/* ar-skbuff.c: socket buffer destruction handling
   *
   * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/module.h>
  #include <linux/net.h>
  #include <linux/skbuff.h>
  #include <net/sock.h>
  #include <net/af_rxrpc.h>
  #include "ar-internal.h"
  
  /*
   * set up for the ACK at the end of the receive phase when we discard the final
   * receive phase data packet
   * - called with softirqs disabled
   */
  static void rxrpc_request_final_ACK(struct rxrpc_call *call)
  {
  	/* the call may be aborted before we have a chance to ACK it */
  	write_lock(&call->state_lock);
  
  	switch (call->state) {
  	case RXRPC_CALL_CLIENT_RECV_REPLY:
  		call->state = RXRPC_CALL_CLIENT_FINAL_ACK;
  		_debug("request final ACK");
  
  		/* get an extra ref on the call for the final-ACK generator to
  		 * release */
  		rxrpc_get_call(call);
  		set_bit(RXRPC_CALL_ACK_FINAL, &call->events);
  		if (try_to_del_timer_sync(&call->ack_timer) >= 0)

  			rxrpc_queue_call(call);

  		break;
  
  	case RXRPC_CALL_SERVER_RECV_REQUEST:
  		call->state = RXRPC_CALL_SERVER_ACK_REQUEST;
  	default:
  		break;
  	}
  
  	write_unlock(&call->state_lock);
  }
  
  /*
   * drop the bottom ACK off of the call ACK window and advance the window
   */
  static void rxrpc_hard_ACK_data(struct rxrpc_call *call,
  				struct rxrpc_skb_priv *sp)
  {
  	int loop;
  	u32 seq;
  
  	spin_lock_bh(&call->lock);
  
  	_debug("hard ACK #%u", ntohl(sp->hdr.seq));
  
  	for (loop = 0; loop < RXRPC_ACKR_WINDOW_ASZ; loop++) {
  		call->ackr_window[loop] >>= 1;
  		call->ackr_window[loop] |=
  			call->ackr_window[loop + 1] << (BITS_PER_LONG - 1);
  	}
  
  	seq = ntohl(sp->hdr.seq);
  	ASSERTCMP(seq, ==, call->rx_data_eaten + 1);
  	call->rx_data_eaten = seq;
  
  	if (call->ackr_win_top < UINT_MAX)
  		call->ackr_win_top++;
  
  	ASSERTIFCMP(call->state <= RXRPC_CALL_COMPLETE,
  		    call->rx_data_post, >=, call->rx_data_recv);
  	ASSERTIFCMP(call->state <= RXRPC_CALL_COMPLETE,
  		    call->rx_data_recv, >=, call->rx_data_eaten);
  
  	if (sp->hdr.flags & RXRPC_LAST_PACKET) {
  		rxrpc_request_final_ACK(call);
  	} else if (atomic_dec_and_test(&call->ackr_not_idle) &&
  		   test_and_clear_bit(RXRPC_CALL_TX_SOFT_ACK, &call->flags)) {
  		_debug("send Rx idle ACK");
  		__rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, sp->hdr.serial,
  				    true);
  	}
  
  	spin_unlock_bh(&call->lock);
  }
  
  /*
   * destroy a packet that has an RxRPC control buffer
   * - advance the hard-ACK state of the parent call (done here in case something
   *   in the kernel bypasses recvmsg() and steals the packet directly off of the
   *   socket receive queue)
   */
  void rxrpc_packet_destructor(struct sk_buff *skb)
  {
  	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
  	struct rxrpc_call *call = sp->call;
  
  	_enter("%p{%p}", skb, call);
  
  	if (call) {
  		/* send the final ACK on a client call */
  		if (sp->hdr.type == RXRPC_PACKET_TYPE_DATA)
  			rxrpc_hard_ACK_data(call, sp);
  		rxrpc_put_call(call);
  		sp->call = NULL;
  	}
  
  	if (skb->sk)
  		sock_rfree(skb);
  	_leave("");
  }

  
  /**
   * rxrpc_kernel_free_skb - Free an RxRPC socket buffer
   * @skb: The socket buffer to be freed
   *
   * Let RxRPC free its own socket buffer, permitting it to maintain debug
   * accounting.
   */
  void rxrpc_kernel_free_skb(struct sk_buff *skb)
  {
  	rxrpc_free_skb(skb);
  }
  
  EXPORT_SYMBOL(rxrpc_kernel_free_skb);