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diff --git a/wsutil/802_11-utils.h b/wsutil/802_11-utils.h
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+/* 802_11-utils.h
+ * 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
+ */
+
+#ifndef __802_11_UTILS_H__
+#define __802_11_UTILS_H__
+
+#include <wireshark.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+/** @file
+ * 802.11 utilities.
+ */
+
+/**
+ * Given a center frequency in MHz, return a channel number.
+ * @param freq Frequency in MHz.
+ * @return The equivalent channel or -1 if no match is found.
+ */
+WS_DLL_PUBLIC
+int
+ieee80211_mhz_to_chan(unsigned freq);
+
+/**
+ * Given an 802.11 channel number and a band type, return a center frequency.
+ * @param chan Channel number
+ * @param is_bg true if the channel is a b/g channel, false otherwise.
+ * @return The equivalent frequency or 0 if no match is found.
+ */
+WS_DLL_PUBLIC
+unsigned
+ieee80211_chan_to_mhz(int chan, bool is_bg);
+
+/**
+ * Given an 802.11 channel center frequency in MHz, return a string
+ * representation.
+ * @param freq Frequench in MHz.
+ * @return A string showing the frequency, channel number, and type.
+ * The string must be freed with g_free() after use.
+ */
+WS_DLL_PUBLIC
+char*
+ieee80211_mhz_to_str(unsigned freq);
+
+/* Should this be "(freq < 4920)", or something else? */
+#define FREQ_IS_BG(freq) ((freq) <= 2484)
+#define CHAN_IS_BG(chan) ((chan) <= 14)
+
+/*
+ * Test whether a data rate is an {HR}/DSSS (legacy DSSS/11b) data rate
+ * and whether it's an OFDM (11a/11g OFDM mode) data rate.
+ *
+ * rate is in units of 500 Kb/s.
+ *
+ * The 22 and 33 Mb/s rates for DSSS use Packet Binary Convolutional
+ * Coding (PBCC).  That was provided by Texas Instruments as 11b+,
+ * and was in section 19.6 "ERP-PBCC operation specifications" of
+ * IEEE Std 802.11g-2003, and sections 18.4.6.6 "DSSS/PBCC data modulation
+ * and modulation rate (optional)" and 19.6 "ERP-PBCC operation
+ * specifications" of IEEE Std 802.11-2007, and sections 17.4.6.7 "DSSS/PBCC
+ * data modulation and modulation rate (optional)" and 19.6 "ERP-PBCC
+ * operation specifications" of IEEE Std 802.11-2012, marked as optional
+ * in both cases, but is not present in IEEE Std 802.11-2016.
+ *
+ * (Note: not to be confused with "peanut butter and chocolate chips":
+ *
+ *    https://www.bigoven.com/recipe/peanut-butter-chocolate-chip-cookies-pbcc-cookies/186266
+ *
+ * :-))
+ */
+#define RATE_IS_DSSS(rate) \
+    ((rate) == 2 /* 1 Mb/s */ || \
+     (rate) == 4 /* 2 Mb/s */ || \
+     (rate) == 11 /* 5.5 Mb/s */ || \
+     (rate) == 22 /* 11 Mb/s */ || \
+     (rate) == 44 /* 22 Mb/s */ || \
+     (rate) == 66 /* 33 Mb/s */)
+
+#define RATE_IS_OFDM(rate) \
+    ((rate) == 12 /* 6 Mb/s */ || \
+     (rate) == 18 /* 9 Mb/s */ || \
+     (rate) == 24 /* 12 Mb/s */ || \
+     (rate) == 36 /* 18 Mb/s */ || \
+     (rate) == 48 /* 24 Mb/s */ || \
+     (rate) == 72 /* 36 Mb/s */ || \
+     (rate) == 96 /* 48 Mb/s */ || \
+     (rate) == 108 /* 54 Mb/s */)
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* __802_11_UTILS_H__ */
+
+/*
+ * Editor modelines
+ *
+ * Local Variables:
+ * c-basic-offset: 4
+ * tab-width: 8
+ * indent-tabs-mode: nil
+ * End:
+ *
+ * vi: set shiftwidth=4 tabstop=8 expandtab:
+ * :indentSize=4:tabSize=8:noTabs=true:
+ */