beacon.c

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/* Copyright 2021 The libwifi Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
#include "beacon.h"
#include "../../core/frame/tag.h"
#include "../../core/frame/tag_iterator.h"
#include "../../core/misc/byteswap.h"
#include "../../core/misc/epoch.h"
#include "common.h"
 
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
 
size_t libwifi_get_beacon_length(struct libwifi_beacon *beacon) {
    return sizeof(struct libwifi_mgmt_unordered_frame_header) +
           sizeof(struct libwifi_beacon_fixed_parameters) +
           beacon->tags.length;
}
 
int libwifi_set_beacon_ssid(struct libwifi_beacon *beacon, const char *ssid) {
    int ret = 0;
 
    if (beacon->tags.length != 0) {
        ret = libwifi_remove_tag(&beacon->tags, TAG_SSID);
        if (ret != 0) {
            return ret;
        }
    }
 
    ret = libwifi_quick_add_tag(&beacon->tags, TAG_SSID, (void *) ssid, strlen(ssid));
 
    return ret;
}
 
int libwifi_set_beacon_channel(struct libwifi_beacon *beacon, uint8_t channel) {
    int ret = 0;
 
    if (beacon->tags.length != 0) {
        ret = libwifi_remove_tag(&beacon->tags, TAG_DS_PARAMETER);
        if (ret != 0) {
            return ret;
        }
    }
 
    const unsigned char *chan = (const unsigned char *) &channel;
 
    ret = libwifi_quick_add_tag(&beacon->tags, TAG_DS_PARAMETER, chan, 1);
 
    return ret;
}
 
int libwifi_create_beacon(struct libwifi_beacon *beacon,
                          const unsigned char receiver[6],
                          const unsigned char transmitter[6],
                          const unsigned char address3[6],
                          const char *ssid,
                          uint8_t channel) {
    memset(beacon, 0, sizeof(struct libwifi_beacon));
 
    beacon->frame_header.frame_control.type = TYPE_MANAGEMENT;
    beacon->frame_header.frame_control.subtype = SUBTYPE_BEACON;
    memcpy(&beacon->frame_header.addr1, receiver, 6);
    memcpy(&beacon->frame_header.addr2, transmitter, 6);
    memcpy(&beacon->frame_header.addr3, address3, 6);
    beacon->frame_header.seq_control.sequence_number = (rand() % 4096);
 
    beacon->fixed_parameters.timestamp = BYTESWAP64(libwifi_get_epoch());
    beacon->fixed_parameters.beacon_interval = BYTESWAP16(LIBWIFI_DEFAULT_BEACON_INTERVAL);
    beacon->fixed_parameters.capabilities_information = BYTESWAP16(LIBWIFI_DEFAULT_AP_CAPABS);
 
    int ret = libwifi_set_beacon_ssid(beacon, ssid);
    if (ret != 0) {
        return ret;
    }
 
    ret = libwifi_set_beacon_channel(beacon, channel);
 
    return ret;
}
 
size_t libwifi_dump_beacon(struct libwifi_beacon *beacon, unsigned char *buf, size_t buf_len) {
    size_t beacon_len = libwifi_get_beacon_length(beacon);
    if (beacon_len > buf_len) {
        return -EINVAL;
    }
 
    size_t offset = 0;
    memcpy(buf + offset, &beacon->frame_header, sizeof(struct libwifi_mgmt_unordered_frame_header));
    offset += sizeof(struct libwifi_mgmt_unordered_frame_header);
 
    memcpy(buf + offset, &beacon->fixed_parameters, sizeof(struct libwifi_beacon_fixed_parameters));
    offset += sizeof(struct libwifi_beacon_fixed_parameters);
 
    memcpy(buf + offset, beacon->tags.parameters, beacon->tags.length);
    offset += beacon->tags.length;
 
    return beacon_len;
}
 
void libwifi_free_beacon(struct libwifi_beacon *beacon) {
    free(beacon->tags.parameters);
}