TUN-5494: Send a RPC with terminate reason to edge if the session is closed locally

datagramsession/session.go

@@ -2,6 +2,7 @@ package datagramsession
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"time"
 
@@ -12,6 +13,10 @@ const (
 	defaultCloseIdleAfter = time.Second * 210
 )
 
+func SessionIdleErr(timeout time.Duration) error {
+	return fmt.Errorf("session idle for %v", timeout)
+}
+
 // 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
@@ -24,47 +29,53 @@ const (
 // - 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
+	ID        uuid.UUID
 	transport transport
 	dstConn   io.ReadWriteCloser
 	// activeAtChan is used to communicate the last read/write time
 	activeAtChan chan time.Time
-	doneChan     chan struct{}
+	closeChan    chan error
 }
 
 func newSession(id uuid.UUID, transport transport, dstConn io.ReadWriteCloser) *Session {
 	return &Session{
-		id:        id,
+		ID:        id,
 		transport: transport,
 		dstConn:   dstConn,
 		// activeAtChan has low capacity. It can be full when there are many concurrent read/write. markActive() will
 		// drop instead of blocking because last active time only needs to be an approximation
 		activeAtChan: make(chan time.Time, 2),
-		doneChan:     make(chan struct{}),
+		// capacity is 2 because close() and dstToTransport routine in Serve() can write to this channel
+		closeChan: make(chan error, 2),
 	}
 }
 
-func (s *Session) Serve(ctx context.Context, closeAfterIdle time.Duration) error {
-	serveCtx, cancel := context.WithCancel(ctx)
-	defer cancel()
-	go s.waitForCloseCondition(serveCtx, closeAfterIdle)
-	// 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, s.transport.MTU())
-	for {
-		if err := s.dstToTransport(readBuffer); err != nil {
-			return err
+func (s *Session) Serve(ctx context.Context, closeAfterIdle time.Duration) (closedByRemote bool, err error) {
+	go func() {
+		// 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, s.transport.MTU())
+		for {
+			if err := s.dstToTransport(readBuffer); err != nil {
+				s.closeChan <- err
+				return
+			}
 		}
+	}()
+	err = s.waitForCloseCondition(ctx, closeAfterIdle)
+	if closeSession, ok := err.(*errClosedSession); ok {
+		closedByRemote = closeSession.byRemote
 	}
+	return closedByRemote, err
 }
 
-func (s *Session) waitForCloseCondition(ctx context.Context, closeAfterIdle time.Duration) {
+func (s *Session) waitForCloseCondition(ctx context.Context, closeAfterIdle time.Duration) error {
+	// Closing dstConn cancels read so dstToTransport routine in Serve() can return
+	defer s.dstConn.Close()
 	if closeAfterIdle == 0 {
 		// provide deafult is caller doesn't specify one
 		closeAfterIdle = defaultCloseIdleAfter
 	}
-	// Closing dstConn cancels read so Serve function can return
-	defer s.dstConn.Close()
 
 	checkIdleFreq := closeAfterIdle / 8
 	checkIdleTicker := time.NewTicker(checkIdleFreq)
@@ -74,14 +85,14 @@ func (s *Session) waitForCloseCondition(ctx context.Context, closeAfterIdle time
 	for {
 		select {
 		case <-ctx.Done():
-			return
-		case <-s.doneChan:
-			return
+			return ctx.Err()
+		case reason := <-s.closeChan:
+			return reason
 		// TODO: TUN-5423 evaluate if using atomic is more efficient
 		case now := <-checkIdleTicker.C:
 			// The session is considered inactive if current time is after (last active time + allowed idle time)
 			if now.After(activeAt.Add(closeAfterIdle)) {
-				return
+				return SessionIdleErr(closeAfterIdle)
 			}
 		case activeAt = <-s.activeAtChan: // Update last active time
 		}
@@ -92,7 +103,7 @@ func (s *Session) dstToTransport(buffer []byte) error {
 	n, err := s.dstConn.Read(buffer)
 	s.markActive()
 	if n > 0 {
-		if err := s.transport.SendTo(s.id, buffer[:n]); err != nil {
+		if err := s.transport.SendTo(s.ID, buffer[:n]); err != nil {
 			return err
 		}
 	}
@@ -113,6 +124,6 @@ func (s *Session) markActive() {
 	}
 }
 
-func (s *Session) close() {
-	close(s.doneChan)
+func (s *Session) close(err *errClosedSession) {
+	s.closeChan <- err
 }