radiotap.c

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/*
 * Radiotap parser
 *
 * Copyright 2007       Andy Green <[email protected]>
 * Copyright 2009       Johannes Berg <[email protected]>
 *
 * 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, },
    [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 = ARRAY_SIZE(rtap_namespace_sizes),
    .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;

    /* 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;
    }
}



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);