1 files changed, 113 insertions, 0 deletions
diff --git a/wsutil/802_11-utils.c b/wsutil/802_11-utils.c
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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:
+ */