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// SPDX-FileCopyrightText: 2018 Citra Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later
#include <cstddef>
#include <cstring>
#include "common/logging/log.h"
#include "input_common/helpers/udp_protocol.h"
namespace InputCommon::CemuhookUDP {
static constexpr std::size_t GetSizeOfResponseType(Type t) {
switch (t) {
case Type::Version:
return sizeof(Response::Version);
case Type::PortInfo:
return sizeof(Response::PortInfo);
case Type::PadData:
return sizeof(Response::PadData);
}
return 0;
}
namespace Response {
/**
* Returns Type if the packet is valid, else none
*
* Note: Modifies the buffer to zero out the crc (since that's the easiest way to check without
* copying the buffer)
*/
std::optional<Type> Validate(u8* data, std::size_t size) {
if (size < sizeof(Header)) {
return std::nullopt;
}
Header header{};
std::memcpy(&header, data, sizeof(Header));
if (header.magic != SERVER_MAGIC) {
LOG_ERROR(Input, "UDP Packet has an unexpected magic value");
return std::nullopt;
}
if (header.protocol_version != PROTOCOL_VERSION) {
LOG_ERROR(Input, "UDP Packet protocol mismatch");
return std::nullopt;
}
if (header.type < Type::Version || header.type > Type::PadData) {
LOG_ERROR(Input, "UDP Packet is an unknown type");
return std::nullopt;
}
// Packet size must equal sizeof(Header) + sizeof(Data)
// and also verify that the packet info mentions the correct size. Since the spec includes the
// type of the packet as part of the data, we need to include it in size calculations here
// ie: payload_length == sizeof(T) + sizeof(Type)
const std::size_t data_len = GetSizeOfResponseType(header.type);
if (header.payload_length != data_len + sizeof(Type) || size < data_len + sizeof(Header)) {
LOG_ERROR(
Input,
"UDP Packet payload length doesn't match. Received: {} PayloadLength: {} Expected: {}",
size, header.payload_length, data_len + sizeof(Type));
return std::nullopt;
}
const u32 crc32 = header.crc;
boost::crc_32_type result;
// zero out the crc in the buffer and then run the crc against it
std::memset(&data[offsetof(Header, crc)], 0, sizeof(u32_le));
result.process_bytes(data, data_len + sizeof(Header));
if (crc32 != result.checksum()) {
LOG_ERROR(Input, "UDP Packet CRC check failed. Offset: {}", offsetof(Header, crc));
return std::nullopt;
}
return header.type;
}
} // namespace Response
} // namespace InputCommon::CemuhookUDP
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