[5/11] sock_diag: Initial skeleton

diff --git a/include/linux/sock_diag.h b/include/linux/sock_diag.h
new file mode 100644
index 0000000..ba4933b
--- /dev/null
+++ b/include/linux/sock_diag.h
@@ -0,0 +1,23 @@ 
+#ifndef __SOCK_DIAG_H__
+#define __SOCK_DIAG_H__
+struct sk_buff;
+struct nlmsghdr;
+
+struct sock_diag_req {
+	__u8	sdiag_family;
+	__u8	sdiag_protocol;
+};
+
+struct sock_diag_handler {
+	__u8 family;
+	int (*dump)(struct sk_buff *skb, struct nlmsghdr *nlh);
+};
+
+int sock_diag_register(struct sock_diag_handler *h);
+void sock_diag_unregister(struct sock_diag_handler *h);
+
+void sock_diag_register_inet_compat(int (*fn)(struct sk_buff *skb, struct nlmsghdr *nlh));
+void sock_diag_unregister_inet_compat(int (*fn)(struct sk_buff *skb, struct nlmsghdr *nlh));
+
+extern struct sock *sock_diag_nlsk;
+#endif
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index cf8be3e..ccbe8ea 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -33,6 +33,7 @@ 
 #include <linux/stddef.h>
 
 #include <linux/inet_diag.h>
+#include <linux/sock_diag.h>
 
 static const struct inet_diag_handler **inet_diag_table;
 
@@ -887,9 +888,91 @@  static int inet_diag_rcv_msg_compat(struct sk_buff *skb, struct nlmsghdr *nlh)
 	return inet_diag_get_exact(skb, nlh);
 }
 
+static int inet_diag_handler_dump(struct sk_buff *skb, struct nlmsghdr *h)
+{
+	int hdrlen = sizeof(struct inet_diag_req);
+
+	if (nlmsg_len(h) < hdrlen)
+		return -EINVAL;
+
+	if (h->nlmsg_flags & NLM_F_DUMP) {
+		return -EAFNOSUPPORT;
+	}
+
+	return -EAFNOSUPPORT;
+}
+
+static struct sock_diag_handler inet_diag_handler = {
+	.family = AF_INET,
+	.dump = inet_diag_handler_dump,
+};
+
+static struct sock_diag_handler inet6_diag_handler = {
+	.family = AF_INET6,
+	.dump = inet_diag_handler_dump,
+};
+
+static struct sock_diag_handler *sock_diag_handlers[AF_MAX];
+static DEFINE_MUTEX(sock_diag_table_mutex);
+
+int sock_diag_register(struct sock_diag_handler *hndl)
+{
+	int err = 0;
+
+	if (hndl->family > AF_MAX)
+		return -EINVAL;
+
+	mutex_lock(&sock_diag_table_mutex);
+	if (sock_diag_handlers[hndl->family])
+		err = -EBUSY;
+	else
+		sock_diag_handlers[hndl->family] = hndl;
+	mutex_unlock(&sock_diag_table_mutex);
+
+	return err;
+}
+
+void sock_diag_unregister(struct sock_diag_handler *hnld)
+{
+	int family = hnld->family;
+
+	if (family > AF_MAX)
+		return;
+
+	mutex_lock(&sock_diag_table_mutex);
+	BUG_ON(sock_diag_handlers[family] != hnld);
+	sock_diag_handlers[family] = NULL;
+	mutex_unlock(&sock_diag_table_mutex);
+}
+
+static inline struct sock_diag_handler *sock_diag_lock_handler(int family)
+{
+	mutex_lock(&sock_diag_table_mutex);
+	return sock_diag_handlers[family];
+}
+
+static inline void sock_diag_unlock_handler(struct sock_diag_handler *h)
+{
+	mutex_unlock(&sock_diag_table_mutex);
+}
+
 static int __sock_diag_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
-	return -EOPNOTSUPP;
+	int err;
+	struct sock_diag_req *req = NLMSG_DATA(nlh);
+	struct sock_diag_handler *hndl;
+
+	if (nlmsg_len(nlh) < sizeof(*req))
+		return -EINVAL;
+
+	hndl = sock_diag_lock_handler(req->sdiag_family);
+	if (hndl == NULL)
+		err = -ENOENT;
+	else
+		err = hndl->dump(skb, nlh);
+	sock_diag_unlock_handler(hndl);
+
+	return err;
 }
 
 static int sock_diag_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
@@ -961,9 +1044,22 @@  static int __init inet_diag_init(void)
 					sock_diag_rcv, NULL, THIS_MODULE);
 	if (sdiagnl == NULL)
 		goto out_free_table;
-	err = 0;
+
+	err = sock_diag_register(&inet_diag_handler);
+	if (err)
+		goto out_free_nl;
+
+	err = sock_diag_register(&inet6_diag_handler);
+	if (err)
+		goto out_free_inet;
+
 out:
 	return err;
+
+out_free_inet:
+	sock_diag_unregister(&inet_diag_handler);
+out_free_nl:
+	netlink_kernel_release(sdiagnl);
 out_free_table:
 	kfree(inet_diag_table);
 	goto out;
@@ -971,6 +1067,8 @@  out_free_table:
 
 static void __exit inet_diag_exit(void)
 {
+	sock_diag_unregister(&inet6_diag_handler);
+	sock_diag_unregister(&inet_diag_handler);
 	netlink_kernel_release(sdiagnl);
 	kfree(inet_diag_table);
 }