OpenVPNAdapter/openvpn/tun/win/client/wintun.hpp

#pragma once

#include <openvpn/tun/client/tunbase.hpp>
#include <openvpn/tun/persist/tunpersist.hpp>
#include <openvpn/tun/win/client/setupbase.hpp>
#include <openvpn/tun/win/client/clientconfig.hpp>
#include <openvpn/win/modname.hpp>

namespace openvpn {
  namespace TunWin {

    class WintunClient : public TunClient
    {
      typedef RCPtr<WintunClient> Ptr;

    public:
      WintunClient(openvpn_io::io_context& io_context_arg,
		   ClientConfig* config_arg,
		   TunClientParent& parent_arg)
	: io_context(io_context_arg),
	  config(config_arg),
	  parent(parent_arg),
	  state(new TunProp::State()),
	  frame(config_arg->frame)
      {
      }

      // Inherited via TunClient
      void tun_start(const OptionList& opt, TransportClient& transcli, CryptoDCSettings&) override
      {
	halt = false;
	if (config->tun_persist)
	  tun_persist = config->tun_persist; // long-term persistent
	else
	  tun_persist.reset(new TunPersist(false, false, nullptr)); // short-term

	try {

	  const IP::Addr server_addr = transcli.server_endpoint_addr();

	  // Check if persisted tun session matches properties of to-be-created session
	  if (tun_persist->use_persisted_tun(server_addr, config->tun_prop, opt))
	    {
	      state = tun_persist->state().state;
	      ring_buffer = tun_persist->state().ring_buffer;
	      OPENVPN_LOG("TunPersist: reused tun context");
	    }
	  else
	    {
	      // notify parent
	      parent.tun_pre_tun_config();

	      // close old TAP handle if persisted
	      tun_persist->close();

	      // parse pushed options
	      TunBuilderCapture::Ptr po(new TunBuilderCapture());
	      TunProp::configure_builder(po.get(),
					 state.get(),
					 config->stats.get(),
					 server_addr,
					 config->tun_prop,
					 opt,
					 nullptr,
					 false);
	      OPENVPN_LOG("CAPTURED OPTIONS:" << std::endl << po->to_string());

	      // create new tun setup object
	      tun_setup = config->new_setup_obj(io_context);

	      ring_buffer.reset(new RingBuffer(io_context));

	      // open/config TAP
	      HANDLE th;
	      {
		std::ostringstream os;
		auto os_print = Cleanup([&os]() { OPENVPN_LOG_STRING(os.str()); });
		th = tun_setup->establish(*po, Win::module_name(), config->stop, os, ring_buffer);
	      }

	      // create ASIO wrapper for HANDLE
	      TAPStream* ts = new TAPStream(io_context, th);

	      // persist tun settings state
	      if (tun_persist->persist_tun_state(ts, { state, ring_buffer }))
		OPENVPN_LOG("TunPersist: saving tun context:" << std::endl << tun_persist->options());

	      // enable tun_setup destructor
	      tun_persist->add_destructor(tun_setup);

	      // assert ownership over TAP device handle
	      tun_setup->confirm();
	    }

	  openvpn_io::post(io_context, [self=Ptr(this)](){
	    self->read();
	  });

	  parent.tun_connected(); // signal that we are connected
	}
	catch (const std::exception& e)
	  {
	    stop();
	    Error::Type err = Error::TUN_SETUP_FAILED;
	    const ExceptionCode* ec = dynamic_cast<const ExceptionCode*>(&e);
	    if (ec && ec->code_defined())
	      err = ec->code();
	    parent.tun_error(err, e.what());
	  }
      }

      void stop() override
      {
	if (!halt)
	  {
	    halt = true;

	    tun_persist.reset();
	  }
      }

      void set_disconnect() override
      {

      }

      bool tun_send(BufferAllocated& buf) override
      {
	TUN_RING* receive_ring = ring_buffer->receive_ring();

	ULONG head = receive_ring->head.load(std::memory_order_acquire);
	if (head > WINTUN_RING_CAPACITY)
	  {
	    if (head == 0xFFFFFFFF)
	      parent.tun_error(Error::TUN_WRITE_ERROR, "invalid ring head/tail or bogus packet received");
	    return false;
	  }

	ULONG tail = receive_ring->tail.load(std::memory_order_acquire);
	if (tail >= WINTUN_RING_CAPACITY)
	  return false;

	ULONG aligned_packet_size = packet_align(sizeof(TUN_PACKET_HEADER) + buf.size());
	ULONG buf_space = wrap(head - tail - WINTUN_PACKET_ALIGN);
	if (aligned_packet_size > buf_space)
	  {
	    OPENVPN_LOG("ring is full");
	    return false;
	  }

	// copy packet size and data into ring
	TUN_PACKET* packet = (TUN_PACKET*)& receive_ring->data[tail];
	packet->size = buf.size();
	std::memcpy(packet->data, buf.data(), buf.size());

	// move ring tail
	receive_ring->tail.store(wrap(tail + aligned_packet_size), std::memory_order_release);
	if (receive_ring->alertable.load(std::memory_order_acquire) != 0)
	  SetEvent(ring_buffer->receive_ring_tail_moved());

	return true;
      }

      std::string tun_name() const override
      {
	return "wintun";
      }

      std::string vpn_ip4() const override
      {
	if (state->vpn_ip4_addr.specified())
	  return state->vpn_ip4_addr.to_string();
	else
	  return "";
      }

      std::string vpn_ip6() const override
      {
	if (state->vpn_ip6_addr.specified())
	  return state->vpn_ip6_addr.to_string();
	else
	  return "";
      }

      std::string vpn_gw4() const override
      {
	if (state->vpn_ip4_gw.specified())
	  return state->vpn_ip4_gw.to_string();
	else
	  return "";
      }

      std::string vpn_gw6() const override
      {
	if (state->vpn_ip6_gw.specified())
	  return state->vpn_ip6_gw.to_string();
	else
	  return "";
      }

    private:
      void read()
      {
	TUN_RING* send_ring = ring_buffer->send_ring();

	if (halt)
	  return;

	ULONG head = send_ring->head.load(std::memory_order_acquire);
	if (head >= WINTUN_RING_CAPACITY)
	  {
	    parent.tun_error(Error::TUN_ERROR, "ring head exceeds ring capacity");
	    return;
	  }

	ULONG tail = send_ring->tail.load(std::memory_order_acquire);
	if (tail >= WINTUN_RING_CAPACITY)
	  {
	    parent.tun_error(Error::TUN_ERROR, "ring tail exceeds ring capacity");
	    return;
	  }

	while (true)
	  {
	    // tail has moved?
	    if (head == tail)
	      {
		ring_buffer->send_tail_moved_asio_event().async_wait([self = Ptr(this)](const openvpn_io::error_code& error) {
		  if (!error)
		    self->read();
		  else
		    {
		      if (!self->halt)
			self->parent.tun_error(Error::TUN_ERROR, "error waiting on ring send tail moved");
		    }
		});
		return;
	      }

	    // read buffer content
	    ULONG content_len = wrap(tail - head);
	    if (content_len < sizeof(TUN_PACKET_HEADER))
	      {
		parent.tun_error(Error::TUN_ERROR, "incomplete packet header in send ring");
		return;
	      }

	    TUN_PACKET* packet = (TUN_PACKET *)&send_ring->data[head];
	    if (packet->size > WINTUN_MAX_PACKET_SIZE)
	      {
		parent.tun_error(Error::TUN_ERROR, "packet too big in send ring");
		return;
	      }

	    ULONG aligned_packet_size = packet_align(sizeof(TUN_PACKET_HEADER) + packet->size);
	    if (aligned_packet_size > content_len)
	      {
		parent.tun_error(Error::TUN_ERROR, "incomplete packet in send ring");
		return;
	      }

	    frame->prepare(Frame::READ_TUN, buf);

	    buf.write(packet->data, packet->size);

	    head = wrap(head + aligned_packet_size);
	    send_ring->head.store(head, std::memory_order_release);

	    parent.tun_recv(buf);

	    if (halt)
	      return;
	  }
      }

      struct TUN_PACKET_HEADER
      {
	uint32_t size;
      };

      struct TUN_PACKET
      {
	uint32_t size;
	UCHAR data[WINTUN_MAX_PACKET_SIZE];
      };

      ULONG packet_align(ULONG size)
      {
	return (size + (WINTUN_PACKET_ALIGN - 1)) & ~(WINTUN_PACKET_ALIGN - 1);
      }

      ULONG wrap(ULONG value)
      {
	return value & (WINTUN_RING_CAPACITY - 1);
      }

      openvpn_io::io_context& io_context;
      TunPersist::Ptr tun_persist; // contains the TAP device HANDLE
      ClientConfig::Ptr config;
      TunClientParent& parent;
      TunProp::State::Ptr state;
      TunWin::SetupBase::Ptr tun_setup;

      TUN_RING* receive_ring = nullptr;
      TUN_RING* send_ring = nullptr;

      BufferAllocated buf;

      Frame::Ptr frame;

      bool halt = false;

      ScopedHANDLE driver_handle;

      RingBuffer::Ptr ring_buffer;
    };
  }
}