Commit 7672d0b5 authored by Evgeniy Polyakov's avatar Evgeniy Polyakov Committed by David S. Miller

[NET]: Add netlink connector.

Kernel connector - new userspace <-> kernel space easy to use
communication module which implements easy to use bidirectional
message bus using netlink as it's backend.  Connector was created to
eliminate complex skb handling both in send and receive message bus
direction.

Connector driver adds possibility to connect various agents using as
one of it's backends netlink based network.  One must register
callback and identifier. When driver receives special netlink message
with appropriate identifier, appropriate callback will be called.

From the userspace point of view it's quite straightforward:

	socket();
	bind();
	send();
	recv();

But if kernelspace want to use full power of such connections, driver
writer must create special sockets, must know about struct sk_buff
handling...  Connector allows any kernelspace agents to use netlink
based networking for inter-process communication in a significantly
easier way:

int cn_add_callback(struct cb_id *id, char *name, void (*callback) (void *));
void cn_netlink_send(struct cn_msg *msg, u32 __groups, int gfp_mask);

struct cb_id
{
	__u32			idx;
	__u32			val;
};

idx and val are unique identifiers which must be registered in
connector.h for in-kernel usage.  void (*callback) (void *) - is a
callback function which will be called when message with above idx.val
will be received by connector core.

Using connector completely hides low-level transport layer from it's
users.

Connector uses new netlink ability to have many groups in one socket.

[ Incorporating many cleanups and fixes by myself and
  Andrew Morton -DaveM ]
Signed-off-by: default avatarEvgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 357d596b
/*
* cn_test.c
*
* 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/skbuff.h>
#include <linux/timer.h>
#include "connector.h"
static struct cb_id cn_test_id = { 0x123, 0x456 };
static char cn_test_name[] = "cn_test";
static struct sock *nls;
static struct timer_list cn_test_timer;
void cn_test_callback(void *data)
{
struct cn_msg *msg = (struct cn_msg *)data;
printk("%s: %lu: idx=%x, val=%x, seq=%u, ack=%u, len=%d: %s.\n",
__func__, jiffies, msg->id.idx, msg->id.val,
msg->seq, msg->ack, msg->len, (char *)msg->data);
}
static int cn_test_want_notify(void)
{
struct cn_ctl_msg *ctl;
struct cn_notify_req *req;
struct cn_msg *msg = NULL;
int size, size0;
struct sk_buff *skb;
struct nlmsghdr *nlh;
u32 group = 1;
size0 = sizeof(*msg) + sizeof(*ctl) + 3 * sizeof(*req);
size = NLMSG_SPACE(size0);
skb = alloc_skb(size, GFP_ATOMIC);
if (!skb) {
printk(KERN_ERR "Failed to allocate new skb with size=%u.\n",
size);
return -ENOMEM;
}
nlh = NLMSG_PUT(skb, 0, 0x123, NLMSG_DONE, size - sizeof(*nlh));
msg = (struct cn_msg *)NLMSG_DATA(nlh);
memset(msg, 0, size0);
msg->id.idx = -1;
msg->id.val = -1;
msg->seq = 0x123;
msg->ack = 0x345;
msg->len = size0 - sizeof(*msg);
ctl = (struct cn_ctl_msg *)(msg + 1);
ctl->idx_notify_num = 1;
ctl->val_notify_num = 2;
ctl->group = group;
ctl->len = msg->len - sizeof(*ctl);
req = (struct cn_notify_req *)(ctl + 1);
/*
* Idx.
*/
req->first = cn_test_id.idx;
req->range = 10;
/*
* Val 0.
*/
req++;
req->first = cn_test_id.val;
req->range = 10;
/*
* Val 1.
*/
req++;
req->first = cn_test_id.val + 20;
req->range = 10;
NETLINK_CB(skb).dst_groups = ctl->group;
//netlink_broadcast(nls, skb, 0, ctl->group, GFP_ATOMIC);
netlink_unicast(nls, skb, 0, 0);
printk(KERN_INFO "Request was sent. Group=0x%x.\n", ctl->group);
return 0;
nlmsg_failure:
printk(KERN_ERR "Failed to send %u.%u\n", msg->seq, msg->ack);
kfree_skb(skb);
return -EINVAL;
}
static u32 cn_test_timer_counter;
static void cn_test_timer_func(unsigned long __data)
{
struct cn_msg *m;
char data[32];
m = kmalloc(sizeof(*m) + sizeof(data), GFP_ATOMIC);
if (m) {
memset(m, 0, sizeof(*m) + sizeof(data));
memcpy(&m->id, &cn_test_id, sizeof(m->id));
m->seq = cn_test_timer_counter;
m->len = sizeof(data);
m->len =
scnprintf(data, sizeof(data), "counter = %u",
cn_test_timer_counter) + 1;
memcpy(m + 1, data, m->len);
cn_netlink_send(m, 0, gfp_any());
kfree(m);
}
cn_test_timer_counter++;
mod_timer(&cn_test_timer, jiffies + HZ);
}
static int cn_test_init(void)
{
int err;
err = cn_add_callback(&cn_test_id, cn_test_name, cn_test_callback);
if (err)
goto err_out;
cn_test_id.val++;
err = cn_add_callback(&cn_test_id, cn_test_name, cn_test_callback);
if (err) {
cn_del_callback(&cn_test_id);
goto err_out;
}
init_timer(&cn_test_timer);
cn_test_timer.function = cn_test_timer_func;
cn_test_timer.expires = jiffies + HZ;
cn_test_timer.data = 0;
add_timer(&cn_test_timer);
return 0;
err_out:
if (nls && nls->sk_socket)
sock_release(nls->sk_socket);
return err;
}
static void cn_test_fini(void)
{
del_timer_sync(&cn_test_timer);
cn_del_callback(&cn_test_id);
cn_test_id.val--;
cn_del_callback(&cn_test_id);
if (nls && nls->sk_socket)
sock_release(nls->sk_socket);
}
module_init(cn_test_init);
module_exit(cn_test_fini);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
MODULE_DESCRIPTION("Connector's test module");
/*****************************************/
Kernel Connector.
/*****************************************/
Kernel connector - new netlink based userspace <-> kernel space easy
to use communication module.
Connector driver adds possibility to connect various agents using
netlink based network. One must register callback and
identifier. When driver receives special netlink message with
appropriate identifier, appropriate callback will be called.
From the userspace point of view it's quite straightforward:
socket();
bind();
send();
recv();
But if kernelspace want to use full power of such connections, driver
writer must create special sockets, must know about struct sk_buff
handling... Connector allows any kernelspace agents to use netlink
based networking for inter-process communication in a significantly
easier way:
int cn_add_callback(struct cb_id *id, char *name, void (*callback) (void *));
void cn_netlink_send(struct cn_msg *msg, u32 __group, int gfp_mask);
struct cb_id
{
__u32 idx;
__u32 val;
};
idx and val are unique identifiers which must be registered in
connector.h for in-kernel usage. void (*callback) (void *) - is a
callback function which will be called when message with above idx.val
will be received by connector core. Argument for that function must
be dereferenced to struct cn_msg *.
struct cn_msg
{
struct cb_id id;
__u32 seq;
__u32 ack;
__u32 len; /* Length of the following data */
__u8 data[0];
};
/*****************************************/
Connector interfaces.
/*****************************************/
int cn_add_callback(struct cb_id *id, char *name, void (*callback) (void *));
Registers new callback with connector core.
struct cb_id *id - unique connector's user identifier.
It must be registered in connector.h for legal in-kernel users.
char *name - connector's callback symbolic name.
void (*callback) (void *) - connector's callback.
Argument must be dereferenced to struct cn_msg *.
void cn_del_callback(struct cb_id *id);
Unregisters new callback with connector core.
struct cb_id *id - unique connector's user identifier.
void cn_netlink_send(struct cn_msg *msg, u32 __groups, int gfp_mask);
Sends message to the specified groups. It can be safely called from
any context, but may silently fail under strong memory pressure.
struct cn_msg * - message header(with attached data).
u32 __group - destination group.
If __group is zero, then appropriate group will
be searched through all registered connector users,
and message will be delivered to the group which was
created for user with the same ID as in msg.
If __group is not zero, then message will be delivered
to the specified group.
int gfp_mask - GFP mask.
Note: When registering new callback user, connector core assigns
netlink group to the user which is equal to it's id.idx.
/*****************************************/
Protocol description.
/*****************************************/
Current offers transport layer with fixed header. Recommended
protocol which uses such header is following:
msg->seq and msg->ack are used to determine message genealogy. When
someone sends message it puts there locally unique sequence and random
acknowledge numbers. Sequence number may be copied into
nlmsghdr->nlmsg_seq too.
Sequence number is incremented with each message to be sent.
If we expect reply to our message, then sequence number in received
message MUST be the same as in original message, and acknowledge
number MUST be the same + 1.
If we receive message and it's sequence number is not equal to one we
are expecting, then it is new message. If we receive message and it's
sequence number is the same as one we are expecting, but it's
acknowledge is not equal acknowledge number in original message + 1,
then it is new message.
Obviously, protocol header contains above id.
connector allows event notification in the following form: kernel
driver or userspace process can ask connector to notify it when
selected id's will be turned on or off(registered or unregistered it's
callback). It is done by sending special command to connector
driver(it also registers itself with id={-1, -1}).
As example of usage Documentation/connector now contains cn_test.c -
testing module which uses connector to request notification and to
send messages.
/*****************************************/
Reliability.
/*****************************************/
Netlink itself is not reliable protocol, that means that messages can
be lost due to memory pressure or process' receiving queue overflowed,
so caller is warned must be prepared. That is why struct cn_msg [main
connector's message header] contains u32 seq and u32 ack fields.
......@@ -4,6 +4,8 @@ menu "Device Drivers"
source "drivers/base/Kconfig"
source "drivers/connector/Kconfig"
source "drivers/mtd/Kconfig"
source "drivers/parport/Kconfig"
......
......@@ -17,6 +17,8 @@ obj-$(CONFIG_PNP) += pnp/
# default.
obj-y += char/
obj-$(CONFIG_CONNECTOR) += connector/
# i810fb and intelfb depend on char/agp/
obj-$(CONFIG_FB_I810) += video/i810/
obj-$(CONFIG_FB_INTEL) += video/intelfb/
......
menu "Connector - unified userspace <-> kernelspace linker"
config CONNECTOR
tristate "Connector - unified userspace <-> kernelspace linker"
depends on NET
---help---
This is unified userspace <-> kernelspace connector working on top
of the netlink socket protocol.
Connector support can also be built as a module. If so, the module
will be called cn.ko.
endmenu
obj-$(CONFIG_CONNECTOR) += cn.o
cn-y += cn_queue.o connector.o
/*
* cn_queue.c
*
* 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/workqueue.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <linux/suspend.h>
#include <linux/connector.h>
#include <linux/delay.h>
static void cn_queue_wrapper(void *data)
{
struct cn_callback_entry *cbq = data;
cbq->cb->callback(cbq->cb->priv);
cbq->destruct_data(cbq->ddata);
cbq->ddata = NULL;
}
static struct cn_callback_entry *cn_queue_alloc_callback_entry(struct cn_callback *cb)
{
struct cn_callback_entry *cbq;
cbq = kzalloc(sizeof(*cbq), GFP_KERNEL);
if (!cbq) {
printk(KERN_ERR "Failed to create new callback queue.\n");
return NULL;
}
cbq->cb = cb;
INIT_WORK(&cbq->work, &cn_queue_wrapper, cbq);
return cbq;
}
static void cn_queue_free_callback(struct cn_callback_entry *cbq)
{
cancel_delayed_work(&cbq->work);
flush_workqueue(cbq->pdev->cn_queue);
kfree(cbq);
}
int cn_cb_equal(struct cb_id *i1, struct cb_id *i2)
{
return ((i1->idx == i2->idx) && (i1->val == i2->val));
}
int cn_queue_add_callback(struct cn_queue_dev *dev, struct cn_callback *cb)
{
struct cn_callback_entry *cbq, *__cbq;
int found = 0;
cbq = cn_queue_alloc_callback_entry(cb);
if (!cbq)
return -ENOMEM;
atomic_inc(&dev->refcnt);
cbq->pdev = dev;
spin_lock_bh(&dev->queue_lock);
list_for_each_entry(__cbq, &dev->queue_list, callback_entry) {
if (cn_cb_equal(&__cbq->cb->id, &cb->id)) {
found = 1;
break;
}
}
if (!found)
list_add_tail(&cbq->callback_entry, &dev->queue_list);
spin_unlock_bh(&dev->queue_lock);
if (found) {
atomic_dec(&dev->refcnt);
cn_queue_free_callback(cbq);
return -EINVAL;
}
cbq->nls = dev->nls;
cbq->seq = 0;
cbq->group = cbq->cb->id.idx;
return 0;
}
void cn_queue_del_callback(struct cn_queue_dev *dev, struct cb_id *id)
{
struct cn_callback_entry *cbq, *n;
int found = 0;
spin_lock_bh(&dev->queue_lock);
list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry) {
if (cn_cb_equal(&cbq->cb->id, id)) {
list_del(&cbq->callback_entry);
found = 1;
break;
}
}
spin_unlock_bh(&dev->queue_lock);
if (found) {
cn_queue_free_callback(cbq);
atomic_dec_and_test(&dev->refcnt);
}
}
struct cn_queue_dev *cn_queue_alloc_dev(char *name, struct sock *nls)
{
struct cn_queue_dev *dev;
dev = kzalloc(sizeof(*dev), GFP_KERNEL);
if (!dev)
return NULL;
snprintf(dev->name, sizeof(dev->name), "%s", name);
atomic_set(&dev->refcnt, 0);
INIT_LIST_HEAD(&dev->queue_list);
spin_lock_init(&dev->queue_lock);
dev->nls = nls;
dev->netlink_groups = 0;
dev->cn_queue = create_workqueue(dev->name);
if (!dev->cn_queue) {
kfree(dev);
return NULL;
}
return dev;
}
void cn_queue_free_dev(struct cn_queue_dev *dev)
{
struct cn_callback_entry *cbq, *n;
flush_workqueue(dev->cn_queue);
destroy_workqueue(dev->cn_queue);
spin_lock_bh(&dev->queue_lock);
list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry)
list_del(&cbq->callback_entry);
spin_unlock_bh(&dev->queue_lock);
while (atomic_read(&dev->refcnt)) {
printk(KERN_INFO "Waiting for %s to become free: refcnt=%d.\n",
dev->name, atomic_read(&dev->refcnt));
msleep(1000);
}
kfree(dev);
dev = NULL;
}
/*
* connector.c
*
* 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <linux/moduleparam.h>
#include <linux/connector.h>
#include <net/sock.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
static u32 cn_idx = CN_IDX_CONNECTOR;
static u32 cn_val = CN_VAL_CONNECTOR;
module_param(cn_idx, uint, 0);
module_param(cn_val, uint, 0);
MODULE_PARM_DESC(cn_idx, "Connector's main device idx.");
MODULE_PARM_DESC(cn_val, "Connector's main device val.");
static DECLARE_MUTEX(notify_lock);
static LIST_HEAD(notify_list);
static struct cn_dev cdev;
int cn_already_initialized = 0;
/*
* msg->seq and msg->ack are used to determine message genealogy.
* When someone sends message it puts there locally unique sequence
* and random acknowledge numbers. Sequence number may be copied into
* nlmsghdr->nlmsg_seq too.
*
* Sequence number is incremented with each message to be sent.
*
* If we expect reply to our message then the sequence number in
* received message MUST be the same as in original message, and
* acknowledge number MUST be the same + 1.
*
* If we receive a message and its sequence number is not equal to the
* one we are expecting then it is a new message.
*
* If we receive a message and its sequence number is the same as one
* we are expecting but it's acknowledgement number is not equal to
* the acknowledgement number in the original message + 1, then it is
* a new message.
*
*/
int cn_netlink_send(struct cn_msg *msg, u32 __group, int gfp_mask)
{
struct cn_callback_entry *__cbq;
unsigned int size;
struct sk_buff *skb;
struct nlmsghdr *nlh;
struct cn_msg *data;
struct cn_dev *dev = &cdev;
u32 group = 0;
int found = 0;
if (!__group) {
spin_lock_bh(&dev->cbdev->queue_lock);
list_for_each_entry(__cbq, &dev->cbdev->queue_list,
callback_entry) {
if (cn_cb_equal(&__cbq->cb->id, &msg->id)) {
found = 1;
group = __cbq->group;
}
}
spin_unlock_bh(&dev->cbdev->queue_lock);
if (!found)
return -ENODEV;
} else {
group = __group;
}
size = NLMSG_SPACE(sizeof(*msg) + msg->len);
skb = alloc_skb(size, gfp_mask);
if (!skb)
return -ENOMEM;
nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));