/*
   * 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/in.h>
  #include <net/tcp.h>
  
  #include "rds.h"
  #include "tcp.h"
  
  static void rds_tcp_cork(struct socket *sock, int val)
  {
  	mm_segment_t oldfs;
  
  	oldfs = get_fs();
  	set_fs(KERNEL_DS);
  	sock->ops->setsockopt(sock, SOL_TCP, TCP_CORK, (char __user *)&val,
  			      sizeof(val));
  	set_fs(oldfs);
  }
  
  void rds_tcp_xmit_prepare(struct rds_connection *conn)
  {
  	struct rds_tcp_connection *tc = conn->c_transport_data;
  
  	rds_tcp_cork(tc->t_sock, 1);
  }
  
  void rds_tcp_xmit_complete(struct rds_connection *conn)
  {
  	struct rds_tcp_connection *tc = conn->c_transport_data;
  
  	rds_tcp_cork(tc->t_sock, 0);
  }
  
  /* the core send_sem serializes this with other xmit and shutdown */

  static int rds_tcp_sendmsg(struct socket *sock, void *data, unsigned int len)

  {
  	struct kvec vec = {
                  .iov_base = data,
                  .iov_len = len,
  	};
          struct msghdr msg = {
                  .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL,
          };
  
  	return kernel_sendmsg(sock, &msg, &vec, 1, vec.iov_len);
  }
  
  /* the core send_sem serializes this with other xmit and shutdown */

  int rds_tcp_xmit(struct rds_connection *conn, struct rds_message *rm,
  	         unsigned int hdr_off, unsigned int sg, unsigned int off)
  {
  	struct rds_tcp_connection *tc = conn->c_transport_data;
  	int done = 0;
  	int ret = 0;
  
  	if (hdr_off == 0) {
  		/*
  		 * m_ack_seq is set to the sequence number of the last byte of
  		 * header and data.  see rds_tcp_is_acked().
  		 */
  		tc->t_last_sent_nxt = rds_tcp_snd_nxt(tc);
  		rm->m_ack_seq = tc->t_last_sent_nxt +
  				sizeof(struct rds_header) +
  				be32_to_cpu(rm->m_inc.i_hdr.h_len) - 1;
  		smp_mb__before_clear_bit();
  		set_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags);
  		tc->t_last_expected_una = rm->m_ack_seq + 1;
  
  		rdsdebug("rm %p tcp nxt %u ack_seq %llu
  ",
  			 rm, rds_tcp_snd_nxt(tc),
  			 (unsigned long long)rm->m_ack_seq);
  	}
  
  	if (hdr_off < sizeof(struct rds_header)) {
  		/* see rds_tcp_write_space() */
  		set_bit(SOCK_NOSPACE, &tc->t_sock->sk->sk_socket->flags);
  
  		ret = rds_tcp_sendmsg(tc->t_sock,
  				      (void *)&rm->m_inc.i_hdr + hdr_off,
  				      sizeof(rm->m_inc.i_hdr) - hdr_off);
  		if (ret < 0)
  			goto out;
  		done += ret;
  		if (hdr_off + done != sizeof(struct rds_header))
  			goto out;
  	}

  	while (sg < rm->data.op_nents) {

  		ret = tc->t_sock->ops->sendpage(tc->t_sock,

  						sg_page(&rm->data.op_sg[sg]),
  						rm->data.op_sg[sg].offset + off,
  						rm->data.op_sg[sg].length - off,

  						MSG_DONTWAIT|MSG_NOSIGNAL);

  		rdsdebug("tcp sendpage %p:%u:%u ret %d
  ", (void *)sg_page(&rm->data.op_sg[sg]),
  			 rm->data.op_sg[sg].offset + off, rm->data.op_sg[sg].length - off,

  			 ret);
  		if (ret <= 0)
  			break;
  
  		off += ret;
  		done += ret;

  		if (off == rm->data.op_sg[sg].length) {

  			off = 0;
  			sg++;
  		}
  	}
  
  out:
  	if (ret <= 0) {
  		/* write_space will hit after EAGAIN, all else fatal */
  		if (ret == -EAGAIN) {
  			rds_tcp_stats_inc(s_tcp_sndbuf_full);
  			ret = 0;
  		} else {

  			printk(KERN_WARNING "RDS/tcp: send to %pI4 "

  			       "returned %d, disconnecting and reconnecting
  ",

  			       &conn->c_faddr, ret);

  			rds_conn_drop(conn);
  		}
  	}
  	if (done == 0)
  		done = ret;
  	return done;
  }
  
  /*
   * rm->m_ack_seq is set to the tcp sequence number that corresponds to the
   * last byte of the message, including the header.  This means that the
   * entire message has been received if rm->m_ack_seq is "before" the next
   * unacked byte of the TCP sequence space.  We have to do very careful
   * wrapping 32bit comparisons here.
   */
  static int rds_tcp_is_acked(struct rds_message *rm, uint64_t ack)
  {
  	if (!test_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags))
  		return 0;
  	return (__s32)((u32)rm->m_ack_seq - (u32)ack) < 0;
  }
  
  void rds_tcp_write_space(struct sock *sk)
  {
  	void (*write_space)(struct sock *sk);
  	struct rds_connection *conn;
  	struct rds_tcp_connection *tc;

  	read_lock(&sk->sk_callback_lock);

  	conn = sk->sk_user_data;

  	if (!conn) {

  		write_space = sk->sk_write_space;
  		goto out;
  	}
  
  	tc = conn->c_transport_data;
  	rdsdebug("write_space for tc %p
  ", tc);
  	write_space = tc->t_orig_write_space;
  	rds_tcp_stats_inc(s_tcp_write_space_calls);
  
  	rdsdebug("tcp una %u
  ", rds_tcp_snd_una(tc));
  	tc->t_last_seen_una = rds_tcp_snd_una(tc);
  	rds_send_drop_acked(conn, rds_tcp_snd_una(tc), rds_tcp_is_acked);

          if ((atomic_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf)
  		queue_delayed_work(rds_wq, &conn->c_send_w, 0);

  out:

  	read_unlock(&sk->sk_callback_lock);

  
  	/*
  	 * write_space is only called when data leaves tcp's send queue if
  	 * SOCK_NOSPACE is set.  We set SOCK_NOSPACE every time we put
  	 * data in tcp's send queue because we use write_space to parse the
  	 * sequence numbers and notice that rds messages have been fully
  	 * received.
  	 *
  	 * tcp's write_space clears SOCK_NOSPACE if the send queue has more
  	 * than a certain amount of space. So we need to set it again *after*
  	 * we call tcp's write_space or else we might only get called on the
  	 * first of a series of incoming tcp acks.
  	 */
  	write_space(sk);
  
  	if (sk->sk_socket)
  		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
  }