scan.c

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/*
 * WPA Supplicant - Scanning
 * Copyright (c) 2003-2010, 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"

#include "utils/common.h"
#include "utils/eloop.h"
#include "common/ieee802_11_defs.h"
#include "config.h"
#include "wpa_supplicant_i.h"
#include "driver_i.h"
#include "mlme.h"
#include "wps_supplicant.h"
#include "notify.h"
#include "bss.h"
#include "scan.h"


static void wpa_supplicant_gen_assoc_event(struct wpa_supplicant *wpa_s)
{
        struct wpa_ssid *ssid;
        union wpa_event_data data;

        ssid = wpa_supplicant_get_ssid(wpa_s);
        if (ssid == NULL)
                return;

        if (wpa_s->current_ssid == NULL) {
                wpa_s->current_ssid = ssid;
                if (wpa_s->current_ssid != NULL)
                        wpas_notify_network_changed(wpa_s);
        }
        wpa_supplicant_initiate_eapol(wpa_s);
        wpa_printf(MSG_DEBUG, "Already associated with a configured network - "
                   "generating associated event");
        os_memset(&data, 0, sizeof(data));
        wpa_supplicant_event(wpa_s, EVENT_ASSOC, &data);
}


#ifdef CONFIG_WPS
static int wpas_wps_in_use(struct wpa_config *conf,
                           enum wps_request_type *req_type)
{
        struct wpa_ssid *ssid;
        int wps = 0;

        for (ssid = conf->ssid; ssid; ssid = ssid->next) {
                if (!(ssid->key_mgmt & WPA_KEY_MGMT_WPS))
                        continue;

                wps = 1;
                *req_type = wpas_wps_get_req_type(ssid);
                if (!ssid->eap.phase1)
                        continue;

                if (os_strstr(ssid->eap.phase1, "pbc=1"))
                        return 2;
        }

        return wps;
}
#endif /* CONFIG_WPS */


int wpa_supplicant_enabled_networks(struct wpa_config *conf)
{
        struct wpa_ssid *ssid = conf->ssid;
        while (ssid) {
                if (!ssid->disabled)
                        return 1;
                ssid = ssid->next;
        }
        return 0;
}


static void wpa_supplicant_assoc_try(struct wpa_supplicant *wpa_s,
                                     struct wpa_ssid *ssid)
{
        while (ssid) {
                if (!ssid->disabled)
                        break;
                ssid = ssid->next;
        }

        /* ap_scan=2 mode - try to associate with each SSID. */
        if (ssid == NULL) {
                wpa_printf(MSG_DEBUG, "wpa_supplicant_scan: Reached "
                           "end of scan list - go back to beginning");
                wpa_s->prev_scan_ssid = WILDCARD_SSID_SCAN;
                wpa_supplicant_req_scan(wpa_s, 0, 0);
                return;
        }
        if (ssid->next) {
                /* Continue from the next SSID on the next attempt. */
                wpa_s->prev_scan_ssid = ssid;
        } else {
                /* Start from the beginning of the SSID list. */
                wpa_s->prev_scan_ssid = WILDCARD_SSID_SCAN;
        }
        wpa_supplicant_associate(wpa_s, NULL, ssid);
}


static int int_array_len(const int *a)
{
        int i;
        for (i = 0; a && a[i]; i++)
                ;
        return i;
}


static void int_array_concat(int **res, const int *a)
{
        int reslen, alen, i;
        int *n;

        reslen = int_array_len(*res);
        alen = int_array_len(a);

        n = os_realloc(*res, (reslen + alen + 1) * sizeof(int));
        if (n == NULL) {
                os_free(*res);
                *res = NULL;
                return;
        }
        for (i = 0; i <= alen; i++)
                n[reslen + i] = a[i];
        *res = n;
}


static int freq_cmp(const void *a, const void *b)
{
        int _a = *(int *) a;
        int _b = *(int *) b;

        if (_a == 0)
                return 1;
        if (_b == 0)
                return -1;
        return _a - _b;
}


static void int_array_sort_unique(int *a)
{
        int alen;
        int i, j;

        if (a == NULL)
                return;

        alen = int_array_len(a);
        qsort(a, alen, sizeof(int), freq_cmp);

        i = 0;
        j = 1;
        while (a[i] && a[j]) {
                if (a[i] == a[j]) {
                        j++;
                        continue;
                }
                a[++i] = a[j++];
        }
        if (a[i])
                i++;
        a[i] = 0;
}


int wpa_supplicant_trigger_scan(struct wpa_supplicant *wpa_s,
                                struct wpa_driver_scan_params *params)
{
        int ret;

        wpa_supplicant_notify_scanning(wpa_s, 1);

        if (wpa_s->drv_flags & WPA_DRIVER_FLAGS_USER_SPACE_MLME)
                ret = ieee80211_sta_req_scan(wpa_s, params);
        else
                ret = wpa_drv_scan(wpa_s, params);

        if (ret) {
                wpa_supplicant_notify_scanning(wpa_s, 0);
                wpas_notify_scan_done(wpa_s, 0);
        } else
                wpa_s->scan_runs++;

        return ret;
}


static struct wpa_driver_scan_filter *
wpa_supplicant_build_filter_ssids(struct wpa_config *conf, size_t *num_ssids)
{
        struct wpa_driver_scan_filter *ssids;
        struct wpa_ssid *ssid;
        size_t count;

        *num_ssids = 0;
        if (!conf->filter_ssids)
                return NULL;

        for (count = 0, ssid = conf->ssid; ssid; ssid = ssid->next) {
                if (ssid->ssid && ssid->ssid_len)
                        count++;
        }
        if (count == 0)
                return NULL;
        ssids = os_zalloc(count * sizeof(struct wpa_driver_scan_filter));
        if (ssids == NULL)
                return NULL;

        for (ssid = conf->ssid; ssid; ssid = ssid->next) {
                if (!ssid->ssid || !ssid->ssid_len)
                        continue;
                os_memcpy(ssids[*num_ssids].ssid, ssid->ssid, ssid->ssid_len);
                ssids[*num_ssids].ssid_len = ssid->ssid_len;
                (*num_ssids)++;
        }

        return ssids;
}


static void wpa_supplicant_scan(void *eloop_ctx, void *timeout_ctx)
{
        struct wpa_supplicant *wpa_s = eloop_ctx;
        struct wpa_ssid *ssid;
        int scan_req = 0, ret;
        struct wpabuf *wps_ie = NULL;
        int wps = 0;
#ifdef CONFIG_WPS
        enum wps_request_type req_type = WPS_REQ_ENROLLEE_INFO;
#endif /* CONFIG_WPS */
        struct wpa_driver_scan_params params;
        size_t max_ssids;
        enum wpa_states prev_state;

        if (wpa_s->disconnected && !wpa_s->scan_req) {
                wpa_supplicant_set_state(wpa_s, WPA_DISCONNECTED);
                return;
        }

        if (!wpa_supplicant_enabled_networks(wpa_s->conf) &&
            !wpa_s->scan_req) {
                wpa_printf(MSG_DEBUG, "No enabled networks - do not scan");
                wpa_supplicant_set_state(wpa_s, WPA_INACTIVE);
                return;
        }

        if (wpa_s->conf->ap_scan != 0 &&
            (wpa_s->drv_flags & WPA_DRIVER_FLAGS_WIRED)) {
                wpa_printf(MSG_DEBUG, "Using wired authentication - "
                           "overriding ap_scan configuration");
                wpa_s->conf->ap_scan = 0;
                wpas_notify_ap_scan_changed(wpa_s);
        }

        if (wpa_s->conf->ap_scan == 0) {
                wpa_supplicant_gen_assoc_event(wpa_s);
                return;
        }

        if ((wpa_s->drv_flags & WPA_DRIVER_FLAGS_USER_SPACE_MLME) ||
            wpa_s->conf->ap_scan == 2)
                max_ssids = 1;
        else {
                max_ssids = wpa_s->max_scan_ssids;
                if (max_ssids > WPAS_MAX_SCAN_SSIDS)
                        max_ssids = WPAS_MAX_SCAN_SSIDS;
        }

#ifdef CONFIG_WPS
        wps = wpas_wps_in_use(wpa_s->conf, &req_type);
#endif /* CONFIG_WPS */

        if ((wpa_s->scan_res_tried == 0 && wpa_s->conf->ap_scan == 1 &&
            !(wpa_s->drv_flags & WPA_DRIVER_FLAGS_USER_SPACE_MLME) &&
            wps != 2 && !wpa_s->conf->filter_ssids &&
            !wpa_s->connect_without_scan) ||
            wpa_s->more_bss_to_try) {
                wpa_s->scan_res_tried++;
                wpa_printf(MSG_DEBUG, "Trying to get current scan results "
                           "first without requesting a new scan to speed up "
                           "initial association");
                wpa_supplicant_event(wpa_s, EVENT_SCAN_RESULTS, NULL);
                return;
        }

        scan_req = wpa_s->scan_req;
        wpa_s->scan_req = 0;

        os_memset(&params, 0, sizeof(params));

        prev_state = wpa_s->wpa_state;
        if (wpa_s->wpa_state == WPA_DISCONNECTED ||
            wpa_s->wpa_state == WPA_INACTIVE)
                wpa_supplicant_set_state(wpa_s, WPA_SCANNING);

        /* Find the starting point from which to continue scanning */
        ssid = wpa_s->conf->ssid;
        if (wpa_s->prev_scan_ssid != WILDCARD_SSID_SCAN) {
                while (ssid) {
                        if (ssid == wpa_s->prev_scan_ssid) {
                                ssid = ssid->next;
                                break;
                        }
                        ssid = ssid->next;
                }
        }

        if (scan_req != 2 && (wpa_s->conf->ap_scan == 2 ||
                              wpa_s->connect_without_scan)) {
                wpa_s->connect_without_scan = 0;
                wpa_supplicant_assoc_try(wpa_s, ssid);
                return;
        } else if (wpa_s->conf->ap_scan == 2) {
                /*
                 * User-initiated scan request in ap_scan == 2; scan with
                 * wildcard SSID.
                 */
                ssid = NULL;
        } else {
                struct wpa_ssid *start = ssid, *tssid;
                int freqs_set = 0;
                if (ssid == NULL && max_ssids > 1)
                        ssid = wpa_s->conf->ssid;
                while (ssid) {
                        if (!ssid->disabled && ssid->scan_ssid) {
                                wpa_hexdump_ascii(MSG_DEBUG, "Scan SSID",
                                                  ssid->ssid, ssid->ssid_len);
                                params.ssids[params.num_ssids].ssid =
                                        ssid->ssid;
                                params.ssids[params.num_ssids].ssid_len =
                                        ssid->ssid_len;
                                params.num_ssids++;
                                if (params.num_ssids + 1 >= max_ssids)
                                        break;
                        }
                        ssid = ssid->next;
                        if (ssid == start)
                                break;
                        if (ssid == NULL && max_ssids > 1 &&
                            start != wpa_s->conf->ssid)
                                ssid = wpa_s->conf->ssid;
                }

                for (tssid = wpa_s->conf->ssid; tssid; tssid = tssid->next) {
                        if (tssid->disabled)
                                continue;
                        if ((params.freqs || !freqs_set) && tssid->scan_freq) {
                                int_array_concat(&params.freqs,
                                                 tssid->scan_freq);
                        } else {
                                os_free(params.freqs);
                                params.freqs = NULL;
                        }
                        freqs_set = 1;
                }
                int_array_sort_unique(params.freqs);
        }

        if (ssid) {
                wpa_s->prev_scan_ssid = ssid;
                if (max_ssids > 1) {
                        wpa_printf(MSG_DEBUG, "Include wildcard SSID in the "
                                   "scan request");
                        params.num_ssids++;
                }
                wpa_printf(MSG_DEBUG, "Starting AP scan for specific SSID(s)");
        } else {
                wpa_s->prev_scan_ssid = WILDCARD_SSID_SCAN;
                params.num_ssids++;
                wpa_printf(MSG_DEBUG, "Starting AP scan for wildcard SSID");
        }

#ifdef CONFIG_WPS
        if (params.freqs == NULL && wpa_s->after_wps && wpa_s->wps_freq) {
                /*
                 * Optimize post-provisioning scan based on channel used
                 * during provisioning.
                 */
                wpa_printf(MSG_DEBUG, "WPS: Scan only frequency %u MHz that "
                           "was used during provisioning", wpa_s->wps_freq);
                params.freqs = os_zalloc(2 * sizeof(int));
                if (params.freqs)
                        params.freqs[0] = wpa_s->wps_freq;
                wpa_s->after_wps--;
        }

        if (wps) {
                wps_ie = wps_build_probe_req_ie(wps == 2, &wpa_s->wps->dev,
                                                wpa_s->wps->uuid, req_type);
                if (wps_ie) {
                        params.extra_ies = wpabuf_head(wps_ie);
                        params.extra_ies_len = wpabuf_len(wps_ie);
                }
        }
#endif /* CONFIG_WPS */

        params.filter_ssids = wpa_supplicant_build_filter_ssids(
                wpa_s->conf, &params.num_filter_ssids);

        ret = wpa_supplicant_trigger_scan(wpa_s, &params);

        wpabuf_free(wps_ie);
        os_free(params.freqs);
        os_free(params.filter_ssids);

        if (ret) {
                wpa_printf(MSG_WARNING, "Failed to initiate AP scan.");
                if (prev_state != wpa_s->wpa_state)
                        wpa_supplicant_set_state(wpa_s, prev_state);
                wpa_supplicant_req_scan(wpa_s, 1, 0);
        } else
                wpa_s->scan_runs++;
}


void wpa_supplicant_req_scan(struct wpa_supplicant *wpa_s, int sec, int usec)
{
        /* If there's at least one network that should be specifically scanned
         * then don't cancel the scan and reschedule.  Some drivers do
         * background scanning which generates frequent scan results, and that
         * causes the specific SSID scan to get continually pushed back and
         * never happen, which causes hidden APs to never get probe-scanned.
         */
        if (eloop_is_timeout_registered(wpa_supplicant_scan, wpa_s, NULL) &&
            wpa_s->conf->ap_scan == 1) {
                struct wpa_ssid *ssid = wpa_s->conf->ssid;

                while (ssid) {
                        if (!ssid->disabled && ssid->scan_ssid)
                                break;
                        ssid = ssid->next;
                }
                if (ssid) {
                        wpa_msg(wpa_s, MSG_DEBUG, "Not rescheduling scan to "
                                "ensure that specific SSID scans occur");
                        return;
                }
        }

        wpa_msg(wpa_s, MSG_DEBUG, "Setting scan request: %d sec %d usec",
                sec, usec);
        eloop_cancel_timeout(wpa_supplicant_scan, wpa_s, NULL);
        eloop_register_timeout(sec, usec, wpa_supplicant_scan, wpa_s, NULL);
}


void wpa_supplicant_cancel_scan(struct wpa_supplicant *wpa_s)
{
        wpa_msg(wpa_s, MSG_DEBUG, "Cancelling scan request");
        eloop_cancel_timeout(wpa_supplicant_scan, wpa_s, NULL);
}


void wpa_supplicant_notify_scanning(struct wpa_supplicant *wpa_s,
                                    int scanning)
{
        if (wpa_s->scanning != scanning) {
                wpa_s->scanning = scanning;
                wpas_notify_scanning(wpa_s);
        }
}


static int wpa_scan_get_max_rate(const struct wpa_scan_res *res)
{
        int rate = 0;
        const u8 *ie;
        int i;

        ie = wpa_scan_get_ie(res, WLAN_EID_SUPP_RATES);
        for (i = 0; ie && i < ie[1]; i++) {
                if ((ie[i + 2] & 0x7f) > rate)
                        rate = ie[i + 2] & 0x7f;
        }

        ie = wpa_scan_get_ie(res, WLAN_EID_EXT_SUPP_RATES);
        for (i = 0; ie && i < ie[1]; i++) {
                if ((ie[i + 2] & 0x7f) > rate)
                        rate = ie[i + 2] & 0x7f;
        }

        return rate;
}


const u8 * wpa_scan_get_ie(const struct wpa_scan_res *res, u8 ie)
{
        const u8 *end, *pos;

        pos = (const u8 *) (res + 1);
        end = pos + res->ie_len;

        while (pos + 1 < end) {
                if (pos + 2 + pos[1] > end)
                        break;
                if (pos[0] == ie)
                        return pos;
                pos += 2 + pos[1];
        }

        return NULL;
}


const u8 * wpa_scan_get_vendor_ie(const struct wpa_scan_res *res,
                                  u32 vendor_type)
{
        const u8 *end, *pos;

        pos = (const u8 *) (res + 1);
        end = pos + res->ie_len;

        while (pos + 1 < end) {
                if (pos + 2 + pos[1] > end)
                        break;
                if (pos[0] == WLAN_EID_VENDOR_SPECIFIC && pos[1] >= 4 &&
                    vendor_type == WPA_GET_BE32(&pos[2]))
                        return pos;
                pos += 2 + pos[1];
        }

        return NULL;
}


struct wpabuf * wpa_scan_get_vendor_ie_multi(const struct wpa_scan_res *res,
                                             u32 vendor_type)
{
        struct wpabuf *buf;
        const u8 *end, *pos;

        buf = wpabuf_alloc(res->ie_len);
        if (buf == NULL)
                return NULL;

        pos = (const u8 *) (res + 1);
        end = pos + res->ie_len;

        while (pos + 1 < end) {
                if (pos + 2 + pos[1] > end)
                        break;
                if (pos[0] == WLAN_EID_VENDOR_SPECIFIC && pos[1] >= 4 &&
                    vendor_type == WPA_GET_BE32(&pos[2]))
                        wpabuf_put_data(buf, pos + 2 + 4, pos[1] - 4);
                pos += 2 + pos[1];
        }

        if (wpabuf_len(buf) == 0) {
                wpabuf_free(buf);
                buf = NULL;
        }

        return buf;
}


/* Compare function for sorting scan results. Return >0 if @b is considered
 * better. */
static int wpa_scan_result_compar(const void *a, const void *b)
{
        struct wpa_scan_res **_wa = (void *) a;
        struct wpa_scan_res **_wb = (void *) b;
        struct wpa_scan_res *wa = *_wa;
        struct wpa_scan_res *wb = *_wb;
        int wpa_a, wpa_b, maxrate_a, maxrate_b;

        /* WPA/WPA2 support preferred */
        wpa_a = wpa_scan_get_vendor_ie(wa, WPA_IE_VENDOR_TYPE) != NULL ||
                wpa_scan_get_ie(wa, WLAN_EID_RSN) != NULL;
        wpa_b = wpa_scan_get_vendor_ie(wb, WPA_IE_VENDOR_TYPE) != NULL ||
                wpa_scan_get_ie(wb, WLAN_EID_RSN) != NULL;

        if (wpa_b && !wpa_a)
                return 1;
        if (!wpa_b && wpa_a)
                return -1;

        /* privacy support preferred */
        if ((wa->caps & IEEE80211_CAP_PRIVACY) == 0 &&
            (wb->caps & IEEE80211_CAP_PRIVACY))
                return 1;
        if ((wa->caps & IEEE80211_CAP_PRIVACY) &&
            (wb->caps & IEEE80211_CAP_PRIVACY) == 0)
                return -1;

        /* best/max rate preferred if signal level close enough XXX */
        if ((wa->level && wb->level && abs(wb->level - wa->level) < 5) ||
            (wa->qual && wb->qual && abs(wb->qual - wa->qual) < 10)) {
                maxrate_a = wpa_scan_get_max_rate(wa);
                maxrate_b = wpa_scan_get_max_rate(wb);
                if (maxrate_a != maxrate_b)
                        return maxrate_b - maxrate_a;
        }

        /* use freq for channel preference */

        /* all things being equal, use signal level; if signal levels are
         * identical, use quality values since some drivers may only report
         * that value and leave the signal level zero */
        if (wb->level == wa->level)
                return wb->qual - wa->qual;
        return wb->level - wa->level;
}


struct wpa_scan_results *
wpa_supplicant_get_scan_results(struct wpa_supplicant *wpa_s,
                                struct scan_info *info, int new_scan)
{
        struct wpa_scan_results *scan_res;
        size_t i;

        if (wpa_s->drv_flags & WPA_DRIVER_FLAGS_USER_SPACE_MLME)
                scan_res = ieee80211_sta_get_scan_results(wpa_s);
        else
                scan_res = wpa_drv_get_scan_results2(wpa_s);
        if (scan_res == NULL) {
                wpa_printf(MSG_DEBUG, "Failed to get scan results");
                return NULL;
        }

        qsort(scan_res->res, scan_res->num, sizeof(struct wpa_scan_res *),
              wpa_scan_result_compar);

        wpa_bss_update_start(wpa_s);
        for (i = 0; i < scan_res->num; i++)
                wpa_bss_update_scan_res(wpa_s, scan_res->res[i]);
        wpa_bss_update_end(wpa_s, info, new_scan);

        return scan_res;
}


int wpa_supplicant_update_scan_results(struct wpa_supplicant *wpa_s)
{
        struct wpa_scan_results *scan_res;
        scan_res = wpa_supplicant_get_scan_results(wpa_s, NULL, 0);
        if (scan_res == NULL)
                return -1;
        wpa_scan_results_free(scan_res);

        return 0;
}


void wpa_scan_results_free(struct wpa_scan_results *res)
{
        size_t i;

        if (res == NULL)
                return;

        for (i = 0; i < res->num; i++)
                os_free(res->res[i]);
        os_free(res->res);
        os_free(res);
}