/*
   * 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 <net/tcp.h>
  
  #include "rds.h"
  #include "tcp.h"
  
  static struct kmem_cache *rds_tcp_incoming_slab;
  
  static void rds_tcp_inc_purge(struct rds_incoming *inc)
  {
  	struct rds_tcp_incoming *tinc;
  	tinc = container_of(inc, struct rds_tcp_incoming, ti_inc);
  	rdsdebug("purging tinc %p inc %p
  ", tinc, inc);
  	skb_queue_purge(&tinc->ti_skb_list);
  }
  
  void rds_tcp_inc_free(struct rds_incoming *inc)
  {
  	struct rds_tcp_incoming *tinc;
  	tinc = container_of(inc, struct rds_tcp_incoming, ti_inc);
  	rds_tcp_inc_purge(inc);
  	rdsdebug("freeing tinc %p inc %p
  ", tinc, inc);
  	kmem_cache_free(rds_tcp_incoming_slab, tinc);
  }
  
  /*
   * this is pretty lame, but, whatever.
   */
  int rds_tcp_inc_copy_to_user(struct rds_incoming *inc, struct iovec *first_iov,
  			     size_t size)
  {
  	struct rds_tcp_incoming *tinc;
  	struct iovec *iov, tmp;
  	struct sk_buff *skb;
  	unsigned long to_copy, skb_off;
  	int ret = 0;
  
  	if (size == 0)
  		goto out;
  
  	tinc = container_of(inc, struct rds_tcp_incoming, ti_inc);
  	iov = first_iov;
  	tmp = *iov;
  
  	skb_queue_walk(&tinc->ti_skb_list, skb) {
  		skb_off = 0;
  		while (skb_off < skb->len) {
  			while (tmp.iov_len == 0) {
  				iov++;
  				tmp = *iov;
  			}
  
  			to_copy = min(tmp.iov_len, size);
  			to_copy = min(to_copy, skb->len - skb_off);
  
  			rdsdebug("ret %d size %zu skb %p skb_off %lu "
  				 "skblen %d iov_base %p iov_len %zu cpy %lu
  ",
  				 ret, size, skb, skb_off, skb->len,
  				 tmp.iov_base, tmp.iov_len, to_copy);
  
  			/* modifies tmp as it copies */
  			if (skb_copy_datagram_iovec(skb, skb_off, &tmp,
  						    to_copy)) {
  				ret = -EFAULT;
  				goto out;
  			}
  
  			rds_stats_add(s_copy_to_user, to_copy);
  			size -= to_copy;
  			ret += to_copy;
  			skb_off += to_copy;
  			if (size == 0)
  				goto out;
  		}
  	}
  out:
  	return ret;
  }
  
  /*
   * We have a series of skbs that have fragmented pieces of the congestion
   * bitmap.  They must add up to the exact size of the congestion bitmap.  We
   * use the skb helpers to copy those into the pages that make up the in-memory
   * congestion bitmap for the remote address of this connection.  We then tell
   * the congestion core that the bitmap has been changed so that it can wake up
   * sleepers.
   *
   * This is racing with sending paths which are using test_bit to see if the
   * bitmap indicates that their recipient is congested.
   */
  
  static void rds_tcp_cong_recv(struct rds_connection *conn,
  			      struct rds_tcp_incoming *tinc)
  {
  	struct sk_buff *skb;
  	unsigned int to_copy, skb_off;
  	unsigned int map_off;
  	unsigned int map_page;
  	struct rds_cong_map *map;
  	int ret;
  
  	/* catch completely corrupt packets */
  	if (be32_to_cpu(tinc->ti_inc.i_hdr.h_len) != RDS_CONG_MAP_BYTES)
  		return;
  
  	map_page = 0;
  	map_off = 0;
  	map = conn->c_fcong;
  
  	skb_queue_walk(&tinc->ti_skb_list, skb) {
  		skb_off = 0;
  		while (skb_off < skb->len) {
  			to_copy = min_t(unsigned int, PAGE_SIZE - map_off,
  					skb->len - skb_off);
  
  			BUG_ON(map_page >= RDS_CONG_MAP_PAGES);
  
  			/* only returns 0 or -error */
  			ret = skb_copy_bits(skb, skb_off,
  				(void *)map->m_page_addrs[map_page] + map_off,
  				to_copy);
  			BUG_ON(ret != 0);
  
  			skb_off += to_copy;
  			map_off += to_copy;
  			if (map_off == PAGE_SIZE) {
  				map_off = 0;
  				map_page++;
  			}
  		}
  	}
  
  	rds_cong_map_updated(map, ~(u64) 0);
  }
  
  struct rds_tcp_desc_arg {
  	struct rds_connection *conn;
  	gfp_t gfp;
  };
  
  static int rds_tcp_data_recv(read_descriptor_t *desc, struct sk_buff *skb,
  			     unsigned int offset, size_t len)
  {
  	struct rds_tcp_desc_arg *arg = desc->arg.data;
  	struct rds_connection *conn = arg->conn;
  	struct rds_tcp_connection *tc = conn->c_transport_data;
  	struct rds_tcp_incoming *tinc = tc->t_tinc;
  	struct sk_buff *clone;
  	size_t left = len, to_copy;
  
  	rdsdebug("tcp data tc %p skb %p offset %u len %zu
  ", tc, skb, offset,
  		 len);
  
  	/*
  	 * tcp_read_sock() interprets partial progress as an indication to stop
  	 * processing.
  	 */
  	while (left) {
  		if (!tinc) {
  			tinc = kmem_cache_alloc(rds_tcp_incoming_slab,
  					        arg->gfp);
  			if (!tinc) {
  				desc->error = -ENOMEM;
  				goto out;
  			}
  			tc->t_tinc = tinc;
  			rdsdebug("alloced tinc %p
  ", tinc);
  			rds_inc_init(&tinc->ti_inc, conn, conn->c_faddr);
  			/*
  			 * XXX * we might be able to use the __ variants when
  			 * we've already serialized at a higher level.
  			 */
  			skb_queue_head_init(&tinc->ti_skb_list);
  		}
  
  		if (left && tc->t_tinc_hdr_rem) {
  			to_copy = min(tc->t_tinc_hdr_rem, left);
  			rdsdebug("copying %zu header from skb %p
  ", to_copy,
  				 skb);
  			skb_copy_bits(skb, offset,
  				      (char *)&tinc->ti_inc.i_hdr +
  						sizeof(struct rds_header) -
  						tc->t_tinc_hdr_rem,
  				      to_copy);
  			tc->t_tinc_hdr_rem -= to_copy;
  			left -= to_copy;
  			offset += to_copy;
  
  			if (tc->t_tinc_hdr_rem == 0) {
  				/* could be 0 for a 0 len message */
  				tc->t_tinc_data_rem =
  					be32_to_cpu(tinc->ti_inc.i_hdr.h_len);
  			}
  		}
  
  		if (left && tc->t_tinc_data_rem) {
  			clone = skb_clone(skb, arg->gfp);
  			if (!clone) {
  				desc->error = -ENOMEM;
  				goto out;
  			}
  
  			to_copy = min(tc->t_tinc_data_rem, left);
  			pskb_pull(clone, offset);
  			pskb_trim(clone, to_copy);
  			skb_queue_tail(&tinc->ti_skb_list, clone);
  
  			rdsdebug("skb %p data %p len %d off %u to_copy %zu -> "
  				 "clone %p data %p len %d
  ",
  				 skb, skb->data, skb->len, offset, to_copy,
  				 clone, clone->data, clone->len);
  
  			tc->t_tinc_data_rem -= to_copy;
  			left -= to_copy;
  			offset += to_copy;
  		}
  
  		if (tc->t_tinc_hdr_rem == 0 && tc->t_tinc_data_rem == 0) {
  			if (tinc->ti_inc.i_hdr.h_flags == RDS_FLAG_CONG_BITMAP)
  				rds_tcp_cong_recv(conn, tinc);
  			else
  				rds_recv_incoming(conn, conn->c_faddr,
  						  conn->c_laddr, &tinc->ti_inc,
  						  arg->gfp);
  
  			tc->t_tinc_hdr_rem = sizeof(struct rds_header);
  			tc->t_tinc_data_rem = 0;
  			tc->t_tinc = NULL;
  			rds_inc_put(&tinc->ti_inc);
  			tinc = NULL;
  		}
  	}
  out:
  	rdsdebug("returning len %zu left %zu skb len %d rx queue depth %d
  ",
  		 len, left, skb->len,
  		 skb_queue_len(&tc->t_sock->sk->sk_receive_queue));
  	return len - left;
  }
  
  /* the caller has to hold the sock lock */
  static int rds_tcp_read_sock(struct rds_connection *conn, gfp_t gfp)
  {
  	struct rds_tcp_connection *tc = conn->c_transport_data;
  	struct socket *sock = tc->t_sock;
  	read_descriptor_t desc;
  	struct rds_tcp_desc_arg arg;
  
  	/* It's like glib in the kernel! */
  	arg.conn = conn;
  	arg.gfp = gfp;
  	desc.arg.data = &arg;
  	desc.error = 0;
  	desc.count = 1; /* give more than one skb per call */
  
  	tcp_read_sock(sock->sk, &desc, rds_tcp_data_recv);
  	rdsdebug("tcp_read_sock for tc %p gfp 0x%x returned %d
  ", tc, gfp,
  		 desc.error);
  
  	return desc.error;
  }
  
  /*
   * We hold the sock lock to serialize our rds_tcp_recv->tcp_read_sock from
   * data_ready.
   *
   * if we fail to allocate we're in trouble.. blindly wait some time before
   * trying again to see if the VM can free up something for us.
   */
  int rds_tcp_recv(struct rds_connection *conn)
  {
  	struct rds_tcp_connection *tc = conn->c_transport_data;
  	struct socket *sock = tc->t_sock;
  	int ret = 0;
  
  	rdsdebug("recv worker conn %p tc %p sock %p
  ", conn, tc, sock);
  
  	lock_sock(sock->sk);
  	ret = rds_tcp_read_sock(conn, GFP_KERNEL);
  	release_sock(sock->sk);
  
  	return ret;
  }
  
  void rds_tcp_data_ready(struct sock *sk, int bytes)
  {
  	void (*ready)(struct sock *sk, int bytes);
  	struct rds_connection *conn;
  	struct rds_tcp_connection *tc;
  
  	rdsdebug("data ready sk %p bytes %d
  ", sk, bytes);
  
  	read_lock(&sk->sk_callback_lock);
  	conn = sk->sk_user_data;
  	if (!conn) { /* check for teardown race */
  		ready = sk->sk_data_ready;
  		goto out;
  	}
  
  	tc = conn->c_transport_data;
  	ready = tc->t_orig_data_ready;
  	rds_tcp_stats_inc(s_tcp_data_ready_calls);
  
  	if (rds_tcp_read_sock(conn, GFP_ATOMIC) == -ENOMEM)
  		queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
  out:
  	read_unlock(&sk->sk_callback_lock);
  	ready(sk, bytes);
  }
  
  int rds_tcp_recv_init(void)
  {
  	rds_tcp_incoming_slab = kmem_cache_create("rds_tcp_incoming",
  					sizeof(struct rds_tcp_incoming),
  					0, 0, NULL);
  	if (!rds_tcp_incoming_slab)
  		return -ENOMEM;
  	return 0;
  }
  
  void rds_tcp_recv_exit(void)
  {
  	kmem_cache_destroy(rds_tcp_incoming_slab);
  }