dist/wpa/src/drivers/scan_helpers.c

   1 /*
   2  * WPA Supplicant - Helper functions for scan result processing
   3  * Copyright (c) 2007, 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 "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 int wpa_scan_get_max_rate(const struct wpa_scan_res *res)
  63 {
  64         int rate = 0;
  65         const u8 *ie;
  66         int i;
  67
  68         ie = wpa_scan_get_ie(res, WLAN_EID_SUPP_RATES);
  69         for (i = 0; ie && i < ie[1]; i++) {
  70                 if ((ie[i + 2] & 0x7f) > rate)
  71                         rate = ie[i + 2] & 0x7f;
  72         }
  73
  74         ie = wpa_scan_get_ie(res, WLAN_EID_EXT_SUPP_RATES);
  75         for (i = 0; ie && i < ie[1]; i++) {
  76                 if ((ie[i + 2] & 0x7f) > rate)
  77                         rate = ie[i + 2] & 0x7f;
  78         }
  79
  80         return rate;
  81 }
  82
  83
  84 void wpa_scan_results_free(struct wpa_scan_results *res)
  85 {
  86         size_t i;
  87
  88         if (res == NULL)
  89                 return;
  90
  91         for (i = 0; i < res->num; i++)
  92                 os_free(res->res[i]);
  93         os_free(res->res);
  94         os_free(res);
  95 }
  96
  97
  98 /* Compare function for sorting scan results. Return >0 if @b is considered
  99  * better. */
 100 static int wpa_scan_result_compar(const void *a, const void *b)
 101 {
 102         struct wpa_scan_res **_wa = (void *) a;
 103         struct wpa_scan_res **_wb = (void *) b;
 104         struct wpa_scan_res *wa = *_wa;
 105         struct wpa_scan_res *wb = *_wb;
 106         int wpa_a, wpa_b, maxrate_a, maxrate_b;
 107
 108         /* WPA/WPA2 support preferred */
 109         wpa_a = wpa_scan_get_vendor_ie(wa, WPA_IE_VENDOR_TYPE) != NULL ||
 110                 wpa_scan_get_ie(wa, WLAN_EID_RSN) != NULL;
 111         wpa_b = wpa_scan_get_vendor_ie(wb, WPA_IE_VENDOR_TYPE) != NULL ||
 112                 wpa_scan_get_ie(wb, WLAN_EID_RSN) != NULL;
 113
 114         if (wpa_b && !wpa_a)
 115                 return 1;
 116         if (!wpa_b && wpa_a)
 117                 return -1;
 118
 119         /* privacy support preferred */
 120         if ((wa->caps & IEEE80211_CAP_PRIVACY) == 0 &&
 121             (wb->caps & IEEE80211_CAP_PRIVACY))
 122                 return 1;
 123         if ((wa->caps & IEEE80211_CAP_PRIVACY) &&
 124             (wb->caps & IEEE80211_CAP_PRIVACY) == 0)
 125                 return -1;
 126
 127         /* best/max rate preferred if signal level close enough XXX */
 128         maxrate_a = wpa_scan_get_max_rate(wa);
 129         maxrate_b = wpa_scan_get_max_rate(wb);
 130         if (maxrate_a != maxrate_b && abs(wb->level - wa->level) < 5)
 131                 return maxrate_b - maxrate_a;
 132
 133         /* use freq for channel preference */
 134
 135         /* all things being equal, use signal level; if signal levels are
 136          * identical, use quality values since some drivers may only report
 137          * that value and leave the signal level zero */
 138         if (wb->level == wa->level)
 139                 return wb->qual - wa->qual;
 140         return wb->level - wa->level;
 141 }
 142
 143
 144 void wpa_scan_sort_results(struct wpa_scan_results *res)
 145 {
 146         qsort(res->res, res->num, sizeof(struct wpa_scan_res *),
 147               wpa_scan_result_compar);
 148 }