quic_socket.cpp

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// BSD 3-Clause License
// Copyright (c) 2024, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#include "quic_socket.h"
 
#include <random>
#include <chrono>
#include <type_traits>
 
namespace kcenon::network::internal
{
 
using namespace protocols::quic;
 
// =============================================================================
// Construction / Destruction
// =============================================================================
 
quic_socket::quic_socket(asio::ip::udp::socket socket, quic_role role)
    : udp_socket_(std::move(socket))
    , role_(role)
    , retransmit_timer_(udp_socket_.get_executor())
    , idle_timer_(udp_socket_.get_executor())
{
    // Generate local connection ID
    local_conn_id_ = generate_connection_id();
 
    // Initialize next stream ID based on role
    // Client-initiated bidi streams: 0, 4, 8, ...
    // Server-initiated bidi streams: 1, 5, 9, ...
    next_stream_id_ = (role_ == quic_role::client) ? 0 : 1;
}
 
quic_socket::~quic_socket()
{
    stop_receive();
 
    // Cancel timers
    retransmit_timer_.cancel();
    idle_timer_.cancel();
}
 
quic_socket::quic_socket(quic_socket&& other) noexcept
    : udp_socket_(std::move(other.udp_socket_))
    , remote_endpoint_(std::move(other.remote_endpoint_))
    , recv_buffer_(std::move(other.recv_buffer_))
    , role_(other.role_)
    , state_(other.state_.load())
    , crypto_(std::move(other.crypto_))
    , local_conn_id_(std::move(other.local_conn_id_))
    , remote_conn_id_(std::move(other.remote_conn_id_))
    , next_packet_number_(other.next_packet_number_)
    , largest_received_pn_(other.largest_received_pn_)
    , next_stream_id_(other.next_stream_id_)
    , pending_crypto_data_(std::move(other.pending_crypto_data_))
    , pending_stream_data_(std::move(other.pending_stream_data_))
    , stream_data_cb_(std::move(other.stream_data_cb_))
    , connected_cb_(std::move(other.connected_cb_))
    , error_cb_(std::move(other.error_cb_))
    , close_cb_(std::move(other.close_cb_))
    , is_receiving_(other.is_receiving_.load())
    , handshake_complete_(other.handshake_complete_.load())
    , retransmit_timer_(std::move(other.retransmit_timer_))
    , idle_timer_(std::move(other.idle_timer_))
{
}
 
quic_socket& quic_socket::operator=(quic_socket&& other) noexcept
{
    if (this != &other)
    {
        stop_receive();
 
        udp_socket_ = std::move(other.udp_socket_);
        remote_endpoint_ = std::move(other.remote_endpoint_);
        recv_buffer_ = std::move(other.recv_buffer_);
        role_ = other.role_;
        state_.store(other.state_.load());
        crypto_ = std::move(other.crypto_);
        local_conn_id_ = std::move(other.local_conn_id_);
        remote_conn_id_ = std::move(other.remote_conn_id_);
        next_packet_number_ = other.next_packet_number_;
        largest_received_pn_ = other.largest_received_pn_;
        next_stream_id_ = other.next_stream_id_;
        pending_crypto_data_ = std::move(other.pending_crypto_data_);
        pending_stream_data_ = std::move(other.pending_stream_data_);
 
        std::lock_guard<std::mutex> lock(callback_mutex_);
        stream_data_cb_ = std::move(other.stream_data_cb_);
        connected_cb_ = std::move(other.connected_cb_);
        error_cb_ = std::move(other.error_cb_);
        close_cb_ = std::move(other.close_cb_);
 
        is_receiving_.store(other.is_receiving_.load());
        handshake_complete_.store(other.handshake_complete_.load());
        retransmit_timer_ = std::move(other.retransmit_timer_);
        idle_timer_ = std::move(other.idle_timer_);
    }
    return *this;
}
 
// =============================================================================
// Callback Registration
// =============================================================================
 
auto quic_socket::set_stream_data_callback(stream_data_callback cb) -> void
{
    std::lock_guard<std::mutex> lock(callback_mutex_);
    stream_data_cb_ = std::move(cb);
}
 
auto quic_socket::set_connected_callback(connected_callback cb) -> void
{
    std::lock_guard<std::mutex> lock(callback_mutex_);
    connected_cb_ = std::move(cb);
}
 
auto quic_socket::set_error_callback(error_callback cb) -> void
{
    std::lock_guard<std::mutex> lock(callback_mutex_);
    error_cb_ = std::move(cb);
}
 
auto quic_socket::set_close_callback(close_callback cb) -> void
{
    std::lock_guard<std::mutex> lock(callback_mutex_);
    close_cb_ = std::move(cb);
}
 
// =============================================================================
// Connection Management
// =============================================================================
 
auto quic_socket::connect(const asio::ip::udp::endpoint& endpoint,
                          const std::string& server_name) -> VoidResult
{
    if (role_ != quic_role::client)
    {
        return error_void(
            error_codes::common_errors::invalid_argument,
            "connect() can only be called on client sockets",
            "quic_socket");
    }
 
    if (state_.load() != quic_connection_state::idle)
    {
        return error_void(
            error_codes::common_errors::invalid_argument,
            "Connection already in progress or established",
            "quic_socket");
    }
 
    remote_endpoint_ = endpoint;
 
    // Initialize client-side crypto
    auto init_result = crypto_.init_client(
        server_name.empty() ? endpoint.address().to_string() : server_name);
    if (init_result.is_err())
    {
        return error_void(
            error_codes::network_system::connection_failed,
            "Failed to initialize TLS client",
            "quic_socket",
            init_result.error().message);
    }
 
    // Generate initial secrets from destination connection ID
    // For client, we use a random connection ID as the destination
    remote_conn_id_ = generate_connection_id();
 
    auto derive_result = crypto_.derive_initial_secrets(remote_conn_id_);
    if (derive_result.is_err())
    {
        return error_void(
            error_codes::network_system::connection_failed,
            "Failed to derive initial secrets",
            "quic_socket",
            derive_result.error().message);
    }
 
    transition_state(quic_connection_state::handshake_start);
 
    // Start handshake - generate ClientHello
    auto handshake_result = crypto_.start_handshake();
    if (handshake_result.is_err())
    {
        transition_state(quic_connection_state::closed);
        return error_void(
            error_codes::network_system::connection_failed,
            "Failed to start TLS handshake",
            "quic_socket",
            handshake_result.error().message);
    }
 
    // Queue the CRYPTO data for sending
    if (!handshake_result.value().empty())
    {
        queue_crypto_data(std::move(handshake_result.value()));
    }
 
    transition_state(quic_connection_state::handshake);
 
    // Start receiving
    start_receive();
 
    // Send initial packet
    send_pending_packets();
 
    return ok();
}
 
auto quic_socket::accept(const std::string& cert_file,
                         const std::string& key_file) -> VoidResult
{
    if (role_ != quic_role::server)
    {
        return error_void(
            error_codes::common_errors::invalid_argument,
            "accept() can only be called on server sockets",
            "quic_socket");
    }
 
    if (state_.load() != quic_connection_state::idle)
    {
        return error_void(
            error_codes::common_errors::invalid_argument,
            "Connection already in progress",
            "quic_socket");
    }
 
    // Initialize server-side crypto
    auto init_result = crypto_.init_server(cert_file, key_file);
    if (init_result.is_err())
    {
        return error_void(
            error_codes::network_system::connection_failed,
            "Failed to initialize TLS server",
            "quic_socket",
            init_result.error().message);
    }
 
    transition_state(quic_connection_state::handshake_start);
 
    // Start receiving - server waits for Initial packet from client
    start_receive();
 
    return ok();
}
 
auto quic_socket::close(uint64_t error_code, const std::string& reason) -> VoidResult
{
    auto current_state = state_.load();
    if (current_state == quic_connection_state::closed ||
        current_state == quic_connection_state::closing ||
        current_state == quic_connection_state::draining)
    {
        return ok();  // Already closing/closed
    }
 
    transition_state(quic_connection_state::closing);
 
    // Build CONNECTION_CLOSE frame
    connection_close_frame close_frame;
    close_frame.error_code = error_code;
    close_frame.reason_phrase = reason;
    close_frame.is_application_error = (error_code != 0);
 
    // Send CONNECTION_CLOSE
    std::vector<frame> frames;
    frames.push_back(close_frame);
 
    auto level = handshake_complete_.load()
        ? encryption_level::application
        : encryption_level::initial;
 
    auto send_result = send_packet(level, std::move(frames));
    if (send_result.is_err())
    {
        // Log error but continue with close
    }
 
    transition_state(quic_connection_state::draining);
 
    // Set a timer for draining period (3 * PTO), then fully close
    idle_timer_.expires_after(std::chrono::milliseconds(300));
    idle_timer_.async_wait(
        [self = shared_from_this()](const std::error_code& ec)
        {
            if (!ec)
            {
                self->transition_state(quic_connection_state::closed);
                self->stop_receive();
            }
        });
 
    return ok();
}
 
// =============================================================================
// I/O Operations
// =============================================================================
 
auto quic_socket::start_receive() -> void
{
    is_receiving_.store(true);
    do_receive();
}
 
auto quic_socket::stop_receive() -> void
{
    is_receiving_.store(false);
}
 
auto quic_socket::send_stream_data(uint64_t stream_id,
                                   std::vector<uint8_t>&& data,
                                   bool fin) -> VoidResult
{
    if (!is_connected())
    {
        return error_void(
            error_codes::network_system::connection_failed,
            "Connection not established",
            "quic_socket");
    }
 
    {
        std::lock_guard<std::mutex> lock(state_mutex_);
        pending_stream_data_[stream_id].push_back({std::move(data), fin});
    }
 
    send_pending_packets();
 
    return ok();
}
 
// =============================================================================
// Stream Management
// =============================================================================
 
auto quic_socket::create_stream(bool unidirectional) -> Result<uint64_t>
{
    if (!is_connected())
    {
        return error<uint64_t>(
            error_codes::network_system::connection_failed,
            "Connection not established",
            "quic_socket");
    }
 
    std::lock_guard<std::mutex> lock(state_mutex_);
 
    // Stream ID encoding (RFC 9000 Section 2.1):
    // - Bits 0-1: Type (0=client-initiated bidi, 1=server-initiated bidi,
    //                   2=client-initiated uni, 3=server-initiated uni)
    // - Bits 2+: Sequence number
 
    uint64_t type_bits = 0;
    if (role_ == quic_role::server)
    {
        type_bits |= 0x01;  // Server-initiated
    }
    if (unidirectional)
    {
        type_bits |= 0x02;  // Unidirectional
    }
 
    uint64_t stream_id = (next_stream_id_ << 2) | type_bits;
    next_stream_id_++;
 
    // Initialize the stream's pending data queue
    pending_stream_data_[stream_id] = {};
 
    return ok(std::move(stream_id));
}
 
auto quic_socket::close_stream(uint64_t stream_id) -> VoidResult
{
    std::lock_guard<std::mutex> lock(state_mutex_);
 
    auto it = pending_stream_data_.find(stream_id);
    if (it == pending_stream_data_.end())
    {
        return error_void(
            error_codes::common_errors::not_found,
            "Stream not found",
            "quic_socket");
    }
 
    // Send FIN on the stream
    it->second.push_back({{}, true});
 
    send_pending_packets();
 
    return ok();
}
 
// =============================================================================
// State Queries
// =============================================================================
 
auto quic_socket::is_connected() const noexcept -> bool
{
    return state_.load() == quic_connection_state::connected;
}
 
auto quic_socket::is_handshake_complete() const noexcept -> bool
{
    return handshake_complete_.load();
}
 
auto quic_socket::state() const noexcept -> quic_connection_state
{
    return state_.load();
}
 
auto quic_socket::role() const noexcept -> quic_role
{
    return role_;
}
 
auto quic_socket::remote_endpoint() const -> asio::ip::udp::endpoint
{
    return remote_endpoint_;
}
 
auto quic_socket::local_connection_id() const -> const connection_id&
{
    return local_conn_id_;
}
 
auto quic_socket::remote_connection_id() const -> const connection_id&
{
    return remote_conn_id_;
}
 
// =============================================================================
// Internal Methods
// =============================================================================
 
auto quic_socket::do_receive() -> void
{
    if (!is_receiving_.load())
    {
        return;
    }
 
    auto self = shared_from_this();
    udp_socket_.async_receive_from(
        asio::buffer(recv_buffer_),
        remote_endpoint_,
        [this, self](std::error_code ec, std::size_t bytes_transferred)
        {
            if (!is_receiving_.load())
            {
                return;
            }
 
            if (ec)
            {
                if (ec != asio::error::operation_aborted)
                {
                    std::lock_guard<std::mutex> lock(callback_mutex_);
                    if (error_cb_)
                    {
                        error_cb_(ec);
                    }
                }
                return;
            }
 
            if (bytes_transferred > 0)
            {
                handle_packet(std::span(recv_buffer_.data(), bytes_transferred));
            }
 
            // Continue receiving
            if (is_receiving_.load())
            {
                do_receive();
            }
        });
}
 
auto quic_socket::handle_packet(std::span<const uint8_t> data) -> void
{
    // Parse packet header
    auto header_result = packet_parser::parse_header(data);
    if (header_result.is_err())
    {
        // Invalid packet - silently ignore
        return;
    }
 
    auto& [header, header_length] = header_result.value();
 
    // Determine encryption level
    auto level = determine_encryption_level(header);
 
    // For server, derive initial secrets on first Initial packet
    if (role_ == quic_role::server &&
        state_.load() == quic_connection_state::handshake_start)
    {
        if (std::holds_alternative<long_header>(header))
        {
            const auto& lh = std::get<long_header>(header);
            if (lh.type() == packet_type::initial)
            {
                // Use client's DCID as our remote connection ID
                remote_conn_id_ = lh.src_conn_id;
 
                // Derive initial secrets from client's DCID
                auto derive_result = crypto_.derive_initial_secrets(lh.dest_conn_id);
                if (derive_result.is_err())
                {
                    return;
                }
 
                transition_state(quic_connection_state::handshake);
            }
        }
    }
 
    // Get read keys for this level
    auto keys_result = crypto_.get_read_keys(level);
    if (keys_result.is_err())
    {
        // Keys not available yet - queue packet for later processing
        return;
    }
 
    // Unprotect (decrypt) the packet
    // First we need to get the packet number offset
    size_t pn_offset = header_length;
    if (std::holds_alternative<long_header>(header))
    {
        // For long headers, packet number is after the header
        // (already accounted for in header_length for Initial/Handshake)
    }
 
    // Determine packet number length from header (after removing header protection)
    size_t sample_offset = pn_offset + 4;  // Sample is 4 bytes after PN start
    if (sample_offset + hp_sample_size > data.size())
    {
        return;  // Not enough data for sample
    }
 
    std::span<const uint8_t> sample(data.data() + sample_offset, hp_sample_size);
 
    // Create mutable copy for header unprotection
    std::vector<uint8_t> packet_copy(data.begin(), data.end());
 
    auto unprotect_header_result = packet_protection::unprotect_header(
        keys_result.value(),
        std::span(packet_copy.data(), header_length + 4),  // Include space for max PN
        pn_offset,
        sample);
 
    if (unprotect_header_result.is_err())
    {
        return;
    }
 
    auto& [first_byte, pn_length] = unprotect_header_result.value();
 
    // Extract packet number
    uint64_t truncated_pn = 0;
    for (size_t i = 0; i < pn_length; ++i)
    {
        truncated_pn = (truncated_pn << 8) | packet_copy[pn_offset + i];
    }
 
    // Decode full packet number
    auto level_idx = static_cast<size_t>(level);
    uint64_t full_pn = packet_number::decode(
        truncated_pn, pn_length, largest_received_pn_[level_idx]);
 
    // Update largest received
    if (full_pn > largest_received_pn_[level_idx])
    {
        largest_received_pn_[level_idx] = full_pn;
    }
 
    // Decrypt packet payload
    size_t payload_offset = pn_offset + pn_length;
    auto unprotect_result = packet_protection::unprotect(
        keys_result.value(),
        std::span(packet_copy),
        payload_offset,
        full_pn);
 
    if (unprotect_result.is_err())
    {
        return;
    }
 
    auto& [unprotected_header, payload] = unprotect_result.value();
 
    // Parse frames from payload
    auto frames_result = frame_parser::parse_all(payload);
    if (frames_result.is_err())
    {
        return;
    }
 
    // Process each frame
    for (const auto& f : frames_result.value())
    {
        process_frame(f);
    }
 
    // Send any pending responses
    send_pending_packets();
}
 
auto quic_socket::process_frame(const frame& f) -> void
{
    std::visit([this](auto&& arg) {
        using T = std::decay_t<decltype(arg)>;
 
        if constexpr (std::is_same_v<T, crypto_frame>)
        {
            process_crypto_frame(arg);
        }
        else if constexpr (std::is_same_v<T, stream_frame>)
        {
            process_stream_frame(arg);
        }
        else if constexpr (std::is_same_v<T, ack_frame>)
        {
            process_ack_frame(arg);
        }
        else if constexpr (std::is_same_v<T, connection_close_frame>)
        {
            process_connection_close_frame(arg);
        }
        else if constexpr (std::is_same_v<T, handshake_done_frame>)
        {
            process_handshake_done_frame();
        }
        else if constexpr (std::is_same_v<T, ping_frame>)
        {
            // PING requires ACK - will be sent with next packet
        }
        else if constexpr (std::is_same_v<T, padding_frame>)
        {
            // PADDING is ignored
        }
        // Other frame types can be added as needed
    }, f);
}
 
auto quic_socket::process_crypto_frame(const crypto_frame& f) -> void
{
    auto level = crypto_.current_level();
 
    // Process the crypto data through TLS
    auto response_result = crypto_.process_crypto_data(level, f.data);
    if (response_result.is_err())
    {
        return;
    }
 
    // Queue any response crypto data
    if (!response_result.value().empty())
    {
        queue_crypto_data(std::move(response_result.value()));
    }
 
    // Check if handshake is now complete
    if (crypto_.is_handshake_complete() && !handshake_complete_.load())
    {
        handshake_complete_.store(true);
 
        // For client, transition to connected
        // For server, we send HANDSHAKE_DONE
        if (role_ == quic_role::client)
        {
            transition_state(quic_connection_state::connected);
 
            std::lock_guard<std::mutex> lock(callback_mutex_);
            if (connected_cb_)
            {
                connected_cb_();
            }
        }
        else
        {
            // Server sends HANDSHAKE_DONE
            std::vector<frame> frames;
            frames.push_back(handshake_done_frame{});
 
            (void)send_packet(encryption_level::application, std::move(frames));
 
            transition_state(quic_connection_state::connected);
 
            std::lock_guard<std::mutex> lock(callback_mutex_);
            if (connected_cb_)
            {
                connected_cb_();
            }
        }
    }
}
 
auto quic_socket::process_stream_frame(const stream_frame& f) -> void
{
    std::lock_guard<std::mutex> lock(callback_mutex_);
    if (stream_data_cb_)
    {
        stream_data_cb_(f.stream_id, f.data, f.fin);
    }
}
 
auto quic_socket::process_ack_frame(const ack_frame& f) -> void
{
    // Process ACK - remove acknowledged packets from retransmission queue
    // For now, just track the largest acknowledged
    (void)f;  // Placeholder for full implementation
}
 
auto quic_socket::process_connection_close_frame(const connection_close_frame& f) -> void
{
    transition_state(quic_connection_state::draining);
 
    std::lock_guard<std::mutex> lock(callback_mutex_);
    if (close_cb_)
    {
        close_cb_(f.error_code, f.reason_phrase);
    }
 
    // Enter draining period
    idle_timer_.expires_after(std::chrono::milliseconds(300));
    idle_timer_.async_wait(
        [self = shared_from_this()](const std::error_code& ec)
        {
            if (!ec)
            {
                self->transition_state(quic_connection_state::closed);
                self->stop_receive();
            }
        });
}
 
auto quic_socket::process_handshake_done_frame() -> void
{
    // Client receives HANDSHAKE_DONE
    if (role_ == quic_role::client && !handshake_complete_.load())
    {
        handshake_complete_.store(true);
        transition_state(quic_connection_state::connected);
 
        std::lock_guard<std::mutex> lock(callback_mutex_);
        if (connected_cb_)
        {
            connected_cb_();
        }
    }
}
 
auto quic_socket::send_pending_packets() -> void
{
    auto current_state = state_.load();
    if (current_state == quic_connection_state::closed ||
        current_state == quic_connection_state::idle)
    {
        return;
    }
 
    // Determine which encryption level to use
    encryption_level level = crypto_.current_level();
 
    std::vector<frame> frames;
 
    // Add pending CRYPTO data
    {
        std::lock_guard<std::mutex> lock(state_mutex_);
        auto level_idx = static_cast<size_t>(level);
        while (!pending_crypto_data_[level_idx].empty())
        {
            auto& data = pending_crypto_data_[level_idx].front();
            crypto_frame cf;
            cf.offset = 0;  // Simplified - full impl needs offset tracking
            cf.data = std::move(data);
            frames.push_back(std::move(cf));
            pending_crypto_data_[level_idx].pop_front();
        }
    }
 
    // Add pending STREAM data (only if connected)
    if (is_connected())
    {
        std::lock_guard<std::mutex> lock(state_mutex_);
        for (auto& [stream_id, queue] : pending_stream_data_)
        {
            while (!queue.empty())
            {
                auto& [data, fin] = queue.front();
                stream_frame sf;
                sf.stream_id = stream_id;
                sf.offset = 0;  // Simplified - full impl needs offset tracking
                sf.data = std::move(data);
                sf.fin = fin;
                frames.push_back(std::move(sf));
                queue.pop_front();
            }
        }
    }
 
    if (!frames.empty())
    {
        (void)send_packet(level, std::move(frames));
    }
}
 
auto quic_socket::send_packet(encryption_level level,
                              std::vector<frame>&& frames) -> VoidResult
{
    // Get write keys
    auto keys_result = crypto_.get_write_keys(level);
    if (keys_result.is_err())
    {
        return error_void(
            error_codes::common_errors::not_initialized,
            "Write keys not available",
            "quic_socket");
    }
 
    // Build frames payload
    std::vector<uint8_t> payload;
    for (const auto& f : frames)
    {
        auto frame_bytes = frame_builder::build(f);
        payload.insert(payload.end(), frame_bytes.begin(), frame_bytes.end());
    }
 
    // Get next packet number
    auto level_idx = static_cast<size_t>(level);
    uint64_t pn = next_packet_number_[level_idx]++;
 
    // Build header
    std::vector<uint8_t> header;
    if (level == encryption_level::initial)
    {
        header = packet_builder::build_initial(
            remote_conn_id_, local_conn_id_, {}, pn);
    }
    else if (level == encryption_level::handshake)
    {
        header = packet_builder::build_handshake(
            remote_conn_id_, local_conn_id_, pn);
    }
    else
    {
        header = packet_builder::build_short(
            remote_conn_id_, pn, crypto_.key_phase());
    }
 
    // Protect (encrypt) the packet
    auto protect_result = packet_protection::protect(
        keys_result.value(), header, payload, pn);
 
    if (protect_result.is_err())
    {
        return error_void(
            error_codes::common_errors::internal_error,
            "Failed to protect packet",
            "quic_socket",
            protect_result.error().message);
    }
 
    // Send the packet
    auto& protected_packet = protect_result.value();
 
    auto self = shared_from_this();
    auto buffer = std::make_shared<std::vector<uint8_t>>(std::move(protected_packet));
 
    udp_socket_.async_send_to(
        asio::buffer(*buffer),
        remote_endpoint_,
        [self, buffer](std::error_code ec, std::size_t /*bytes_sent*/)
        {
            if (ec && ec != asio::error::operation_aborted)
            {
                std::lock_guard<std::mutex> lock(self->callback_mutex_);
                if (self->error_cb_)
                {
                    self->error_cb_(ec);
                }
            }
        });
 
    return ok();
}
 
auto quic_socket::queue_crypto_data(std::vector<uint8_t>&& data) -> void
{
    auto level = crypto_.current_level();
    auto level_idx = static_cast<size_t>(level);
 
    std::lock_guard<std::mutex> lock(state_mutex_);
    pending_crypto_data_[level_idx].push_back(std::move(data));
}
 
auto quic_socket::determine_encryption_level(const packet_header& header) const noexcept
    -> encryption_level
{
    if (std::holds_alternative<long_header>(header))
    {
        const auto& lh = std::get<long_header>(header);
        switch (lh.type())
        {
            case packet_type::initial:
                return encryption_level::initial;
            case packet_type::zero_rtt:
                return encryption_level::zero_rtt;
            case packet_type::handshake:
                return encryption_level::handshake;
            default:
                return encryption_level::initial;
        }
    }
    else
    {
        // Short header = 1-RTT = application level
        return encryption_level::application;
    }
}
 
auto quic_socket::generate_connection_id() -> connection_id
{
    std::random_device rd;
    std::mt19937 gen(rd());
    std::uniform_int_distribution<unsigned int> dis(0, 255);
 
    std::array<uint8_t, 8> id_bytes;
    for (auto& byte : id_bytes)
    {
        byte = static_cast<uint8_t>(dis(gen));
    }
 
    return connection_id(std::span<const uint8_t>(id_bytes));
}
 
auto quic_socket::on_retransmit_timeout() -> void
{
    // Retransmission logic would go here
    // For now, just resend pending packets
    send_pending_packets();
}
 
auto quic_socket::transition_state(quic_connection_state new_state) -> void
{
    state_.store(new_state);
}
 
} // namespace kcenon::network::internal