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468 lines
12 KiB
Go
468 lines
12 KiB
Go
package webtransport
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import (
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"context"
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"encoding/binary"
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"io"
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"math/rand/v2"
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"net"
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"sync"
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"time"
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"unicode/utf8"
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"github.com/quic-go/quic-go"
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"github.com/quic-go/quic-go/http3"
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"github.com/quic-go/quic-go/quicvarint"
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)
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// sessionID is the WebTransport Session ID
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type sessionID uint64
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const closeSessionCapsuleType http3.CapsuleType = 0x2843
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const maxCloseCapsuleErrorMsgLen = 1024
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type acceptQueue[T any] struct {
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mx sync.Mutex
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// The channel is used to notify consumers (via Chan) about new incoming items.
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// Needs to be buffered to preserve the notification if an item is enqueued
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// between a call to Next and to Chan.
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c chan struct{}
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// Contains all the streams waiting to be accepted.
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// There's no explicit limit to the length of the queue, but it is implicitly
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// limited by the stream flow control provided by QUIC.
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queue []T
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}
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func newAcceptQueue[T any]() *acceptQueue[T] {
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return &acceptQueue[T]{c: make(chan struct{}, 1)}
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}
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func (q *acceptQueue[T]) Add(str T) {
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q.mx.Lock()
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q.queue = append(q.queue, str)
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q.mx.Unlock()
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select {
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case q.c <- struct{}{}:
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default:
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}
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}
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func (q *acceptQueue[T]) Next() T {
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q.mx.Lock()
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defer q.mx.Unlock()
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if len(q.queue) == 0 {
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return *new(T)
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}
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str := q.queue[0]
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q.queue = q.queue[1:]
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return str
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}
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func (q *acceptQueue[T]) Chan() <-chan struct{} { return q.c }
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type http3Stream interface {
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io.ReadWriteCloser
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ReceiveDatagram(context.Context) ([]byte, error)
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SendDatagram([]byte) error
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CancelRead(quic.StreamErrorCode)
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CancelWrite(quic.StreamErrorCode)
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SetWriteDeadline(time.Time) error
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}
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var (
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_ http3Stream = &http3.Stream{}
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_ http3Stream = &http3.RequestStream{}
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)
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// SessionState contains the state of a WebTransport session
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type SessionState struct {
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// ConnectionState contains the QUIC connection state, including TLS handshake information
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ConnectionState quic.ConnectionState
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// ApplicationProtocol contains the application protocol negotiated for the session
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ApplicationProtocol string
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}
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type Session struct {
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sessionID sessionID
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conn *quic.Conn
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str http3Stream
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applicationProtocol string
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streamHdr []byte
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uniStreamHdr []byte
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ctx context.Context
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closeMx sync.Mutex
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closeErr error // not nil once the session is closed
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// streamCtxs holds all the context.CancelFuncs of calls to Open{Uni}StreamSync calls currently active.
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// When the session is closed, this allows us to cancel all these contexts and make those calls return.
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streamCtxs map[int]context.CancelFunc
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bidiAcceptQueue acceptQueue[*Stream]
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uniAcceptQueue acceptQueue[*ReceiveStream]
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streams streamsMap
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}
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func newSession(ctx context.Context, sessionID sessionID, conn *quic.Conn, str http3Stream, applicationProtocol string) *Session {
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ctx, ctxCancel := context.WithCancel(ctx)
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c := &Session{
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sessionID: sessionID,
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conn: conn,
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str: str,
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applicationProtocol: applicationProtocol,
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ctx: ctx,
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streamCtxs: make(map[int]context.CancelFunc),
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bidiAcceptQueue: *newAcceptQueue[*Stream](),
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uniAcceptQueue: *newAcceptQueue[*ReceiveStream](),
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streams: *newStreamsMap(),
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}
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// precompute the headers for unidirectional streams
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c.uniStreamHdr = make([]byte, 0, 2+quicvarint.Len(uint64(c.sessionID)))
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c.uniStreamHdr = quicvarint.Append(c.uniStreamHdr, webTransportUniStreamType)
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c.uniStreamHdr = quicvarint.Append(c.uniStreamHdr, uint64(c.sessionID))
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// precompute the headers for bidirectional streams
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c.streamHdr = make([]byte, 0, 2+quicvarint.Len(uint64(c.sessionID)))
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c.streamHdr = quicvarint.Append(c.streamHdr, webTransportFrameType)
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c.streamHdr = quicvarint.Append(c.streamHdr, uint64(c.sessionID))
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go func() {
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defer ctxCancel()
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c.handleConn()
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}()
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return c
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}
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func (s *Session) handleConn() {
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err := s.parseNextCapsule()
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s.closeWithError(err)
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}
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// parseNextCapsule parses the next Capsule sent on the request stream.
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// It returns a SessionError, if the capsule received is a WT_CLOSE_SESSION Capsule.
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func (s *Session) parseNextCapsule() error {
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for {
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typ, r, err := http3.ParseCapsule(quicvarint.NewReader(s.str))
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if err != nil {
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return err
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}
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switch typ {
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case closeSessionCapsuleType:
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var b [4]byte
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if _, err := io.ReadFull(r, b[:]); err != nil {
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return err
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}
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appErrCode := binary.BigEndian.Uint32(b[:])
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// the length of the error message is limited to 1024 bytes
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appErrMsg, err := io.ReadAll(io.LimitReader(r, maxCloseCapsuleErrorMsgLen))
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if err != nil {
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return err
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}
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return &SessionError{
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Remote: true,
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ErrorCode: SessionErrorCode(appErrCode),
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Message: string(appErrMsg),
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}
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default:
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// unknown capsule, skip it
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if _, err := io.ReadAll(r); err != nil {
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return err
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}
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}
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}
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}
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func (s *Session) addStream(qstr *quic.Stream, addStreamHeader bool) *Stream {
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var hdr []byte
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if addStreamHeader {
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hdr = s.streamHdr
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}
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str := newStream(qstr, hdr, func() { s.streams.RemoveStream(qstr.StreamID()) })
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s.streams.AddStream(qstr.StreamID(), str.closeWithSession)
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return str
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}
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func (s *Session) addReceiveStream(qstr *quic.ReceiveStream) *ReceiveStream {
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str := newReceiveStream(qstr, func() { s.streams.RemoveStream(qstr.StreamID()) })
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s.streams.AddStream(qstr.StreamID(), str.closeWithSession)
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return str
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}
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func (s *Session) addSendStream(qstr *quic.SendStream) *SendStream {
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str := newSendStream(qstr, s.uniStreamHdr, func() { s.streams.RemoveStream(qstr.StreamID()) })
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s.streams.AddStream(qstr.StreamID(), str.closeWithSession)
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return str
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}
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// addIncomingStream adds a bidirectional stream that the remote peer opened
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func (s *Session) addIncomingStream(qstr *quic.Stream) {
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s.closeMx.Lock()
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closeErr := s.closeErr
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if closeErr != nil {
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s.closeMx.Unlock()
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qstr.CancelRead(WTSessionGoneErrorCode)
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qstr.CancelWrite(WTSessionGoneErrorCode)
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return
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}
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str := s.addStream(qstr, false)
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s.closeMx.Unlock()
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s.bidiAcceptQueue.Add(str)
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}
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// addIncomingUniStream adds a unidirectional stream that the remote peer opened
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func (s *Session) addIncomingUniStream(qstr *quic.ReceiveStream) {
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s.closeMx.Lock()
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closeErr := s.closeErr
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if closeErr != nil {
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s.closeMx.Unlock()
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qstr.CancelRead(WTSessionGoneErrorCode)
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return
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}
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str := s.addReceiveStream(qstr)
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s.closeMx.Unlock()
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s.uniAcceptQueue.Add(str)
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}
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// Context returns a context that is closed when the session is closed.
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func (s *Session) Context() context.Context {
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return s.ctx
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}
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func (s *Session) AcceptStream(ctx context.Context) (*Stream, error) {
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s.closeMx.Lock()
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closeErr := s.closeErr
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s.closeMx.Unlock()
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if closeErr != nil {
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return nil, closeErr
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}
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for {
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// If there's a stream in the accept queue, return it immediately.
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if str := s.bidiAcceptQueue.Next(); str != nil {
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return str, nil
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}
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// No stream in the accept queue. Wait until we accept one.
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select {
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case <-s.ctx.Done():
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return nil, s.closeErr
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case <-ctx.Done():
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return nil, ctx.Err()
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case <-s.bidiAcceptQueue.Chan():
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}
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}
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}
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func (s *Session) AcceptUniStream(ctx context.Context) (*ReceiveStream, error) {
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s.closeMx.Lock()
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closeErr := s.closeErr
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s.closeMx.Unlock()
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if closeErr != nil {
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return nil, s.closeErr
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}
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for {
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// If there's a stream in the accept queue, return it immediately.
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if str := s.uniAcceptQueue.Next(); str != nil {
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return str, nil
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}
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// No stream in the accept queue. Wait until we accept one.
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select {
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case <-s.ctx.Done():
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return nil, s.closeErr
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case <-ctx.Done():
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return nil, ctx.Err()
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case <-s.uniAcceptQueue.Chan():
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}
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}
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}
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func (s *Session) OpenStream() (*Stream, error) {
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s.closeMx.Lock()
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defer s.closeMx.Unlock()
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if s.closeErr != nil {
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return nil, s.closeErr
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}
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qstr, err := s.conn.OpenStream()
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if err != nil {
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return nil, err
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}
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return s.addStream(qstr, true), nil
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}
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func (s *Session) addStreamCtxCancel(cancel context.CancelFunc) (id int) {
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rand:
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id = rand.Int()
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if _, ok := s.streamCtxs[id]; ok {
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goto rand
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}
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s.streamCtxs[id] = cancel
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return id
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}
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func (s *Session) OpenStreamSync(ctx context.Context) (*Stream, error) {
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s.closeMx.Lock()
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if s.closeErr != nil {
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s.closeMx.Unlock()
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return nil, s.closeErr
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}
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ctx, cancel := context.WithCancel(ctx)
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id := s.addStreamCtxCancel(cancel)
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s.closeMx.Unlock()
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// open a new bidirectional stream without holding the mutex: this call might block
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qstr, err := s.conn.OpenStreamSync(ctx)
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s.closeMx.Lock()
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defer s.closeMx.Unlock()
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delete(s.streamCtxs, id)
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// the session might have been closed concurrently with OpenStreamSync returning
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if qstr != nil && s.closeErr != nil {
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qstr.CancelRead(WTSessionGoneErrorCode)
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qstr.CancelWrite(WTSessionGoneErrorCode)
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return nil, s.closeErr
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}
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if err != nil {
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if s.closeErr != nil {
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return nil, s.closeErr
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}
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return nil, err
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}
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return s.addStream(qstr, true), nil
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}
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func (s *Session) OpenUniStream() (*SendStream, error) {
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s.closeMx.Lock()
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defer s.closeMx.Unlock()
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if s.closeErr != nil {
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return nil, s.closeErr
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}
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qstr, err := s.conn.OpenUniStream()
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if err != nil {
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return nil, err
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}
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return s.addSendStream(qstr), nil
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}
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func (s *Session) OpenUniStreamSync(ctx context.Context) (str *SendStream, err error) {
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s.closeMx.Lock()
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if s.closeErr != nil {
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s.closeMx.Unlock()
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return nil, s.closeErr
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}
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ctx, cancel := context.WithCancel(ctx)
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id := s.addStreamCtxCancel(cancel)
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s.closeMx.Unlock()
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// open a new unidirectional stream without holding the mutex: this call might block
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qstr, err := s.conn.OpenUniStreamSync(ctx)
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s.closeMx.Lock()
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defer s.closeMx.Unlock()
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delete(s.streamCtxs, id)
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// the session might have been closed concurrently with OpenStreamSync returning
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if qstr != nil && s.closeErr != nil {
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qstr.CancelWrite(WTSessionGoneErrorCode)
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return nil, s.closeErr
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}
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if err != nil {
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if s.closeErr != nil {
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return nil, s.closeErr
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}
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return nil, err
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}
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return s.addSendStream(qstr), nil
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}
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func (s *Session) LocalAddr() net.Addr {
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return s.conn.LocalAddr()
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}
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func (s *Session) RemoteAddr() net.Addr {
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return s.conn.RemoteAddr()
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}
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func (s *Session) CloseWithError(code SessionErrorCode, msg string) error {
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first, err := s.closeWithError(&SessionError{ErrorCode: code, Message: msg})
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if err != nil || !first {
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return err
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}
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// truncate the message if it's too long
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if len(msg) > maxCloseCapsuleErrorMsgLen {
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msg = truncateUTF8(msg, maxCloseCapsuleErrorMsgLen)
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}
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b := make([]byte, 4, 4+len(msg))
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binary.BigEndian.PutUint32(b, uint32(code))
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b = append(b, []byte(msg)...)
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// Optimistically send the WT_CLOSE_SESSION Capsule:
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// If we're flow-control limited, we don't want to wait for the receiver to issue new flow control credits.
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// There's no idiomatic way to do a non-blocking write in Go, so we set a short deadline.
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s.str.SetWriteDeadline(time.Now().Add(10 * time.Millisecond))
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if err := http3.WriteCapsule(quicvarint.NewWriter(s.str), closeSessionCapsuleType, b); err != nil {
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s.str.CancelWrite(WTSessionGoneErrorCode)
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}
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s.str.CancelRead(WTSessionGoneErrorCode)
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err = s.str.Close()
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<-s.ctx.Done()
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return err
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}
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func (s *Session) SendDatagram(b []byte) error {
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return s.str.SendDatagram(b)
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}
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func (s *Session) ReceiveDatagram(ctx context.Context) ([]byte, error) {
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return s.str.ReceiveDatagram(ctx)
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}
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func (s *Session) closeWithError(closeErr error) (bool /* first call to close session */, error) {
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s.closeMx.Lock()
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defer s.closeMx.Unlock()
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// Duplicate call, or the remote already closed this session.
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if s.closeErr != nil {
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return false, nil
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}
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s.closeErr = closeErr
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for _, cancel := range s.streamCtxs {
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cancel()
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}
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s.streams.CloseSession(closeErr)
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return true, nil
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}
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// SessionState returns the current state of the session
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func (s *Session) SessionState() SessionState {
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return SessionState{
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ConnectionState: s.conn.ConnectionState(),
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ApplicationProtocol: s.applicationProtocol,
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}
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}
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// truncateUTF8 cuts a string to max n bytes without breaking UTF-8 characters.
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func truncateUTF8(s string, n int) string {
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if len(s) <= n {
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return s
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}
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for n > 0 && !utf8.RuneStart(s[n]) {
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n--
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}
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return s[:n]
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}
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