diff options
| -rw-r--r-- | pkg/tcpip/stack/stack.go | 13 | ||||
| -rw-r--r-- | pkg/tcpip/stack/stack_options.go | 25 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/connect.go | 7 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/endpoint.go | 20 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/endpoint_state.go | 10 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/rcv.go | 4 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/snd.go | 10 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/tcp_state_autogen.go | 4 |
8 files changed, 88 insertions, 5 deletions
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go index 57ad412a1..a51d758d0 100644 --- a/pkg/tcpip/stack/stack.go +++ b/pkg/tcpip/stack/stack.go @@ -458,6 +458,18 @@ type Stack struct { // receiveBufferSize holds the min/default/max receive buffer sizes for // endpoints other than TCP. receiveBufferSize ReceiveBufferSizeOption + + // tcpInvalidRateLimit is the maximal rate for sending duplicate + // acknowledgements in response to incoming TCP packets that are for an existing + // connection but that are invalid due to any of the following reasons: + // + // a) out-of-window sequence number. + // b) out-of-window acknowledgement number. + // c) PAWS check failure (when implemented). + // + // This is required to prevent potential ACK loops. + // Setting this to 0 will disable all rate limiting. + tcpInvalidRateLimit time.Duration } // UniqueID is an abstract generator of unique identifiers. @@ -668,6 +680,7 @@ func New(opts Options) *Stack { Default: DefaultBufferSize, Max: DefaultMaxBufferSize, }, + tcpInvalidRateLimit: defaultTCPInvalidRateLimit, } // Add specified network protocols. diff --git a/pkg/tcpip/stack/stack_options.go b/pkg/tcpip/stack/stack_options.go index 8d9b20b7e..3066f4ffd 100644 --- a/pkg/tcpip/stack/stack_options.go +++ b/pkg/tcpip/stack/stack_options.go @@ -15,6 +15,8 @@ package stack import ( + "time" + "gvisor.dev/gvisor/pkg/tcpip" ) @@ -29,6 +31,10 @@ const ( // DefaultMaxBufferSize is the default maximum permitted size of a // send/receive buffer. DefaultMaxBufferSize = 4 << 20 // 4 MiB + + // defaultTCPInvalidRateLimit is the default value for + // stack.TCPInvalidRateLimit. + defaultTCPInvalidRateLimit = 500 * time.Millisecond ) // ReceiveBufferSizeOption is used by stack.(Stack*).Option/SetOption to @@ -39,6 +45,10 @@ type ReceiveBufferSizeOption struct { Max int } +// TCPInvalidRateLimitOption is used by stack.(Stack*).Option/SetOption to get/set +// stack.tcpInvalidRateLimit. +type TCPInvalidRateLimitOption time.Duration + // SetOption allows setting stack wide options. func (s *Stack) SetOption(option interface{}) tcpip.Error { switch v := option.(type) { @@ -74,6 +84,15 @@ func (s *Stack) SetOption(option interface{}) tcpip.Error { s.mu.Unlock() return nil + case TCPInvalidRateLimitOption: + if v < 0 { + return &tcpip.ErrInvalidOptionValue{} + } + s.mu.Lock() + s.tcpInvalidRateLimit = time.Duration(v) + s.mu.Unlock() + return nil + default: return &tcpip.ErrUnknownProtocolOption{} } @@ -94,6 +113,12 @@ func (s *Stack) Option(option interface{}) tcpip.Error { s.mu.RUnlock() return nil + case *TCPInvalidRateLimitOption: + s.mu.RLock() + *v = TCPInvalidRateLimitOption(s.tcpInvalidRateLimit) + s.mu.RUnlock() + return nil + default: return &tcpip.ErrUnknownProtocolOption{} } diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go index 4695b66d6..34a631b53 100644 --- a/pkg/tcpip/transport/tcp/connect.go +++ b/pkg/tcpip/transport/tcp/connect.go @@ -333,7 +333,9 @@ func (h *handshake) synRcvdState(s *segment) tcpip.Error { // number and "After sending the acknowledgment, drop the unacceptable // segment and return." if !s.sequenceNumber.InWindow(h.ackNum, h.rcvWnd) { - h.ep.sendRaw(buffer.VectorisedView{}, header.TCPFlagAck, h.iss+1, h.ackNum, h.rcvWnd) + if h.ep.allowOutOfWindowAck() { + h.ep.sendRaw(buffer.VectorisedView{}, header.TCPFlagAck, h.iss+1, h.ackNum, h.rcvWnd) + } return nil } @@ -1185,8 +1187,7 @@ func (e *endpoint) handleSegment(s *segment) (cont bool, err tcpip.Error) { // endpoint MUST terminate its connection. The local TCP endpoint // should then rely on SYN retransmission from the remote end to // re-establish the connection. - - e.snd.sendAck() + e.snd.maybeSendOutOfWindowAck(s) } else if s.flagIsSet(header.TCPFlagAck) { // Patch the window size in the segment according to the // send window scale. diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go index e645aa194..4e5a6089f 100644 --- a/pkg/tcpip/transport/tcp/endpoint.go +++ b/pkg/tcpip/transport/tcp/endpoint.go @@ -688,6 +688,10 @@ type endpoint struct { // ops is used to get socket level options. ops tcpip.SocketOptions + + // lastOutOfWindowAckTime is the time at which the an ACK was sent in response + // to an out of window segment being received by this endpoint. + lastOutOfWindowAckTime time.Time `state:".(unixTime)"` } // UniqueID implements stack.TransportEndpoint.UniqueID. @@ -3125,3 +3129,19 @@ func GetTCPSendBufferLimits(s tcpip.StackHandler) tcpip.SendBufferSizeOption { Max: ss.Max, } } + +// allowOutOfWindowAck returns true if an out-of-window ACK can be sent now. +func (e *endpoint) allowOutOfWindowAck() bool { + var limit stack.TCPInvalidRateLimitOption + if err := e.stack.Option(&limit); err != nil { + panic(fmt.Sprintf("e.stack.Option(%+v) failed with error: %s", limit, err)) + } + + now := time.Now() + if now.Sub(e.lastOutOfWindowAckTime) < time.Duration(limit) { + return false + } + + e.lastOutOfWindowAckTime = now + return true +} diff --git a/pkg/tcpip/transport/tcp/endpoint_state.go b/pkg/tcpip/transport/tcp/endpoint_state.go index c21dbc682..e4368026f 100644 --- a/pkg/tcpip/transport/tcp/endpoint_state.go +++ b/pkg/tcpip/transport/tcp/endpoint_state.go @@ -308,6 +308,16 @@ func (e *endpoint) loadRecentTSTime(unix unixTime) { e.recentTSTime = time.Unix(unix.second, unix.nano) } +// saveLastOutOfWindowAckTime is invoked by stateify. +func (e *endpoint) saveLastOutOfWindowAckTime() unixTime { + return unixTime{e.lastOutOfWindowAckTime.Unix(), e.lastOutOfWindowAckTime.UnixNano()} +} + +// loadLastOutOfWindowAckTime is invoked by stateify. +func (e *endpoint) loadLastOutOfWindowAckTime(unix unixTime) { + e.lastOutOfWindowAckTime = time.Unix(unix.second, unix.nano) +} + // saveMeasureTime is invoked by stateify. func (r *rcvBufAutoTuneParams) saveMeasureTime() unixTime { return unixTime{r.measureTime.Unix(), r.measureTime.UnixNano()} diff --git a/pkg/tcpip/transport/tcp/rcv.go b/pkg/tcpip/transport/tcp/rcv.go index 7a7c402c4..a5c82b8fa 100644 --- a/pkg/tcpip/transport/tcp/rcv.go +++ b/pkg/tcpip/transport/tcp/rcv.go @@ -385,7 +385,7 @@ func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, clo // fails, we ignore the packet: // https://github.com/torvalds/linux/blob/v5.8/net/ipv4/tcp_input.c#L5591 if r.ep.snd.sndNxt.LessThan(s.ackNumber) { - r.ep.snd.sendAck() + r.ep.snd.maybeSendOutOfWindowAck(s) return true, nil } @@ -454,7 +454,7 @@ func (r *receiver) handleRcvdSegment(s *segment) (drop bool, err tcpip.Error) { // send an ACK and stop further processing of the segment. // This is according to RFC 793, page 68. if !r.acceptable(segSeq, segLen) { - r.ep.snd.sendAck() + r.ep.snd.maybeSendOutOfWindowAck(s) return true, nil } diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go index dfc8fd248..538edd6cf 100644 --- a/pkg/tcpip/transport/tcp/snd.go +++ b/pkg/tcpip/transport/tcp/snd.go @@ -1548,3 +1548,13 @@ func (s *sender) sendSegmentFromView(data buffer.VectorisedView, flags byte, seq return s.ep.sendRaw(data, flags, seq, rcvNxt, rcvWnd) } + +// maybeSendOutOfWindowAck sends an ACK if we are not being rate limited +// currently. +func (s *sender) maybeSendOutOfWindowAck(seg *segment) { + // Data packets are unlikely to be part of an ACK loop. So always send + // an ACK for a packet w/ data. + if seg.payloadSize() > 0 || s.ep.allowOutOfWindowAck() { + s.sendAck() + } +} diff --git a/pkg/tcpip/transport/tcp/tcp_state_autogen.go b/pkg/tcpip/transport/tcp/tcp_state_autogen.go index cb49e63fe..f19781bfe 100644 --- a/pkg/tcpip/transport/tcp/tcp_state_autogen.go +++ b/pkg/tcpip/transport/tcp/tcp_state_autogen.go @@ -217,6 +217,7 @@ func (e *endpoint) StateFields() []string { "txHash", "owner", "ops", + "lastOutOfWindowAckTime", } } @@ -228,6 +229,8 @@ func (e *endpoint) StateSave(stateSinkObject state.Sink) { stateSinkObject.SaveValue(26, recentTSTimeValue) var acceptedChanValue []*endpoint = e.saveAcceptedChan() stateSinkObject.SaveValue(49, acceptedChanValue) + var lastOutOfWindowAckTimeValue unixTime = e.saveLastOutOfWindowAckTime() + stateSinkObject.SaveValue(61, lastOutOfWindowAckTimeValue) stateSinkObject.Save(0, &e.EndpointInfo) stateSinkObject.Save(1, &e.DefaultSocketOptionsHandler) stateSinkObject.Save(2, &e.waiterQueue) @@ -350,6 +353,7 @@ func (e *endpoint) StateLoad(stateSourceObject state.Source) { stateSourceObject.LoadValue(13, new(EndpointState), func(y interface{}) { e.loadState(y.(EndpointState)) }) stateSourceObject.LoadValue(26, new(unixTime), func(y interface{}) { e.loadRecentTSTime(y.(unixTime)) }) stateSourceObject.LoadValue(49, new([]*endpoint), func(y interface{}) { e.loadAcceptedChan(y.([]*endpoint)) }) + stateSourceObject.LoadValue(61, new(unixTime), func(y interface{}) { e.loadLastOutOfWindowAckTime(y.(unixTime)) }) stateSourceObject.AfterLoad(e.afterLoad) } |