cloudflared-mirror/datagramsession/session.go

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package datagramsession
import (
"context"
"io"
"github.com/google/uuid"
)
// Each Session is a bidirectional pipe of datagrams between transport and dstConn
// Currently the only implementation of transport is quic DatagramMuxer
// Destination can be a connection with origin or with eyeball
// When the destination is origin:
// - Datagrams from edge are read by Manager from the transport. Manager finds the corresponding Session and calls the
// write method of the Session to send to origin
// - Datagrams from origin are read from conn and SentTo transport. Transport will return them to eyeball
// When the destination is eyeball:
// - Datagrams from eyeball are read from conn and SentTo transport. Transport will send them to cloudflared
// - Datagrams from cloudflared are read by Manager from the transport. Manager finds the corresponding Session and calls the
// write method of the Session to send to eyeball
type Session struct {
id uuid.UUID
transport transport
dstConn io.ReadWriteCloser
doneChan chan struct{}
}
func newSession(id uuid.UUID, transport transport, dstConn io.ReadWriteCloser) *Session {
return &Session{
id: id,
transport: transport,
dstConn: dstConn,
doneChan: make(chan struct{}),
}
}
func (s *Session) Serve(ctx context.Context) error {
serveCtx, cancel := context.WithCancel(ctx)
defer cancel()
go func() {
select {
case <-serveCtx.Done():
case <-s.doneChan:
}
s.dstConn.Close()
}()
// QUIC implementation copies data to another buffer before returning https://github.com/lucas-clemente/quic-go/blob/v0.24.0/session.go#L1967-L1975
// This makes it safe to share readBuffer between iterations
readBuffer := make([]byte, 1280)
for {
// TODO: TUN-5303: origin proxy should determine the buffer size
n, err := s.dstConn.Read(readBuffer)
if n > 0 {
if err := s.transport.SendTo(s.id, readBuffer[:n]); err != nil {
return err
}
}
if err != nil {
return err
}
}
}
func (s *Session) writeToDst(payload []byte) (int, error) {
return s.dstConn.Write(payload)
}
func (s *Session) close() {
close(s.doneChan)
}