buf.c

This a framework to test new ideas in transmission technology. Actual development is a LDPC-coder in

/***************************************************************************
 *    buf.c  -  Implement the buffering of the ip-packets
 *                           -------------------
 *   begin                :  2003
 *   authors              :  Linus Gasser
 *   emails               :  [e-mail]
 ***************************************************************************/

/***************************************************************************
 *                                Changes
 *                                -------
 * date - name - description
 * 03/05/02 - ineiti - start
 *
 **************************************************************************/

/***************************************************************************
 *                                                                         *
 *   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 "spc.h"
#include "system.h"
#include "tcpip.h"
#include "net.h"
#include "buf.h"
#include "ack.h"

#define DBG_LVL 1

/**
 * @short initialise the buffers
 *
 * Initialises enough memory for a couple of IP-packets...
 *
 * @param buf where all the stuff shall be stored
 */
void buf_init( struct buffer_t *buf ) {
  buf->ip_buf_rcv = swr_malloc( IP_BUF_LEN );
  buf->ip_buf_rcv_pos = 0;
  buf->ip_buf_send = swr_malloc( IP_BUF_LEN );
  buf->ip_buf_send_pos = 0;

  ack_init( &buf->ack_sent );
  ack_init( &buf->ack_rcvd );
  ack_init( &buf->rcvd );
  ack_init( &buf->send );
}

/**
 * Clean up the buffers
 */
void buf_cleanup( struct buffer_t *buf ) {
  if ( buf ) {
    swr_free( buf->ip_buf_rcv );
    swr_free( buf->ip_buf_send );
    ack_free( &buf->ack_sent );
    ack_free( &buf->ack_rcvd );
    ack_free( &buf->rcvd );
    ack_free( &buf->send );
  }
}


/**
 * @short update the references
 *
 * When receiving an acknowledge over the air, we can delete some
 * references from our table...
 *
 * TODO: is it possible to have two acks with same pos but different
 * length?
 *
 * @param buf the buffer-structure
 * @param pack what to remove
 */
void buf_update_ack_sent( struct buffer_t *buf, struct rf_packet *pack ) {

  if ( !buf->ack_sent->len ) {
    PR_DBG( 0, "Receiving acknowledge while no waiting acks!\n" );
  } else {
    if ( ack_delete( buf->ack_sent, pack->pos ) < 0 ) {
      PR_DBG( 0, "Couldn't find the packet to ack!\n" );
    }
  }
}


/**
 * @short copies b to a with wrap-over in the destination 
 *
 * Copies b to a and takes care about an eventual overflow in the
 * destination block. It then returns the new position.
 *
 * @param a destination
 * @param b source
 * @param pos the position in the destination
 * @param len how many bytes
 * @param wrap the size of the destination
 * @return the new position in the destination
 */
int buf_copy_wrap_dst( void *a, void *b, int pos, int len, int wrap ) {
  int ret;

  if ( pos + len > wrap ) {
    // Do some magick on the boundaries
    ret = wrap - pos;
    memcpy( a + pos, b, ret );
    memcpy( a, b + ret, len - ret );
    ret = len - ret;
  } else {
    memcpy( a + pos, b, len );
    ret = pos + len;
  }
  return ret;
}


/**
 * @short copies b to a with wrap-over in the source
 *
 * Copies b to a and takes care about an eventual overflow in the
 * source block. It then returns the new position.
 *
 * @param a destination
 * @param b source
 * @param pos the position in the source
 * @param len how many bytes
 * @param wrap the size of the source
 * @return the new position in the source
 */
int buf_copy_wrap_src( void *a, void *b, int pos, int len, int wrap ) {
  int ret;

  if ( pos + len > wrap ) {
    // Do some magick on the boundaries
    ret = wrap - pos;
    memcpy( a, b + pos, ret );
    memcpy( a + ret, b, len - ret );
    ret = len - ret;
  } else {
    memcpy( a, b + pos, len );
    ret = pos + len;
  }
  return ret;
}


/**
 * @short inserts a rf-packet in the buffer
 *
 * Puts together received data that comes from the rf-interface.
 * Also inserts acks in the list and calls the kernel-rx 
 * function if a packet has been received successfully.
 *
 * @param buf the buffer-structure
 * @param pack the received packet
 */
void buf_rf_to_net( struct buffer_t *buf, struct rf_packet *pack ) {
  struct ack *a;
  char *block;
  int ip_len, half, pa, pb;

  // Copy the received data in the ip-buffer
  buf_copy_wrap_dst( buf->ip_buf_rcv, &pack->data,
                     pack->pos, pack->len, IP_BUF_LEN );

  // Append in the ack_rcvd
  ack_append( buf->ack_rcvd, pack->pos, pack->len );

  // Look if the packet is new or resent due to a lost ack
  half = IP_BUF_LEN / 2;
  pa = pack->pos;
  pb = buf->ip_buf_rcv_pos;
  if ( ( ( pa >= pb ) && ( pa - pb >= half ) ) ||
       ( ( pa < pb ) && ( pb - pa <= half ) ) ) {
    PR_DBG( 1, "Rejected packet because it already got processed\n" );
    // Reject packet
  } else {
    PR_DBG( 4, "Incoming: %i, last good: %i\n", pack->pos, buf->ip_buf_rcv_pos );
    // Append in the rcvd list
    ack_ins_sorted( buf->rcvd, pack->pos, pack->len );

    // Search if we have already enough bytes to build a ip-packet
    a = ack_join_blocks( buf->rcvd );
    if ( a->len > 2 ) {
      PR_DBG( 4, "Received a block of len %i and allocating\n", a->len );
      block = swr_malloc( a->len );
      buf->ip_buf_rcv_pos = buf_copy_wrap_src( block, buf->ip_buf_rcv,
                            a->pos, a->len, IP_BUF_LEN );
      ip_len = *((u16*)block);
      if ( ip_len <= a->len ) {
        PR_DBG( 1, "Block contains at least one ip-packet with len %i and CRC %x\n",
                ip_len, *((U32*)( block + 2 ) ) );
        // If we have enough data, we cut a packet from the beginnning
        // but without the length-indicator and send it to the kernel
        net_send_to_kernel( buf->dev, block + 2, ip_len );
        ack_cut_begin( buf->rcvd, ip_len + 2 );
      }
      swr_free( block );
    }
  }
}


/**
 * @short prepare a packet over the air
 *
 */
void buf_net_to_rf( struct buffer_t *buf, char *packet, int len ) {

  PR_DBG( 1, "Putting packet to rf, len:%i\n", len );
  // Add it to the packets to send
  ack_append( buf->send, buf->ip_buf_send_pos, len );

  // And copy the data to send into the ring-buffer
  buf->ip_buf_send_pos = buf_copy_wrap_dst( buf->ip_buf_send, packet,
                         buf->ip_buf_send_pos, len, IP_BUF_LEN );
}