#include <sys/types.h>
#include <sys/module.h>
#include <sys/socket.h>
Fd #define ACCEPT_FILTER_MOD
#include <sys/socketvar.h> int
accept_filt_add (struct accept_filter *filt); int
accept_filt_del (char *name); int
accept_filt_generic_mod_event (module_t mod int event void *data); struct accept_filter *
accept_filt_get (char *name);
DESCRIPTION
Accept filters allow an application to request
that the kernel pre-process incoming connections.
An accept filter is requested via the
setsockopt(2)
system call, passing in an
Fa optname
of
SO_ACCEPTFILTER
IMPLEMENTATION NOTES
A module that wants to be an accept filter
must provide a
Vt struct accept_filter
to the system:
struct accept_filter {
char accf_name[16];
void (*accf_callback)(struct socket *so, void *arg, int waitflag);
void * (*accf_create)(struct socket *so, char *arg);
void (*accf_destroy)(struct socket *so);
SLIST_ENTRY(accept_filter) accf_next; /* next on the list */
};
The module should register it with the function
accept_filt_add (,);
passing a pointer to a
Vt struct accept_filter ,
allocated with
malloc(9).
The fields of
Vt struct accept_filter
are as follows:
accf_name
Name of the filter;
this is how it will be accessed from userland.
accf_callback
The callback that the kernel will do
once the connection is established.
It is the same as a socket upcall
and will be called when the connection is established
and whenever new data arrives on the socket,
unless the callback modifies the socket's flags.
accf_create
Called whenever a
setsockopt(2)
installs the filter onto
a listening socket.
accf_destroy
Called whenever the user removes the accept filter on the socket.
The
accept_filt_del ();
function
passed the same string used in
accept_filter.accf_name
during registration with
accept_filt_add (,);
the kernel will then disallow and further userland use of the filter.
The
accept_filt_get ();
function is used internally to locate which accept filter to use via the
setsockopt(2)
system call.
The
accept_filt_generic_mod_event ();
function provides a simple way to avoid duplication of code
for accept filters which do not use the argument field to load
and unload themselves.
This function can be used in the
Vt moduledata_t
struct for the
DECLARE_MODULE9
macro.