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If you've been using WFP callouts in the kernel, you'll have probably noticed that socket bind requests were shoe-horned into the same callout model. The relevant WFP layers are FWPM_LAYER_ALE_BIND_REDIRECT_V4 and FWPM_LAYER_ALE_BIND_REDIRECT_V6.
For code that needs to support Windows 7-10, it's suitable to use the specific callout version defined as FWPS_CALLOUT_CLASSIFY_FN1.
The MSDN page documenting FWPS_CALLOUT_CLASSIFY_FN1 states that the callback may be activated at IRQL <= DISPATCH_LEVEL.
However, for the bind redirect layers specifically, I'm fairly certain that I've seen documentation stating the callouts will always be activated at PASSIVE_LEVEL. The problem right now is I can't find that documentation. I can't even find forum post here or elsewhere that discuss this.
Nor can I find sample code or open source code that in a meaningful way contribute to resolving this mystery.
Empirically, callouts at the bind redirect layers are always activated at PASSIVE_LEVEL. But it would be nice to have some stronger indicator whether this can be relied upon.