src/drivers/scan_helpers.c

   1 /*
   2  * WPA Supplicant - Helper functions for scan result processing
   3  * Copyright (c) 2007-2008, Jouni Malinen <j@w1.fi>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Alternatively, this software may be distributed under the terms of BSD
  10  * license.
  11  *
  12  * See README and COPYING for more details.
  13  */
  14
  15 #include "includes.h"
  16
  17 #include "common.h"
  18 #include "drivers/driver.h"
  19 #include "common/ieee802_11_defs.h"
  20
  21
  22 const u8 * wpa_scan_get_ie(const struct wpa_scan_res *res, u8 ie)
  23 {
  24         const u8 *end, *pos;
  25
  26         pos = (const u8 *) (res + 1);
  27         end = pos + res->ie_len;
  28
  29         while (pos + 1 < end) {
  30                 if (pos + 2 + pos[1] > end)
  31                         break;
  32                 if (pos[0] == ie)
  33                         return pos;
  34                 pos += 2 + pos[1];
  35         }
  36
  37         return NULL;
  38 }
  39
  40
  41 const u8 * wpa_scan_get_vendor_ie(const struct wpa_scan_res *res,
  42                                   u32 vendor_type)
  43 {
  44         const u8 *end, *pos;
  45
  46         pos = (const u8 *) (res + 1);
  47         end = pos + res->ie_len;
  48
  49         while (pos + 1 < end) {
  50                 if (pos + 2 + pos[1] > end)
  51                         break;
  52                 if (pos[0] == WLAN_EID_VENDOR_SPECIFIC && pos[1] >= 4 &&
  53                     vendor_type == WPA_GET_BE32(&pos[2]))
  54                         return pos;
  55                 pos += 2 + pos[1];
  56         }
  57
  58         return NULL;
  59 }
  60
  61
  62 struct wpabuf * wpa_scan_get_vendor_ie_multi(const struct wpa_scan_res *res,
  63                                              u32 vendor_type)
  64 {
  65         struct wpabuf *buf;
  66         const u8 *end, *pos;
  67
  68         buf = wpabuf_alloc(res->ie_len);
  69         if (buf == NULL)
  70                 return NULL;
  71
  72         pos = (const u8 *) (res + 1);
  73         end = pos + res->ie_len;
  74
  75         while (pos + 1 < end) {
  76                 if (pos + 2 + pos[1] > end)
  77                         break;
  78                 if (pos[0] == WLAN_EID_VENDOR_SPECIFIC && pos[1] >= 4 &&
  79                     vendor_type == WPA_GET_BE32(&pos[2]))
  80                         wpabuf_put_data(buf, pos + 2 + 4, pos[1] - 4);
  81                 pos += 2 + pos[1];
  82         }
  83
  84         if (wpabuf_len(buf) == 0) {
  85                 wpabuf_free(buf);
  86                 buf = NULL;
  87         }
  88
  89         return buf;
  90 }
  91
  92
  93 int wpa_scan_get_max_rate(const struct wpa_scan_res *res)
  94 {
  95         int rate = 0;
  96         const u8 *ie;
  97         int i;
  98
  99         ie = wpa_scan_get_ie(res, WLAN_EID_SUPP_RATES);
 100         for (i = 0; ie && i < ie[1]; i++) {
 101                 if ((ie[i + 2] & 0x7f) > rate)
 102                         rate = ie[i + 2] & 0x7f;
 103         }
 104
 105         ie = wpa_scan_get_ie(res, WLAN_EID_EXT_SUPP_RATES);
 106         for (i = 0; ie && i < ie[1]; i++) {
 107                 if ((ie[i + 2] & 0x7f) > rate)
 108                         rate = ie[i + 2] & 0x7f;
 109         }
 110
 111         return rate;
 112 }
 113
 114
 115 void wpa_scan_results_free(struct wpa_scan_results *res)
 116 {
 117         size_t i;
 118
 119         if (res == NULL)
 120                 return;
 121
 122         for (i = 0; i < res->num; i++)
 123                 os_free(res->res[i]);
 124         os_free(res->res);
 125         os_free(res);
 126 }
 127
 128
 129 /* Compare function for sorting scan results. Return >0 if @b is considered
 130  * better. */
 131 static int wpa_scan_result_compar(const void *a, const void *b)
 132 {
 133         struct wpa_scan_res **_wa = (void *) a;
 134         struct wpa_scan_res **_wb = (void *) b;
 135         struct wpa_scan_res *wa = *_wa;
 136         struct wpa_scan_res *wb = *_wb;
 137         int wpa_a, wpa_b, maxrate_a, maxrate_b;
 138
 139         /* WPA/WPA2 support preferred */
 140         wpa_a = wpa_scan_get_vendor_ie(wa, WPA_IE_VENDOR_TYPE) != NULL ||
 141                 wpa_scan_get_ie(wa, WLAN_EID_RSN) != NULL;
 142         wpa_b = wpa_scan_get_vendor_ie(wb, WPA_IE_VENDOR_TYPE) != NULL ||
 143                 wpa_scan_get_ie(wb, WLAN_EID_RSN) != NULL;
 144
 145         if (wpa_b && !wpa_a)
 146                 return 1;
 147         if (!wpa_b && wpa_a)
 148                 return -1;
 149
 150         /* privacy support preferred */
 151         if ((wa->caps & IEEE80211_CAP_PRIVACY) == 0 &&
 152             (wb->caps & IEEE80211_CAP_PRIVACY))
 153                 return 1;
 154         if ((wa->caps & IEEE80211_CAP_PRIVACY) &&
 155             (wb->caps & IEEE80211_CAP_PRIVACY) == 0)
 156                 return -1;
 157
 158         /* best/max rate preferred if signal level close enough XXX */
 159         if ((wa->level && wb->level && abs(wb->level - wa->level) < 5) ||
 160             (wa->qual && wb->qual && abs(wb->qual - wa->qual) < 10)) {
 161                 maxrate_a = wpa_scan_get_max_rate(wa);
 162                 maxrate_b = wpa_scan_get_max_rate(wb);
 163                 if (maxrate_a != maxrate_b)
 164                         return maxrate_b - maxrate_a;
 165         }
 166
 167         /* use freq for channel preference */
 168
 169         /* all things being equal, use signal level; if signal levels are
 170          * identical, use quality values since some drivers may only report
 171          * that value and leave the signal level zero */
 172         if (wb->level == wa->level)
 173                 return wb->qual - wa->qual;
 174         return wb->level - wa->level;
 175 }
 176
 177
 178 void wpa_scan_sort_results(struct wpa_scan_results *res)
 179 {
 180         qsort(res->res, res->num, sizeof(struct wpa_scan_res *),
 181               wpa_scan_result_compar);
 182 }