/*

   * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.

   *
   * This software is available to you under a choice of one of two
   * licenses.  You may choose to be licensed under the terms of the GNU
   * General Public License (GPL) Version 2, available from the file
   * COPYING in the main directory of this source tree, or the
   * OpenIB.org BSD license below:
   *
   *     Redistribution and use in source and binary forms, with or
   *     without modification, are permitted provided that the following
   *     conditions are met:
   *
   *      - Redistributions of source code must retain the above
   *        copyright notice, this list of conditions and the following
   *        disclaimer.
   *
   *      - Redistributions in binary form must reproduce the above
   *        copyright notice, this list of conditions and the following
   *        disclaimer in the documentation and/or other materials
   *        provided with the distribution.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
   * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
   * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   *
   */
  #include <linux/kernel.h>

  #include <linux/slab.h>

  #include <linux/in.h>

  #include <linux/module.h>

  #include <net/tcp.h>

  #include <net/net_namespace.h>
  #include <net/netns/generic.h>

  #include <net/addrconf.h>

  
  #include "rds.h"
  #include "tcp.h"
  
  /* only for info exporting */
  static DEFINE_SPINLOCK(rds_tcp_tc_list_lock);
  static LIST_HEAD(rds_tcp_tc_list);

  
  /* rds_tcp_tc_count counts only IPv4 connections.
   * rds6_tcp_tc_count counts both IPv4 and IPv6 connections.
   */

  static unsigned int rds_tcp_tc_count;

  #if IS_ENABLED(CONFIG_IPV6)

  static unsigned int rds6_tcp_tc_count;

  #endif

  
  /* Track rds_tcp_connection structs so they can be cleaned up */
  static DEFINE_SPINLOCK(rds_tcp_conn_lock);
  static LIST_HEAD(rds_tcp_conn_list);

  static atomic_t rds_tcp_unloading = ATOMIC_INIT(0);

  
  static struct kmem_cache *rds_tcp_conn_slab;

  static int rds_tcp_skbuf_handler(struct ctl_table *ctl, int write,

  				 void *buffer, size_t *lenp, loff_t *fpos);

  static int rds_tcp_min_sndbuf = SOCK_MIN_SNDBUF;
  static int rds_tcp_min_rcvbuf = SOCK_MIN_RCVBUF;

  
  static struct ctl_table rds_tcp_sysctl_table[] = {
  #define	RDS_TCP_SNDBUF	0
  	{
  		.procname       = "rds_tcp_sndbuf",
  		/* data is per-net pointer */
  		.maxlen         = sizeof(int),
  		.mode           = 0644,
  		.proc_handler   = rds_tcp_skbuf_handler,
  		.extra1		= &rds_tcp_min_sndbuf,
  	},
  #define	RDS_TCP_RCVBUF	1
  	{
  		.procname       = "rds_tcp_rcvbuf",
  		/* data is per-net pointer */
  		.maxlen         = sizeof(int),
  		.mode           = 0644,
  		.proc_handler   = rds_tcp_skbuf_handler,
  		.extra1		= &rds_tcp_min_rcvbuf,
  	},
  	{ }
  };

  u32 rds_tcp_write_seq(struct rds_tcp_connection *tc)

  {

  	/* seq# of the last byte of data in tcp send buffer */
  	return tcp_sk(tc->t_sock->sk)->write_seq;

  }
  
  u32 rds_tcp_snd_una(struct rds_tcp_connection *tc)
  {
  	return tcp_sk(tc->t_sock->sk)->snd_una;
  }
  
  void rds_tcp_restore_callbacks(struct socket *sock,
  			       struct rds_tcp_connection *tc)
  {
  	rdsdebug("restoring sock %p callbacks from tc %p
  ", sock, tc);
  	write_lock_bh(&sock->sk->sk_callback_lock);
  
  	/* done under the callback_lock to serialize with write_space */
  	spin_lock(&rds_tcp_tc_list_lock);
  	list_del_init(&tc->t_list_item);

  #if IS_ENABLED(CONFIG_IPV6)

  	rds6_tcp_tc_count--;

  #endif

  	if (!tc->t_cpath->cp_conn->c_isv6)
  		rds_tcp_tc_count--;

  	spin_unlock(&rds_tcp_tc_list_lock);
  
  	tc->t_sock = NULL;
  
  	sock->sk->sk_write_space = tc->t_orig_write_space;
  	sock->sk->sk_data_ready = tc->t_orig_data_ready;
  	sock->sk->sk_state_change = tc->t_orig_state_change;
  	sock->sk->sk_user_data = NULL;
  
  	write_unlock_bh(&sock->sk->sk_callback_lock);
  }
  
  /*

   * rds_tcp_reset_callbacks() switches the to the new sock and
   * returns the existing tc->t_sock.
   *
   * The only functions that set tc->t_sock are rds_tcp_set_callbacks
   * and rds_tcp_reset_callbacks.  Send and receive trust that
   * it is set.  The absence of RDS_CONN_UP bit protects those paths
   * from being called while it isn't set.
   */
  void rds_tcp_reset_callbacks(struct socket *sock,

  			     struct rds_conn_path *cp)

  {

  	struct rds_tcp_connection *tc = cp->cp_transport_data;

  	struct socket *osock = tc->t_sock;
  
  	if (!osock)
  		goto newsock;
  
  	/* Need to resolve a duelling SYN between peers.
  	 * We have an outstanding SYN to this peer, which may
  	 * potentially have transitioned to the RDS_CONN_UP state,
  	 * so we must quiesce any send threads before resetting

  	 * cp_transport_data. We quiesce these threads by setting
  	 * cp_state to something other than RDS_CONN_UP, and then

  	 * waiting for any existing threads in rds_send_xmit to
  	 * complete release_in_xmit(). (Subsequent threads entering
  	 * rds_send_xmit() will bail on !rds_conn_up().

  	 *
  	 * However an incoming syn-ack at this point would end up
  	 * marking the conn as RDS_CONN_UP, and would again permit
  	 * rds_send_xmi() threads through, so ideally we would
  	 * synchronize on RDS_CONN_UP after lock_sock(), but cannot
  	 * do that: waiting on !RDS_IN_XMIT after lock_sock() may
  	 * end up deadlocking with tcp_sendmsg(), and the RDS_IN_XMIT
  	 * would not get set. As a result, we set c_state to
  	 * RDS_CONN_RESETTTING, to ensure that rds_tcp_state_change
  	 * cannot mark rds_conn_path_up() in the window before lock_sock()

  	 */

  	atomic_set(&cp->cp_state, RDS_CONN_RESETTING);
  	wait_event(cp->cp_waitq, !test_bit(RDS_IN_XMIT, &cp->cp_flags));

  	lock_sock(osock->sk);
  	/* reset receive side state for rds_tcp_data_recv() for osock  */

  	cancel_delayed_work_sync(&cp->cp_send_w);
  	cancel_delayed_work_sync(&cp->cp_recv_w);

  	if (tc->t_tinc) {
  		rds_inc_put(&tc->t_tinc->ti_inc);
  		tc->t_tinc = NULL;
  	}
  	tc->t_tinc_hdr_rem = sizeof(struct rds_header);
  	tc->t_tinc_data_rem = 0;

  	rds_tcp_restore_callbacks(osock, tc);

  	release_sock(osock->sk);
  	sock_release(osock);
  newsock:

  	rds_send_path_reset(cp);

  	lock_sock(sock->sk);

  	rds_tcp_set_callbacks(sock, cp);

  	release_sock(sock->sk);
  }
  
  /* Add tc to rds_tcp_tc_list and set tc->t_sock. See comments
   * above rds_tcp_reset_callbacks for notes about synchronization
   * with data path

   */

  void rds_tcp_set_callbacks(struct socket *sock, struct rds_conn_path *cp)

  {

  	struct rds_tcp_connection *tc = cp->cp_transport_data;

  
  	rdsdebug("setting sock %p callbacks to tc %p
  ", sock, tc);
  	write_lock_bh(&sock->sk->sk_callback_lock);
  
  	/* done under the callback_lock to serialize with write_space */
  	spin_lock(&rds_tcp_tc_list_lock);
  	list_add_tail(&tc->t_list_item, &rds_tcp_tc_list);

  #if IS_ENABLED(CONFIG_IPV6)

  	rds6_tcp_tc_count++;

  #endif

  	if (!tc->t_cpath->cp_conn->c_isv6)
  		rds_tcp_tc_count++;

  	spin_unlock(&rds_tcp_tc_list_lock);
  
  	/* accepted sockets need our listen data ready undone */
  	if (sock->sk->sk_data_ready == rds_tcp_listen_data_ready)
  		sock->sk->sk_data_ready = sock->sk->sk_user_data;
  
  	tc->t_sock = sock;

  	tc->t_cpath = cp;

  	tc->t_orig_data_ready = sock->sk->sk_data_ready;
  	tc->t_orig_write_space = sock->sk->sk_write_space;
  	tc->t_orig_state_change = sock->sk->sk_state_change;

  	sock->sk->sk_user_data = cp;

  	sock->sk->sk_data_ready = rds_tcp_data_ready;
  	sock->sk->sk_write_space = rds_tcp_write_space;
  	sock->sk->sk_state_change = rds_tcp_state_change;
  
  	write_unlock_bh(&sock->sk->sk_callback_lock);
  }

  /* Handle RDS_INFO_TCP_SOCKETS socket option.  It only returns IPv4
   * connections for backward compatibility.
   */

  static void rds_tcp_tc_info(struct socket *rds_sock, unsigned int len,

  			    struct rds_info_iterator *iter,
  			    struct rds_info_lengths *lens)
  {
  	struct rds_info_tcp_socket tsinfo;
  	struct rds_tcp_connection *tc;
  	unsigned long flags;

  
  	spin_lock_irqsave(&rds_tcp_tc_list_lock, flags);
  
  	if (len / sizeof(tsinfo) < rds_tcp_tc_count)
  		goto out;
  
  	list_for_each_entry(tc, &rds_tcp_tc_list, t_list_item) {

  		struct inet_sock *inet = inet_sk(tc->t_sock->sk);

  		if (tc->t_cpath->cp_conn->c_isv6)
  			continue;
  
  		tsinfo.local_addr = inet->inet_saddr;
  		tsinfo.local_port = inet->inet_sport;
  		tsinfo.peer_addr = inet->inet_daddr;
  		tsinfo.peer_port = inet->inet_dport;

  
  		tsinfo.hdr_rem = tc->t_tinc_hdr_rem;
  		tsinfo.data_rem = tc->t_tinc_data_rem;
  		tsinfo.last_sent_nxt = tc->t_last_sent_nxt;
  		tsinfo.last_expected_una = tc->t_last_expected_una;
  		tsinfo.last_seen_una = tc->t_last_seen_una;

  		tsinfo.tos = tc->t_cpath->cp_conn->c_tos;

  
  		rds_info_copy(iter, &tsinfo, sizeof(tsinfo));
  	}
  
  out:
  	lens->nr = rds_tcp_tc_count;
  	lens->each = sizeof(tsinfo);
  
  	spin_unlock_irqrestore(&rds_tcp_tc_list_lock, flags);
  }

  #if IS_ENABLED(CONFIG_IPV6)

  /* Handle RDS6_INFO_TCP_SOCKETS socket option. It returns both IPv4 and
   * IPv6 connections. IPv4 connection address is returned in an IPv4 mapped
   * address.
   */
  static void rds6_tcp_tc_info(struct socket *sock, unsigned int len,
  			     struct rds_info_iterator *iter,
  			     struct rds_info_lengths *lens)
  {
  	struct rds6_info_tcp_socket tsinfo6;
  	struct rds_tcp_connection *tc;
  	unsigned long flags;
  
  	spin_lock_irqsave(&rds_tcp_tc_list_lock, flags);
  
  	if (len / sizeof(tsinfo6) < rds6_tcp_tc_count)
  		goto out;
  
  	list_for_each_entry(tc, &rds_tcp_tc_list, t_list_item) {
  		struct sock *sk = tc->t_sock->sk;
  		struct inet_sock *inet = inet_sk(sk);
  
  		tsinfo6.local_addr = sk->sk_v6_rcv_saddr;
  		tsinfo6.local_port = inet->inet_sport;
  		tsinfo6.peer_addr = sk->sk_v6_daddr;
  		tsinfo6.peer_port = inet->inet_dport;
  
  		tsinfo6.hdr_rem = tc->t_tinc_hdr_rem;
  		tsinfo6.data_rem = tc->t_tinc_data_rem;
  		tsinfo6.last_sent_nxt = tc->t_last_sent_nxt;
  		tsinfo6.last_expected_una = tc->t_last_expected_una;
  		tsinfo6.last_seen_una = tc->t_last_seen_una;
  
  		rds_info_copy(iter, &tsinfo6, sizeof(tsinfo6));
  	}
  
  out:
  	lens->nr = rds6_tcp_tc_count;
  	lens->each = sizeof(tsinfo6);
  
  	spin_unlock_irqrestore(&rds_tcp_tc_list_lock, flags);
  }

  #endif

  static int rds_tcp_laddr_check(struct net *net, const struct in6_addr *addr,
  			       __u32 scope_id)

  {

  	struct net_device *dev = NULL;

  #if IS_ENABLED(CONFIG_IPV6)

  	int ret;

  #endif

  
  	if (ipv6_addr_v4mapped(addr)) {
  		if (inet_addr_type(net, addr->s6_addr32[3]) == RTN_LOCAL)
  			return 0;
  		return -EADDRNOTAVAIL;
  	}
  
  	/* If the scope_id is specified, check only those addresses
  	 * hosted on the specified interface.
  	 */
  	if (scope_id != 0) {
  		rcu_read_lock();
  		dev = dev_get_by_index_rcu(net, scope_id);
  		/* scope_id is not valid... */
  		if (!dev) {
  			rcu_read_unlock();
  			return -EADDRNOTAVAIL;
  		}
  		rcu_read_unlock();
  	}

  #if IS_ENABLED(CONFIG_IPV6)

  	ret = ipv6_chk_addr(net, addr, dev, 0);
  	if (ret)

  		return 0;

  #endif

  	return -EADDRNOTAVAIL;
  }

  static void rds_tcp_conn_free(void *arg)
  {
  	struct rds_tcp_connection *tc = arg;

  	unsigned long flags;

  
  	rdsdebug("freeing tc %p
  ", tc);

  	spin_lock_irqsave(&rds_tcp_conn_lock, flags);

  	if (!tc->t_tcp_node_detached)
  		list_del(&tc->t_tcp_node);

  	spin_unlock_irqrestore(&rds_tcp_conn_lock, flags);

  
  	kmem_cache_free(rds_tcp_conn_slab, tc);
  }

  static int rds_tcp_conn_alloc(struct rds_connection *conn, gfp_t gfp)
  {
  	struct rds_tcp_connection *tc;

  	int i, j;
  	int ret = 0;

  	for (i = 0; i < RDS_MPATH_WORKERS; i++) {
  		tc = kmem_cache_alloc(rds_tcp_conn_slab, gfp);

  		if (!tc) {
  			ret = -ENOMEM;

  			goto fail;

  		}

  		mutex_init(&tc->t_conn_path_lock);
  		tc->t_sock = NULL;
  		tc->t_tinc = NULL;
  		tc->t_tinc_hdr_rem = sizeof(struct rds_header);
  		tc->t_tinc_data_rem = 0;

  		conn->c_path[i].cp_transport_data = tc;
  		tc->t_cpath = &conn->c_path[i];

  		tc->t_tcp_node_detached = true;

  		rdsdebug("rds_conn_path [%d] tc %p
  ", i,
  			 conn->c_path[i].cp_transport_data);
  	}

  	spin_lock_irq(&rds_tcp_conn_lock);

  	for (i = 0; i < RDS_MPATH_WORKERS; i++) {
  		tc = conn->c_path[i].cp_transport_data;
  		tc->t_tcp_node_detached = false;
  		list_add_tail(&tc->t_tcp_node, &rds_tcp_conn_list);
  	}

  	spin_unlock_irq(&rds_tcp_conn_lock);

  fail:

  	if (ret) {
  		for (j = 0; j < i; j++)
  			rds_tcp_conn_free(conn->c_path[j].cp_transport_data);
  	}
  	return ret;

  }

  static bool list_has_conn(struct list_head *list, struct rds_connection *conn)
  {
  	struct rds_tcp_connection *tc, *_tc;
  
  	list_for_each_entry_safe(tc, _tc, list, t_tcp_node) {
  		if (tc->t_cpath->cp_conn == conn)
  			return true;
  	}
  	return false;
  }

  static void rds_tcp_set_unloading(void)
  {
  	atomic_set(&rds_tcp_unloading, 1);
  }
  
  static bool rds_tcp_is_unloading(struct rds_connection *conn)
  {
  	return atomic_read(&rds_tcp_unloading) != 0;
  }

  static void rds_tcp_destroy_conns(void)
  {
  	struct rds_tcp_connection *tc, *_tc;
  	LIST_HEAD(tmp_list);
  
  	/* avoid calling conn_destroy with irqs off */
  	spin_lock_irq(&rds_tcp_conn_lock);

  	list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {
  		if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn))
  			list_move_tail(&tc->t_tcp_node, &tmp_list);
  	}

  	spin_unlock_irq(&rds_tcp_conn_lock);

  	list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node)

  		rds_conn_destroy(tc->t_cpath->cp_conn);

  }

  static void rds_tcp_exit(void);

  static u8 rds_tcp_get_tos_map(u8 tos)
  {
  	/* all user tos mapped to default 0 for TCP transport */
  	return 0;
  }

  struct rds_transport rds_tcp_transport = {
  	.laddr_check		= rds_tcp_laddr_check,

  	.xmit_path_prepare	= rds_tcp_xmit_path_prepare,
  	.xmit_path_complete	= rds_tcp_xmit_path_complete,

  	.xmit			= rds_tcp_xmit,

  	.recv_path		= rds_tcp_recv_path,

  	.conn_alloc		= rds_tcp_conn_alloc,
  	.conn_free		= rds_tcp_conn_free,

  	.conn_path_connect	= rds_tcp_conn_path_connect,

  	.conn_path_shutdown	= rds_tcp_conn_path_shutdown,

  	.inc_copy_to_user	= rds_tcp_inc_copy_to_user,

  	.inc_free		= rds_tcp_inc_free,
  	.stats_info_copy	= rds_tcp_stats_info_copy,
  	.exit			= rds_tcp_exit,

  	.get_tos_map		= rds_tcp_get_tos_map,

  	.t_owner		= THIS_MODULE,
  	.t_name			= "tcp",

  	.t_type			= RDS_TRANS_TCP,

  	.t_prefer_loopback	= 1,

  	.t_mp_capable		= 1,

  	.t_unloading		= rds_tcp_is_unloading,

  };

  static unsigned int rds_tcp_netid;

  
  /* per-network namespace private data for this module */
  struct rds_tcp_net {
  	struct socket *rds_tcp_listen_sock;
  	struct work_struct rds_tcp_accept_w;

  	struct ctl_table_header *rds_tcp_sysctl;
  	struct ctl_table *ctl_table;
  	int sndbuf_size;
  	int rcvbuf_size;

  };

  /* All module specific customizations to the RDS-TCP socket should be done in
   * rds_tcp_tune() and applied after socket creation.
   */
  void rds_tcp_tune(struct socket *sock)
  {
  	struct sock *sk = sock->sk;
  	struct net *net = sock_net(sk);
  	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);

  	tcp_sock_set_nodelay(sock->sk);

  	lock_sock(sk);
  	if (rtn->sndbuf_size > 0) {
  		sk->sk_sndbuf = rtn->sndbuf_size;
  		sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
  	}
  	if (rtn->rcvbuf_size > 0) {
  		sk->sk_sndbuf = rtn->rcvbuf_size;
  		sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
  	}
  	release_sock(sk);
  }

  static void rds_tcp_accept_worker(struct work_struct *work)
  {
  	struct rds_tcp_net *rtn = container_of(work,
  					       struct rds_tcp_net,
  					       rds_tcp_accept_w);
  
  	while (rds_tcp_accept_one(rtn->rds_tcp_listen_sock) == 0)
  		cond_resched();
  }
  
  void rds_tcp_accept_work(struct sock *sk)
  {
  	struct net *net = sock_net(sk);
  	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
  
  	queue_work(rds_wq, &rtn->rds_tcp_accept_w);
  }
  
  static __net_init int rds_tcp_init_net(struct net *net)
  {
  	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);

  	struct ctl_table *tbl;
  	int err = 0;

  	memset(rtn, 0, sizeof(*rtn));
  
  	/* {snd, rcv}buf_size default to 0, which implies we let the
  	 * stack pick the value, and permit auto-tuning of buffer size.
  	 */
  	if (net == &init_net) {
  		tbl = rds_tcp_sysctl_table;
  	} else {
  		tbl = kmemdup(rds_tcp_sysctl_table,
  			      sizeof(rds_tcp_sysctl_table), GFP_KERNEL);
  		if (!tbl) {

  			pr_warn("could not set allocate sysctl table
  ");

  			return -ENOMEM;
  		}
  		rtn->ctl_table = tbl;
  	}
  	tbl[RDS_TCP_SNDBUF].data = &rtn->sndbuf_size;
  	tbl[RDS_TCP_RCVBUF].data = &rtn->rcvbuf_size;
  	rtn->rds_tcp_sysctl = register_net_sysctl(net, "net/rds/tcp", tbl);
  	if (!rtn->rds_tcp_sysctl) {
  		pr_warn("could not register sysctl
  ");
  		err = -ENOMEM;
  		goto fail;
  	}

  
  #if IS_ENABLED(CONFIG_IPV6)

  	rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net, true);

  #else
  	rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net, false);
  #endif

  	if (!rtn->rds_tcp_listen_sock) {

  		pr_warn("could not set up IPv6 listen sock
  ");

  #if IS_ENABLED(CONFIG_IPV6)

  		/* Try IPv4 as some systems disable IPv6 */
  		rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net, false);
  		if (!rtn->rds_tcp_listen_sock) {

  #endif

  			unregister_net_sysctl_table(rtn->rds_tcp_sysctl);
  			rtn->rds_tcp_sysctl = NULL;
  			err = -EAFNOSUPPORT;
  			goto fail;

  #if IS_ENABLED(CONFIG_IPV6)

  		}

  #endif

  	}
  	INIT_WORK(&rtn->rds_tcp_accept_w, rds_tcp_accept_worker);
  	return 0;

  
  fail:
  	if (net != &init_net)
  		kfree(tbl);
  	return err;

  }

  static void rds_tcp_kill_sock(struct net *net)
  {
  	struct rds_tcp_connection *tc, *_tc;

  	LIST_HEAD(tmp_list);
  	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);

  	struct socket *lsock = rtn->rds_tcp_listen_sock;

  	rtn->rds_tcp_listen_sock = NULL;

  	rds_tcp_listen_stop(lsock, &rtn->rds_tcp_accept_w);

  	spin_lock_irq(&rds_tcp_conn_lock);

  	list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {

  		struct net *c_net = read_pnet(&tc->t_cpath->cp_conn->c_net);

  		if (net != c_net)

  			continue;

  		if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn)) {

  			list_move_tail(&tc->t_tcp_node, &tmp_list);

  		} else {
  			list_del(&tc->t_tcp_node);
  			tc->t_tcp_node_detached = true;
  		}

  	}

  	spin_unlock_irq(&rds_tcp_conn_lock);

  	list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node)

  		rds_conn_destroy(tc->t_cpath->cp_conn);

  }

  static void __net_exit rds_tcp_exit_net(struct net *net)

  {
  	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);

  	rds_tcp_kill_sock(net);

  	if (rtn->rds_tcp_sysctl)
  		unregister_net_sysctl_table(rtn->rds_tcp_sysctl);

  	if (net != &init_net)

  		kfree(rtn->ctl_table);

  }

  static struct pernet_operations rds_tcp_net_ops = {
  	.init = rds_tcp_init_net,
  	.exit = rds_tcp_exit_net,
  	.id = &rds_tcp_netid,
  	.size = sizeof(struct rds_tcp_net),

  };
  
  void *rds_tcp_listen_sock_def_readable(struct net *net)

  {

  	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
  	struct socket *lsock = rtn->rds_tcp_listen_sock;

  	if (!lsock)
  		return NULL;

  	return lsock->sk->sk_user_data;

  }

  /* when sysctl is used to modify some kernel socket parameters,this
   * function  resets the RDS connections in that netns  so that we can
   * restart with new parameters.  The assumption is that such reset
   * events are few and far-between.
   */
  static void rds_tcp_sysctl_reset(struct net *net)
  {
  	struct rds_tcp_connection *tc, *_tc;

  	spin_lock_irq(&rds_tcp_conn_lock);

  	list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {

  		struct net *c_net = read_pnet(&tc->t_cpath->cp_conn->c_net);

  
  		if (net != c_net || !tc->t_sock)
  			continue;

  		/* reconnect with new parameters */

  		rds_conn_path_drop(tc->t_cpath, false);

  	}

  	spin_unlock_irq(&rds_tcp_conn_lock);

  }
  
  static int rds_tcp_skbuf_handler(struct ctl_table *ctl, int write,

  				 void *buffer, size_t *lenp, loff_t *fpos)

  {
  	struct net *net = current->nsproxy->net_ns;
  	int err;
  
  	err = proc_dointvec_minmax(ctl, write, buffer, lenp, fpos);
  	if (err < 0) {
  		pr_warn("Invalid input. Must be >= %d
  ",
  			*(int *)(ctl->extra1));
  		return err;
  	}
  	if (write)
  		rds_tcp_sysctl_reset(net);
  	return 0;
  }

  static void rds_tcp_exit(void)
  {

  	rds_tcp_set_unloading();
  	synchronize_rcu();

  	rds_info_deregister_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);

  #if IS_ENABLED(CONFIG_IPV6)

  	rds_info_deregister_func(RDS6_INFO_TCP_SOCKETS, rds6_tcp_tc_info);

  #endif

  	unregister_pernet_device(&rds_tcp_net_ops);

  	rds_tcp_destroy_conns();
  	rds_trans_unregister(&rds_tcp_transport);
  	rds_tcp_recv_exit();
  	kmem_cache_destroy(rds_tcp_conn_slab);
  }
  module_exit(rds_tcp_exit);

  static int rds_tcp_init(void)

  {
  	int ret;
  
  	rds_tcp_conn_slab = kmem_cache_create("rds_tcp_connection",
  					      sizeof(struct rds_tcp_connection),
  					      0, 0, NULL);

  	if (!rds_tcp_conn_slab) {

  		ret = -ENOMEM;
  		goto out;
  	}

  	ret = rds_tcp_recv_init();
  	if (ret)

  		goto out_slab;

  	ret = register_pernet_device(&rds_tcp_net_ops);

  	if (ret)

  		goto out_recv;

  	rds_trans_register(&rds_tcp_transport);

  	rds_info_register_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);

  #if IS_ENABLED(CONFIG_IPV6)

  	rds_info_register_func(RDS6_INFO_TCP_SOCKETS, rds6_tcp_tc_info);

  #endif

  
  	goto out;

  out_recv:
  	rds_tcp_recv_exit();

  out_slab:

  	kmem_cache_destroy(rds_tcp_conn_slab);
  out:
  	return ret;
  }
  module_init(rds_tcp_init);
  
  MODULE_AUTHOR("Oracle Corporation <rds-devel@oss.oracle.com>");
  MODULE_DESCRIPTION("RDS: TCP transport");
  MODULE_LICENSE("Dual BSD/GPL");