/*

   * Copyright (c) 2006, 2017 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 <net/net_namespace.h>
  #include <net/netns/generic.h>

  #include <linux/ipv6.h>

  #include "rds_single_path.h"

  #include "rds.h"
  #include "loop.h"
  
  static DEFINE_SPINLOCK(loop_conns_lock);
  static LIST_HEAD(loop_conns);

  static atomic_t rds_loop_unloading = ATOMIC_INIT(0);
  
  static void rds_loop_set_unloading(void)
  {
  	atomic_set(&rds_loop_unloading, 1);
  }
  
  static bool rds_loop_is_unloading(struct rds_connection *conn)
  {
  	return atomic_read(&rds_loop_unloading) != 0;
  }

  
  /*
   * This 'loopback' transport is a special case for flows that originate
   * and terminate on the same machine.
   *
   * Connection build-up notices if the destination address is thought of
   * as a local address by a transport.  At that time it decides to use the
   * loopback transport instead of the bound transport of the sending socket.
   *
   * The loopback transport's sending path just hands the sent rds_message
   * straight to the receiving path via an embedded rds_incoming.
   */
  
  /*
   * Usually a message transits both the sender and receiver's conns as it
   * flows to the receiver.  In the loopback case, though, the receive path
   * is handed the sending conn so the sense of the addresses is reversed.
   */
  static int rds_loop_xmit(struct rds_connection *conn, struct rds_message *rm,
  			 unsigned int hdr_off, unsigned int sg,
  			 unsigned int off)
  {

  	struct scatterlist *sgp = &rm->data.op_sg[sg];
  	int ret = sizeof(struct rds_header) +
  			be32_to_cpu(rm->m_inc.i_hdr.h_len);

  	/* Do not send cong updates to loopback */
  	if (rm->m_inc.i_hdr.h_flags & RDS_FLAG_CONG_BITMAP) {
  		rds_cong_map_updated(conn->c_fcong, ~(u64) 0);

  		ret = min_t(int, ret, sgp->length - conn->c_xmit_data_off);
  		goto out;

  	}

  	BUG_ON(hdr_off || sg || off);

  	rds_inc_init(&rm->m_inc, conn, &conn->c_laddr);

  	/* For the embedded inc. Matching put is in loop_inc_free() */
  	rds_message_addref(rm);

  	rds_recv_incoming(conn, &conn->c_laddr, &conn->c_faddr, &rm->m_inc,

  			  GFP_KERNEL);

  
  	rds_send_drop_acked(conn, be64_to_cpu(rm->m_inc.i_hdr.h_sequence),
  			    NULL);
  
  	rds_inc_put(&rm->m_inc);

  out:
  	return ret;

  }

  /*
   * See rds_loop_xmit(). Since our inc is embedded in the rm, we
   * make sure the rm lives at least until the inc is done.
   */
  static void rds_loop_inc_free(struct rds_incoming *inc)
  {

  	struct rds_message *rm = container_of(inc, struct rds_message, m_inc);
  
  	rds_message_put(rm);

  }

  /* we need to at least give the thread something to succeed */

  static int rds_loop_recv_path(struct rds_conn_path *cp)

  {
  	return 0;
  }
  
  struct rds_loop_connection {
  	struct list_head loop_node;
  	struct rds_connection *conn;
  };
  
  /*
   * Even the loopback transport needs to keep track of its connections,
   * so it can call rds_conn_destroy() on them on exit. N.B. there are
   * 1+ loopback addresses (127.*.*.*) so it's not a bug to have
   * multiple loopback conns allocated, although rather useless.
   */
  static int rds_loop_conn_alloc(struct rds_connection *conn, gfp_t gfp)
  {
  	struct rds_loop_connection *lc;
  	unsigned long flags;

  	lc = kzalloc(sizeof(struct rds_loop_connection), gfp);

  	if (!lc)

  		return -ENOMEM;
  
  	INIT_LIST_HEAD(&lc->loop_node);
  	lc->conn = conn;
  	conn->c_transport_data = lc;
  
  	spin_lock_irqsave(&loop_conns_lock, flags);
  	list_add_tail(&lc->loop_node, &loop_conns);
  	spin_unlock_irqrestore(&loop_conns_lock, flags);
  
  	return 0;
  }
  
  static void rds_loop_conn_free(void *arg)
  {
  	struct rds_loop_connection *lc = arg;

  	unsigned long flags;

  	rdsdebug("lc %p
  ", lc);

  	spin_lock_irqsave(&loop_conns_lock, flags);

  	list_del(&lc->loop_node);

  	spin_unlock_irqrestore(&loop_conns_lock, flags);

  	kfree(lc);
  }

  static int rds_loop_conn_path_connect(struct rds_conn_path *cp)

  {

  	rds_connect_complete(cp->cp_conn);

  	return 0;
  }

  static void rds_loop_conn_path_shutdown(struct rds_conn_path *cp)

  {
  }
  
  void rds_loop_exit(void)
  {
  	struct rds_loop_connection *lc, *_lc;
  	LIST_HEAD(tmp_list);

  	rds_loop_set_unloading();
  	synchronize_rcu();

  	/* avoid calling conn_destroy with irqs off */
  	spin_lock_irq(&loop_conns_lock);
  	list_splice(&loop_conns, &tmp_list);
  	INIT_LIST_HEAD(&loop_conns);
  	spin_unlock_irq(&loop_conns_lock);
  
  	list_for_each_entry_safe(lc, _lc, &tmp_list, loop_node) {
  		WARN_ON(lc->conn->c_passive);
  		rds_conn_destroy(lc->conn);
  	}
  }

  static void rds_loop_kill_conns(struct net *net)
  {
  	struct rds_loop_connection *lc, *_lc;
  	LIST_HEAD(tmp_list);
  
  	spin_lock_irq(&loop_conns_lock);
  	list_for_each_entry_safe(lc, _lc, &loop_conns, loop_node)  {
  		struct net *c_net = read_pnet(&lc->conn->c_net);
  
  		if (net != c_net)
  			continue;
  		list_move_tail(&lc->loop_node, &tmp_list);
  	}
  	spin_unlock_irq(&loop_conns_lock);
  
  	list_for_each_entry_safe(lc, _lc, &tmp_list, loop_node) {
  		WARN_ON(lc->conn->c_passive);
  		rds_conn_destroy(lc->conn);
  	}
  }
  
  static void __net_exit rds_loop_exit_net(struct net *net)
  {
  	rds_loop_kill_conns(net);
  }
  
  static struct pernet_operations rds_loop_net_ops = {
  	.exit = rds_loop_exit_net,
  };
  
  int rds_loop_net_init(void)
  {
  	return register_pernet_device(&rds_loop_net_ops);
  }
  
  void rds_loop_net_exit(void)
  {
  	unregister_pernet_device(&rds_loop_net_ops);
  }

  /*
   * This is missing .xmit_* because loop doesn't go through generic
   * rds_send_xmit() and doesn't call rds_recv_incoming().  .listen_stop and
   * .laddr_check are missing because transport.c doesn't iterate over
   * rds_loop_transport.
   */
  struct rds_transport rds_loop_transport = {
  	.xmit			= rds_loop_xmit,

  	.recv_path		= rds_loop_recv_path,

  	.conn_alloc		= rds_loop_conn_alloc,
  	.conn_free		= rds_loop_conn_free,

  	.conn_path_connect	= rds_loop_conn_path_connect,

  	.conn_path_shutdown	= rds_loop_conn_path_shutdown,

  	.inc_copy_to_user	= rds_message_inc_copy_to_user,

  	.inc_free		= rds_loop_inc_free,

  	.t_name			= "loopback",

  	.t_type			= RDS_TRANS_LOOP,

  	.t_unloading		= rds_loop_is_unloading,

  };