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/*
* Copyright (c) 2017, Matias Fontanini
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <tins/utils/radiotap_writer.h>
#ifdef TINS_HAVE_DOT11
#include <cmath>
#include <tins/utils/radiotap_parser.h>
#include <tins/exceptions.h>
using std::vector;
namespace Tins {
namespace Utils {
uint32_t calculate_padding(uint32_t alignment, uint32_t offset) {
uint32_t extra = offset % alignment;
return extra == 0 ? 0 : alignment - extra;
}
uint32_t get_bit(uint32_t value) {
return round(log2(value));
}
RadioTapWriter::RadioTapWriter(vector<uint8_t>& buffer)
: buffer_(buffer) {
}
void RadioTapWriter::write_option(const RadioTap::option& option) {
const uint32_t bit = get_bit(option.option());
if (bit >= RadioTapParser::MAX_RADIOTAP_FIELD) {
throw malformed_option();
}
const bool is_empty = buffer_.empty();
RadioTapParser parser(buffer_);
const uint8_t* candidate_ptr = parser.current_option_ptr();
// Loop while we find lower fields and we're still in the first namespace
while (parser.has_fields()) {
if (parser.current_field() > option.option()) {
break;
}
else if (parser.current_field() == option.option()) {
memcpy(const_cast<uint8_t*>(parser.current_option_ptr()),
option.data_ptr(), option.data_size());
return;
}
else {
const uint32_t bit = get_bit(parser.current_field());
const RadioTapParser::FieldMetadata& meta = RadioTapParser::RADIOTAP_METADATA[bit];
candidate_ptr = parser.current_option_ptr() + meta.size;
}
parser.advance_field();
}
size_t offset = is_empty ? 0 : candidate_ptr - &*buffer_.begin();
const RadioTapParser::FieldMetadata& meta = RadioTapParser::RADIOTAP_METADATA[bit];
vector<uint8_t> paddings = build_padding_vector(candidate_ptr, parser);
// Calculate the offset based on the RadioTap header (add 4 bytes)
const uint32_t padding = calculate_padding(meta.alignment, offset + sizeof(uint32_t));
// Now actually insert our new field (padding first)
buffer_.insert(buffer_.begin() + offset, padding, 0);
buffer_.insert(buffer_.begin() + offset + padding, option.data_ptr(),
option.data_ptr() + option.data_size());
update_paddings(paddings, offset + padding + option.data_size());
// Finally, update the flags
uint32_t flags = 0;
if (is_empty) {
buffer_.insert(buffer_.begin(), sizeof(flags), 0);
}
else {
memcpy(&flags, &*buffer_.begin(), sizeof(flags));
}
flags |= Endian::host_to_le<uint32_t>(option.option());
memcpy(&*buffer_.begin(), &flags, sizeof(flags));
}
// Builds a vector that will contain the padding required for every position.
// e.g. if a 2 byte field is found, then in those 2 indexes we'll have the values [2, 1].
// 2 to indicate that the first field requires 16 bit padding and the second one is fine
// with 1 byte padding as long as the first one is as well.
//
// Padding bytes are filled with the value 0 to indicate a special index that can be
// compacted/removed if less/more padding is required
vector<uint8_t> RadioTapWriter::build_padding_vector(const uint8_t* last_ptr,
RadioTapParser& parser) {
vector<uint8_t> paddings;
while (parser.has_fields()) {
const uint32_t flag = static_cast<uint32_t>(parser.current_field());
const uint32_t bit = get_bit(flag);
const RadioTapParser::FieldMetadata& meta = RadioTapParser::RADIOTAP_METADATA[bit];
const uint8_t* current_ptr = parser.current_option_ptr();
// These are just paddings
paddings.insert(paddings.end(), current_ptr - last_ptr, 0);
// Say this byte has to be padded to whatever the alignment is for this field
paddings.push_back(meta.alignment);
// The rest of the bytes for this field don't really need alignment
for (size_t i = 0; i < meta.size - 1; ++i) {
paddings.push_back(1);
}
last_ptr = current_ptr + meta.size;
parser.advance_field();
}
return paddings;
}
// Iterates the padding vector and extends/compacts the paddings as needed
void RadioTapWriter::update_paddings(const vector<uint8_t>& paddings, uint32_t offset) {
size_t i = 0;
while (i != paddings.size()) {
// Skip everything that doesn't need padding
while (i != paddings.size() && paddings[i] == 1) {
++i;
}
const size_t start = i;
// Find the next field
while (i != paddings.size() && paddings[i] == 0) {
++i;
}
if (i == paddings.size()) {
break;
}
offset += start;
const uint8_t needed_padding = calculate_padding(paddings[i], offset + sizeof(uint32_t));
const size_t existing_padding = i - start;
// Remove padding if there's too much
if (existing_padding > needed_padding) {
buffer_.erase(buffer_.begin() + offset,
buffer_.begin() + offset + (existing_padding - needed_padding));
offset -= existing_padding - needed_padding;
}
// Add padding if there's too little
else if (existing_padding < needed_padding) {
buffer_.insert(buffer_.begin() + offset, needed_padding - existing_padding, 0);
offset += needed_padding - existing_padding;
}
offset += i - start;
++i;
}
}
} // Utils
} // Tins
#endif // TINS_HAVE_DOT11
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