Android WiFi 扫描流程分析(wpa_supplicant选择网络)
阅读原文时间:2020年09月21日阅读:4
扫描流程
1.如果之前就已经有相关记录,优化扫描,扫描记录部分的频率信道。
2.如果1中的扫描没有结果,清除黑名单中的进行选择。
3.如果2中没有结果,进行所有频率的信道进行扫描

相关log参考:
https://www.cnblogs.com/helloworldtoyou/p/9958084.html

external\wpa_supplicant_8\wpa_supplicant\src\drivers\driver_nl80211_event.c
static void do_process_drv_event(struct i802_bss *bss, int cmd,
                 struct nlattr **tb)
{
    struct wpa_driver_nl80211_data *drv = bss->drv;
    union wpa_event_data data;
    int external_scan_event = 0;

    wpa_printf(MSG_DEBUG, "nl80211: Drv Event %d (%s) received for %s",
           cmd, nl80211_command_to_string(cmd), bss->ifname);

    if (cmd == NL80211_CMD_ROAM &&
        (drv->capa.flags & WPA_DRIVER_FLAGS_KEY_MGMT_OFFLOAD)) {
        /*
         * Device will use roam+auth vendor event to indicate
         * roaming, so ignore the regular roam event.
         */
        wpa_printf(MSG_DEBUG,
               "nl80211: Ignore roam event (cmd=%d), device will use vendor event roam+auth",
               cmd);
        return;
    }

    if (drv->ap_scan_as_station != NL80211_IFTYPE_UNSPECIFIED &&
        (cmd == NL80211_CMD_NEW_SCAN_RESULTS ||
         cmd == NL80211_CMD_SCAN_ABORTED)) {
        wpa_driver_nl80211_set_mode(drv->first_bss,
                        drv->ap_scan_as_station);
        drv->ap_scan_as_station = NL80211_IFTYPE_UNSPECIFIED;
    }

    switch (cmd) {
    case NL80211_CMD_TRIGGER_SCAN:
        wpa_dbg(drv->ctx, MSG_DEBUG, "nl80211: Scan trigger");
        drv->scan_state = SCAN_STARTED;
        if (drv->scan_for_auth) {
            /*
             * Cannot indicate EVENT_SCAN_STARTED here since we skip
             * EVENT_SCAN_RESULTS in scan_for_auth case and the
             * upper layer implementation could get confused about
             * scanning state.
             */
            wpa_printf(MSG_DEBUG, "nl80211: Do not indicate scan-start event due to internal scan_for_auth");
            break;
        }
        wpa_supplicant_event(drv->ctx, EVENT_SCAN_STARTED, NULL);
        break;
    case NL80211_CMD_START_SCHED_SCAN:
        wpa_dbg(drv->ctx, MSG_DEBUG, "nl80211: Sched scan started");
        drv->scan_state = SCHED_SCAN_STARTED;
        break;
    case NL80211_CMD_SCHED_SCAN_STOPPED:
        wpa_dbg(drv->ctx, MSG_DEBUG, "nl80211: Sched scan stopped");
        drv->scan_state = SCHED_SCAN_STOPPED;
        wpa_supplicant_event(drv->ctx, EVENT_SCHED_SCAN_STOPPED, NULL);
        break;
    case NL80211_CMD_NEW_SCAN_RESULTS:
        wpa_dbg(drv->ctx, MSG_DEBUG,
            "nl80211: New scan results available");
        if (drv->last_scan_cmd != NL80211_CMD_VENDOR)
            drv->scan_state = SCAN_COMPLETED;
        drv->scan_complete_events = 1;
        if (drv->last_scan_cmd == NL80211_CMD_TRIGGER_SCAN) {
            eloop_cancel_timeout(wpa_driver_nl80211_scan_timeout,
                         drv, drv->ctx);
            drv->last_scan_cmd = 0;
        } else {
            external_scan_event = 1;
        }
        send_scan_event(drv, 0, tb, external_scan_event);
        break;

}

static void send_scan_event(struct wpa_driver_nl80211_data *drv, int aborted,
                struct nlattr *tb[], int external_scan)
{
    union wpa_event_data event;
    struct nlattr *nl;
    int rem;
    struct scan_info *info;
#define MAX_REPORT_FREQS 50
    int freqs[MAX_REPORT_FREQS];
    int num_freqs = 0;

    if (!external_scan && drv->scan_for_auth) {
        drv->scan_for_auth = 0;
        wpa_printf(MSG_DEBUG, "nl80211: Scan results for missing "
               "cfg80211 BSS entry");
        wpa_driver_nl80211_authenticate_retry(drv);
        return;
    }

    os_memset(&event, 0, sizeof(event));
    info = &event.scan_info;
    info->aborted = aborted;
    info->external_scan = external_scan;
    info->nl_scan_event = 1;

    if (tb[NL80211_ATTR_SCAN_SSIDS]) {
        nla_for_each_nested(nl, tb[NL80211_ATTR_SCAN_SSIDS], rem) {
            struct wpa_driver_scan_ssid *s =
                &info->ssids[info->num_ssids];
            s->ssid = nla_data(nl);
            s->ssid_len = nla_len(nl);
            wpa_printf(MSG_DEBUG, "nl80211: Scan probed for SSID '%s'",
                   wpa_ssid_txt(s->ssid, s->ssid_len));
            info->num_ssids++;
            if (info->num_ssids == WPAS_MAX_SCAN_SSIDS)
                break;
        }
    }
    if (tb[NL80211_ATTR_SCAN_FREQUENCIES]) {
        char msg[300], *pos, *end;
        int res;

        pos = msg;
        end = pos + sizeof(msg);
        *pos = '\0';

        nla_for_each_nested(nl, tb[NL80211_ATTR_SCAN_FREQUENCIES], rem)
        {
            freqs[num_freqs] = nla_get_u32(nl);
            res = os_snprintf(pos, end - pos, " %d",
                      freqs[num_freqs]);
            if (!os_snprintf_error(end - pos, res))
                pos += res;
            num_freqs++;
            if (num_freqs == MAX_REPORT_FREQS - 1)
                break;
        }
        info->freqs = freqs;
        info->num_freqs = num_freqs;
        // 显示扫面结果中包含的频率
        //10-26 20:35:38.999  2215  2215 D wpa_supplicant: wlan0: nl80211: New scan results available
        //10-26 20:35:39.000  2215  2215 D wpa_supplicant: nl80211: Scan included frequencies: 5805 5240 5745 5200 5180 5220 2437 5785 2462 57
        wpa_printf(MSG_DEBUG, "nl80211: Scan included frequencies:%s",
               msg);
    }

    if (tb[NL80211_ATTR_SCAN_START_TIME_TSF] &&
        tb[NL80211_ATTR_SCAN_START_TIME_TSF_BSSID]) {
        info->scan_start_tsf =
            nla_get_u64(tb[NL80211_ATTR_SCAN_START_TIME_TSF]);
        os_memcpy(info->scan_start_tsf_bssid,
              nla_data(tb[NL80211_ATTR_SCAN_START_TIME_TSF_BSSID]),
              ETH_ALEN);
    }

    wpa_supplicant_event(drv->ctx, EVENT_SCAN_RESULTS, &event);
}

Z:\eda51\external\wpa_supplicant_8\wpa_supplicant\events.c
void wpa_supplicant_event(void *ctx, enum wpa_event_type event,
              union wpa_event_data *data)
{
    struct wpa_supplicant *wpa_s = ctx;
    int resched;

    if (wpa_s->wpa_state == WPA_INTERFACE_DISABLED &&
        event != EVENT_INTERFACE_ENABLED &&
        event != EVENT_INTERFACE_STATUS &&
        event != EVENT_SCAN_RESULTS &&
        event != EVENT_SCHED_SCAN_STOPPED) {
        wpa_dbg(wpa_s, MSG_DEBUG,
            "Ignore event %s (%d) while interface is disabled",
            event_to_string(event), event);
        return;
    }

#ifndef CONFIG_NO_STDOUT_DEBUG
{
    int level = MSG_DEBUG;

    if (event == EVENT_RX_MGMT && data->rx_mgmt.frame_len >= 24) {
        const struct ieee80211_hdr *hdr;
        u16 fc;
        hdr = (const struct ieee80211_hdr *) data->rx_mgmt.frame;
        fc = le_to_host16(hdr->frame_control);
        if (WLAN_FC_GET_TYPE(fc) == WLAN_FC_TYPE_MGMT &&
            WLAN_FC_GET_STYPE(fc) == WLAN_FC_STYPE_BEACON)
            level = MSG_EXCESSIVE;
    }
    // wpa_supplicant: wlan0: Event SCAN_RESULTS (3) received
    wpa_dbg(wpa_s, level, "Event %s (%d) received",
        event_to_string(event), event);
}
#endif /* CONFIG_NO_STDOUT_DEBUG */

    switch (event) {
    case EVENT_AUTH:
#ifdef CONFIG_FST
        if (!wpas_fst_update_mbie(wpa_s, data->auth.ies,
                      data->auth.ies_len))
            wpa_printf(MSG_DEBUG,
                   "FST: MB IEs updated from auth IE");
#endif /* CONFIG_FST */
        sme_event_auth(wpa_s, data);
        break;
    case EVENT_ASSOC:
#ifdef CONFIG_TESTING_OPTIONS
        if (wpa_s->ignore_auth_resp) {
            wpa_printf(MSG_INFO,
                   "EVENT_ASSOC - ignore_auth_resp active!");
            break;
        }
#endif /* CONFIG_TESTING_OPTIONS */
        wpa_supplicant_event_assoc(wpa_s, data);
        if (data &&
            (data->assoc_info.authorized ||
             (!(wpa_s->drv_flags & WPA_DRIVER_FLAGS_SME) &&
              wpa_fils_is_completed(wpa_s->wpa))))
            wpa_supplicant_event_assoc_auth(wpa_s, data);
        if (data) {
            wpa_msg(wpa_s, MSG_INFO,
                WPA_EVENT_SUBNET_STATUS_UPDATE "status=%u",
                data->assoc_info.subnet_status);
        }
        break;

            case EVENT_SCAN_RESULTS:
        if (wpa_s->wpa_state == WPA_INTERFACE_DISABLED) {
            wpa_s->scan_res_handler = NULL;
            wpa_s->own_scan_running = 0;
            wpa_s->radio->external_scan_running = 0;
            wpa_s->last_scan_req = NORMAL_SCAN_REQ;
            break;
        }

        if (!(data && data->scan_info.external_scan) &&
            os_reltime_initialized(&wpa_s->scan_start_time)) {
            struct os_reltime now, diff;
            os_get_reltime(&now);
            os_reltime_sub(&now, &wpa_s->scan_start_time, &diff);
            wpa_s->scan_start_time.sec = 0;
            wpa_s->scan_start_time.usec = 0;
            wpa_dbg(wpa_s, MSG_DEBUG, "Scan completed in %ld.%06ld seconds",
                diff.sec, diff.usec);
        }
        if (wpa_supplicant_event_scan_results(wpa_s, data))
            break; /* interface may have been removed */
        if (!(data && data->scan_info.external_scan))
            wpa_s->own_scan_running = 0;
        if (data && data->scan_info.nl_scan_event)
            wpa_s->radio->external_scan_running = 0;
        radio_work_check_next(wpa_s);
        break;
        ...
}

static int wpa_supplicant_event_scan_results(struct wpa_supplicant *wpa_s,
                         union wpa_event_data *data)
{
    struct wpa_supplicant *ifs;
    int res;

    res = _wpa_supplicant_event_scan_results(wpa_s, data, 1, 0);
    if (res == 2) {
        /*
         * Interface may have been removed, so must not dereference
         * wpa_s after this.
         */
        return 1;
    }

    if (res < 0) {
        /*
         * If no scan results could be fetched, then no need to
         * notify those interfaces that did not actually request
         * this scan. Similarly, if scan results started a new operation on this
         * interface, do not notify other interfaces to avoid concurrent
         * operations during a connection attempt.
         */
        return 0;
    }

    /*
     * Check other interfaces to see if they share the same radio. If
     * so, they get updated with this same scan info.
     */
    dl_list_for_each(ifs, &wpa_s->radio->ifaces, struct wpa_supplicant,
             radio_list) {
        if (ifs != wpa_s) {
            wpa_printf(MSG_DEBUG, "%s: Updating scan results from "
                   "sibling", ifs->ifname);
            res = _wpa_supplicant_event_scan_results(ifs, data, 0,
                                 res > 0);
            if (res < 0)
                return 0;
        }
    }

    return 0;
}

static int _wpa_supplicant_event_scan_results(struct wpa_supplicant *wpa_s,
                          union wpa_event_data *data,
                          int own_request, int update_only)
{
    struct wpa_scan_results *scan_res = NULL;
    int ret = 0;
    int ap = 0;
#ifndef CONFIG_NO_RANDOM_POOL
    size_t i, num;
#endif /* CONFIG_NO_RANDOM_POOL */

#ifdef CONFIG_AP
    if (wpa_s->ap_iface)
        ap = 1;
#endif /* CONFIG_AP */

    wpa_supplicant_notify_scanning(wpa_s, 0);

    scan_res = wpa_supplicant_get_scan_results(wpa_s,
                           data ? &data->scan_info :
                           NULL, 1);
    if (scan_res == NULL) {
        if (wpa_s->conf->ap_scan == 2 || ap ||
            wpa_s->scan_res_handler == scan_only_handler)
            return -1;
        if (!own_request)
            return -1;
        if (data && data->scan_info.external_scan)
            return -1;
        // 扫描结果为空,从新扫描
        wpa_dbg(wpa_s, MSG_DEBUG, "Failed to get scan results - try "
            "scanning again");
        wpa_supplicant_req_new_scan(wpa_s, 1, 0);
        ret = -1;
        goto scan_work_done;
    }

#ifndef CONFIG_NO_RANDOM_POOL
    num = scan_res->num;
    if (num > 10)
        num = 10;
    for (i = 0; i < num; i++) {
#ifdef CONFIG_WAPI
        u8 buf[6];
#else
        u8 buf[5];
#endif
        struct wpa_scan_res *res = scan_res->res[i];
        buf[0] = res->bssid[5];
        buf[1] = res->qual & 0xff;
        buf[2] = res->noise & 0xff;
        buf[3] = res->level & 0xff;
        buf[4] = res->tsf & 0xff;
#ifdef CONFIG_WAPI
        buf[5] = res->wapi_ie_len & 0xff;
#endif
        random_add_randomness(buf, sizeof(buf));
    }
#endif /* CONFIG_NO_RANDOM_POOL */

    if (update_only) {
        ret = 1;
        goto scan_work_done;
    }

    if (own_request && wpa_s->scan_res_handler &&
        !(data && data->scan_info.external_scan)) {
        void (*scan_res_handler)(struct wpa_supplicant *wpa_s,
                     struct wpa_scan_results *scan_res);

        scan_res_handler = wpa_s->scan_res_handler;
        wpa_s->scan_res_handler = NULL;
        scan_res_handler(wpa_s, scan_res);
        ret = 1;
        goto scan_work_done;
    }
    // AP 模式忽略扫描
    if (ap) {
        wpa_dbg(wpa_s, MSG_DEBUG, "Ignore scan results in AP mode");
#ifdef CONFIG_AP
        if (wpa_s->ap_iface->scan_cb)
            wpa_s->ap_iface->scan_cb(wpa_s->ap_iface);
#endif /* CONFIG_AP */
        goto scan_work_done;
    }

    wpa_dbg(wpa_s, MSG_DEBUG, "New scan results available (own=%u ext=%u)",
        wpa_s->own_scan_running,
        data ? data->scan_info.external_scan : 0);
    if (wpa_s->last_scan_req == MANUAL_SCAN_REQ &&
        wpa_s->manual_scan_use_id && wpa_s->own_scan_running &&
        own_request && !(data && data->scan_info.external_scan)) {
        wpa_msg_ctrl(wpa_s, MSG_INFO, WPA_EVENT_SCAN_RESULTS "id=%u",
                 wpa_s->manual_scan_id);
        wpa_s->manual_scan_use_id = 0;
    } else {
        wpa_msg_ctrl(wpa_s, MSG_INFO, WPA_EVENT_SCAN_RESULTS);
    }
    wpas_notify_scan_results(wpa_s);

    wpas_notify_scan_done(wpa_s, 1);

    if (data && data->scan_info.external_scan) {
        wpa_dbg(wpa_s, MSG_DEBUG, "Do not use results from externally requested scan operation for network selection");
        wpa_scan_results_free(scan_res);
        return 0;
    }

    if (wnm_scan_process(wpa_s, 1) > 0)
        goto scan_work_done;

    if (sme_proc_obss_scan(wpa_s) > 0)
        goto scan_work_done;

    if (own_request &&
        wpas_beacon_rep_scan_process(wpa_s, scan_res, &data->scan_info) > 0)
        goto scan_work_done;

    if ((wpa_s->conf->ap_scan == 2 && !wpas_wps_searching(wpa_s)))
        goto scan_work_done;

    if (autoscan_notify_scan(wpa_s, scan_res))
        goto scan_work_done;

    if (wpa_s->disconnected) {
        wpa_supplicant_set_state(wpa_s, WPA_DISCONNECTED);
        goto scan_work_done;
    }

    if (!wpas_driver_bss_selection(wpa_s) &&
        bgscan_notify_scan(wpa_s, scan_res) == 1)
        goto scan_work_done;

    wpas_wps_update_ap_info(wpa_s, scan_res);

    if (wpa_s->wpa_state >= WPA_AUTHENTICATING &&
        wpa_s->wpa_state < WPA_COMPLETED)
        goto scan_work_done;

    wpa_scan_results_free(scan_res);

    if (own_request && wpa_s->scan_work) {
        struct wpa_radio_work *work = wpa_s->scan_work;
        wpa_s->scan_work = NULL;
        radio_work_done(work);
    }

    return wpas_select_network_from_last_scan(wpa_s, 1, own_request);

scan_work_done:
    wpa_scan_results_free(scan_res);
    if (own_request && wpa_s->scan_work) {
        struct wpa_radio_work *work = wpa_s->scan_work;
        wpa_s->scan_work = NULL;
        radio_work_done(work);
    }
    return ret;
}

// 这里对扫描结果进行处理,找到了就进行连接,没找到就继续扫描。
static int wpas_select_network_from_last_scan(struct wpa_supplicant *wpa_s,
                          int new_scan, int own_request)
{
    struct wpa_bss *selected;
    struct wpa_ssid *ssid = NULL;
    int time_to_reenable = wpas_reenabled_network_time(wpa_s);

    if (time_to_reenable > 0) {
        wpa_dbg(wpa_s, MSG_DEBUG,
            "Postpone network selection by %d seconds since all networks are disabled",
            time_to_reenable);
        eloop_cancel_timeout(wpas_network_reenabled, wpa_s, NULL);
        eloop_register_timeout(time_to_reenable, 0,
                       wpas_network_reenabled, wpa_s, NULL);
        return 0;
    }

    if (wpa_s->p2p_mgmt)
        return 0; /* no normal connection on p2p_mgmt interface */

    selected = wpa_supplicant_pick_network(wpa_s, &ssid);                             // 选择网络

#ifdef CONFIG_MESH
    if (wpa_s->ifmsh) {
        wpa_msg(wpa_s, MSG_INFO,
            "Avoiding join because we already joined a mesh group");
        return 0;
    }
#endif /* CONFIG_MESH */

    if (selected) {
        int skip;

        skip = !wpa_supplicant_need_to_roam(wpa_s, selected, ssid);        // 是否需要漫游, 后面再分析
        if (skip) {

            if (new_scan)
                wpa_supplicant_rsn_preauth_scan_results(wpa_s);            // 快速漫游,预认证, 漫游才会用到
            return 0;
        }

        if (ssid != wpa_s->current_ssid &&
            wpa_s->wpa_state >= WPA_AUTHENTICATING) {
            wpa_s->own_disconnect_req = 1;
            wpa_supplicant_deauthenticate(
                wpa_s, WLAN_REASON_DEAUTH_LEAVING);
        }

        if (wpa_supplicant_connect(wpa_s, selected, ssid) < 0) {                // 连接网络
            wpa_dbg(wpa_s, MSG_DEBUG, "Connect failed");
            return -1;
        }
        if (new_scan)
            wpa_supplicant_rsn_preauth_scan_results(wpa_s);
        /*
         * Do not allow other virtual radios to trigger operations based
         * on these scan results since we do not want them to start
         * other associations at the same time.
         */
        return 1;
    } else {
        // 没找到合适的网络
        wpa_dbg(wpa_s, MSG_DEBUG, "No suitable network found");
        ssid = wpa_supplicant_pick_new_network(wpa_s);
        if (ssid) {
            wpa_dbg(wpa_s, MSG_DEBUG, "Setup a new network");
            wpa_supplicant_associate(wpa_s, NULL, ssid);
            if (new_scan)
                wpa_supplicant_rsn_preauth_scan_results(wpa_s);
        } else if (own_request) {
            /*
             * No SSID found. If SCAN results are as a result of
             * own scan request and not due to a scan request on
             * another shared interface, try another scan.
             */
            int timeout_sec = wpa_s->scan_interval;
            int timeout_usec = 0;

            ......

            // 重新扫描
            if (wpa_supplicant_req_sched_scan(wpa_s))
                wpa_supplicant_req_new_scan(wpa_s, timeout_sec,
                                timeout_usec);

            wpa_msg_ctrl(wpa_s, MSG_INFO,
                     WPA_EVENT_NETWORK_NOT_FOUND);
        }
    }
    return 0;
}

// 选择网络
struct wpa_bss * wpa_supplicant_pick_network(struct wpa_supplicant *wpa_s,
                         struct wpa_ssid **selected_ssid)
{
    struct wpa_bss *selected = NULL;
    int prio;
    struct wpa_ssid *next_ssid = NULL;
    struct wpa_ssid *ssid;

    if (wpa_s->last_scan_res == NULL ||
        wpa_s->last_scan_res_used == 0)
        return NULL; /* no scan results from last update */

    if (wpa_s->next_ssid) {
        /* check that next_ssid is still valid */
        for (ssid = wpa_s->conf->ssid; ssid; ssid = ssid->next) {
            if (ssid == wpa_s->next_ssid)
                break;
        }
        next_ssid = ssid;
        wpa_s->next_ssid = NULL;
    }

    while (selected == NULL) {
        for (prio = 0; prio < wpa_s->conf->num_prio; prio++) {
            if (next_ssid && next_ssid->priority ==
                wpa_s->conf->pssid[prio]->priority) {
                selected = wpa_supplicant_select_bss(                       // 选择网络
                    wpa_s, next_ssid, selected_ssid, 1);
                if (selected)
                    break;
            }
            selected = wpa_supplicant_select_bss(
                wpa_s, wpa_s->conf->pssid[prio],
                selected_ssid, 0);
            if (selected)
                break;
        }

        if (selected == NULL && wpa_s->blacklist &&                     // 选择之后,没有合适的AP,清除黑名单
            !wpa_s->countermeasures) {
            wpa_dbg(wpa_s, MSG_DEBUG, "No APs found - clear "
                "blacklist and try again");
            wpa_blacklist_clear(wpa_s);
            wpa_s->blacklist_cleared++;
        } else if (selected == NULL)
            break;
    }

    ssid = *selected_ssid;
    if (selected && ssid && ssid->mem_only_psk && !ssid->psk_set &&
        !ssid->passphrase && !ssid->ext_psk) {
        const char *field_name, *txt = NULL;

        wpa_dbg(wpa_s, MSG_DEBUG,
            "PSK/passphrase not yet available for the selected network");

        wpas_notify_network_request(wpa_s, ssid,
                        WPA_CTRL_REQ_PSK_PASSPHRASE, NULL);

        field_name = wpa_supplicant_ctrl_req_to_string(
            WPA_CTRL_REQ_PSK_PASSPHRASE, NULL, &txt);
        if (field_name == NULL)
            return NULL;

        wpas_send_ctrl_req(wpa_s, ssid, field_name, txt);

        selected = NULL;
    }

    return selected;
}

static struct wpa_bss *
wpa_supplicant_select_bss(struct wpa_supplicant *wpa_s,
              struct wpa_ssid *group,
              struct wpa_ssid **selected_ssid,
              int only_first_ssid)
{
    unsigned int i;

    if (wpa_s->current_ssid) {
        struct wpa_ssid *ssid;

        wpa_dbg(wpa_s, MSG_DEBUG,
            "Scan results matching the currently selected network");
        for (i = 0; i < wpa_s->last_scan_res_used; i++) {
            struct wpa_bss *bss = wpa_s->last_scan_res[i];

            ssid = wpa_scan_res_match(wpa_s, i, bss, group,
                          only_first_ssid, 0);
            if (ssid != wpa_s->current_ssid)
                continue;
            wpa_dbg(wpa_s, MSG_DEBUG, "%u: " MACSTR
                " freq=%d level=%d snr=%d est_throughput=%u",
                i, MAC2STR(bss->bssid), bss->freq, bss->level,
                bss->snr, bss->est_throughput);
        }
    }

    if (only_first_ssid)
        wpa_dbg(wpa_s, MSG_DEBUG, "Try to find BSS matching pre-selected network id=%d",
            group->id);
    else
        wpa_dbg(wpa_s, MSG_DEBUG, "Selecting BSS from priority group %d",
            group->priority);

    for (i = 0; i < wpa_s->last_scan_res_used; i++) {
        struct wpa_bss *bss = wpa_s->last_scan_res[i];
        *selected_ssid = wpa_scan_res_match(wpa_s, i, bss, group,           // 匹配
                            only_first_ssid, 1);
        if (!*selected_ssid)
            continue;
        wpa_dbg(wpa_s, MSG_DEBUG, "   selected BSS " MACSTR
            " ssid='%s'",
            MAC2STR(bss->bssid),
            wpa_ssid_txt(bss->ssid, bss->ssid_len));
        return bss;
    }

    return NULL;
}

// 将发过来的ssid中的数据帧和配置文件中的参数进行匹配,查看是否正常
struct wpa_ssid * wpa_scan_res_match(struct wpa_supplicant *wpa_s,
                     int i, struct wpa_bss *bss,
                     struct wpa_ssid *group,
                     int only_first_ssid, int debug_print)
{
    u8 wpa_ie_len, rsn_ie_len;
    int wpa;
    struct wpa_blacklist *e;
    const u8 *ie;
    struct wpa_ssid *ssid;
    int osen;
#ifdef CONFIG_WAPI
    u8 wapi_ie_len;
#endif
#ifdef CONFIG_MBO
    const u8 *assoc_disallow;
#endif /* CONFIG_MBO */
    // 获取vendor信息
    ie = wpa_bss_get_vendor_ie(bss, WPA_IE_VENDOR_TYPE);
    wpa_ie_len = ie ? ie[1] : 0;

    ie = wpa_bss_get_ie(bss, WLAN_EID_RSN);
    rsn_ie_len = ie ? ie[1] : 0;

    ie = wpa_bss_get_vendor_ie(bss, OSEN_IE_VENDOR_TYPE);
    osen = ie != NULL;

    if (debug_print) {
        wpa_dbg(wpa_s, MSG_DEBUG, "%d: " MACSTR
            " ssid='%s' wpa_ie_len=%u rsn_ie_len=%u caps=0x%x level=%d freq=%d %s%s%s",
            i, MAC2STR(bss->bssid),
            wpa_ssid_txt(bss->ssid, bss->ssid_len),
            wpa_ie_len, rsn_ie_len, bss->caps, bss->level,
            bss->freq,
            wpa_bss_get_vendor_ie(bss, WPS_IE_VENDOR_TYPE) ?
            " wps" : "",
            (wpa_bss_get_vendor_ie(bss, P2P_IE_VENDOR_TYPE) ||
             wpa_bss_get_vendor_ie_beacon(bss, P2P_IE_VENDOR_TYPE))
            ? " p2p" : "",
            osen ? " osen=1" : "");
    }

    e = wpa_blacklist_get(wpa_s, bss->bssid);
    if (e) {
        int limit = 1;
        if (wpa_supplicant_enabled_networks(wpa_s) == 1) {
            /*
             * When only a single network is enabled, we can
             * trigger blacklisting on the first failure. This
             * should not be done with multiple enabled networks to
             * avoid getting forced to move into a worse ESS on
             * single error if there are no other BSSes of the
             * current ESS.
             */
            limit = 0;
        }
        if (e->count > limit) {
            if (debug_print) {
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - blacklisted (count=%d limit=%d)",
                    e->count, limit);
            }
            return NULL;
        }
    }
    // 对SSID的参数进行比对,不匹配的推出
    if (bss->ssid_len == 0) {
        if (debug_print)
            wpa_dbg(wpa_s, MSG_DEBUG, "   skip - SSID not known");
        return NULL;
    }

    if (disallowed_bssid(wpa_s, bss->bssid)) {
        if (debug_print)
            wpa_dbg(wpa_s, MSG_DEBUG, "   skip - BSSID disallowed");
        return NULL;
    }

    if (disallowed_ssid(wpa_s, bss->ssid, bss->ssid_len)) {
        if (debug_print)
            wpa_dbg(wpa_s, MSG_DEBUG, "   skip - SSID disallowed");
        return NULL;
    }

    wpa = wpa_ie_len > 0 || rsn_ie_len > 0;
    ......

    for (ssid = group; ssid; ssid = only_first_ssid ? NULL : ssid->pnext) {
        int check_ssid = wpa ? 1 : (ssid->ssid_len != 0);
        int res;

        if (wpas_network_disabled(wpa_s, ssid)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG, "   skip - disabled");
            continue;
        }

        res = wpas_temp_disabled(wpa_s, ssid);
        if (res > 0) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - disabled temporarily for %d second(s)",
                    res);
            continue;
        }

        if (ssid->bssid_set && ssid->ssid_len == 0 &&
            os_memcmp(bss->bssid, ssid->bssid, ETH_ALEN) == 0)
            check_ssid = 0;

        if (check_ssid &&
            (bss->ssid_len != ssid->ssid_len ||
             os_memcmp(bss->ssid, ssid->ssid, bss->ssid_len) != 0)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - SSID mismatch");
            continue;
        }

        if (ssid->bssid_set &&
            os_memcmp(bss->bssid, ssid->bssid, ETH_ALEN) != 0) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - BSSID mismatch");
            continue;
        }
        // 黑名单的跳过,不进行匹配
        /* check blacklist */
        if (ssid->num_bssid_blacklist &&
            addr_in_list(bss->bssid, ssid->bssid_blacklist,
                 ssid->num_bssid_blacklist)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - BSSID blacklisted");
            continue;
        }

        /* if there is a whitelist, only accept those APs */
        if (ssid->num_bssid_whitelist &&
            !addr_in_list(bss->bssid, ssid->bssid_whitelist,
                  ssid->num_bssid_whitelist)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - BSSID not in whitelist");
            continue;
        }

        if (!wpa_supplicant_ssid_bss_match(wpa_s, ssid, bss,
                           debug_print))
            continue;
        // 判断密钥类型是否匹配
        if (!osen && !wpa &&
            !(ssid->key_mgmt & WPA_KEY_MGMT_NONE) &&
            !(ssid->key_mgmt & WPA_KEY_MGMT_WPS) &&
#ifdef CONFIG_WAPI
            !(ssid->key_mgmt & WPA_KEY_MGMT_WAPI_PSK) &&
            !(ssid->key_mgmt & WPA_KEY_MGMT_WAPI_CERT) &&
#endif
            !(ssid->key_mgmt & WPA_KEY_MGMT_IEEE8021X_NO_WPA)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - non-WPA network not allowed");
            continue;
        }

        if (wpa && !wpa_key_mgmt_wpa(ssid->key_mgmt) &&
            has_wep_key(ssid)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - ignore WPA/WPA2 AP for WEP network block");
            continue;
        }

        if ((ssid->key_mgmt & WPA_KEY_MGMT_OSEN) && !osen) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - non-OSEN network not allowed");
            continue;
        }

......

        if (ssid->mode != IEEE80211_MODE_MESH && !bss_is_ess(bss) &&
            !bss_is_pbss(bss)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - not ESS, PBSS, or MBSS");
            continue;
        }

        if (ssid->pbss != 2 && ssid->pbss != bss_is_pbss(bss)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - PBSS mismatch (ssid %d bss %d)",
                    ssid->pbss, bss_is_pbss(bss));
            continue;
        }

        if (!freq_allowed(ssid->freq_list, bss->freq)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - frequency not allowed");
            continue;
        }
......

        if (!rate_match(wpa_s, bss, debug_print)) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - rate sets do not match");
            continue;
        }

#ifndef CONFIG_IBSS_RSN
        if (ssid->mode == WPAS_MODE_IBSS &&
            !(ssid->key_mgmt & (WPA_KEY_MGMT_NONE |
                    WPA_KEY_MGMT_WPA_NONE))) {
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - IBSS RSN not supported in the build");
            continue;
        }
#endif /* !CONFIG_IBSS_RSN */

......
        if (os_reltime_before(&bss->last_update, &wpa_s->scan_min_time))
        {
            struct os_reltime diff;

            os_reltime_sub(&wpa_s->scan_min_time,
                       &bss->last_update, &diff);
            if (debug_print)
                wpa_dbg(wpa_s, MSG_DEBUG,
                    "   skip - scan result not recent enough (%u.%06u seconds too old)",
                (unsigned int) diff.sec,
                (unsigned int) diff.usec);
            continue;
        }

        /* Matching configuration found */
        return ssid;
    }

    /* No matching configuration found */
    return NULL;
}

// 各种认证方式定义
external\wpa_supplicant_8\src\common\defs.h
#define WPA_KEY_MGMT_IEEE8021X BIT(0)            // 802.1X认证
#define WPA_KEY_MGMT_PSK BIT(1)                    // psk
#define WPA_KEY_MGMT_NONE BIT(2)                // 无密钥
#define WPA_KEY_MGMT_IEEE8021X_NO_WPA BIT(3)
#define WPA_KEY_MGMT_WPA_NONE BIT(4)
#define WPA_KEY_MGMT_FT_IEEE8021X BIT(5)        // Fast transition + 802.1X
#define WPA_KEY_MGMT_FT_PSK BIT(6)                // Fast transition
#define WPA_KEY_MGMT_IEEE8021X_SHA256 BIT(7)
#define WPA_KEY_MGMT_PSK_SHA256 BIT(8)
#define WPA_KEY_MGMT_WPS BIT(9)
#define WPA_KEY_MGMT_SAE BIT(10)
#define WPA_KEY_MGMT_FT_SAE BIT(11)
#define WPA_KEY_MGMT_WAPI_PSK BIT(12)
#define WPA_KEY_MGMT_WAPI_CERT BIT(13)
#define WPA_KEY_MGMT_CCKM BIT(14)
#define WPA_KEY_MGMT_OSEN BIT(15)
#define WPA_KEY_MGMT_IEEE8021X_SUITE_B BIT(16)
#define WPA_KEY_MGMT_IEEE8021X_SUITE_B_192 BIT(17)
#define WPA_KEY_MGMT_FILS_SHA256 BIT(18)
#define WPA_KEY_MGMT_FILS_SHA384 BIT(19)
#define WPA_KEY_MGMT_FT_FILS_SHA256 BIT(20)
#define WPA_KEY_MGMT_FT_FILS_SHA384 BIT(21)
#define WPA_KEY_MGMT_OWE BIT(22)
#define WPA_KEY_MGMT_DPP BIT(23)