From Johannes Berg via bug 4421:

radiotap: new parser

The current parser has a number of bugs, most
importantly not being able to parse radiotap
files with multiple presence bitmaps. It is
also rather hard extend. Use a generic library
for parsing radiotap that can be extended very
easily.


From me:

Dumb down some initializers and add some casts to make Visual C++ happy.


git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@34515 f5534014-38df-0310-8fa8-9805f1628bb7

1 files changed, 396 insertions, 0 deletions

diff --git a/epan/dissectors/packet-radiotap-iter.c b/epan/dissectors/packet-radiotap-iter.c
new file mode 100644
index 0000000000..7691a5449a
--- /dev/null
+++ b/epan/dissectors/packet-radiotap-iter.c
@@ -0,0 +1,396 @@
+/*
+ * Radiotap parser
+ *
+ * Copyright 2007		Andy Green <andy@warmcat.com>
+ * Copyright 2009		Johannes Berg <johannes@sipsolutions.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Alternatively, this software may be distributed under the terms of BSD
+ * license.
+ *
+ * See COPYING for more details.
+ */
+
+#include <stddef.h>
+#include <errno.h>
+#include <glib.h>
+#include "pint.h"
+
+#define le16_to_cpu		GINT16_FROM_LE
+#define le32_to_cpu		GINT32_FROM_LE
+#define get_unaligned_le16	pletohs
+#define get_unaligned_le32	pletohl
+
+#include "packet-radiotap-iter.h"
+
+/* function prototypes and related defs are in radiotap_iter.h */
+
+static const struct radiotap_align_size rtap_namespace_sizes[] = {
+	/* [IEEE80211_RADIOTAP_TSFT] = 0 */			{ 8, 8 },
+	/* [IEEE80211_RADIOTAP_FLAGS] = 1 */			{ 1, 1 },
+	/* [IEEE80211_RADIOTAP_RATE] = 2 */			{ 1, 1 },
+	/* [IEEE80211_RADIOTAP_CHANNEL] = 3 */			{ 2, 4 },
+	/* [IEEE80211_RADIOTAP_FHSS] = 4 */			{ 2, 2 },
+	/* [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = 5 */		{ 1, 1 },
+	/* [IEEE80211_RADIOTAP_DBM_ANTNOISE] = 6 */		{ 1, 1 },
+	/* [IEEE80211_RADIOTAP_LOCK_QUALITY] = 7 */		{ 2, 2 },
+	/* [IEEE80211_RADIOTAP_TX_ATTENUATION] = 8 */		{ 2, 2 },
+	/* [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = 9 */	{ 2, 2 },
+	/* [IEEE80211_RADIOTAP_DBM_TX_POWER] = 10 */		{ 1, 1 },
+	/* [IEEE80211_RADIOTAP_ANTENNA] = 11 */			{ 1, 1 },
+	/* [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = 12 */		{ 1, 1 },
+	/* [IEEE80211_RADIOTAP_DB_ANTNOISE] = 13 */		{ 1, 1 },
+	/* [IEEE80211_RADIOTAP_RX_FLAGS] = 14 */		{ 2, 2 },
+	/* [IEEE80211_RADIOTAP_TX_FLAGS] = 15 */		{ 2, 2 },
+	/* [IEEE80211_RADIOTAP_RTS_RETRIES] = 16 */		{ 1, 1 },
+	/* [IEEE80211_RADIOTAP_DATA_RETRIES] = 17 */		{ 1, 1 }
+	/*
+	 * add more here as they are defined in
+	 * include/net/ieee80211_radiotap.h
+	 */
+};
+
+static const struct ieee80211_radiotap_namespace radiotap_ns = {
+	rtap_namespace_sizes,
+	(int)(sizeof(rtap_namespace_sizes) / sizeof(rtap_namespace_sizes[0])),
+	0,
+	0
+};
+
+/**
+ * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
+ * @iterator: radiotap_iterator to initialize
+ * @radiotap_header: radiotap header to parse
+ * @max_length: total length we can parse into (eg, whole packet length)
+ *
+ * Returns: 0 or a negative error code if there is a problem.
+ *
+ * This function initializes an opaque iterator struct which can then
+ * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
+ * argument which is present in the header.  It knows about extended
+ * present headers and handles them.
+ *
+ * How to use:
+ * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
+ * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
+ * checking for a good 0 return code.  Then loop calling
+ * __ieee80211_radiotap_iterator_next()... it returns either 0,
+ * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
+ * The iterator's @this_arg member points to the start of the argument
+ * associated with the current argument index that is present, which can be
+ * found in the iterator's @this_arg_index member.  This arg index corresponds
+ * to the IEEE80211_RADIOTAP_... defines.
+ *
+ * Radiotap header length:
+ * You can find the CPU-endian total radiotap header length in
+ * iterator->max_length after executing ieee80211_radiotap_iterator_init()
+ * successfully.
+ *
+ * Alignment Gotcha:
+ * You must take care when dereferencing iterator.this_arg
+ * for multibyte types... the pointer is not aligned.  Use
+ * get_unaligned((type *)iterator.this_arg) to dereference
+ * iterator.this_arg for type "type" safely on all arches.
+ *
+ * Example code:
+ * See Documentation/networking/radiotap-headers.txt
+ */
+
+int ieee80211_radiotap_iterator_init(
+	struct ieee80211_radiotap_iterator *iterator,
+	struct ieee80211_radiotap_header *radiotap_header,
+	int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
+{
+	/* Linux only supports version 0 radiotap format */
+	if (radiotap_header->it_version)
+		return -EINVAL;
+
+	/* sanity check for allowed length and radiotap length field */
+	if (max_length < get_unaligned_le16(&radiotap_header->it_len))
+		return -EINVAL;
+
+	iterator->_rtheader = radiotap_header;
+	iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
+	iterator->_arg_index = 0;
+	iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
+	iterator->_arg = (guint8 *)radiotap_header + sizeof(*radiotap_header);
+	iterator->_reset_on_ext = 0;
+	iterator->_next_bitmap = &radiotap_header->it_present;
+	iterator->_next_bitmap++;
+	iterator->_vns = vns;
+	iterator->current_namespace = &radiotap_ns;
+	iterator->is_radiotap_ns = 1;
+#ifdef RADIOTAP_SUPPORT_OVERRIDES
+	iterator->n_overrides = 0;
+	iterator->overrides = NULL;
+#endif
+
+	/* find payload start allowing for extended bitmap(s) */
+
+	if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
+		while (get_unaligned_le32(iterator->_arg) &
+					(1 << IEEE80211_RADIOTAP_EXT)) {
+			iterator->_arg += sizeof(guint32);
+
+			/*
+			 * check for insanity where the present bitmaps
+			 * keep claiming to extend up to or even beyond the
+			 * stated radiotap header length
+			 */
+
+			if ((unsigned long)iterator->_arg -
+			    (unsigned long)iterator->_rtheader >
+			    (unsigned long)iterator->_max_length)
+				return -EINVAL;
+		}
+
+		iterator->_arg += sizeof(guint32);
+
+		/*
+		 * no need to check again for blowing past stated radiotap
+		 * header length, because ieee80211_radiotap_iterator_next
+		 * checks it before it is dereferenced
+		 */
+	}
+
+	iterator->this_arg = iterator->_arg;
+
+	/* we are all initialized happily */
+
+	return 0;
+}
+
+static void find_ns(struct ieee80211_radiotap_iterator *iterator,
+		    guint32 oui, guint8 subns)
+{
+	int i;
+
+	iterator->current_namespace = NULL;
+
+	if (!iterator->_vns)
+		return;
+
+	for (i = 0; i < iterator->_vns->n_ns; i++) {
+		if (iterator->_vns->ns[i].oui != oui)
+			continue;
+		if (iterator->_vns->ns[i].subns != subns)
+			continue;
+
+		iterator->current_namespace = &iterator->_vns->ns[i];
+		break;
+	}
+}
+
+#ifdef RADIOTAP_SUPPORT_OVERRIDES
+static int find_override(struct ieee80211_radiotap_iterator *iterator,
+			 int *align, int *size)
+{
+	int i;
+
+	if (!iterator->overrides)
+		return 0;
+
+	for (i = 0; i < iterator->n_overrides; i++) {
+		if (iterator->_arg_index == iterator->overrides[i].field) {
+			*align = iterator->overrides[i].align;
+			*size = iterator->overrides[i].size;
+			if (!*align) /* erroneous override */
+				return 0;
+			return 1;
+		}
+	}
+
+	return 0;
+}
+#endif
+
+
+/**
+ * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
+ * @iterator: radiotap_iterator to move to next arg (if any)
+ *
+ * Returns: 0 if there is an argument to handle,
+ * -ENOENT if there are no more args or -EINVAL
+ * if there is something else wrong.
+ *
+ * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
+ * in @this_arg_index and sets @this_arg to point to the
+ * payload for the field.  It takes care of alignment handling and extended
+ * present fields.  @this_arg can be changed by the caller (eg,
+ * incremented to move inside a compound argument like
+ * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
+ * little-endian format whatever the endianess of your CPU.
+ *
+ * Alignment Gotcha:
+ * You must take care when dereferencing iterator.this_arg
+ * for multibyte types... the pointer is not aligned.  Use
+ * get_unaligned((type *)iterator.this_arg) to dereference
+ * iterator.this_arg for type "type" safely on all arches.
+ */
+
+int ieee80211_radiotap_iterator_next(
+	struct ieee80211_radiotap_iterator *iterator)
+{
+	while (1) {
+		int hit = 0;
+		int pad, align, size, subns;
+		guint32 oui;
+
+		/* if no more EXT bits, that's it */
+		if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
+		    !(iterator->_bitmap_shifter & 1))
+			return -ENOENT;
+
+		if (!(iterator->_bitmap_shifter & 1))
+			goto next_entry; /* arg not present */
+
+		/* get alignment/size of data */
+		switch (iterator->_arg_index % 32) {
+		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
+		case IEEE80211_RADIOTAP_EXT:
+			align = 1;
+			size = 0;
+			break;
+		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
+			align = 2;
+			size = 6;
+			break;
+		default:
+#ifdef RADIOTAP_SUPPORT_OVERRIDES
+			if (find_override(iterator, &align, &size)) {
+				/* all set */
+			} else
+#endif
+			if (!iterator->current_namespace ||
+			    iterator->_arg_index >= iterator->current_namespace->n_bits) {
+				if (iterator->current_namespace == &radiotap_ns)
+					return -ENOENT;
+				align = 0;
+			} else {
+				align = iterator->current_namespace->align_size[iterator->_arg_index].align;
+				size = iterator->current_namespace->align_size[iterator->_arg_index].size;
+			}
+			if (!align) {
+				/* skip all subsequent data */
+				iterator->_arg = iterator->_next_ns_data;
+				/* give up on this namespace */
+				iterator->current_namespace = NULL;
+				goto next_entry;
+			}
+			break;
+		}
+
+		/*
+		 * arg is present, account for alignment padding
+		 *
+		 * Note that these alignments are relative to the start
+		 * of the radiotap header.  There is no guarantee
+		 * that the radiotap header itself is aligned on any
+		 * kind of boundary.
+		 *
+		 * The above is why get_unaligned() is used to dereference
+		 * multibyte elements from the radiotap area.
+		 */
+
+		pad = ((unsigned long)iterator->_arg -
+		       (unsigned long)iterator->_rtheader) & (align - 1);
+
+		if (pad)
+			iterator->_arg += align - pad;
+
+		if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
+			int vnslen;
+
+			if ((unsigned long)iterator->_arg + size -
+			    (unsigned long)iterator->_rtheader >
+			    (unsigned long)iterator->_max_length)
+				return -EINVAL;
+
+			oui = (*iterator->_arg << 16) |
+				(*(iterator->_arg + 1) << 8) |
+				*(iterator->_arg + 2);
+			subns = *(iterator->_arg + 3);
+
+			find_ns(iterator, oui, subns);
+
+			vnslen = get_unaligned_le16(iterator->_arg + 4);
+			iterator->_next_ns_data = iterator->_arg + size + vnslen;
+			if (!iterator->current_namespace)
+				size += vnslen;
+		}
+
+		/*
+		 * this is what we will return to user, but we need to
+		 * move on first so next call has something fresh to test
+		 */
+		iterator->this_arg_index = iterator->_arg_index;
+		iterator->this_arg = iterator->_arg;
+		iterator->this_arg_size = size;
+
+		/* internally move on the size of this arg */
+		iterator->_arg += size;
+
+		/*
+		 * check for insanity where we are given a bitmap that
+		 * claims to have more arg content than the length of the
+		 * radiotap section.  We will normally end up equalling this
+		 * max_length on the last arg, never exceeding it.
+		 */
+
+		if ((unsigned long)iterator->_arg -
+		    (unsigned long)iterator->_rtheader >
+		    (unsigned long)iterator->_max_length)
+			return -EINVAL;
+
+		/* these special ones are valid in each bitmap word */
+		switch (iterator->_arg_index % 32) {
+		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
+			iterator->_reset_on_ext = 1;
+
+			iterator->is_radiotap_ns = 0;
+			/*
+			 * If parser didn't register this vendor
+			 * namespace with us, allow it to show it
+			 * as 'raw. Do do that, set argument index
+			 * to vendor namespace.
+			 */
+			iterator->this_arg_index =
+				IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
+			if (!iterator->current_namespace)
+				hit = 1;
+			goto next_entry;
+		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
+			iterator->_reset_on_ext = 1;
+			iterator->current_namespace = &radiotap_ns;
+			iterator->is_radiotap_ns = 1;
+			goto next_entry;
+		case IEEE80211_RADIOTAP_EXT:
+			/*
+			 * bit 31 was set, there is more
+			 * -- move to next u32 bitmap
+			 */
+			iterator->_bitmap_shifter =
+				get_unaligned_le32(iterator->_next_bitmap);
+			iterator->_next_bitmap++;
+			if (iterator->_reset_on_ext)
+				iterator->_arg_index = 0;
+			else
+				iterator->_arg_index++;
+			iterator->_reset_on_ext = 0;
+			break;
+		default:
+			/* we've got a hit! */
+			hit = 1;
+ next_entry:
+			iterator->_bitmap_shifter >>= 1;
+			iterator->_arg_index++;
+		}
+
+		/* if we found a valid arg earlier, return it now */
+		if (hit)
+			return 0;
+	}
+}