File-copy from v4.4.100

This is the result of 'cp' from a linux-stable tree with the 'v4.4.100'
tag checked out (commit 26d6298789e695c9f627ce49a7bbd2286405798a) on
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Please refer to that tree for all history prior to this point.

Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/net/ipv4/tcp_diag.c b/net/ipv4/tcp_diag.c
new file mode 100644
index 0000000..b316040
--- /dev/null
+++ b/net/ipv4/tcp_diag.c
@@ -0,0 +1,70 @@
+/*
+ * tcp_diag.c	Module for monitoring TCP transport protocols sockets.
+ *
+ * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
+ *
+ *	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.
+ */
+
+#include <linux/module.h>
+#include <linux/inet_diag.h>
+
+#include <linux/tcp.h>
+
+#include <net/tcp.h>
+
+static void tcp_diag_get_info(struct sock *sk, struct inet_diag_msg *r,
+			      void *_info)
+{
+	struct tcp_info *info = _info;
+
+	if (sk_state_load(sk) == TCP_LISTEN) {
+		r->idiag_rqueue = sk->sk_ack_backlog;
+		r->idiag_wqueue = sk->sk_max_ack_backlog;
+	} else if (sk->sk_type == SOCK_STREAM) {
+		const struct tcp_sock *tp = tcp_sk(sk);
+
+		r->idiag_rqueue = max_t(int, tp->rcv_nxt - tp->copied_seq, 0);
+		r->idiag_wqueue = tp->write_seq - tp->snd_una;
+	}
+	if (info)
+		tcp_get_info(sk, info);
+}
+
+static void tcp_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
+			  const struct inet_diag_req_v2 *r, struct nlattr *bc)
+{
+	inet_diag_dump_icsk(&tcp_hashinfo, skb, cb, r, bc);
+}
+
+static int tcp_diag_dump_one(struct sk_buff *in_skb, const struct nlmsghdr *nlh,
+			     const struct inet_diag_req_v2 *req)
+{
+	return inet_diag_dump_one_icsk(&tcp_hashinfo, in_skb, nlh, req);
+}
+
+static const struct inet_diag_handler tcp_diag_handler = {
+	.dump		 = tcp_diag_dump,
+	.dump_one	 = tcp_diag_dump_one,
+	.idiag_get_info	 = tcp_diag_get_info,
+	.idiag_type	 = IPPROTO_TCP,
+	.idiag_info_size = sizeof(struct tcp_info),
+};
+
+static int __init tcp_diag_init(void)
+{
+	return inet_diag_register(&tcp_diag_handler);
+}
+
+static void __exit tcp_diag_exit(void)
+{
+	inet_diag_unregister(&tcp_diag_handler);
+}
+
+module_init(tcp_diag_init);
+module_exit(tcp_diag_exit);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_NETLINK, NETLINK_SOCK_DIAG, 2-6 /* AF_INET - IPPROTO_TCP */);