/*
   * Copyright (c) 2006 Oracle.  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 "rds.h"
  #include "loop.h"
  
  static DEFINE_SPINLOCK(loop_conns_lock);
  static LIST_HEAD(loop_conns);
  
  /*
   * 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(struct rds_connection *conn)
  {
  	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_connect(struct rds_connection *conn)
  {
  	rds_connect_complete(conn);
  	return 0;
  }
  
  static void rds_loop_conn_shutdown(struct rds_connection *conn)
  {
  }
  
  void rds_loop_exit(void)
  {
  	struct rds_loop_connection *lc, *_lc;
  	LIST_HEAD(tmp_list);
  
  	/* 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);
  	}
  }
  
  /*
   * 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			= rds_loop_recv,
  	.conn_alloc		= rds_loop_conn_alloc,
  	.conn_free		= rds_loop_conn_free,
  	.conn_connect		= rds_loop_conn_connect,
  	.conn_shutdown		= rds_loop_conn_shutdown,
  	.inc_copy_to_user	= rds_message_inc_copy_to_user,
  	.inc_free		= rds_loop_inc_free,
  	.t_name			= "loopback",
  };