NetBSD-5.0.2/sys/lkm/net/tap/if_tap_lkm.c
/* $NetBSD: if_tap_lkm.c,v 1.7 2008/06/13 14:25:06 cegger Exp $ */
/*
* Copyright (c) 2003, 2004, 2005 The NetBSD Foundation.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* tap is a NetBSD Loadable Kernel Module that demonstrates the use of
* several kernel mechanisms, mostly in the networking subsytem.
*
* 1. it is example LKM, with the standard LKM management routines and
* 2. example Ethernet driver.
* 3. example of use of autoconf stuff inside a LKM.
* 4. example clonable network interface.
* 5. example sysctl interface use from a LKM.
* 6. example LKM character device, with read, write, ioctl, poll
* and kqueue available.
* 7. example cloning device, using the MOVEFD semantics.
*
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: if_tap_lkm.c,v 1.7 2008/06/13 14:25:06 cegger Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/conf.h>
#include <sys/device.h>
#include <sys/ksyms.h>
#include <sys/lkm.h>
#include <sys/sysctl.h>
#include <net/if.h>
/* autoconf(9) structures */
CFDRIVER_DECL(tap, DV_DULL, NULL);
/* LKM management routines */
int tap_lkmentry(struct lkm_table *, int, int);
static int tap_lkmload(struct lkm_table *, int);
static int tap_lkmunload(struct lkm_table *, int);
void tapattach(int);
int tapdetach(void);
int tap_clone_destroyer(struct device *);
SYSCTL_SETUP_PROTO(sysctl_tap_setup);
extern struct cfattach tap_ca;
extern const struct cdevsw tap_cdevsw;
extern struct if_clone tap_cloners;
static struct sysctllog *tap_log;
/*
* The type of the module is actually userland-oriented. For a
* traditional Ethernet driver, MOD_MISC would be enough since
* the userland manipulates interfaces through operations on
* sockets.
*
* Here MOD_DEV is chosen because a direct access interface is
* exposed, and the easiest way to achieve this is through a
* regular device node.
*/
MOD_DEV("tap", "tap", NULL, -1, &tap_cdevsw, -1);
/* We don't have anything to do on 'modstat' */
int
tap_lkmentry(struct lkm_table *lkmtp, int cmd, int ver)
{
DISPATCH(lkmtp, cmd, ver,
tap_lkmload, tap_lkmunload, lkm_nofunc);
}
/*
* autoconf(9) is a rather complicated piece of work, but in the end
* it is rather flexible, so you can easily add a device somewhere in
* the tree, and make almost anything attach to something known.
*
* Here the idea is taken from Jason R. Thorpe's ataraid(4) pseudo-
* device. Instead of needing a declaration in the kernel
* configuration, we teach autoconf(9) the availability of the
* pseudo-device at run time.
*
* Once our autoconf(9) structures are committed to the kernel's
* arrays, we can attach a device. It is done through config_attach
* for a real device, but for a pseudo-device it is a bit different
* and one has to use config_pseudo_attach.
*
* And since we want the user to be responsible for creating device,
* we use the interface cloning mechanism, and advertise our interface
* to the kernel.
*/
static int
tap_lkmload(struct lkm_table *lkmtp, int cmd)
{
int error = 0;
error = config_cfdriver_attach(&tap_cd);
if (error) {
aprint_error("%s: unable to register cfdriver\n",
tap_cd.cd_name);
goto out;
}
/* XXX: no way to detect an error for config_cfattach_attach() */
tapattach(1);
sysctl_tap_setup(&tap_log);
out:
return error;
}
/*
* Cleaning up is the most critical part of a LKM, since a module is not
* actually made to be loadable, but rather "unloadable". If it is only
* to be loaded, you'd better link it to the kernel in the first place.
*
* The interface cloning mechanism is really simple, with only two void
* returning functions. It will always do its job. You should note though
* that if an instance of tap can't be detached, the module won't
* unload and you won't be able to create interfaces anymore.
*
* We have to make sure the devices really exist, because they can be
* destroyed through ifconfig, hence the test whether cd_devs[i] is NULL
* or not.
*
* The cd_devs array is somehow the downside of the whole autoconf(9)
* mechanism, since if you only create 'tap150', you'll get an array of
* 150 elements which 149 of them are NULL.
*/
static int
tap_lkmunload(struct lkm_table *lkmtp, int cmd)
{
int error, i;
device_t dev;
if_clone_detach(&tap_cloners);
for (i = 0; i < tap_cd.cd_ndevs; i++) {
dev = device_lookup(&tap_cd, i);
if (dev != NULL &&
(error = tap_clone_destroyer(dev)) != 0)
return error;
}
sysctl_teardown(&tap_log);
if ((error = config_cfattach_detach(tap_cd.cd_name,
&tap_ca)) != 0) {
aprint_error("%s: unable to deregister cfattach\n",
tap_cd.cd_name);
return error;
}
if ((error = config_cfdriver_detach(&tap_cd)) != 0) {
aprint_error("%s: unable to deregister cfdriver\n",
tap_cd.cd_name);
return error;
}
return 0;
}