mirror of
https://source.quilibrium.com/quilibrium/ceremonyclient.git
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282 lines
8.5 KiB
Go
282 lines
8.5 KiB
Go
package libp2pwebrtc
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import (
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"errors"
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"os"
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"sync"
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"time"
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"github.com/libp2p/go-libp2p/core/network"
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"github.com/libp2p/go-libp2p/p2p/transport/webrtc/pb"
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"github.com/libp2p/go-msgio/pbio"
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"github.com/pion/datachannel"
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"github.com/pion/webrtc/v3"
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)
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const (
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// maxMessageSize is the maximum message size of the Protobuf message we send / receive.
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maxMessageSize = 16384
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// maxSendBuffer is the maximum data we enqueue on the underlying data channel for writes.
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// The underlying SCTP layer has an unbounded buffer for writes. We limit the amount enqueued
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// per stream is limited to avoid a single stream monopolizing the entire connection.
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maxSendBuffer = 2 * maxMessageSize
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// sendBufferLowThreshold is the threshold below which we write more data on the underlying
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// data channel. We want a notification as soon as we can write 1 full sized message.
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sendBufferLowThreshold = maxSendBuffer - maxMessageSize
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// maxTotalControlMessagesSize is the maximum total size of all control messages we will
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// write on this stream.
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// 4 control messages of size 10 bytes + 10 bytes buffer. This number doesn't need to be
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// exact. In the worst case, we enqueue these many bytes more in the webrtc peer connection
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// send queue.
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maxTotalControlMessagesSize = 50
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// Proto overhead assumption is 5 bytes
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protoOverhead = 5
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// Varint overhead is assumed to be 2 bytes. This is safe since
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// 1. This is only used and when writing message, and
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// 2. We only send messages in chunks of `maxMessageSize - varintOverhead`
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// which includes the data and the protobuf header. Since `maxMessageSize`
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// is less than or equal to 2 ^ 14, the varint will not be more than
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// 2 bytes in length.
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varintOverhead = 2
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// maxFINACKWait is the maximum amount of time a stream will wait to read
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// FIN_ACK before closing the data channel
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maxFINACKWait = 10 * time.Second
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)
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type receiveState uint8
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const (
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receiveStateReceiving receiveState = iota
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receiveStateDataRead // received and read the FIN
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receiveStateReset // either by calling CloseRead locally, or by receiving
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)
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type sendState uint8
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const (
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sendStateSending sendState = iota
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sendStateDataSent
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sendStateDataReceived
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sendStateReset
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)
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// Package pion detached data channel into a net.Conn
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// and then a network.MuxedStream
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type stream struct {
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mx sync.Mutex
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// readerMx ensures that only a single goroutine reads from the reader. Read is not threadsafe
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// But we may need to read from reader for control messages from a different goroutine.
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readerMx sync.Mutex
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reader pbio.Reader
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// this buffer is limited up to a single message. Reason we need it
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// is because a reader might read a message midway, and so we need a
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// wait to buffer that for as long as the remaining part is not (yet) read
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nextMessage *pb.Message
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receiveState receiveState
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writer pbio.Writer // concurrent writes prevented by mx
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writeStateChanged chan struct{}
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sendState sendState
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writeDeadline time.Time
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controlMessageReaderOnce sync.Once
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// controlMessageReaderEndTime is the end time for reading FIN_ACK from the control
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// message reader. We cannot rely on SetReadDeadline to do this since that is prone to
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// race condition where a previous deadline timer fires after the latest call to
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// SetReadDeadline
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// See: https://github.com/pion/sctp/pull/290
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controlMessageReaderEndTime time.Time
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onDoneOnce sync.Once
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onDone func()
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id uint16 // for logging purposes
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dataChannel *datachannel.DataChannel
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closeForShutdownErr error
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}
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var _ network.MuxedStream = &stream{}
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func newStream(
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channel *webrtc.DataChannel,
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rwc datachannel.ReadWriteCloser,
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onDone func(),
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) *stream {
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s := &stream{
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reader: pbio.NewDelimitedReader(rwc, maxMessageSize),
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writer: pbio.NewDelimitedWriter(rwc),
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writeStateChanged: make(chan struct{}, 1),
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id: *channel.ID(),
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dataChannel: rwc.(*datachannel.DataChannel),
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onDone: onDone,
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}
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s.dataChannel.SetBufferedAmountLowThreshold(sendBufferLowThreshold)
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s.dataChannel.OnBufferedAmountLow(func() {
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s.notifyWriteStateChanged()
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})
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return s
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}
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func (s *stream) Close() error {
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s.mx.Lock()
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isClosed := s.closeForShutdownErr != nil
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s.mx.Unlock()
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if isClosed {
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return nil
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}
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defer s.cleanup()
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closeWriteErr := s.CloseWrite()
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closeReadErr := s.CloseRead()
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if closeWriteErr != nil || closeReadErr != nil {
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s.Reset()
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return errors.Join(closeWriteErr, closeReadErr)
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}
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s.mx.Lock()
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if s.controlMessageReaderEndTime.IsZero() {
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s.controlMessageReaderEndTime = time.Now().Add(maxFINACKWait)
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s.setDataChannelReadDeadline(time.Now().Add(-1 * time.Hour))
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}
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s.mx.Unlock()
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return nil
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}
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func (s *stream) Reset() error {
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s.mx.Lock()
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isClosed := s.closeForShutdownErr != nil
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s.mx.Unlock()
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if isClosed {
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return nil
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}
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defer s.cleanup()
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cancelWriteErr := s.cancelWrite()
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closeReadErr := s.CloseRead()
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s.setDataChannelReadDeadline(time.Now().Add(-1 * time.Hour))
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return errors.Join(closeReadErr, cancelWriteErr)
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}
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func (s *stream) closeForShutdown(closeErr error) {
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defer s.cleanup()
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s.mx.Lock()
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defer s.mx.Unlock()
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s.closeForShutdownErr = closeErr
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s.notifyWriteStateChanged()
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}
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func (s *stream) SetDeadline(t time.Time) error {
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_ = s.SetReadDeadline(t)
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return s.SetWriteDeadline(t)
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}
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// processIncomingFlag process the flag on an incoming message
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// It needs to be called while the mutex is locked.
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func (s *stream) processIncomingFlag(flag *pb.Message_Flag) {
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if flag == nil {
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return
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}
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switch *flag {
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case pb.Message_STOP_SENDING:
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// We must process STOP_SENDING after sending a FIN(sendStateDataSent). Remote peer
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// may not send a FIN_ACK once it has sent a STOP_SENDING
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if s.sendState == sendStateSending || s.sendState == sendStateDataSent {
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s.sendState = sendStateReset
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}
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s.notifyWriteStateChanged()
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case pb.Message_FIN_ACK:
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s.sendState = sendStateDataReceived
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s.notifyWriteStateChanged()
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case pb.Message_FIN:
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if s.receiveState == receiveStateReceiving {
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s.receiveState = receiveStateDataRead
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}
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if err := s.writer.WriteMsg(&pb.Message{Flag: pb.Message_FIN_ACK.Enum()}); err != nil {
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log.Debugf("failed to send FIN_ACK: %s", err)
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// Remote has finished writing all the data It'll stop waiting for the
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// FIN_ACK eventually or will be notified when we close the datachannel
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}
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s.spawnControlMessageReader()
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case pb.Message_RESET:
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if s.receiveState == receiveStateReceiving {
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s.receiveState = receiveStateReset
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}
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s.spawnControlMessageReader()
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}
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}
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// spawnControlMessageReader is used for processing control messages after the reader is closed.
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func (s *stream) spawnControlMessageReader() {
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s.controlMessageReaderOnce.Do(func() {
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// Spawn a goroutine to ensure that we're not holding any locks
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go func() {
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// cleanup the sctp deadline timer goroutine
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defer s.setDataChannelReadDeadline(time.Time{})
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defer s.dataChannel.Close()
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// Unblock any Read call waiting on reader.ReadMsg
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s.setDataChannelReadDeadline(time.Now().Add(-1 * time.Hour))
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s.readerMx.Lock()
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// We have the lock: any readers blocked on reader.ReadMsg have exited.
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s.mx.Lock()
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defer s.mx.Unlock()
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// From this point onwards only this goroutine will do reader.ReadMsg.
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// We just wanted to ensure any exising readers have exited.
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// Read calls from this point onwards will exit immediately on checking
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// s.readState
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s.readerMx.Unlock()
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if s.nextMessage != nil {
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s.processIncomingFlag(s.nextMessage.Flag)
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s.nextMessage = nil
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}
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var msg pb.Message
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for {
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// Connection closed. No need to cleanup the data channel.
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if s.closeForShutdownErr != nil {
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return
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}
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// Write half of the stream completed.
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if s.sendState == sendStateDataReceived || s.sendState == sendStateReset {
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return
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}
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// FIN_ACK wait deadling exceeded.
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if !s.controlMessageReaderEndTime.IsZero() && time.Now().After(s.controlMessageReaderEndTime) {
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return
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}
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s.setDataChannelReadDeadline(s.controlMessageReaderEndTime)
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s.mx.Unlock()
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err := s.reader.ReadMsg(&msg)
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s.mx.Lock()
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if err != nil {
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// We have to manually manage deadline exceeded errors since pion/sctp can
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// return deadline exceeded error for cancelled deadlines
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// see: https://github.com/pion/sctp/pull/290/files
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if errors.Is(err, os.ErrDeadlineExceeded) {
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continue
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}
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return
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}
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s.processIncomingFlag(msg.Flag)
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}
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}()
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})
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}
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func (s *stream) cleanup() {
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s.onDoneOnce.Do(func() {
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if s.onDone != nil {
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s.onDone()
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}
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})
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}
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