SolidSyslogSwitchingSender`'s active inner — UDP by default, TCP after
+`switch tcp`). Each `send N` line over the UART emits N RFC 5424
+messages to `{10.0.2.2, port=g_port}` over whichever transport is
+currently selected.
 
 The FreeRTOS GCC ARM_CM3 port supplies `vPortSVCHandler`,
 `xPortPendSVHandler`, and `xPortSysTickHandler`.

Bdd/Targets/FreeRtos/main.c

@@ -451,7 +451,7 @@ static void InteractiveTask(void* argument)
     SolidSyslog_SetErrorHandler(ErrorHandler, NULL);
     SolidSyslog_Create(&config);
 
-    BddTargetInteractive_Run(&g_message, stdin, NULL, OnSet);
+    BddTargetInteractive_Run(&g_message, stdin, BddTargetSwitchConfig_SetByName, OnSet);
 
     SolidSyslog_Destroy();
     SolidSyslogOriginSd_Destroy();

Bdd/features/switching_transport.feature

@@ -4,6 +4,7 @@ Feature: Switch transport at runtime
   SwitchingSender. The --transport CLI flag sets the initial selector
   value, and the interactive `switch` command updates it at runtime.
 
+  @udp @tcp
   Scenario: Switch from UDP to TCP mid-run delivers via both
     Given the syslog oracle is running
     And the BDD target is running with default transport udp

CLAUDE.md

@@ -329,8 +329,9 @@ live under `Core/Interface/`; platform-specific helpers (the `SolidSyslogPosix*`
 | `SolidSyslogFreeRtosDatagram.h` | System setup code on FreeRTOS targets using FreeRTOS-Plus-TCP for UDP | `SolidSyslogFreeRtosDatagramStorage`, `SOLIDSYSLOG_FREERTOSDATAGRAM_SIZE`, `SolidSyslogFreeRtosDatagram_Create(storage)`, `_Destroy(datagram)` (wraps `FreeRTOS_socket` / `FreeRTOS_sendto` / `FreeRTOS_closesocket`) |
 | `SolidSyslogStream.h` | Sender implementors using stream transport | `SolidSyslogStream_Open`, `_Send`, `_Read`, `_Close`, `SolidSyslogSsize` |
 | `SolidSyslogStreamDefinition.h` | Stream implementors (extension point) | `SolidSyslogStream` vtable struct (`Open`, `Send`, `Read`, `Close`) |
+| `SolidSyslogFreeRtosTcpStream.h` | System setup code on FreeRTOS targets using FreeRTOS-Plus-TCP for TCP | `SolidSyslogFreeRtosTcpStreamStorage`, `SOLIDSYSLOG_FREERTOSTCPSTREAM_SIZE`, `SolidSyslogFreeRtosTcpStream_Create(storage)`, `_Destroy(stream)` (wraps `FreeRTOS_socket` / `FreeRTOS_connect` / `FreeRTOS_send` / `FreeRTOS_recv` / `FreeRTOS_closesocket`; bounded blocking connect via `SO_SNDTIMEO=200ms`, cleared post-connect so Send/Read are non-blocking) |
 | `SolidSyslogUdpSender.h` | System setup code using UDP transport | `SolidSyslogUdpSenderConfig` (resolver, datagram, endpoint, endpointVersion), `SolidSyslogUdpSender_Create`, `_Destroy` |
-| `SolidSyslogStreamSender.h` | System setup code using octet-framed transport (RFC 6587) over any Stream — `SolidSyslogPosixTcpStream` (POSIX TCP), `SolidSyslogWinsockTcpStream` (Windows TCP), `SolidSyslogTlsStream` (TLS; OpenSSL reference integration), or a caller-supplied Stream backend | `SolidSyslogStreamSenderConfig` (resolver, stream, endpoint, endpointVersion), `SolidSyslogStreamSender_Create`, `_Destroy` |
+| `SolidSyslogStreamSender.h` | System setup code using octet-framed transport (RFC 6587) over any Stream — `SolidSyslogPosixTcpStream` (POSIX TCP), `SolidSyslogWinsockTcpStream` (Windows TCP), `SolidSyslogFreeRtosTcpStream` (FreeRTOS-Plus-TCP), `SolidSyslogTlsStream` (TLS; OpenSSL reference integration), or a caller-supplied Stream backend | `SolidSyslogStreamSenderConfig` (resolver, stream, endpoint, endpointVersion), `SolidSyslogStreamSender_Create`, `_Destroy` |
 | `SolidSyslogSwitchingSender.h` | System setup code composing multiple inner senders | `SolidSyslogSwitchingSenderConfig` (senders, senderCount, selector), `SolidSyslogSwitchingSenderSelector`, `SolidSyslogSwitchingSender_Create`, `_Destroy` |
 | `SolidSyslogBuffer.h` | Library internals consuming a buffer (Service algorithm) | `SolidSyslogBuffer_Write`, `_Read` |
 | `SolidSyslogBufferDefinition.h` | Buffer implementors (extension point) | `SolidSyslogBuffer` vtable struct |

DEVLOG.md

@@ -1,5 +1,61 @@
 # Dev Log
 
+## 2026-05-11 — S08.11 switching_transport BDD scenario (UDP↔TCP) on QEMU (#340)
+
+Third and final slice of S08.06. With the TCP stream (S08.09) and TCP
+reconnect verification (S08.10) in place, this slice lights up the
+runtime `switch` command in the FreeRTOS BDD target and admits the
+non-`@tls` `switching_transport.feature` scenario to the QEMU runner.
+
+### Decisions
+
+- **Wire `BddTargetSwitchConfig_SetByName` as the `onSwitch` callback,
+  not just `set transport`.** S08.09 already routed `set transport
+  <udp|tcp>` through `BddTargetSwitchConfig`, so the harness could
+  flip the initial transport via `--transport tcp` translated to a
+  `set transport tcp` UART line. The runtime `switch tcp` command
+  path is a separate dispatch in `BddTargetInteractive.c` — guarded
+  on `onSwitch != NULL`, so leaving `onSwitch = NULL` meant `switch
+  tcp` from the BDD step `the client switches to transport tcp`
+  silently no-op'd. Passing `BddTargetSwitchConfig_SetByName` lines
+  the FreeRTOS target up with Linux (`Bdd/Targets/Linux/main.c:286`)
+  and Windows (`Bdd/Targets/Windows/BddTargetWindows.c:357`), which
+  already pass it.
+- **Tag the non-`@tls` scenario `@udp @tcp` at the scenario level,
+  not the feature level.** The feature is feature-level `@buffered`
+  only — invisible to the FreeRTOS `(@udp or @tcp)` admission clause.
+  The `@tls` sibling must stay excluded until S08.07 lands TLS on
+  FreeRTOS, so feature-level `@tcp` would over-admit. Scenario-level
+  `@udp @tcp` on the first scenario keeps the second one out without
+  restructuring the docker-compose filter.
+- **No new unit tests.** Pure wiring: the only code change is the
+  callback argument at the `BddTargetInteractive_Run` call site, and
+  `BddTargetSwitchConfig_SetByName` is the same function the existing
+  `set transport` path in `OnSet` already calls. The end-to-end
+  `switching_transport.feature` scenario is the test for the dispatch.
+
+### Deferred
+
+- **TLS switching scenario (`@tls`-tagged second scenario of
+  `switching_transport.feature`)** — S08.07 (#272).
+- **Unit test for the `BddTargetInteractive` `switch` dispatch.** The
+  `onSwitch` slot was added in the S20.x SwitchingSender stories
+  without a paired unit test in `BddTargetInteractiveTest`; the
+  existing tests cover the `set` path only. Out of scope here (pure
+  wiring story) but worth a hygiene follow-up — every other dispatch
+  in this file is pinned, so `switch`'s absence is the odd one out.
+- **CMake-driven memory scaling** still open from S08.09 — memory
+  `project_freertos_stack_budget`. The S08.09 `INTERACTIVE_TASK_
+  STACK_DEPTH = configMINIMAL_STACK_SIZE * 48U` already carries the
+  SwitchingSender + TCP path overhead, so no further bump here.
+
+### Open questions
+
+- None new. The S08.10 question about the 200ms SO_SNDTIMEO cap
+  potentially starving the Service task during outage is unrelated
+  to switching; CI is the arbiter and the answer is "raise the
+  deadline if it flakes" per `feedback_no_flaky_ci`.
+
 ## 2026-05-11 — S08.10 tcp_reconnect BDD scenario on QEMU (#339)
 
 Second slice of S08.06. The reconnect-on-the-wire is already a property

ci/docker-compose.bdd.yml

@@ -106,6 +106,9 @@ services:
     # marks features that need a file-backed store (no FreeRTOS file
     # abstraction yet), while plain @buffered just means "uses the long-lived
     # interactive process" and is supported on FreeRTOS via QEMU's UART.
+    # S08.11 tags the non-@tls switching_transport scenario @udp @tcp so the
+    # existing (@udp or @tcp) clause admits it; the @tls sibling stays
+    # excluded until S08.07 lights up TLS on FreeRTOS.
     # @windows_wip excludes the Windows-only TCP singletask variant.
     command: behave --junit --junit-directory Bdd/junit --tags='not @wip and not @freertoswip and not @rtc and not @store and not @windows_wip and (@udp or @tcp)' Bdd/features/