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FWP_E_RESERVED
FWP_E_RESERVED — 0x80320029
This code places the first failure in nonzero reserved WFP fields. Operationally, a WFP structure contains data in a member or flag space reserved for the platform and required to be zero.
Meaning in the subsystem
A Windows Filtering Platform management call is defined by the exact FWPM structure revision, layer, sublayer, action, conditions, provider context, and BFE transaction. Zero-initialization and backing-buffer lifetime matter because the engine validates the submitted object graph, not the caller’s high-level intent.
Do not collapse this result into a nearby status. Unsupported flags are named semantic values; reserved-field failure often indicates initialization or version-layout misuse. Compare lifecycle, identity, caller, and first API.
Minimum useful evidence
| Capture | Why it matters |
|---|---|
| Structure type/version, complete byte dump with sensitive fields redacted, and SDK definition | Tests whether the first boundary moves. |
| Initialization method, packing, size, and uninitialized padding risk | Pins evidence to one attempt. |
| Flags and reserved members added by wrappers or deserialization | Separates contract failure from environment. |
| Caller/compiler architecture and header/runtime version | Creates a stable before/after control. |
Identifiers, timestamps, versions, counts, state flags, hashes, and redacted paths normally provide enough correlation. Keep credentials, private keys, message bodies, recovery material, and personal data out of routine incident logs.
Isolate the responsible condition
- Zero-initialize the full documented structure before assigning fields; retain one negative control so that a broad workaround is not mistaken for a root-cause correction.
- Compare native SDK construction with the language wrapper output; keep every other input fixed and record the first event that differs from the failing run.
- Run memory-initialization diagnostics to detect uninitialized bytes; use a disposable or backed-up environment when the comparison changes boot, security, device, queue, or encryption state.
Do not use repeated retries as the primary test. In this case, a successful later attempt may reflect a new object, refreshed policy, restarted service, different token, or completed background transition, so record exactly what changed between attempts.
Avoid the common misdiagnosis
Use the outcomes to narrow the failing layer rather than to accumulate unrelated fixes:
| Observed result | Interpretation |
|---|---|
| The minimal or known-good comparison succeeds | The control works; inspect production-specific state. |
| The control fails at the same first operation | The control also fails; inspect host/provider evidence. |
| A new HRESULT marks another boundary | this boundary moved; diagnose the new status separately rather than treating it as confirmation that the entire operation is fixed. |
Regression proof
Apply the smallest change that addresses the first rejected condition: Use the runtime-appropriate structure revision, zero all reserved storage, and avoid copying larger/newer structures into older APIs. Preserve the pre-change configuration or trace.
Close the incident only when the same object succeeds across supported architectures and poisoned-reserved-field tests are rejected deterministically. Repeat under the original identity and state. A different environment is comparison, not proof.
Technical references
These references define the HRESULT family and subsystem contract used above:
- Microsoft Open Specifications: HRESULT values.
- Microsoft: Windows Filtering Platform.
- Microsoft: FWPM_FILTER0.
- Microsoft: FwpmFilterAdd0.
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