lokinet/llarp/quic/tunnel.cpp

#include "tunnel.hpp"
#include "log.hpp"
#include "stream.hpp"

namespace llarp::quic::tunnel
{
  // Takes data from the tcp connection and pushes it down the quic tunnel
  void
  on_outgoing_data(uvw::DataEvent& event, uvw::TCPHandle& client)
  {
    auto stream = client.data<llarp::quic::Stream>();
    assert(stream);
    std::string_view data{event.data.get(), event.length};
    auto peer = client.peer();
    llarp::quic::Debug(peer.ip, ":", peer.port, " → lokinet ", llarp::quic::buffer_printer{data});
    // Steal the buffer from the DataEvent's unique_ptr<char[]>:
    stream->append_buffer(reinterpret_cast<const std::byte*>(event.data.release()), event.length);
    if (stream->used() >= PAUSE_SIZE)
    {
      llarp::quic::Debug(
          "quic tunnel is congested (have ",
          stream->used(),
          " bytes in flight); pausing local tcp connection reads");
      client.stop();
      stream->when_available([](llarp::quic::Stream& s) {
        auto client = s.data<uvw::TCPHandle>();
        if (s.used() < PAUSE_SIZE)
        {
          llarp::quic::Debug("quic tunnel is no longer congested; resuming tcp connection reading");
          client->read();
          return true;
        }
        return false;
      });
    }
    else
    {
      llarp::quic::Debug("Queued ", event.length, " bytes");
    }
  }

  // Received data from the quic tunnel and sends it to the TCP connection
  void
  on_incoming_data(llarp::quic::Stream& stream, llarp::quic::bstring_view bdata)
  {
    auto tcp = stream.data<uvw::TCPHandle>();
    assert(tcp);
    std::string_view data{reinterpret_cast<const char*>(bdata.data()), bdata.size()};
    auto peer = tcp->peer();
    llarp::quic::Debug(peer.ip, ":", peer.port, " ← lokinet ", llarp::quic::buffer_printer{data});

    if (data.empty())
      return;

    // Try first to write immediately from the existing buffer to avoid needing an
    // allocation and copy:
    auto written = tcp->tryWrite(const_cast<char*>(data.data()), data.size());
    if (written < (int)data.size())
    {
      data.remove_prefix(written);

      auto wdata = std::make_unique<char[]>(data.size());
      std::copy(data.begin(), data.end(), wdata.get());
      tcp->write(std::move(wdata), data.size());
    }
  }

  void
  install_stream_forwarding(uvw::TCPHandle& tcp, llarp::quic::Stream& stream)
  {
    tcp.data(stream.shared_from_this());
    stream.weak_data(tcp.weak_from_this());

    tcp.on<uvw::CloseEvent>([](auto&, uvw::TCPHandle& c) {
      // This fires sometime after we call `close()` to signal that the close is done.
      llarp::quic::Error(
          "Connection with ",
          c.peer().ip,
          ":",
          c.peer().port,
          " closed directly, closing quic stream");
      c.data<llarp::quic::Stream>()->close();
    });
    tcp.on<uvw::EndEvent>([](auto&, uvw::TCPHandle& c) {
      // This fires on eof, most likely because the other side of the TCP connection closed it.
      llarp::quic::Error(
          "EOF on connection with ", c.peer().ip, ":", c.peer().port, ", closing quic stream");
      c.data<llarp::quic::Stream>()->close();
    });
    tcp.on<uvw::ErrorEvent>([](const uvw::ErrorEvent& e, uvw::TCPHandle& tcp) {
      llarp::quic::Error(
          "ErrorEvent[",
          e.name(),
          ": ",
          e.what(),
          "] on connection with ",
          tcp.peer().ip,
          ":",
          tcp.peer().port,
          ", shutting down quic stream");
      // Failed to open connection, so close the quic stream
      auto stream = tcp.data<llarp::quic::Stream>();
      if (stream)
        stream->close(ERROR_TCP);
      tcp.close();
    });
    tcp.on<uvw::DataEvent>(tunnel::on_outgoing_data);
    stream.data_callback = on_incoming_data;
  }

}  // namespace tunnel