diff options
Diffstat (limited to 'pkg/tcpip/transport/tcp')
| -rw-r--r-- | pkg/tcpip/transport/tcp/accept.go | 33 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/connect.go | 31 |
2 files changed, 32 insertions, 32 deletions
diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go index a32e20b06..d05259c0a 100644 --- a/pkg/tcpip/transport/tcp/accept.go +++ b/pkg/tcpip/transport/tcp/accept.go @@ -251,7 +251,7 @@ func (l *listenContext) createEndpointAndPerformHandshake(s *segment, opts *head // Perform the 3-way handshake. h := newHandshake(ep, l.rcvWnd) - h.resetToSynRcvd(cookie, irs, opts, l.listenEP) + h.resetToSynRcvd(cookie, irs, opts) if err := h.execute(); err != nil { ep.stack.Stats().TCP.FailedConnectionAttempts.Increment() ep.Close() @@ -294,7 +294,6 @@ func (e *endpoint) handleSynSegment(ctx *listenContext, s *segment, opts *header defer decSynRcvdCount() defer e.decSynRcvdCount() defer s.decRef() - n, err := ctx.createEndpointAndPerformHandshake(s, opts) if err != nil { e.stack.Stats().TCP.FailedConnectionAttempts.Increment() @@ -306,7 +305,7 @@ func (e *endpoint) handleSynSegment(ctx *listenContext, s *segment, opts *header func (e *endpoint) incSynRcvdCount() bool { e.mu.Lock() - if l, c := len(e.acceptedChan), cap(e.acceptedChan); l == c && e.synRcvdCount >= c { + if e.synRcvdCount >= cap(e.acceptedChan) { e.mu.Unlock() return false } @@ -321,6 +320,16 @@ func (e *endpoint) decSynRcvdCount() { e.mu.Unlock() } +func (e *endpoint) acceptQueueIsFull() bool { + e.mu.Lock() + if l, c := len(e.acceptedChan)+e.synRcvdCount, cap(e.acceptedChan); l >= c { + e.mu.Unlock() + return true + } + e.mu.Unlock() + return false +} + // handleListenSegment is called when a listening endpoint receives a segment // and needs to handle it. func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) { @@ -328,17 +337,27 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) { case header.TCPFlagSyn: opts := parseSynSegmentOptions(s) if incSynRcvdCount() { - // Drop the SYN if the listen endpoint's accept queue is - // overflowing. - if e.incSynRcvdCount() { + // Only handle the syn if the following conditions hold + // - accept queue is not full. + // - number of connections in synRcvd state is less than the + // backlog. + if !e.acceptQueueIsFull() && e.incSynRcvdCount() { s.incRef() go e.handleSynSegment(ctx, s, &opts) // S/R-SAFE: synRcvdCount is the barrier. return } + decSynRcvdCount() e.stack.Stats().TCP.ListenOverflowSynDrop.Increment() e.stack.Stats().DroppedPackets.Increment() return } else { + // If cookies are in use but the endpoint accept queue + // is full then drop the syn. + if e.acceptQueueIsFull() { + e.stack.Stats().TCP.ListenOverflowSynDrop.Increment() + e.stack.Stats().DroppedPackets.Increment() + return + } cookie := ctx.createCookie(s.id, s.sequenceNumber, encodeMSS(opts.MSS)) // Send SYN with window scaling because we currently // dont't encode this information in the cookie. @@ -356,7 +375,7 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) { } case header.TCPFlagAck: - if len(e.acceptedChan) == cap(e.acceptedChan) { + if e.acceptQueueIsFull() { // Silently drop the ack as the application can't accept // the connection at this point. The ack will be // retransmitted by the sender anyway and we can diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go index 0ad7bfb38..dd671f7ce 100644 --- a/pkg/tcpip/transport/tcp/connect.go +++ b/pkg/tcpip/transport/tcp/connect.go @@ -60,12 +60,11 @@ const ( // handshake holds the state used during a TCP 3-way handshake. type handshake struct { - ep *endpoint - listenEP *endpoint // only non nil when doing passive connects. - state handshakeState - active bool - flags uint8 - ackNum seqnum.Value + ep *endpoint + state handshakeState + active bool + flags uint8 + ackNum seqnum.Value // iss is the initial send sequence number, as defined in RFC 793. iss seqnum.Value @@ -142,7 +141,7 @@ func (h *handshake) effectiveRcvWndScale() uint8 { // resetToSynRcvd resets the state of the handshake object to the SYN-RCVD // state. -func (h *handshake) resetToSynRcvd(iss seqnum.Value, irs seqnum.Value, opts *header.TCPSynOptions, listenEP *endpoint) { +func (h *handshake) resetToSynRcvd(iss seqnum.Value, irs seqnum.Value, opts *header.TCPSynOptions) { h.active = false h.state = handshakeSynRcvd h.flags = header.TCPFlagSyn | header.TCPFlagAck @@ -150,7 +149,6 @@ func (h *handshake) resetToSynRcvd(iss seqnum.Value, irs seqnum.Value, opts *hea h.ackNum = irs + 1 h.mss = opts.MSS h.sndWndScale = opts.WS - h.listenEP = listenEP h.ep.mu.Lock() h.ep.state = StateSynRecv h.ep.mu.Unlock() @@ -287,23 +285,6 @@ func (h *handshake) synRcvdState(s *segment) *tcpip.Error { // We have previously received (and acknowledged) the peer's SYN. If the // peer acknowledges our SYN, the handshake is completed. if s.flagIsSet(header.TCPFlagAck) { - // listenContext is also used by a tcp.Forwarder and in that - // context we do not have a listening endpoint to check the - // backlog. So skip this check if listenEP is nil. - if h.listenEP != nil { - h.listenEP.mu.Lock() - if len(h.listenEP.acceptedChan) == cap(h.listenEP.acceptedChan) { - h.listenEP.mu.Unlock() - // If there is no space in the accept queue to accept - // this endpoint then silently drop this ACK. The peer - // will anyway resend the ack and we can complete the - // connection the next time it's retransmitted. - h.ep.stack.Stats().TCP.ListenOverflowAckDrop.Increment() - h.ep.stack.Stats().DroppedPackets.Increment() - return nil - } - h.listenEP.mu.Unlock() - } // If the timestamp option is negotiated and the segment does // not carry a timestamp option then the segment must be dropped // as per https://tools.ietf.org/html/rfc7323#section-3.2. |