--- /dev/null
+/*
+ * 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 "radiotap_iter.h"
+#include "platform.h"
+
+/* function prototypes and related defs are in radiotap_iter.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 = sizeof(rtap_namespace_sizes) / sizeof(rtap_namespace_sizes[0]),
+ .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: parse.c
+ */
+
+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;
+#ifdef RADIOTAP_SUPPORT_OVERRIDES
+ iterator->n_overrides = 0;
+ iterator->overrides = NULL;
+#endif
+
+ /* 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;
+}
+
+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;
+ }
+}
+
+#ifdef RADIOTAP_SUPPORT_OVERRIDES
+static int find_override(struct ieee80211_radiotap_iterator *iterator,
+ int *align, int *size)
+{
+ int i;
+
+ if (!iterator->overrides)
+ return 0;
+
+ for (i = 0; i < iterator->n_overrides; i++) {
+ if (iterator->_arg_index == iterator->overrides[i].field) {
+ *align = iterator->overrides[i].align;
+ *size = iterator->overrides[i].size;
+ if (!*align) /* erroneous override */
+ return 0;
+ return 1;
+ }
+ }
+
+ return 0;
+}
+#endif
+
+
+/**
+ * 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, vnslen;
+ 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:
+#ifdef RADIOTAP_SUPPORT_OVERRIDES
+ if (find_override(iterator, &align, &size)) {
+ /* all set */
+ } else
+#endif
+ 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;
+
+ /*
+ * 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->_bitmap_shifter >>= 1;
+ iterator->_arg_index++;
+
+ iterator->_reset_on_ext = 1;
+
+ vnslen = get_unaligned_le16(iterator->this_arg + 4);
+ iterator->_next_ns_data = iterator->_arg + vnslen;
+ oui = (*iterator->this_arg << 16) |
+ (*(iterator->this_arg + 1) << 8) |
+ *(iterator->this_arg + 2);
+ subns = *(iterator->this_arg + 3);
+
+ find_ns(iterator, oui, subns);
+
+ iterator->is_radiotap_ns = 0;
+ /* allow parsers to show this information */
+ iterator->this_arg_index =
+ IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
+ iterator->this_arg_size += vnslen;
+ if ((unsigned long)iterator->this_arg +
+ iterator->this_arg_size -
+ (unsigned long)iterator->_rtheader >
+ (unsigned long)(unsigned long)iterator->_max_length)
+ return -EINVAL;
+ hit = 1;
+ break;
+ case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
+ iterator->_bitmap_shifter >>= 1;
+ iterator->_arg_index++;
+
+ iterator->_reset_on_ext = 1;
+ iterator->current_namespace = &radiotap_ns;
+ iterator->is_radiotap_ns = 1;
+ break;
+ 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;
+ }
+}
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