/*

   * 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/in.h>
  #include <net/tcp.h>

  #include "rds_single_path.h"

  #include "rds.h"
  #include "tcp.h"

  void rds_tcp_xmit_path_prepare(struct rds_conn_path *cp)

  {

  	struct rds_tcp_connection *tc = cp->cp_transport_data;

  	tcp_sock_set_cork(tc->t_sock->sk, true);

  }

  void rds_tcp_xmit_path_complete(struct rds_conn_path *cp)

  {

  	struct rds_tcp_connection *tc = cp->cp_transport_data;

  	tcp_sock_set_cork(tc->t_sock->sk, false);

  }
  
  /* 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_conn_path *cp = rm->m_inc.i_conn_path;
  	struct rds_tcp_connection *tc = cp->cp_transport_data;

  	int done = 0;
  	int ret = 0;

  	int more;

  
  	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_write_seq(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_atomic();

  		set_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags);
  		tc->t_last_expected_una = rm->m_ack_seq + 1;

  		if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
  			rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;

  		rdsdebug("rm %p tcp nxt %u ack_seq %llu
  ",

  			 rm, rds_tcp_write_seq(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;
  	}

  	more = rm->data.op_nents > 1 ? (MSG_MORE | MSG_SENDPAGE_NOTLAST) : 0;

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

  		int flags = MSG_DONTWAIT | MSG_NOSIGNAL | more;

  		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,

  						flags);

  		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++;
  		}

  		if (sg == rm->data.op_nents - 1)
  			more = 0;

  	}
  
  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 {

  			/* No need to disconnect/reconnect if path_drop
  			 * has already been triggered, because, e.g., of
  			 * an incoming RST.
  			 */
  			if (rds_conn_path_up(cp)) {

  				pr_warn("RDS/tcp: send to %pI6c on cp [%d]"

  					"returned %d, "
  					"disconnecting and reconnecting
  ",
  					&conn->c_faddr, cp->cp_index, ret);

  				rds_conn_path_drop(cp, false);

  			}

  		}
  	}
  	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_conn_path *cp;

  	struct rds_tcp_connection *tc;

  	read_lock_bh(&sk->sk_callback_lock);

  	cp = sk->sk_user_data;
  	if (!cp) {

  		write_space = sk->sk_write_space;
  		goto out;
  	}

  	tc = cp->cp_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_path_drop_acked(cp, rds_tcp_snd_una(tc), rds_tcp_is_acked);

  	rcu_read_lock();
  	if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf &&

  	    !rds_destroy_pending(cp->cp_conn))

  		queue_delayed_work(rds_wq, &cp->cp_send_w, 0);

  	rcu_read_unlock();

  out:

  	read_unlock_bh(&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);
  }