feat(bmc-mock): model the BlueField DPU/NIC mode flip

The Bluefield OEM endpoint now accepts the BF-3 `Mode.Set` action and applies
it the way real hardware does: the requested DPU/NIC mode is staged and only
takes effect on the next power cycle, so a read-back before then still reports
the old mode. The staged mode is applied on the `PowerOn` event, alongside the
existing Dell BIOS-job completion.

Until now the mock could report a Bluefield's mode but not change it, so a test
could only stand up a host whose DPU was already in NIC mode -- never watch one
get flipped through the same `set_nic_mode` + power-cycle path site-explorer
drives. This is the harness piece the end-to-end DPU-to-NIC re-registration
test (#2632) builds on.

Adds a smoke test: a Bluefield starting in DPU mode reports NIC mode only after
a staged `Mode.Set` followed by a power-on, and an unstaged power-on leaves the
mode untouched.

Signed-off-by: Chet Nichols III <chetn@nvidia.com>

Author: chet

crates/bmc-mock/src/bmc_state.rs

@@ -52,6 +52,7 @@ impl BmcState {
         match event {
             BmcEvent::PowerOn => {
                 self.complete_all_bios_jobs();
+                self.apply_pending_bluefield_mode();
             }
             BmcEvent::BootCompleted => {
                 self.system_state.on_boot_completed();
@@ -64,4 +65,13 @@ impl BmcState {
             v.complete_all_bios_jobs()
         }
     }
+
+    /// Apply a BlueField's queued `Mode.Set` (the BF-3 OEM DPU/NIC mode flip),
+    /// if any. Real hardware picks up the staged mode only after a power cycle,
+    /// so this runs on `PowerOn`.
+    fn apply_pending_bluefield_mode(&self) {
+        if let redfish::oem::State::NvidiaBluefield(v) = &self.oem_state {
+            v.apply_pending_mode();
+        }
+    }
 }

crates/bmc-mock/src/http.rs

@@ -28,6 +28,10 @@ pub(crate) fn not_found() -> Response {
     json!("").into_response(StatusCode::NOT_FOUND)
 }
 
+pub(crate) fn bad_request(message: &str) -> Response {
+    json!({ "error": message }).into_response(StatusCode::BAD_REQUEST)
+}
+
 pub(crate) fn ok_no_content() -> Response {
     StatusCode::NO_CONTENT.into_response()
 }

crates/bmc-mock/src/redfish/oem/nvidia/bluefield.rs

@@ -16,6 +16,7 @@
  */
 
 use std::borrow::Cow;
+use std::sync::{Arc, Mutex};
 
 use axum::Router;
 use axum::extract::State;
@@ -30,13 +31,46 @@ use crate::{http, redfish};
 
 #[derive(Clone)]
 pub struct BluefieldState {
-    nic_mode: bool,
+    mode: Arc<Mutex<ModeState>>,
     base_mac: MacAddress,
 }
 
+struct ModeState {
+    nic_mode: bool,
+    /// A `Mode.Set` queues the requested mode here. A real BlueField applies it
+    /// only after the host power-cycles, so it lands on `nic_mode` on the next
+    /// `PowerOn` event (see `BmcState::on_event`), not immediately.
+    pending_nic_mode: Option<bool>,
+}
+
 impl BluefieldState {
     pub fn new(nic_mode: bool, base_mac: MacAddress) -> Self {
-        Self { nic_mode, base_mac }
+        Self {
+            mode: Arc::new(Mutex::new(ModeState {
+                nic_mode,
+                pending_nic_mode: None,
+            })),
+            base_mac,
+        }
+    }
+
+    /// Whether the BlueField currently reports NIC mode.
+    fn nic_mode(&self) -> bool {
+        self.mode.lock().unwrap().nic_mode
+    }
+
+    /// Queue a `Mode.Set`; it takes effect on the next power cycle.
+    fn stage_mode(&self, nic_mode: bool) {
+        self.mode.lock().unwrap().pending_nic_mode = Some(nic_mode);
+    }
+
+    /// Apply a queued `Mode.Set`, if any -- called on power-on, the point at
+    /// which a real BlueField picks up a staged mode change.
+    pub fn apply_pending_mode(&self) {
+        let mut mode = self.mode.lock().unwrap();
+        if let Some(pending) = mode.pending_nic_mode.take() {
+            mode.nic_mode = pending;
+        }
     }
 }
 
@@ -59,6 +93,12 @@ pub fn add_routes(r: Router<BmcState>) -> Router<BmcState> {
             &format!("{}/Actions/HostRshim.Set", resource().odata_id),
             post(hostrshim_set),
         )
+        .route(
+            // BF-3 OEM mode flip. Staged here and applied on the next power
+            // cycle, the same as real hardware.
+            &format!("{}/Actions/Mode.Set", resource().odata_id),
+            post(mode_set),
+        )
         .route(
             "/redfish/v1/Managers/Bluefield_BMC/Oem/Nvidia",
             patch(patch_managers_oem_nvidia),
@@ -73,7 +113,11 @@ async fn get_oem_nvidia(State(state): State<BmcState>) -> Response {
     let redfish::oem::State::NvidiaBluefield(state) = state.oem_state else {
         return http::not_found();
     };
-    let mode = if state.nic_mode { "NicMode" } else { "DpuMode" };
+    let mode = if state.nic_mode() {
+        "NicMode"
+    } else {
+        "DpuMode"
+    };
     resource()
         .json_patch()
         .patch(json!({
@@ -88,3 +132,84 @@ async fn patch_managers_oem_nvidia() -> Response {
     // This is used by enable_rshim_bmc() of libredfish client.
     json!({}).into_ok_response()
 }
+
+/// BF-3 OEM `Mode.Set`: queue a DPU/NIC mode flip. Like real hardware, the
+/// change is staged and only takes effect on the next power cycle (applied in
+/// `BmcState::on_event` on `PowerOn`), so a read-back before then still shows
+/// the old mode.
+async fn mode_set(
+    State(state): State<BmcState>,
+    axum::Json(body): axum::Json<serde_json::Value>,
+) -> Response {
+    let redfish::oem::State::NvidiaBluefield(bluefield) = state.oem_state else {
+        return http::not_found();
+    };
+    let Some(nic_mode) = parse_requested_mode(&body) else {
+        return http::bad_request("Mode.Set requires a `Mode` of `NicMode` or `DpuMode`");
+    };
+    bluefield.stage_mode(nic_mode);
+    // No response payload -- 204, per Redfish for an action with nothing to return.
+    http::ok_no_content()
+}
+
+/// Parse a `Mode.Set` body into the requested NIC-mode flag, validating
+/// strictly: `Some(true)` for `NicMode`, `Some(false)` for `DpuMode`, `None`
+/// for a missing or unrecognized value. A real BF-3 rejects those, and a strict
+/// mock turns a drifted client payload into a loud failure rather than a
+/// silently wrong flip.
+fn parse_requested_mode(body: &serde_json::Value) -> Option<bool> {
+    match body.get("Mode").and_then(|mode| mode.as_str()) {
+        Some(mode) if mode.eq_ignore_ascii_case("NicMode") => Some(true),
+        Some(mode) if mode.eq_ignore_ascii_case("DpuMode") => Some(false),
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn mode_set_is_staged_and_applied_on_power_on() {
+        // Starts in DPU mode.
+        let bf = BluefieldState::new(false, MacAddress::new([0, 0, 0, 0, 0, 1]));
+        assert!(!bf.nic_mode());
+
+        // A `Mode.Set` to NIC mode is staged, not applied immediately -- a
+        // read-back still reports DPU mode, like a real BF-3 before its power
+        // cycle.
+        bf.stage_mode(true);
+        assert!(!bf.nic_mode());
+
+        // The next power-on applies the staged mode.
+        bf.apply_pending_mode();
+        assert!(bf.nic_mode());
+
+        // A power-on with nothing staged leaves the mode untouched.
+        bf.apply_pending_mode();
+        assert!(bf.nic_mode());
+    }
+
+    #[test]
+    fn parse_requested_mode_validates_strictly() {
+        assert_eq!(
+            parse_requested_mode(&serde_json::json!({ "Mode": "NicMode" })),
+            Some(true)
+        );
+        assert_eq!(
+            parse_requested_mode(&serde_json::json!({ "Mode": "DpuMode" })),
+            Some(false)
+        );
+        // Case-insensitive, matching the handler.
+        assert_eq!(
+            parse_requested_mode(&serde_json::json!({ "Mode": "nicmode" })),
+            Some(true)
+        );
+        // Missing or unrecognized -> rejected (the handler returns 400).
+        assert_eq!(parse_requested_mode(&serde_json::json!({})), None);
+        assert_eq!(
+            parse_requested_mode(&serde_json::json!({ "Mode": "bogus" })),
+            None
+        );
+    }
+}