---
title: iff_event_func
framework: Kernel
role: symbol
role_heading: Type Alias
platforms: [macOS 10.4+]
path: kernel/iff_event_func
---

# iff_event_func

## Declaration

```occ
typedef void (*iff_event_func)(void *cookie, ifnet_t interface, protocol_family_t protocol, const struct kev_msg *event_msg);
```

## Parameters

- `cookie`: The cookie specified when this filter was attached.
- `interface`: The interface the packet is being transmitted on.
- `event_msg`: The kernel event, may not be changed.

## Discussion

Discussion iff_event_func is used to filter interface specific events. The interface is only valid for the duration of the filter call. If you need to keep a reference to the interface, be sure to call ifnet_reference and ifnet_release.