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don't spawn a new Go routine to send a CONNECTION_REFUSED packet #4091

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merged 1 commit into from
Sep 25, 2023
Merged

don't spawn a new Go routine to send a CONNECTION_REFUSED packet #4091

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39 changes: 23 additions & 16 deletions server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,7 @@ type baseServer struct {
running chan struct{} // closed as soon as run() returns
versionNegotiationQueue chan receivedPacket
invalidTokenQueue chan rejectedPacket
connectionRefusedQueue chan rejectedPacket

connQueue chan quicConn
connQueueLen int32 // to be used as an atomic
Expand Down Expand Up @@ -251,6 +252,7 @@ func newServer(
receivedPackets: make(chan receivedPacket, protocol.MaxServerUnprocessedPackets),
versionNegotiationQueue: make(chan receivedPacket, 4),
invalidTokenQueue: make(chan rejectedPacket, 4),
connectionRefusedQueue: make(chan rejectedPacket, 4),
newConn: newConnection,
tracer: tracer,
logger: utils.DefaultLogger.WithPrefix("server"),
Expand Down Expand Up @@ -295,6 +297,8 @@ func (s *baseServer) runSendQueue() {
s.maybeSendVersionNegotiationPacket(p)
case p := <-s.invalidTokenQueue:
s.maybeSendInvalidToken(p)
case p := <-s.connectionRefusedQueue:
s.sendConnectionRefused(p)
}
}
}
Expand Down Expand Up @@ -588,7 +592,7 @@ func (s *baseServer) handleInitialImpl(p receivedPacket, hdr *wire.Header) error
select {
case s.invalidTokenQueue <- rejectedPacket{receivedPacket: p, hdr: hdr}:
default:
// it's fine to drop INVALID_TOKEN packets when we are busy
// drop packet if we can't send out the INVALID_TOKEN packets fast enough
p.buffer.Release()
}
return nil
Expand All @@ -608,12 +612,12 @@ func (s *baseServer) handleInitialImpl(p receivedPacket, hdr *wire.Header) error

if queueLen := atomic.LoadInt32(&s.connQueueLen); queueLen >= protocol.MaxAcceptQueueSize {
s.logger.Debugf("Rejecting new connection. Server currently busy. Accept queue length: %d (max %d)", queueLen, protocol.MaxAcceptQueueSize)
go func() {
defer p.buffer.Release()
if err := s.sendConnectionRefused(p.remoteAddr, hdr, p.info); err != nil {
s.logger.Debugf("Error rejecting connection: %s", err)
}
}()
select {
case s.connectionRefusedQueue <- rejectedPacket{receivedPacket: p, hdr: hdr}:
default:
// drop packet if we can't send out the CONNECTION_REFUSED fast enough
p.buffer.Release()
}
return nil
}

Expand Down Expand Up @@ -673,12 +677,12 @@ func (s *baseServer) handleInitialImpl(p receivedPacket, hdr *wire.Header) error

return conn, true
}); !added {
go func() {
defer p.buffer.Release()
if err := s.sendConnectionRefused(p.remoteAddr, hdr, p.info); err != nil {
s.logger.Debugf("Error rejecting connection: %s", err)
}
}()
select {
case s.connectionRefusedQueue <- rejectedPacket{receivedPacket: p, hdr: hdr}:
default:
// drop packet if we can't send out the CONNECTION_REFUSED fast enough
p.buffer.Release()
}
return nil
}
go conn.run()
Expand Down Expand Up @@ -790,9 +794,12 @@ func (s *baseServer) maybeSendInvalidToken(p rejectedPacket) {
}
}

func (s *baseServer) sendConnectionRefused(remoteAddr net.Addr, hdr *wire.Header, info packetInfo) error {
sealer, _ := handshake.NewInitialAEAD(hdr.DestConnectionID, protocol.PerspectiveServer, hdr.Version)
return s.sendError(remoteAddr, hdr, sealer, qerr.ConnectionRefused, info)
func (s *baseServer) sendConnectionRefused(p rejectedPacket) {
defer p.buffer.Release()
sealer, _ := handshake.NewInitialAEAD(p.hdr.DestConnectionID, protocol.PerspectiveServer, p.hdr.Version)
if err := s.sendError(p.remoteAddr, p.hdr, sealer, qerr.ConnectionRefused, p.info); err != nil {
s.logger.Debugf("Error sending CONNECTION_REFUSED error: %s", err)
}
}

// sendError sends the error as a response to the packet received with header hdr
Expand Down