illumos: manual page: hook

HOOK_T(9S) Data Structures for Drivers HOOK_T(9S)

NAME

hook_t - callback structure for subscribing to netinfo events

SYNOPSIS

#include <sys/hook.h>

INTERFACE LEVEL

illumos DDI specific (illumos DDI).

DESCRIPTION

The hook_t data structure defines a callback that is to be inserted into
a networking event. This data structure must be allocated with a call to
hook_alloc() and released with a call to hook_free().

STRUCTURE MEMBERS

hook_func_t h_func; /* callback function to invoke */
char *h_name; /* unique name given to the hook */
int h_flags;
hook_hint_t h_hint; /* insertion hint type */
uintptr_t h_hintvalue; /* used with h_hint */
void *h_arg; /* value to pass into h_func */

typedef int (*hook_func_t)(net_event_t token, hook_data_t info,
void *);

CALLBACK RETURN VALUES

The value returned by the hook_func_t function indicates whether or not
the packet should still be considered valid. If the callback function has
modified the packet in such a way that it should no longer be processed
or considered valid, e.g. called freemsg(9F), then the callback should
return 1. Otherwise it should return 0.

HINT TYPES

Hook hints are hints that are used at the time of insertion and are not
rules that enforce where a hook lives for its entire lifetime on an
event. The valid values for the h_hint field are:

HH_NONE
Insert the hook wherever convenient.

HH_FIRST
Place the hook first on the list of hooks.

HH_LAST
Place the hook last on the list of hooks.

HH_BEFORE
Place the hook before another hook on the list of hooks. The
value in h_hintvalue must be a pointer to the name of
another hook.

HH_AFTER
Place the hook after another hook on the list of hooks. The
value in h_hintvalue must be a pointer to the name of
another hook.

ATTRIBUTES