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/* 802_11-utils.c
* 802.11 utility definitions
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 2007 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include "802_11-utils.h"
typedef struct freq_cvt_s {
unsigned fmin; /* Minimum frequency in MHz */
unsigned fmax; /* Maximum frequency in MHz */
int cmin; /* Minimum/base channel */
bool is_bg; /* B/G channel? */
} freq_cvt_t;
#define FREQ_STEP 5 /* MHz. This seems to be consistent, thankfully */
/*
* XXX - Japanese channels 182 through 196 actually have center
* frequencies that are off by 2.5 MHz from these values, according
* to the IEEE standard, although the table in ARIB STD T-71 version 5.2:
*
* http://www.arib.or.jp/english/html/overview/doc/1-STD-T71v5_2.pdf
*
* section 5.3.8.3.3 doesn't show that.
*
* XXX - what about the U.S. public safety 4.9 GHz band?
*
* XXX - what about 802.11ad?
*/
static freq_cvt_t freq_cvt[] = {
{ 2412, 2472, 1, true }, /* IEEE Std 802.11-2020: Section 15.4.4.3 and Annex E */
{ 2484, 2484, 14, true }, /* IEEE Std 802.11-2020: Section 15.4.4.3 and Annex E */
{ 5000, 5925, 0, false }, /* IEEE Std 802.11-2020: Annex E */
{ 5950, 7125, 0, false }, /* IEEE Std 802.11ax-2021: Annex E */
{ 4910, 4980, 182, false },
};
#define NUM_FREQ_CVT (sizeof(freq_cvt) / sizeof(freq_cvt_t))
#define MAX_CHANNEL(fc) ( (int) ((fc.fmax - fc.fmin) / FREQ_STEP) + fc.cmin )
/*
* Get channel number given a Frequency
*/
int
ieee80211_mhz_to_chan(unsigned freq) {
unsigned i;
for (i = 0; i < NUM_FREQ_CVT; i++) {
if (freq >= freq_cvt[i].fmin && freq <= freq_cvt[i].fmax) {
return ((freq - freq_cvt[i].fmin) / FREQ_STEP) + freq_cvt[i].cmin;
}
}
return -1;
}
/*
* Get Frequency given a Channel number
*
* XXX - Because channel numbering schemes for 2.4 and 5 overlap with 6 GHz,
* this function may not return the correct channel. For example, the frequency
* for channel 1 in 2.4 GHz band is 2412 MHz, while the frequency for channel 1
* in the 6 GHz band is 5955 MHz. To resolve this problem, this function needs
* to take a starting frequency to convert channel to frequencies correctly.
* Unfortunately, this is not possible in some cases, so for now, the order on
* which frequency ranges are defined will favor 2.4 and 5 GHz over 6 GHz.
*/
unsigned
ieee80211_chan_to_mhz(int chan, bool is_bg) {
unsigned i;
for (i = 0; i < NUM_FREQ_CVT; i++) {
if (is_bg == freq_cvt[i].is_bg &&
chan >= freq_cvt[i].cmin && chan <= MAX_CHANNEL(freq_cvt[i])) {
return ((chan - freq_cvt[i].cmin) * FREQ_STEP) + freq_cvt[i].fmin;
}
}
return 0;
}
/*
* Get channel representation string given a Frequency
*/
char*
ieee80211_mhz_to_str(unsigned freq){
int chan = ieee80211_mhz_to_chan(freq);
bool is_bg = FREQ_IS_BG(freq);
if (chan < 0) {
return ws_strdup_printf("%u", freq);
} else {
return ws_strdup_printf("%u [%s %u]", freq, is_bg ? "BG" : "A",
chan);
}
}
/*
* Editor modelines
*
* Local Variables:
* c-basic-offset: 4
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* ex: set shiftwidth=4 tabstop=8 expandtab:
* :indentSize=4:tabSize=8:noTabs=true:
*/
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