119 lines
3.6 KiB
Go
119 lines
3.6 KiB
Go
package datagramsession
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import (
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"context"
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"io"
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"time"
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"github.com/google/uuid"
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)
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const (
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defaultCloseIdleAfter = time.Second * 210
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)
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// Each Session is a bidirectional pipe of datagrams between transport and dstConn
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// Currently the only implementation of transport is quic DatagramMuxer
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// Destination can be a connection with origin or with eyeball
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// When the destination is origin:
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// - Datagrams from edge are read by Manager from the transport. Manager finds the corresponding Session and calls the
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// write method of the Session to send to origin
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// - Datagrams from origin are read from conn and SentTo transport. Transport will return them to eyeball
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// When the destination is eyeball:
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// - Datagrams from eyeball are read from conn and SentTo transport. Transport will send them to cloudflared
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// - Datagrams from cloudflared are read by Manager from the transport. Manager finds the corresponding Session and calls the
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// write method of the Session to send to eyeball
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type Session struct {
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id uuid.UUID
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transport transport
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dstConn io.ReadWriteCloser
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// activeAtChan is used to communicate the last read/write time
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activeAtChan chan time.Time
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doneChan chan struct{}
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}
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func newSession(id uuid.UUID, transport transport, dstConn io.ReadWriteCloser) *Session {
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return &Session{
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id: id,
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transport: transport,
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dstConn: dstConn,
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// activeAtChan has low capacity. It can be full when there are many concurrent read/write. markActive() will
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// drop instead of blocking because last active time only needs to be an approximation
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activeAtChan: make(chan time.Time, 2),
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doneChan: make(chan struct{}),
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}
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}
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func (s *Session) Serve(ctx context.Context, closeAfterIdle time.Duration) error {
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serveCtx, cancel := context.WithCancel(ctx)
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defer cancel()
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go s.waitForCloseCondition(serveCtx, closeAfterIdle)
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// QUIC implementation copies data to another buffer before returning https://github.com/lucas-clemente/quic-go/blob/v0.24.0/session.go#L1967-L1975
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// This makes it safe to share readBuffer between iterations
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readBuffer := make([]byte, s.transport.MTU())
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for {
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if err := s.dstToTransport(readBuffer); err != nil {
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return err
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}
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}
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}
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func (s *Session) waitForCloseCondition(ctx context.Context, closeAfterIdle time.Duration) {
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if closeAfterIdle == 0 {
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// provide deafult is caller doesn't specify one
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closeAfterIdle = defaultCloseIdleAfter
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}
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// Closing dstConn cancels read so Serve function can return
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defer s.dstConn.Close()
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checkIdleFreq := closeAfterIdle / 8
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checkIdleTicker := time.NewTicker(checkIdleFreq)
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defer checkIdleTicker.Stop()
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activeAt := time.Now()
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for {
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select {
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case <-ctx.Done():
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return
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case <-s.doneChan:
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return
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// TODO: TUN-5423 evaluate if using atomic is more efficient
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case now := <-checkIdleTicker.C:
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// The session is considered inactive if current time is after (last active time + allowed idle time)
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if now.After(activeAt.Add(closeAfterIdle)) {
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return
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}
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case activeAt = <-s.activeAtChan: // Update last active time
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}
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}
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}
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func (s *Session) dstToTransport(buffer []byte) error {
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n, err := s.dstConn.Read(buffer)
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s.markActive()
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if n > 0 {
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if err := s.transport.SendTo(s.id, buffer[:n]); err != nil {
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return err
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}
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}
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return err
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}
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func (s *Session) transportToDst(payload []byte) (int, error) {
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s.markActive()
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return s.dstConn.Write(payload)
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}
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// Sends the last active time to the idle checker loop without blocking. activeAtChan will only be full when there
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// are many concurrent read/write. It is fine to lose some precision
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func (s *Session) markActive() {
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select {
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case s.activeAtChan <- time.Now():
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default:
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}
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}
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func (s *Session) close() {
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close(s.doneChan)
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}
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