/*
   * Radiotap parser
   *
   * Copyright 2007		Andy Green <andy@warmcat.com>

   * Copyright 2009		Johannes Berg <johannes@sipsolutions.net>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * Alternatively, this software may be distributed under the terms of BSD
   * license.
   *
   * See COPYING for more details.

   */

  #include <linux/kernel.h>

  #include <linux/export.h>

  #include <net/cfg80211.h>
  #include <net/ieee80211_radiotap.h>
  #include <asm/unaligned.h>
  
  /* function prototypes and related defs are in include/net/cfg80211.h */

  static const struct radiotap_align_size rtap_namespace_sizes[] = {
  	[IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
  	[IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
  	[IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
  	[IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
  	[IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
  	[IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
  	[IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
  	[IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
  	[IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
  	[IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
  	[IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
  	[IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
  	[IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
  	[IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
  	[IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
  	[IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
  	[IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
  	[IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
  	/*
  	 * add more here as they are defined in radiotap.h
  	 */
  };
  
  static const struct ieee80211_radiotap_namespace radiotap_ns = {

  	.n_bits = ARRAY_SIZE(rtap_namespace_sizes),

  	.align_size = rtap_namespace_sizes,
  };

  /**
   * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
   * @iterator: radiotap_iterator to initialize
   * @radiotap_header: radiotap header to parse
   * @max_length: total length we can parse into (eg, whole packet length)
   *
   * Returns: 0 or a negative error code if there is a problem.
   *
   * This function initializes an opaque iterator struct which can then
   * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
   * argument which is present in the header.  It knows about extended
   * present headers and handles them.
   *
   * How to use:
   * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
   * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
   * checking for a good 0 return code.  Then loop calling
   * __ieee80211_radiotap_iterator_next()... it returns either 0,
   * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
   * The iterator's @this_arg member points to the start of the argument
   * associated with the current argument index that is present, which can be
   * found in the iterator's @this_arg_index member.  This arg index corresponds
   * to the IEEE80211_RADIOTAP_... defines.
   *
   * Radiotap header length:
   * You can find the CPU-endian total radiotap header length in
   * iterator->max_length after executing ieee80211_radiotap_iterator_init()
   * successfully.
   *
   * Alignment Gotcha:
   * You must take care when dereferencing iterator.this_arg
   * for multibyte types... the pointer is not aligned.  Use
   * get_unaligned((type *)iterator.this_arg) to dereference
   * iterator.this_arg for type "type" safely on all arches.
   *
   * Example code:
   * See Documentation/networking/radiotap-headers.txt
   */
  
  int ieee80211_radiotap_iterator_init(

  	struct ieee80211_radiotap_iterator *iterator,
  	struct ieee80211_radiotap_header *radiotap_header,
  	int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)

  {
  	/* Linux only supports version 0 radiotap format */
  	if (radiotap_header->it_version)
  		return -EINVAL;
  
  	/* sanity check for allowed length and radiotap length field */

  	if (max_length < get_unaligned_le16(&radiotap_header->it_len))

  		return -EINVAL;

  	iterator->_rtheader = radiotap_header;
  	iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
  	iterator->_arg_index = 0;
  	iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
  	iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
  	iterator->_reset_on_ext = 0;
  	iterator->_next_bitmap = &radiotap_header->it_present;
  	iterator->_next_bitmap++;
  	iterator->_vns = vns;
  	iterator->current_namespace = &radiotap_ns;
  	iterator->is_radiotap_ns = 1;

  
  	/* find payload start allowing for extended bitmap(s) */

  	if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
  		while (get_unaligned_le32(iterator->_arg) &
  					(1 << IEEE80211_RADIOTAP_EXT)) {
  			iterator->_arg += sizeof(uint32_t);

  
  			/*
  			 * check for insanity where the present bitmaps
  			 * keep claiming to extend up to or even beyond the
  			 * stated radiotap header length
  			 */

  			if ((unsigned long)iterator->_arg -
  			    (unsigned long)iterator->_rtheader >
  			    (unsigned long)iterator->_max_length)

  				return -EINVAL;
  		}

  		iterator->_arg += sizeof(uint32_t);

  
  		/*
  		 * no need to check again for blowing past stated radiotap
  		 * header length, because ieee80211_radiotap_iterator_next
  		 * checks it before it is dereferenced
  		 */
  	}

  	iterator->this_arg = iterator->_arg;

  	/* we are all initialized happily */
  
  	return 0;
  }
  EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);

  static void find_ns(struct ieee80211_radiotap_iterator *iterator,
  		    uint32_t oui, uint8_t subns)
  {
  	int i;
  
  	iterator->current_namespace = NULL;
  
  	if (!iterator->_vns)
  		return;
  
  	for (i = 0; i < iterator->_vns->n_ns; i++) {
  		if (iterator->_vns->ns[i].oui != oui)
  			continue;
  		if (iterator->_vns->ns[i].subns != subns)
  			continue;
  
  		iterator->current_namespace = &iterator->_vns->ns[i];
  		break;
  	}
  }

  
  /**
   * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
   * @iterator: radiotap_iterator to move to next arg (if any)
   *
   * Returns: 0 if there is an argument to handle,
   * -ENOENT if there are no more args or -EINVAL
   * if there is something else wrong.
   *
   * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
   * in @this_arg_index and sets @this_arg to point to the
   * payload for the field.  It takes care of alignment handling and extended
   * present fields.  @this_arg can be changed by the caller (eg,
   * incremented to move inside a compound argument like
   * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
   * little-endian format whatever the endianess of your CPU.
   *
   * Alignment Gotcha:
   * You must take care when dereferencing iterator.this_arg
   * for multibyte types... the pointer is not aligned.  Use
   * get_unaligned((type *)iterator.this_arg) to dereference
   * iterator.this_arg for type "type" safely on all arches.
   */
  
  int ieee80211_radiotap_iterator_next(

  	struct ieee80211_radiotap_iterator *iterator)

  {

  	while (1) {

  		int hit = 0;

  		int pad, align, size, subns;

  		uint32_t oui;

  		/* if no more EXT bits, that's it */
  		if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
  		    !(iterator->_bitmap_shifter & 1))
  			return -ENOENT;
  
  		if (!(iterator->_bitmap_shifter & 1))

  			goto next_entry; /* arg not present */

  		/* get alignment/size of data */
  		switch (iterator->_arg_index % 32) {
  		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
  		case IEEE80211_RADIOTAP_EXT:
  			align = 1;
  			size = 0;
  			break;
  		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
  			align = 2;
  			size = 6;
  			break;
  		default:
  			if (!iterator->current_namespace ||
  			    iterator->_arg_index >= iterator->current_namespace->n_bits) {
  				if (iterator->current_namespace == &radiotap_ns)
  					return -ENOENT;
  				align = 0;
  			} else {
  				align = iterator->current_namespace->align_size[iterator->_arg_index].align;
  				size = iterator->current_namespace->align_size[iterator->_arg_index].size;
  			}
  			if (!align) {
  				/* skip all subsequent data */
  				iterator->_arg = iterator->_next_ns_data;
  				/* give up on this namespace */
  				iterator->current_namespace = NULL;
  				goto next_entry;
  			}
  			break;
  		}

  		/*
  		 * arg is present, account for alignment padding

  		 *

  		 * Note that these alignments are relative to the start
  		 * of the radiotap header.  There is no guarantee

  		 * that the radiotap header itself is aligned on any
  		 * kind of boundary.
  		 *

  		 * The above is why get_unaligned() is used to dereference
  		 * multibyte elements from the radiotap area.

  		 */

  		pad = ((unsigned long)iterator->_arg -
  		       (unsigned long)iterator->_rtheader) & (align - 1);

  
  		if (pad)

  			iterator->_arg += align - pad;

  		if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
  			int vnslen;
  
  			if ((unsigned long)iterator->_arg + size -
  			    (unsigned long)iterator->_rtheader >
  			    (unsigned long)iterator->_max_length)
  				return -EINVAL;
  
  			oui = (*iterator->_arg << 16) |
  				(*(iterator->_arg + 1) << 8) |
  				*(iterator->_arg + 2);
  			subns = *(iterator->_arg + 3);
  
  			find_ns(iterator, oui, subns);
  
  			vnslen = get_unaligned_le16(iterator->_arg + 4);
  			iterator->_next_ns_data = iterator->_arg + size + vnslen;
  			if (!iterator->current_namespace)
  				size += vnslen;
  		}

  		/*
  		 * this is what we will return to user, but we need to
  		 * move on first so next call has something fresh to test
  		 */

  		iterator->this_arg_index = iterator->_arg_index;
  		iterator->this_arg = iterator->_arg;
  		iterator->this_arg_size = size;

  
  		/* internally move on the size of this arg */

  		iterator->_arg += size;

  
  		/*
  		 * check for insanity where we are given a bitmap that
  		 * claims to have more arg content than the length of the
  		 * radiotap section.  We will normally end up equalling this
  		 * max_length on the last arg, never exceeding it.
  		 */

  		if ((unsigned long)iterator->_arg -
  		    (unsigned long)iterator->_rtheader >
  		    (unsigned long)iterator->_max_length)

  			return -EINVAL;

  		/* these special ones are valid in each bitmap word */
  		switch (iterator->_arg_index % 32) {
  		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:

  			iterator->_reset_on_ext = 1;

  			iterator->is_radiotap_ns = 0;

  			/*
  			 * If parser didn't register this vendor
  			 * namespace with us, allow it to show it
  			 * as 'raw. Do do that, set argument index
  			 * to vendor namespace.
  			 */

  			iterator->this_arg_index =
  				IEEE80211_RADIOTAP_VENDOR_NAMESPACE;

  			if (!iterator->current_namespace)
  				hit = 1;
  			goto next_entry;

  		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:

  			iterator->_reset_on_ext = 1;
  			iterator->current_namespace = &radiotap_ns;
  			iterator->is_radiotap_ns = 1;

  			goto next_entry;

  		case IEEE80211_RADIOTAP_EXT:
  			/*
  			 * bit 31 was set, there is more
  			 * -- move to next u32 bitmap
  			 */
  			iterator->_bitmap_shifter =
  				get_unaligned_le32(iterator->_next_bitmap);
  			iterator->_next_bitmap++;
  			if (iterator->_reset_on_ext)
  				iterator->_arg_index = 0;
  			else
  				iterator->_arg_index++;
  			iterator->_reset_on_ext = 0;
  			break;
  		default:
  			/* we've got a hit! */
  			hit = 1;
   next_entry:
  			iterator->_bitmap_shifter >>= 1;
  			iterator->_arg_index++;
  		}

  
  		/* if we found a valid arg earlier, return it now */
  		if (hit)
  			return 0;
  	}

  }
  EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);