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STATUS_FWP_TOO_MANY_CALLOUTS
Callout registration exhausted the engine’s capacity
STATUS_FWP_TOO_MANY_CALLOUTS indicates that the engine has reached its concurrent callout limit. A WFP callout is a classification component that enables custom packet processing at an applicable layer; it is not the same as an individual filter that references it.
WFP documents a limit of 100,000 simultaneously registered callouts. Reaching it normally points to leaked registrations, repeated load/reload behavior, or a design that creates a new callout for data that should be represented by filters or provider context. Raising filter counts will not resolve a callout leak.
What to inspect
- The registration and unregistration paths across driver load, unload, and crash recovery.
- Whether each policy update registers a new callout instead of reusing a stable callout key.
- Filters that reference a callout and their required installation order.
- Callout counts over time, not just the count at the failing operation.
References
- Microsoft: WFP callout error limit
- Microsoft: callout registration and filter-add order
- Microsoft: WFP callout drivers
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