/*
    MODULE -- Radiotap header for WiFi packets

    Copyright (c) Alberto Ornaghi

    $Id: wifi_radiotap.c 2672 2010-07-13 09:05:28Z alor $
*/

#include <main.h>
#include <decode.h>
#include <capture.h>

/* globals */

struct __attribute__ ((__packed__)) radiotap_header {
   u_int8  version;
   u_int8  pad;
   u_int16 len;
   u_int32 present_flags;
      #define RADIO_PRESENT_TSFT    0x01
      #define RADIO_PRESENT_FLAGS   0x02
      #define RADIO_PRESENT_RATE    0x04
      #define RADIO_PRESENT_CHANNEL 0x08
};

#define RADIO_FLAGS_FCS  0x10

/* protos */

FUNC_DECODER(decode_radiotap);
void radiotap_init(void);

/*******************************************/

/*
 * this function is the initializer.
 * it adds the entry in the table of registered decoder
 */

void __init radiotap_init(void)
{
   add_decoder(LINK_LAYER, IL_TYPE_RADIO, decode_radiotap);
}


FUNC_DECODER(decode_radiotap)
{
   FUNC_DECODER_PTR(next_decoder);
   struct radiotap_header *radio;
   u_char *rh;
   u_int8 flags = 0;

   DEBUG_MSG(D_EXCESSIVE, "%s", __FUNCTION__);

   /* get the header */
   radio = (struct radiotap_header *)DECODE_DATA;
   rh = (u_char *)(radio + 1);

   /* get the length of the header */
   DECODED_LEN = radio->len;

   /*
    * scan for the presence of the information
    * we are lucky since the FLAGS we are searching is the second field
    * and we don't have to scan for all of them
    */
   if ((radio->present_flags & RADIO_PRESENT_TSFT)) {
      /* the TSFT is 1 byte */
      rh += 1;
   }

   if ((radio->present_flags & RADIO_PRESENT_FLAGS)) {
      /* read the flags (1 byte) */
      flags = *rh;
   }

   /* mark the packet, since we have an FCS at the end */
   if ((flags & RADIO_FLAGS_FCS))
      PACKET->L2.flags |= PO_L2_FCS;

   next_decoder = get_decoder(LINK_LAYER, IL_TYPE_WIFI);
   EXECUTE_DECODER(next_decoder);

   return NULL;
}

/* EOF */

// vim:ts=3:expandtab