[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: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 159 insertions, 0 deletions

diff --git a/include/linux/connector.h b/include/linux/connector.h
new file mode 100644
index 000000000000..96de26301f84
--- /dev/null
+++ b/include/linux/connector.h
@@ -0,0 +1,158 @@
+/*
+ * 	connector.h
+ * 
+ * 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
+ */
+
+#ifndef __CONNECTOR_H
+#define __CONNECTOR_H
+
+#include <asm/types.h>
+
+#define CN_IDX_CONNECTOR		0xffffffff
+#define CN_VAL_CONNECTOR		0xffffffff
+
+#define CN_NETLINK_USERS		1
+
+/*
+ * Maximum connector's message size.
+ */
+#define CONNECTOR_MAX_MSG_SIZE 	1024
+
+/*
+ * idx and val are unique identifiers which 
+ * are used for message routing and 
+ * must be registered in connector.h for in-kernel usage.
+ */
+
+struct cb_id {
+	__u32 idx;
+	__u32 val;
+};
+
+struct cn_msg {
+	struct cb_id id;
+
+	__u32 seq;
+	__u32 ack;
+
+	__u16 len;		/* Length of the following data */
+	__u16 flags;
+	__u8 data[0];
+};
+
+/*
+ * Notify structure - requests notification about
+ * registering/unregistering idx/val in range [first, first+range].
+ */
+struct cn_notify_req {
+	__u32 first;
+	__u32 range;
+};
+
+/*
+ * Main notification control message
+ * *_notify_num 	- number of appropriate cn_notify_req structures after 
+ *				this struct.
+ * group 		- notification receiver's idx.
+ * len 			- total length of the attached data.
+ */
+struct cn_ctl_msg {
+	__u32 idx_notify_num;
+	__u32 val_notify_num;
+	__u32 group;
+	__u32 len;
+	__u8 data[0];
+};
+
+#ifdef __KERNEL__
+
+#include <asm/atomic.h>
+
+#include <linux/list.h>
+#include <linux/workqueue.h>
+
+#include <net/sock.h>
+
+#define CN_CBQ_NAMELEN		32
+
+struct cn_queue_dev {
+	atomic_t refcnt;
+	unsigned char name[CN_CBQ_NAMELEN];
+
+	struct workqueue_struct *cn_queue;
+
+	struct list_head queue_list;
+	spinlock_t queue_lock;
+
+	int netlink_groups;
+	struct sock *nls;
+};
+
+struct cn_callback {
+	unsigned char name[CN_CBQ_NAMELEN];
+
+	struct cb_id id;
+	void (*callback) (void *);
+	void *priv;
+};
+
+struct cn_callback_entry {
+	struct list_head callback_entry;
+	struct cn_callback *cb;
+	struct work_struct work;
+	struct cn_queue_dev *pdev;
+
+	void (*destruct_data) (void *);
+	void *ddata;
+
+	int seq, group;
+	struct sock *nls;
+};
+
+struct cn_ctl_entry {
+	struct list_head notify_entry;
+	struct cn_ctl_msg *msg;
+};
+
+struct cn_dev {
+	struct cb_id id;
+
+	u32 seq, groups;
+	struct sock *nls;
+	void (*input) (struct sock * sk, int len);
+
+	struct cn_queue_dev *cbdev;
+};
+
+int cn_add_callback(struct cb_id *, char *, void (*callback) (void *));
+void cn_del_callback(struct cb_id *);
+int cn_netlink_send(struct cn_msg *, u32, int);
+
+int cn_queue_add_callback(struct cn_queue_dev *dev, struct cn_callback *cb);
+void cn_queue_del_callback(struct cn_queue_dev *dev, struct cb_id *id);
+
+struct cn_queue_dev *cn_queue_alloc_dev(char *name, struct sock *);
+void cn_queue_free_dev(struct cn_queue_dev *dev);
+
+int cn_cb_equal(struct cb_id *, struct cb_id *);
+
+extern int cn_already_initialized;
+
+#endif				/* __KERNEL__ */
+#endif				/* __CONNECTOR_H */
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 167518668936..7bbd25970c9e 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -15,6 +15,7 @@
 #define NETLINK_ISCSI		8	/* Open-iSCSI */
 #define NETLINK_AUDIT		9	/* auditing */
 #define NETLINK_FIB_LOOKUP	10	
+#define NETLINK_CONNECTOR	11
 #define NETLINK_NETFILTER	12	/* netfilter subsystem */
 #define NETLINK_IP6_FW		13
 #define NETLINK_DNRTMSG		14	/* DECnet routing messages */