[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>

1 files changed, 194 insertions, 0 deletions

diff --git a/Documentation/connector/cn_test.c b/Documentation/connector/cn_test.c
new file mode 100644
index 000000000000..b7de82e9c0e0
--- /dev/null
+++ b/Documentation/connector/cn_test.c
@@ -0,0 +1,194 @@
+/*
+ *      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");