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kpi_interfacefilter.h

Includes:
<sys/kernel_types.h>
<net/kpi_interface.h>

Introduction

This header defines an API to attach interface filters. Interface filters may be attached to a specific interface. The filters can intercept all packets in to and out of the specific interface. In addition, the filters may intercept interface specific events and ioctls.


Functions

iflt_attach
iflt_detach

iflt_attach

errno_t iflt_attach(
    ifnet_t interface,
    const struct iff_filter*filter, 
    interface_filter_t *filter_ref);
Parameters
interface
The interface the filter should be attached to.
filter
A structure defining the filter.
filter_ref
A reference to the filter used to detach.
Return Value

0 on success otherwise the errno error.

Discussion

Attaches an interface filter to an interface.

iflt_detach

void iflt_detach(
    interface_filter_t filter_ref);
Parameters
filter_ref
The reference to the filter from iflt_attach.
Discussion

Detaches an interface filter from an interface.

Typedefs

iff_detached_func

typedef void (*iff_detached_func)(
    void*cookie,
    ifnet_t interface);
Parameters
cookie
The cookie specified when this filter was attached.
interface
The interface this filter was detached from.
Discussion

iff_detached_func is called to notify the filter that it has been detached from an interface. This is the last call to the filter that will be made. A filter may be detached if the interface is detached or the detach filter function is called. In the case that the interface is being detached, your filter's event function will be called with the interface detaching event before the your detached function will be called.

iff_event_func

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

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.

iff_input_func

typedef errno_t (*iff_input_func)(
    void*cookie,
    ifnet_t interface,
    protocol_family_t protocol, 
    mbuf_t *data,
    char **frame_ptr);
Parameters
cookie
The cookie specified when this filter was attached.
interface
The interface the packet was recieved on.
protocol
The protocol of this packet. If you specified a protocol when attaching your filter, the protocol will only ever be the protocol you specified.
data
The inbound packet, after the frame header as determined by the interface.
frame_ptr
A pointer to the pointer to the frame header. The frame header length can be found by inspecting the interface's frame header length (ifnet_hdrlen).
Return Value

Return: 0 - The caller will continue with normal processing of the packet. EJUSTRETURN - The caller will stop processing the packet, the packet will not be freed. Anything Else - The caller will free the packet and stop processing.

Discussion

iff_input_func is used to filter incoming packets. 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. The packets passed to the inbound filter are different from those passed to the outbound filter. Packets to the inbound filter have the frame header passed in separately from the rest of the packet. The outbound data filters is passed the whole packet including the frame header.

The frame header usually preceeds the data in the mbuf. This ensures that the frame header will be a valid pointer as long as the mbuf is not freed. If you need to change the frame header to point somewhere else, the recommended method is to prepend a new frame header to the mbuf chain (mbuf_prepend), set the header to point to that data, then call mbuf_adj to move the mbuf data pointer back to the start of the packet payload.

iff_ioctl_func

typedef errno_t (*iff_ioctl_func)(
    void*cookie,
    ifnet_t interface,
    protocol_family_t protocol, 
    u_long ioctl_cmd,
    void*ioctl_arg);
Parameters
cookie
The cookie specified when this filter was attached.
interface
The interface the packet is being transmitted on.
ioctl_cmd
The ioctl command.
ioctl_arg
A pointer to the ioctl argument.
Return Value

Return: 0 - This filter function handled the ioctl. EOPNOTSUPP - This filter function does not understand/did not handle this ioctl. EJUSTRETURN - This filter function handled the ioctl, processing should stop. Anything Else - Processing will stop, the error will be returned.

Discussion

iff_ioctl_func is used to filter ioctls sent to an interface. 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.

All undefined ioctls are reserved for future use by Apple. If you need to communicate with your kext using an ioctl, please use SIOCSIFKPI and SIOCGIFKPI.

iff_output_func

typedef errno_t (*iff_output_func)(
    void*cookie,
    ifnet_t interface,
    protocol_family_t protocol, 
    mbuf_t *data);
Parameters
cookie
The cookie specified when this filter was attached.
interface
The interface the packet is being transmitted on.
data
The fully formed outbound packet in a chain of mbufs. The frame header is already included. The filter function may modify the packet or return a different mbuf chain.
Return Value

Return: 0 - The caller will continue with normal processing of the packet. EJUSTRETURN - The caller will stop processing the packet, the packet will not be freed. Anything Else - The caller will free the packet and stop processing.

Discussion

iff_output_func is used to filter fully formed outbound packets. 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.

Structs and Unions

iff_filter

struct iff_filter { 
    void*iff_cookie; 
    const char*iff_name; 
    protocol_family_t iff_protocol; 
    iff_input_func iff_input; 
    iff_output_func iff_output; 
    iff_event_func iff_event; 
    iff_ioctl_func iff_ioctl; 
    iff_detached_func iff_detached; 
};
Fields
iff_cookie
A kext defined cookie that will be passed to all filter functions.
iff_name
A filter name used for debugging purposes.
iff_protocol
The protocol of the packets this filter is interested in. If you specify zero, packets from all protocols will be passed to the filter.
iff_input
The filter function to handle inbound packets, may be NULL.
iff_output
The filter function to handle outbound packets, may be NULL.
iff_event
The filter function to handle interface events, may be null.
iff_ioctl
The filter function to handle interface ioctls, may be null.
iff_detached
The filter function used to notify the filter that it has been detached.
Discussion

This structure is used to define an interface filter for use with the iflt_attach function.


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Last Updated: 2006-07-17