fix(machine-controller): wait for a zero-DPU host's boot NIC instead of faulting

Boot configuration resolves the host's boot interface from its primary
`machine_interface`. A zero-DPU host -- `NoDpu`, or a BlueField flipped to
`NicMode` -- boots from a plain NIC that only takes its first HostInband lease
once the host is up, so for a window after registration it has no boot
interface yet. The boot steps (`CheckHostConfig`, `SetBootOrder`,
`CheckBootOrder`) now treat that as a wait-and-retry rather than an error. A
host with managed DPUs always has its DPU-facing primary set at promotion, so a
missing boot interface there is still a genuine fault.

The wait-versus-fault decision is centralized in `resolve_boot_interface`, and
`SetBootOrderOutcome` gains a `Wait` variant distinct from `WaitingForReboot`
so the wait reads as an unmet precondition, not a reboot. Adds unit tests for
the classification: a zero-DPU host with no boot interface waits, a DPU host
without one faults, and a resolved interface is used as-is.

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

Author: chet

crates/machine-controller/src/boot_interface.rs

@@ -38,3 +38,78 @@ pub fn boot_interface_target(
         .boot_interface_mac()
         .map(BootInterfaceTarget::MacOnly)
 }
+
+/// What a Redfish boot step should do with a host's boot interface.
+///
+/// Separates "not ready yet" from "broken". A zero-DPU host (`NoDpu` or
+/// `NicMode`) boots from a plain NIC that takes its first HostInband lease only
+/// after the host comes up, so until then it has no boot interface to
+/// resolve -- the controller should wait, not fail. A host with managed DPUs
+/// always has its DPU-facing primary set at promotion, so a missing boot
+/// interface there is a genuine fault.
+pub enum BootInterfaceResolution {
+    /// The boot interface resolved; target it.
+    Ready(BootInterfaceTarget),
+    /// A zero-DPU host whose boot NIC has not been discovered yet -- wait.
+    AwaitingNic,
+    /// A host that should already have a boot interface is missing one.
+    Missing,
+}
+
+/// Resolve this host's boot interface for a Redfish boot step, classifying a
+/// missing one as either "wait for the NIC" (zero-DPU) or "fault".
+pub fn resolve_boot_interface(mh_snapshot: &ManagedHostStateSnapshot) -> BootInterfaceResolution {
+    classify_boot_interface(
+        boot_interface_target(mh_snapshot),
+        mh_snapshot.has_managed_dpus(),
+    )
+}
+
+/// The decision behind [`resolve_boot_interface`], split out from the snapshot
+/// lookup so it can be unit-tested directly.
+fn classify_boot_interface(
+    boot_interface: Option<BootInterfaceTarget>,
+    has_managed_dpus: bool,
+) -> BootInterfaceResolution {
+    match boot_interface {
+        Some(target) => BootInterfaceResolution::Ready(target),
+        None if !has_managed_dpus => BootInterfaceResolution::AwaitingNic,
+        None => BootInterfaceResolution::Missing,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use mac_address::MacAddress;
+
+    use super::*;
+
+    #[test]
+    fn classify_waits_for_a_zero_dpu_host_without_a_boot_interface() {
+        // The zero-DPU host's boot NIC has not taken its first lease yet: wait
+        // for it instead of faulting.
+        assert!(matches!(
+            classify_boot_interface(None, false),
+            BootInterfaceResolution::AwaitingNic
+        ));
+    }
+
+    #[test]
+    fn classify_faults_when_a_dpu_host_has_no_boot_interface() {
+        // A host with managed DPUs always has its DPU-facing primary set at
+        // promotion, so a missing boot interface is a real fault.
+        assert!(matches!(
+            classify_boot_interface(None, true),
+            BootInterfaceResolution::Missing
+        ));
+    }
+
+    #[test]
+    fn classify_uses_the_resolved_interface_when_present() {
+        let target = BootInterfaceTarget::MacOnly(MacAddress::new([0, 0, 0, 0, 0, 1]));
+        assert!(matches!(
+            classify_boot_interface(Some(target), false),
+            BootInterfaceResolution::Ready(_)
+        ));
+    }
+}

crates/machine-controller/src/handler.rs

@@ -98,7 +98,7 @@ use tokio::sync::Semaphore;
 use tracing::instrument;
 use version_compare::Cmp;
 
-use crate::boot_interface::boot_interface_target;
+use crate::boot_interface::{BootInterfaceResolution, resolve_boot_interface};
 use crate::config::{
     FirmwareGlobal, MachineStateHandlerSiteConfig, MachineValidationConfig, TimePeriod,
 };
@@ -4176,6 +4176,10 @@ enum SetBootOrderOutcome {
     Continue(SetBootOrderInfo),
     Done,
     WaitingForReboot(String),
+    /// No boot interface to act on yet -- e.g. a zero-DPU host whose boot NIC
+    /// has not been discovered. Distinct from `WaitingForReboot`: nothing was
+    /// rebooted, the caller just waits and retries.
+    Wait(String),
 }
 
 /// In case machine does not come up until a specified duration, this function tries to reboot
@@ -4564,6 +4568,9 @@ async fn handle_host_boot_order_setup(
                 SetBootOrderOutcome::WaitingForReboot(reason) => {
                     return Ok(StateHandlerOutcome::wait(reason));
                 }
+                SetBootOrderOutcome::Wait(reason) => {
+                    return Ok(StateHandlerOutcome::wait(reason));
+                }
             }
         }
         None => ManagedHostState::HostInit {
@@ -10019,13 +10026,24 @@ async fn handle_instance_host_platform_config(
             //
             // For zero-DPU hosts, it's the operator-declared primary host
             // NIC (which comes from `ExpectedHostNic.primary`) *or* the
-            // "lowest" deterministic-fallback host NIC.
-            let boot_interface = boot_interface_target(mh_snapshot).ok_or_else(|| {
-                StateHandlerError::GenericError(eyre::eyre!(
-                    "Missing boot interface for host: {}",
-                    mh_snapshot.host_snapshot.id
-                ))
-            })?;
+            // "lowest" deterministic-fallback host NIC. A zero-DPU host whose
+            // boot NIC has not taken its first HostInband lease yet has no boot
+            // interface to resolve -- wait for it rather than failing.
+            let boot_interface = match resolve_boot_interface(mh_snapshot) {
+                BootInterfaceResolution::Ready(target) => target,
+                BootInterfaceResolution::AwaitingNic => {
+                    return Ok(StateHandlerOutcome::wait(format!(
+                        "Waiting for zero-DPU host {} to discover its boot NIC before configuring boot.",
+                        mh_snapshot.host_snapshot.id
+                    )));
+                }
+                BootInterfaceResolution::Missing => {
+                    return Err(StateHandlerError::GenericError(eyre::eyre!(
+                        "Missing boot interface for host: {}",
+                        mh_snapshot.host_snapshot.id
+                    )));
+                }
+            };
 
             let vendor = mh_snapshot.host_snapshot.bmc_vendor();
 
@@ -10256,6 +10274,9 @@ async fn handle_instance_host_platform_config(
                 SetBootOrderOutcome::WaitingForReboot(reason) => {
                     return Ok(StateHandlerOutcome::wait(reason));
                 }
+                SetBootOrderOutcome::Wait(reason) => {
+                    return Ok(StateHandlerOutcome::wait(reason));
+                }
             }
         }
         HostPlatformConfigurationState::LockHost => {
@@ -10302,13 +10323,24 @@ async fn set_host_boot_order(
             // for verification.
             //
             // Resolve the boot NIC MAC the same way `CheckHostConfig` does,
-            // supporting hosts with DPU(s) and zero DPUs alike.
-            let boot_interface = boot_interface_target(mh_snapshot).ok_or_else(|| {
-                StateHandlerError::GenericError(eyre::eyre!(
-                    "Missing boot interface for host: {}",
-                    mh_snapshot.host_snapshot.id
-                ))
-            })?;
+            // supporting hosts with DPU(s) and zero DPUs alike. A zero-DPU host
+            // whose boot NIC has not taken its first HostInband lease yet has no
+            // boot interface to resolve -- wait for it rather than failing.
+            let boot_interface = match resolve_boot_interface(mh_snapshot) {
+                BootInterfaceResolution::Ready(target) => target,
+                BootInterfaceResolution::AwaitingNic => {
+                    return Ok(SetBootOrderOutcome::Wait(format!(
+                        "Waiting for zero-DPU host {} to discover its boot NIC before setting boot order.",
+                        mh_snapshot.host_snapshot.id
+                    )));
+                }
+                BootInterfaceResolution::Missing => {
+                    return Err(StateHandlerError::GenericError(eyre::eyre!(
+                        "Missing boot interface for host: {}",
+                        mh_snapshot.host_snapshot.id
+                    )));
+                }
+            };
 
             let jid = match set_boot_order_dpu_first_and_handle_no_dpu_error(
                 redfish_client,
@@ -10587,12 +10619,21 @@ async fn set_host_boot_order(
 
             let retry_count = set_boot_order_info.retry_count;
 
-            let boot_interface = boot_interface_target(mh_snapshot).ok_or_else(|| {
-                StateHandlerError::GenericError(eyre::eyre!(
-                    "Missing boot interface for host: {}",
-                    mh_snapshot.host_snapshot.id
-                ))
-            })?;
+            let boot_interface = match resolve_boot_interface(mh_snapshot) {
+                BootInterfaceResolution::Ready(target) => target,
+                BootInterfaceResolution::AwaitingNic => {
+                    return Ok(SetBootOrderOutcome::Wait(format!(
+                        "Waiting for zero-DPU host {} to discover its boot NIC before verifying boot order.",
+                        mh_snapshot.host_snapshot.id
+                    )));
+                }
+                BootInterfaceResolution::Missing => {
+                    return Err(StateHandlerError::GenericError(eyre::eyre!(
+                        "Missing boot interface for host: {}",
+                        mh_snapshot.host_snapshot.id
+                    )));
+                }
+            };
 
             let boot_order_configured = boot_interface
                 .run(|bi| redfish_client.is_boot_order_setup(bi))