radiotap.c

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/*
 * 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, },
        [IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
        [IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
        /*
         * 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,
};

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


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:
#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;

                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;
        }
}