/* 802_11-utils.c * 802.11 utility definitions * * Wireshark - Network traffic analyzer * By Gerald Combs * 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: */