path: root/nuttx/net/tcp/tcp_callback.c

/****************************************************************************
 * net/tcp/tcp_callback.c
 *
 *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#if defined(CONFIG_NET) && defined(CONFIG_NET_TCP)

#include <stdint.h>
#include <string.h>
#include <debug.h>

#include <nuttx/net/netconfig.h>
#include <nuttx/net/uip/uip.h>
#include <nuttx/net/uip/uip-arch.h>

#include "uip/uip_internal.h"

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Function: uip_readahead
 *
 * Description:
 *   Copy as much received data as possible into the read-ahead buffer
 *
 * Assumptions:
 *   This function is called at the interrupt level with interrupts disabled.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_TCP_READAHEAD
static int uip_readahead(FAR struct uip_readahead_s *readahead,
                         FAR uint8_t *buf, int len)
{
  int available = CONFIG_NET_TCP_READAHEAD_BUFSIZE - readahead->rh_nbytes;
  int recvlen   = 0;

  if (len > 0 && available > 0)
    {
      /* Get the length of the data to buffer. */

      if (len > available)
        {
          recvlen = available;
        }
      else
        {
          recvlen = len;
        }

      /* Copy the new appdata into the read-ahead buffer */

      memcpy(&readahead->rh_buffer[readahead->rh_nbytes], buf, recvlen);
      readahead->rh_nbytes += recvlen;
    }

  return recvlen;
}
#endif

/****************************************************************************
 * Function: uip_dataevent
 *
 * Description:
 *   Handle data that is not accepted by the application because there is no
 *   listener in place ready to receive the data.
 *
 * Assumptions:
 * - The caller has checked that UIP_NEWDATA is set in flags and that is no
 *   other handler available to process the incoming data.
 * - This function is called at the interrupt level with interrupts disabled.
 *
 ****************************************************************************/

static inline uint16_t
uip_dataevent(FAR struct uip_driver_s *dev, FAR struct uip_conn *conn,
              uint16_t flags)
{
  uint16_t ret;

  /* Assume that we will ACK the data.  The data will be ACKed if it is
   * placed in the read-ahead buffer -OR- if it zero length
   */

  ret = (flags & ~UIP_NEWDATA) | UIP_SNDACK;

  /* Is there new data?  With non-zero length?  (Certain connection events
   * can have zero-length with UIP_NEWDATA set just to cause an ACK).
   */

  if (dev->d_len > 0)
    {
#ifdef CONFIG_NET_TCP_READAHEAD
      uint8_t *buffer = dev->d_appdata;
      int      buflen = dev->d_len;
      uint16_t recvlen;
#endif

      nllvdbg("No listener on connection\n");

#ifdef CONFIG_NET_TCP_READAHEAD
      /* Save as much data as possible in the read-ahead buffers */

      recvlen = uip_datahandler(conn, buffer, buflen);

      /* There are several complicated buffering issues that are not addressed
       * properly here.  For example, what if we cannot buffer the entire
       * packet?  In that case, some data will be accepted but not ACKed.
       * Therefore it will be resent and duplicated.  Fixing this could be tricky.
       */

     if (recvlen < buflen)
#endif
        {
          /* There is no handler to receive new data and there are no free
           * read-ahead buffers to retain the data -- drop the packet.
           */

         nllvdbg("Dropped %d bytes\n", dev->d_len);

 #ifdef CONFIG_NET_STATISTICS
          uip_stat.tcp.syndrop++;
          uip_stat.tcp.drop++;
#endif
          /* Clear the UIP_SNDACK bit so that no ACK will be sent */

          ret &= ~UIP_SNDACK;
        }
    }

  /* In any event, the new data has now been handled */

  dev->d_len = 0;
  return ret;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Function: uip_tcpcallback
 *
 * Description:
 *   Inform the application holding the TCP socket of a change in state.
 *
 * Assumptions:
 *   This function is called at the interrupt level with interrupts disabled.
 *
 ****************************************************************************/

uint16_t uip_tcpcallback(struct uip_driver_s *dev, struct uip_conn *conn,
                         uint16_t flags)
{
  /* Preserve the UIP_ACKDATA, UIP_CLOSE, and UIP_ABORT in the response.
   * These is needed by uIP to handle responses and buffer state.  The
   * UIP_NEWDATA indication will trigger the ACK response, but must be
   * explicitly set in the callback.
   */

  nllvdbg("flags: %04x\n", flags);

  /* Perform the data callback.  When a data callback is executed from 'list',
   * the input flags are normally returned, however, the implementation
   * may set one of the following:
   *
   *   UIP_CLOSE   - Gracefully close the current connection
   *   UIP_ABORT   - Abort (reset) the current connection on an error that
   *                 prevents UIP_CLOSE from working.
   *
   * And/Or set/clear the following:
   *
   *   UIP_NEWDATA - May be cleared to indicate that the data was consumed
   *                 and that no further process of the new data should be
   *                 attempted.
   *   UIP_SNDACK  - If UIP_NEWDATA is cleared, then UIP_SNDACK may be set
   *                 to indicate that an ACK should be included in the response.
   *                 (In UIP_NEWDATA is cleared but UIP_SNDACK is not set, then
   *                 dev->d_len should also be cleared).
   */

  flags = uip_callbackexecute(dev, conn, flags, conn->list);

  /* There may be no new data handler in place at them moment that the new
   * incoming data is received.  If the new incoming data was not handled, then
   * either (1) put the unhandled incoming data in the read-ahead buffer (if
   * enabled) or (2) suppress the ACK to the data in the hope that it will
   * be re-transmitted at a better time.
   */

  if ((flags & UIP_NEWDATA) != 0)
    {
      /* Data was not handled.. dispose of it appropriately */

      flags = uip_dataevent(dev, conn, flags);
    }

  /* Check if there is a connection-related event and a connection
   * callback.
   */

  if (((flags & UIP_CONN_EVENTS) != 0) && conn->connection_event)
    {
      /* Perform the callback */

      conn->connection_event(conn, flags);
    }

  return flags;
}

/****************************************************************************
 * Function: uip_datahandler
 *
 * Description:
 *   Handle data that is not accepted by the application.  This may be called
 *   either (1) from the data receive logic if it cannot buffer the data, or
 *   (2) from the TCP event logic is there is no listener in place ready to
 *   receive the data.
 *
 * Input Parameters:
 *   conn - A pointer to the TCP connection structure
 *   buffer - A pointer to the buffer to be copied to the read-ahead
 *     buffers
 *   buflen - The number of bytes to copy to the read-ahead buffer.
 *
 * Returned value:
 *   The number of bytes actually buffered.  This could be less than 'nbytes'
 *   if there is insufficient buffering available.
 *
 * Assumptions:
 * - The caller has checked that UIP_NEWDATA is set in flags and that is no
 *   other handler available to process the incoming data.
 * - This function is called at the interrupt level with interrupts disabled.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_TCP_READAHEAD
uint16_t uip_datahandler(FAR struct uip_conn *conn, FAR uint8_t *buffer,
                         uint16_t buflen)
{
  FAR struct uip_readahead_s *readahead1;
  FAR struct uip_readahead_s *readahead2 = NULL;
  uint16_t remaining;
  uint16_t recvlen = 0;

  /* First, we need to determine if we have space to buffer the data.  This
   * needs to be verified before we actually begin buffering the data. We
   * will use any remaining space in the last allocated read-ahead buffer
   * plus as much one additional buffer.  It is expected that the size of
   * read-ahead buffers are tuned so that one full packet will always fit
   * into one read-ahead buffer (for example if the buffer size is 420, then
   * a read-ahead buffer of 366 will hold a full packet of TCP data).
   */

  readahead1 = (FAR struct uip_readahead_s*)conn->readahead.tail;
  if ((readahead1 &&
      (CONFIG_NET_TCP_READAHEAD_BUFSIZE - readahead1->rh_nbytes) > buflen) ||
      (readahead2 = uip_tcpreadahead_alloc()) != NULL)
    {
      /* We have buffer space.  Now try to append add as much data as possible
       * to the last read-ahead buffer attached to this connection.
       */

      remaining = buflen;
      if (readahead1)
        {
          recvlen = uip_readahead(readahead1, buffer, remaining);
          if (recvlen > 0)
            {
              buffer    += recvlen;
              remaining -= recvlen;
            }
        }

      /* Do we need to buffer into the newly allocated buffer as well? */

      if (readahead2)
        {
          readahead2->rh_nbytes = 0;
          recvlen += uip_readahead(readahead2, buffer, remaining);

          /* Save the read-ahead buffer in the connection structure where
           * it can be found with recv() is called.
           */

          sq_addlast(&readahead2->rh_node, &conn->readahead);
        }
    }

  nllvdbg("Buffered %d bytes (of %d)\n", recvlen, buflen);
  return recvlen;
}
#endif /* CONFIG_NET_TCP_READAHEAD */

#endif /* CONFIG_NET && CONFIG_NET_TCP */