wsutil/802_11-utils.c

   1 /* 802_11-utils.c
   2  * 802.11 utility definitions
   3  *
   4  * Wireshark - Network traffic analyzer
   5  * By Gerald Combs <gerald@wireshark.org>
   6  * Copyright 2007 Gerald Combs
   7  *
   8  * SPDX-License-Identifier: GPL-2.0-or-later
   9  */
  10
  11 #include "config.h"
  12 #include "802_11-utils.h"
  13 #include <wsutil/array.h>
  14
  15 typedef struct freq_cvt_s {
  16     unsigned fmin;         /* Minimum frequency in MHz */
  17     unsigned fmax;         /* Maximum frequency in MHz */
  18     int cmin;          /* Minimum/base channel */
  19     bool is_bg;     /* B/G channel? */
  20 } freq_cvt_t;
  21
  22 #define FREQ_STEP 5     /* MHz. This seems to be consistent, thankfully */
  23
  24 /*
  25  * XXX - Japanese channels 182 through 196 actually have center
  26  * frequencies that are off by 2.5 MHz from these values, according
  27  * to the IEEE standard, although the table in ARIB STD T-71 version 5.2:
  28  *
  29  *     http://www.arib.or.jp/english/html/overview/doc/1-STD-T71v5_2.pdf
  30  *
  31  * section 5.3.8.3.3 doesn't show that.
  32  *
  33  * XXX - what about the U.S. public safety 4.9 GHz band?
  34  *
  35  * XXX - what about 802.11ad?
  36  */
  37 static freq_cvt_t freq_cvt[] = {
  38     { 2412, 2472,   1, true },  /* IEEE Std 802.11-2020: Section 15.4.4.3 and Annex E */
  39     { 2484, 2484,  14, true },  /* IEEE Std 802.11-2020: Section 15.4.4.3 and Annex E */
  40     { 5000, 5925,   0, false }, /* IEEE Std 802.11-2020: Annex E */
  41     { 5950, 7125,   0, false }, /* IEEE Std 802.11ax-2021: Annex E */
  42     { 4910, 4980, 182, false },
  43 };
  44
  45 #define NUM_FREQ_CVT array_length(freq_cvt)
  46 #define MAX_CHANNEL(fc) ( (int) ((fc.fmax - fc.fmin) / FREQ_STEP) + fc.cmin )
  47
  48 /*
  49  * Get channel number given a Frequency
  50  */
  51 int
  52 ieee80211_mhz_to_chan(unsigned freq) {
  53     unsigned i;
  54
  55     for (i = 0; i < NUM_FREQ_CVT; i++) {
  56         if (freq >= freq_cvt[i].fmin && freq <= freq_cvt[i].fmax) {
  57             return ((freq - freq_cvt[i].fmin) / FREQ_STEP) + freq_cvt[i].cmin;
  58         }
  59     }
  60     return -1;
  61 }
  62
  63 /*
  64  * Get Frequency given a Channel number
  65  *
  66  * XXX - Because channel numbering schemes for 2.4 and 5 overlap with 6 GHz,
  67  * this function may not return the correct channel. For example, the frequency
  68  * for channel 1 in 2.4 GHz band is 2412 MHz, while the frequency for channel 1
  69  * in the 6 GHz band is 5955 MHz. To resolve this problem, this function needs
  70  * to take a starting frequency to convert channel to frequencies correctly.
  71  * Unfortunately, this is not possible in some cases, so for now, the order on
  72  * which frequency ranges are defined will favor 2.4 and 5 GHz over 6 GHz.
  73  */
  74 unsigned
  75 ieee80211_chan_to_mhz(int chan, bool is_bg) {
  76     unsigned i;
  77
  78     for (i = 0; i < NUM_FREQ_CVT; i++) {
  79         if (is_bg == freq_cvt[i].is_bg &&
  80                 chan >= freq_cvt[i].cmin && chan <= MAX_CHANNEL(freq_cvt[i])) {
  81             return ((chan - freq_cvt[i].cmin) * FREQ_STEP) + freq_cvt[i].fmin;
  82         }
  83     }
  84     return 0;
  85 }
  86
  87 /*
  88  * Get Frequency given a Channel number and band.
  89  */
  90 unsigned
  91 ieee80211_chan_band_to_mhz(int chan, bool is_bg, bool is_6ghz) {
  92     unsigned i;
  93
  94     int start_idx = 0;
  95     if (is_6ghz) {
  96         start_idx = 3;
  97     }
  98     for (i = start_idx; i < NUM_FREQ_CVT; i++) {
  99         if (is_bg == freq_cvt[i].is_bg &&
 100                 chan >= freq_cvt[i].cmin && chan <= MAX_CHANNEL(freq_cvt[i])) {
 101             return ((chan - freq_cvt[i].cmin) * FREQ_STEP) + freq_cvt[i].fmin;
 102         }
 103     }
 104     return 0;
 105 }
 106
 107 /*
 108  * Get channel representation string given a Frequency
 109  */
 110 char*
 111 ieee80211_mhz_to_str(unsigned freq){
 112     int chan = ieee80211_mhz_to_chan(freq);
 113     const char* band;
 114     if (FREQ_IS_BG(freq)) {
 115         band = "2.4 GHz";
 116     } else if (FREQ_IS_6G(freq)) {
 117         band = "6 GHz";
 118     } else {
 119         band = "5 GHz";
 120     }
 121
 122     if (chan < 0) {
 123         return ws_strdup_printf("%u", freq);
 124     } else {
 125         return ws_strdup_printf("%u [%s %u]", freq, band,
 126             chan);
 127     }
 128 }
 129
 130 /*
 131  * Editor modelines
 132  *
 133  * Local Variables:
 134  * c-basic-offset: 4
 135  * tab-width: 8
 136  * indent-tabs-mode: nil
 137  * End:
 138  *
 139  * ex: set shiftwidth=4 tabstop=8 expandtab:
 140  * :indentSize=4:tabSize=8:noTabs=true:
 141  */