targets/host/system_rpc_server.cc

// Copyright 2020 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.

#include <cstddef>
#include <cstdint>
#include <cstdio>

#include "pw_assert/check.h"
#include "pw_hdlc/encoded_size.h"
#include "pw_hdlc/rpc_channel.h"
#include "pw_hdlc/rpc_packets.h"
#include "pw_log/log.h"
#include "pw_rpc_system_server/rpc_server.h"
#include "pw_stream/socket_stream.h"

namespace pw::rpc::system_server {
namespace {

// Hard-coded to 1055 bytes, which is enough to fit 512-byte payloads when using
// HDLC framing.
constexpr size_t kMaxTransmissionUnit = 1055;
uint16_t socket_port = 33000;

static_assert(kMaxTransmissionUnit ==
              hdlc::MaxEncodedFrameSize(rpc::cfg::kEncodingBufferSizeBytes));

stream::SocketStream socket_stream;

hdlc::FixedMtuChannelOutput<kMaxTransmissionUnit> hdlc_channel_output(
    socket_stream, hdlc::kDefaultRpcAddress, "HDLC channel");
Channel channels[] = {rpc::Channel::Create<1>(&hdlc_channel_output)};
rpc::Server server(channels);

}  // namespace

void set_socket_port(uint16_t new_socket_port) {
  socket_port = new_socket_port;
}

int GetServerSocketFd() { return socket_stream.connection_fd(); }

void Init() {
  log_basic::SetOutput([](std::string_view log) {
    std::fprintf(stderr, "%.*s\n", static_cast<int>(log.size()), log.data());
    hdlc::WriteUIFrame(1, as_bytes(span(log)), socket_stream)
        .IgnoreError();  // TODO(b/242598609): Handle Status properly
  });

  PW_LOG_INFO("Starting pw_rpc server on port %d", socket_port);
  PW_CHECK_OK(socket_stream.Serve(socket_port));
}

rpc::Server& Server() { return server; }

Status Start() {
  constexpr size_t kDecoderBufferSize =
      hdlc::Decoder::RequiredBufferSizeForFrameSize(kMaxTransmissionUnit);
  // Declare a buffer for decoding incoming HDLC frames.
  std::array<std::byte, kDecoderBufferSize> input_buffer;
  hdlc::Decoder decoder(input_buffer);

  while (true) {
    std::array<std::byte, kMaxTransmissionUnit> data;
    auto ret_val = socket_stream.Read(data);
    if (!ret_val.ok()) {
      if (ret_val.status() == Status::OutOfRange()) {
        // An out of range status indicates the remote end has disconnected.
        return OkStatus();
      }
      continue;
    }

    for (std::byte byte : ret_val.value()) {
      auto result = decoder.Process(byte);
      if (!result.ok()) {
        // Non-OK means there isn't a complete packet yet, or there was some
        // other issue. Wait for more bytes that form a complete packet.
        continue;
      }
      hdlc::Frame& frame = result.value();
      if (frame.address() != hdlc::kDefaultRpcAddress) {
        // Wrong address; ignore the packet for now. In the future, this branch
        // could expand to add packet routing or metrics.
        continue;
      }

      server.ProcessPacket(frame.data()).IgnoreError();
    }
  }
}

}  // namespace pw::rpc::system_server