beacon.c

Go to the documentation of this file.

/*
 * hostapd / IEEE 802.11 Management: Beacon and Probe Request/Response
 * Copyright (c) 2002-2004, Instant802 Networks, Inc.
 * Copyright (c) 2005-2006, Devicescape Software, Inc.
 * Copyright (c) 2008-2009, Jouni Malinen <j@w1.fi>
 *
 * 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 README and COPYING for more details.
 */

#include "utils/includes.h"

#ifndef CONFIG_NATIVE_WINDOWS

#include "utils/common.h"
#include "common/ieee802_11_defs.h"
#include "common/ieee802_11_common.h"
#include "drivers/driver.h"
#include "hostapd.h"
#include "ieee802_11.h"
#include "wpa_auth.h"
#include "wmm.h"
#include "ap_config.h"
#include "sta_info.h"
#include "beacon.h"


static u8 ieee802_11_erp_info(struct hostapd_data *hapd)
{
        u8 erp = 0;

        if (hapd->iface->current_mode == NULL ||
            hapd->iface->current_mode->mode != HOSTAPD_MODE_IEEE80211G)
                return 0;

        switch (hapd->iconf->cts_protection_type) {
        case CTS_PROTECTION_FORCE_ENABLED:
                erp |= ERP_INFO_NON_ERP_PRESENT | ERP_INFO_USE_PROTECTION;
                break;
        case CTS_PROTECTION_FORCE_DISABLED:
                erp = 0;
                break;
        case CTS_PROTECTION_AUTOMATIC:
                if (hapd->iface->olbc)
                        erp |= ERP_INFO_USE_PROTECTION;
                /* continue */
        case CTS_PROTECTION_AUTOMATIC_NO_OLBC:
                if (hapd->iface->num_sta_non_erp > 0) {
                        erp |= ERP_INFO_NON_ERP_PRESENT |
                                ERP_INFO_USE_PROTECTION;
                }
                break;
        }
        if (hapd->iface->num_sta_no_short_preamble > 0)
                erp |= ERP_INFO_BARKER_PREAMBLE_MODE;

        return erp;
}


static u8 * hostapd_eid_ds_params(struct hostapd_data *hapd, u8 *eid)
{
        *eid++ = WLAN_EID_DS_PARAMS;
        *eid++ = 1;
        *eid++ = hapd->iconf->channel;
        return eid;
}


static u8 * hostapd_eid_erp_info(struct hostapd_data *hapd, u8 *eid)
{
        if (hapd->iface->current_mode == NULL ||
            hapd->iface->current_mode->mode != HOSTAPD_MODE_IEEE80211G)
                return eid;

        /* Set NonERP_present and use_protection bits if there
         * are any associated NonERP stations. */
        /* TODO: use_protection bit can be set to zero even if
         * there are NonERP stations present. This optimization
         * might be useful if NonERP stations are "quiet".
         * See 802.11g/D6 E-1 for recommended practice.
         * In addition, Non ERP present might be set, if AP detects Non ERP
         * operation on other APs. */

        /* Add ERP Information element */
        *eid++ = WLAN_EID_ERP_INFO;
        *eid++ = 1;
        *eid++ = ieee802_11_erp_info(hapd);

        return eid;
}


static u8 * hostapd_eid_country_add(u8 *pos, u8 *end, int chan_spacing,
                                    struct hostapd_channel_data *start,
                                    struct hostapd_channel_data *prev)
{
        if (end - pos < 3)
                return pos;

        /* first channel number */
        *pos++ = start->chan;
        /* number of channels */
        *pos++ = (prev->chan - start->chan) / chan_spacing + 1;
        /* maximum transmit power level */
        *pos++ = start->max_tx_power;

        return pos;
}


static u8 * hostapd_eid_country(struct hostapd_data *hapd, u8 *eid,
                                int max_len)
{
        u8 *pos = eid;
        u8 *end = eid + max_len;
        int i;
        struct hostapd_hw_modes *mode;
        struct hostapd_channel_data *start, *prev;
        int chan_spacing = 1;

        if (!hapd->iconf->ieee80211d || max_len < 6 ||
            hapd->iface->current_mode == NULL)
                return eid;

        *pos++ = WLAN_EID_COUNTRY;
        pos++; /* length will be set later */
        os_memcpy(pos, hapd->iconf->country, 3); /* e.g., 'US ' */
        pos += 3;

        mode = hapd->iface->current_mode;
        if (mode->mode == HOSTAPD_MODE_IEEE80211A)
                chan_spacing = 4;

        start = prev = NULL;
        for (i = 0; i < mode->num_channels; i++) {
                struct hostapd_channel_data *chan = &mode->channels[i];
                if (chan->flag & HOSTAPD_CHAN_DISABLED)
                        continue;
                if (start && prev &&
                    prev->chan + chan_spacing == chan->chan &&
                    start->max_tx_power == chan->max_tx_power) {
                        prev = chan;
                        continue; /* can use same entry */
                }

                if (start) {
                        pos = hostapd_eid_country_add(pos, end, chan_spacing,
                                                      start, prev);
                        start = NULL;
                }

                /* Start new group */
                start = prev = chan;
        }

        if (start) {
                pos = hostapd_eid_country_add(pos, end, chan_spacing,
                                              start, prev);
        }

        if ((pos - eid) & 1) {
                if (end - pos < 1)
                        return eid;
                *pos++ = 0; /* pad for 16-bit alignment */
        }

        eid[1] = (pos - eid) - 2;

        return pos;
}


static u8 * hostapd_eid_wpa(struct hostapd_data *hapd, u8 *eid, size_t len,
                            struct sta_info *sta)
{
        const u8 *ie;
        size_t ielen;

        ie = wpa_auth_get_wpa_ie(hapd->wpa_auth, &ielen);
        if (ie == NULL || ielen > len)
                return eid;

        os_memcpy(eid, ie, ielen);
        return eid + ielen;
}


void handle_probe_req(struct hostapd_data *hapd,
                      const struct ieee80211_mgmt *mgmt, size_t len)
{
        struct ieee80211_mgmt *resp;
        struct ieee802_11_elems elems;
        char *ssid;
        u8 *pos, *epos;
        const u8 *ie;
        size_t ssid_len, ie_len;
        struct sta_info *sta = NULL;
        size_t buflen;
        size_t i;

        ie = mgmt->u.probe_req.variable;
        ie_len = len - (IEEE80211_HDRLEN + sizeof(mgmt->u.probe_req));

        for (i = 0; hapd->probereq_cb && i < hapd->num_probereq_cb; i++)
                if (hapd->probereq_cb[i].cb(hapd->probereq_cb[i].ctx,
                                            mgmt->sa, ie, ie_len) > 0)
                        return;

        if (!hapd->iconf->send_probe_response)
                return;

        if (ieee802_11_parse_elems(ie, ie_len, &elems, 0) == ParseFailed) {
                wpa_printf(MSG_DEBUG, "Could not parse ProbeReq from " MACSTR,
                           MAC2STR(mgmt->sa));
                return;
        }

        ssid = NULL;
        ssid_len = 0;

        if ((!elems.ssid || !elems.supp_rates)) {
                wpa_printf(MSG_DEBUG, "STA " MACSTR " sent probe request "
                           "without SSID or supported rates element",
                           MAC2STR(mgmt->sa));
                return;
        }

        if (hapd->conf->ignore_broadcast_ssid && elems.ssid_len == 0) {
                wpa_printf(MSG_MSGDUMP, "Probe Request from " MACSTR " for "
                           "broadcast SSID ignored", MAC2STR(mgmt->sa));
                return;
        }

        sta = ap_get_sta(hapd, mgmt->sa);

        if (elems.ssid_len == 0 ||
            (elems.ssid_len == hapd->conf->ssid.ssid_len &&
             os_memcmp(elems.ssid, hapd->conf->ssid.ssid, elems.ssid_len) ==
             0)) {
                ssid = hapd->conf->ssid.ssid;
                ssid_len = hapd->conf->ssid.ssid_len;
                if (sta)
                        sta->ssid_probe = &hapd->conf->ssid;
        }

        if (!ssid) {
                if (!(mgmt->da[0] & 0x01)) {
                        char ssid_txt[33];
                        ieee802_11_print_ssid(ssid_txt, elems.ssid,
                                              elems.ssid_len);
                        wpa_printf(MSG_MSGDUMP, "Probe Request from " MACSTR
                                   " for foreign SSID '%s'",
                                   MAC2STR(mgmt->sa), ssid_txt);
                }
                return;
        }

        /* TODO: verify that supp_rates contains at least one matching rate
         * with AP configuration */
#define MAX_PROBERESP_LEN 768
        buflen = MAX_PROBERESP_LEN;
#ifdef CONFIG_WPS
        if (hapd->wps_probe_resp_ie)
                buflen += wpabuf_len(hapd->wps_probe_resp_ie);
#endif /* CONFIG_WPS */
        resp = os_zalloc(buflen);
        if (resp == NULL)
                return;
        epos = ((u8 *) resp) + MAX_PROBERESP_LEN;

        resp->frame_control = IEEE80211_FC(WLAN_FC_TYPE_MGMT,
                                           WLAN_FC_STYPE_PROBE_RESP);
        os_memcpy(resp->da, mgmt->sa, ETH_ALEN);
        os_memcpy(resp->sa, hapd->own_addr, ETH_ALEN);

        os_memcpy(resp->bssid, hapd->own_addr, ETH_ALEN);
        resp->u.probe_resp.beacon_int =
                host_to_le16(hapd->iconf->beacon_int);

        /* hardware or low-level driver will setup seq_ctrl and timestamp */
        resp->u.probe_resp.capab_info =
                host_to_le16(hostapd_own_capab_info(hapd, sta, 1));

        pos = resp->u.probe_resp.variable;
        *pos++ = WLAN_EID_SSID;
        *pos++ = ssid_len;
        os_memcpy(pos, ssid, ssid_len);
        pos += ssid_len;

        /* Supported rates */
        pos = hostapd_eid_supp_rates(hapd, pos);

        /* DS Params */
        pos = hostapd_eid_ds_params(hapd, pos);

        pos = hostapd_eid_country(hapd, pos, epos - pos);

        /* ERP Information element */
        pos = hostapd_eid_erp_info(hapd, pos);

        /* Extended supported rates */
        pos = hostapd_eid_ext_supp_rates(hapd, pos);

        pos = hostapd_eid_wpa(hapd, pos, epos - pos, sta);

        /* Wi-Fi Alliance WMM */
        pos = hostapd_eid_wmm(hapd, pos);

#ifdef CONFIG_IEEE80211N
        pos = hostapd_eid_ht_capabilities(hapd, pos);
        pos = hostapd_eid_ht_operation(hapd, pos);
#endif /* CONFIG_IEEE80211N */

#ifdef CONFIG_WPS
        if (hapd->conf->wps_state && hapd->wps_probe_resp_ie) {
                os_memcpy(pos, wpabuf_head(hapd->wps_probe_resp_ie),
                          wpabuf_len(hapd->wps_probe_resp_ie));
                pos += wpabuf_len(hapd->wps_probe_resp_ie);
        }
#endif /* CONFIG_WPS */

        if (hapd->drv.send_mgmt_frame(hapd, resp, pos - (u8 *) resp) < 0)
                perror("handle_probe_req: send");

        os_free(resp);

        wpa_printf(MSG_MSGDUMP, "STA " MACSTR " sent probe request for %s "
                   "SSID", MAC2STR(mgmt->sa),
                   elems.ssid_len == 0 ? "broadcast" : "our");
}


void ieee802_11_set_beacon(struct hostapd_data *hapd)
{
        struct ieee80211_mgmt *head;
        u8 *pos, *tail, *tailpos;
        u16 capab_info;
        size_t head_len, tail_len;

#define BEACON_HEAD_BUF_SIZE 256
#define BEACON_TAIL_BUF_SIZE 512
        head = os_zalloc(BEACON_HEAD_BUF_SIZE);
        tail_len = BEACON_TAIL_BUF_SIZE;
#ifdef CONFIG_WPS
        if (hapd->conf->wps_state && hapd->wps_beacon_ie)
                tail_len += wpabuf_len(hapd->wps_beacon_ie);
#endif /* CONFIG_WPS */
        tailpos = tail = os_malloc(tail_len);
        if (head == NULL || tail == NULL) {
                wpa_printf(MSG_ERROR, "Failed to set beacon data");
                os_free(head);
                os_free(tail);
                return;
        }

        head->frame_control = IEEE80211_FC(WLAN_FC_TYPE_MGMT,
                                           WLAN_FC_STYPE_BEACON);
        head->duration = host_to_le16(0);
        os_memset(head->da, 0xff, ETH_ALEN);

        os_memcpy(head->sa, hapd->own_addr, ETH_ALEN);
        os_memcpy(head->bssid, hapd->own_addr, ETH_ALEN);
        head->u.beacon.beacon_int =
                host_to_le16(hapd->iconf->beacon_int);

        /* hardware or low-level driver will setup seq_ctrl and timestamp */
        capab_info = hostapd_own_capab_info(hapd, NULL, 0);
        head->u.beacon.capab_info = host_to_le16(capab_info);
        pos = &head->u.beacon.variable[0];

        /* SSID */
        *pos++ = WLAN_EID_SSID;
        if (hapd->conf->ignore_broadcast_ssid == 2) {
                /* clear the data, but keep the correct length of the SSID */
                *pos++ = hapd->conf->ssid.ssid_len;
                os_memset(pos, 0, hapd->conf->ssid.ssid_len);
                pos += hapd->conf->ssid.ssid_len;
        } else if (hapd->conf->ignore_broadcast_ssid) {
                *pos++ = 0; /* empty SSID */
        } else {
                *pos++ = hapd->conf->ssid.ssid_len;
                os_memcpy(pos, hapd->conf->ssid.ssid,
                          hapd->conf->ssid.ssid_len);
                pos += hapd->conf->ssid.ssid_len;
        }

        /* Supported rates */
        pos = hostapd_eid_supp_rates(hapd, pos);

        /* DS Params */
        pos = hostapd_eid_ds_params(hapd, pos);

        head_len = pos - (u8 *) head;

        tailpos = hostapd_eid_country(hapd, tailpos,
                                      tail + BEACON_TAIL_BUF_SIZE - tailpos);

        /* ERP Information element */
        tailpos = hostapd_eid_erp_info(hapd, tailpos);

        /* Extended supported rates */
        tailpos = hostapd_eid_ext_supp_rates(hapd, tailpos);

        tailpos = hostapd_eid_wpa(hapd, tailpos, tail + BEACON_TAIL_BUF_SIZE -
                                  tailpos, NULL);

        /* Wi-Fi Alliance WMM */
        tailpos = hostapd_eid_wmm(hapd, tailpos);

#ifdef CONFIG_IEEE80211N
        tailpos = hostapd_eid_ht_capabilities(hapd, tailpos);
        tailpos = hostapd_eid_ht_operation(hapd, tailpos);
#endif /* CONFIG_IEEE80211N */

#ifdef CONFIG_WPS
        if (hapd->conf->wps_state && hapd->wps_beacon_ie) {
                os_memcpy(tailpos, wpabuf_head(hapd->wps_beacon_ie),
                          wpabuf_len(hapd->wps_beacon_ie));
                tailpos += wpabuf_len(hapd->wps_beacon_ie);
        }
#endif /* CONFIG_WPS */

        tail_len = tailpos > tail ? tailpos - tail : 0;

        if (hapd->drv.set_beacon(hapd, (u8 *) head, head_len,
                                 tail, tail_len, hapd->conf->dtim_period,
                                 hapd->iconf->beacon_int))
                wpa_printf(MSG_ERROR, "Failed to set beacon head/tail or DTIM "
                           "period");

        os_free(tail);
        os_free(head);

        hapd->drv.set_bss_params(hapd, !!(ieee802_11_erp_info(hapd) &
                                          ERP_INFO_USE_PROTECTION));
}


void ieee802_11_set_beacons(struct hostapd_iface *iface)
{
        size_t i;
        for (i = 0; i < iface->num_bss; i++)
                ieee802_11_set_beacon(iface->bss[i]);
}

#endif /* CONFIG_NATIVE_WINDOWS */