diff options
Diffstat (limited to 'vendor/github.com/google/gopacket/reassembly/tcpcheck.go')
| -rw-r--r-- | vendor/github.com/google/gopacket/reassembly/tcpcheck.go | 246 |
1 files changed, 0 insertions, 246 deletions
diff --git a/vendor/github.com/google/gopacket/reassembly/tcpcheck.go b/vendor/github.com/google/gopacket/reassembly/tcpcheck.go deleted file mode 100644 index 4b52aba..0000000 --- a/vendor/github.com/google/gopacket/reassembly/tcpcheck.go +++ /dev/null @@ -1,246 +0,0 @@ -// Copyright 2012 Google, Inc. All rights reserved. -// -// Use of this source code is governed by a BSD-style license -// that can be found in the LICENSE file in the root of the source -// tree. - -package reassembly - -import ( - "encoding/binary" - "fmt" - - "github.com/google/gopacket" - "github.com/google/gopacket/layers" -) - -/* - * Check TCP packet against options (window, MSS) - */ - -type tcpStreamOptions struct { - mss int - scale int - receiveWindow uint -} - -// TCPOptionCheck contains options for the two directions -type TCPOptionCheck struct { - options [2]tcpStreamOptions -} - -func (t *TCPOptionCheck) getOptions(dir TCPFlowDirection) *tcpStreamOptions { - if dir == TCPDirClientToServer { - return &t.options[0] - } - return &t.options[1] -} - -// NewTCPOptionCheck creates default options -func NewTCPOptionCheck() TCPOptionCheck { - return TCPOptionCheck{ - options: [2]tcpStreamOptions{ - tcpStreamOptions{ - mss: 0, - scale: -1, - receiveWindow: 0, - }, tcpStreamOptions{ - mss: 0, - scale: -1, - receiveWindow: 0, - }, - }, - } -} - -// Accept checks whether the packet should be accepted by checking TCP options -func (t *TCPOptionCheck) Accept(tcp *layers.TCP, ci gopacket.CaptureInfo, dir TCPFlowDirection, acked Sequence, start *bool) error { - options := t.getOptions(dir) - if tcp.SYN { - mss := -1 - scale := -1 - for _, o := range tcp.Options { - // MSS - if o.OptionType == 2 { - if len(o.OptionData) != 2 { - return fmt.Errorf("MSS option data length expected 2, got %d", len(o.OptionData)) - } - mss = int(binary.BigEndian.Uint16(o.OptionData[:2])) - } - // Window scaling - if o.OptionType == 3 { - if len(o.OptionData) != 1 { - return fmt.Errorf("Window scaling length expected: 1, got %d", len(o.OptionData)) - } - scale = int(o.OptionData[0]) - } - } - options.mss = mss - options.scale = scale - } else { - if acked != invalidSequence { - revOptions := t.getOptions(dir.Reverse()) - length := len(tcp.Payload) - - // Check packet is in the correct window - diff := acked.Difference(Sequence(tcp.Seq)) - if diff == -1 && (length == 1 || length == 0) { - // This is probably a Keep-alive - // TODO: check byte is ok - } else if diff < 0 { - return fmt.Errorf("Re-emitted packet (diff:%d,seq:%d,rev-ack:%d)", diff, - tcp.Seq, acked) - } else if revOptions.mss > 0 && length > revOptions.mss { - return fmt.Errorf("%d > mss (%d)", length, revOptions.mss) - } else if revOptions.receiveWindow != 0 && revOptions.scale < 0 && diff > int(revOptions.receiveWindow) { - return fmt.Errorf("%d > receiveWindow(%d)", diff, revOptions.receiveWindow) - } - } - } - // Compute receiveWindow - options.receiveWindow = uint(tcp.Window) - if options.scale > 0 { - options.receiveWindow = options.receiveWindow << (uint(options.scale)) - } - return nil -} - -// TCPSimpleFSM implements a very simple TCP state machine -// -// Usage: -// When implementing a Stream interface and to avoid to consider packets that -// would be rejected due to client/server's TCP stack, the Accept() can call -// TCPSimpleFSM.CheckState(). -// -// Limitations: -// - packet should be received in-order. -// - no check on sequence number is performed -// - no RST -type TCPSimpleFSM struct { - dir TCPFlowDirection - state int - options TCPSimpleFSMOptions -} - -// TCPSimpleFSMOptions holds options for TCPSimpleFSM -type TCPSimpleFSMOptions struct { - SupportMissingEstablishment bool // Allow missing SYN, SYN+ACK, ACK -} - -// Internal values of state machine -const ( - TCPStateClosed = 0 - TCPStateSynSent = 1 - TCPStateEstablished = 2 - TCPStateCloseWait = 3 - TCPStateLastAck = 4 - TCPStateReset = 5 -) - -// NewTCPSimpleFSM creates a new TCPSimpleFSM -func NewTCPSimpleFSM(options TCPSimpleFSMOptions) *TCPSimpleFSM { - return &TCPSimpleFSM{ - state: TCPStateClosed, - options: options, - } -} - -func (t *TCPSimpleFSM) String() string { - switch t.state { - case TCPStateClosed: - return "Closed" - case TCPStateSynSent: - return "SynSent" - case TCPStateEstablished: - return "Established" - case TCPStateCloseWait: - return "CloseWait" - case TCPStateLastAck: - return "LastAck" - case TCPStateReset: - return "Reset" - } - return "?" -} - -// CheckState returns false if tcp is invalid wrt current state or update the state machine's state -func (t *TCPSimpleFSM) CheckState(tcp *layers.TCP, dir TCPFlowDirection) bool { - if t.state == TCPStateClosed && t.options.SupportMissingEstablishment && !(tcp.SYN && !tcp.ACK) { - /* try to figure out state */ - switch true { - case tcp.SYN && tcp.ACK: - t.state = TCPStateSynSent - t.dir = dir.Reverse() - case tcp.FIN && !tcp.ACK: - t.state = TCPStateEstablished - case tcp.FIN && tcp.ACK: - t.state = TCPStateCloseWait - t.dir = dir.Reverse() - default: - t.state = TCPStateEstablished - } - } - - switch t.state { - /* openning connection */ - case TCPStateClosed: - if tcp.SYN && !tcp.ACK { - t.dir = dir - t.state = TCPStateSynSent - return true - } - case TCPStateSynSent: - if tcp.RST { - t.state = TCPStateReset - return true - } - - if tcp.SYN && tcp.ACK && dir == t.dir.Reverse() { - t.state = TCPStateEstablished - return true - } - if tcp.SYN && !tcp.ACK && dir == t.dir { - // re-transmission - return true - } - /* established */ - case TCPStateEstablished: - if tcp.RST { - t.state = TCPStateReset - return true - } - - if tcp.FIN { - t.state = TCPStateCloseWait - t.dir = dir - return true - } - // accept any packet - return true - /* closing connection */ - case TCPStateCloseWait: - if tcp.RST { - t.state = TCPStateReset - return true - } - - if tcp.FIN && tcp.ACK && dir == t.dir.Reverse() { - t.state = TCPStateLastAck - return true - } - if tcp.ACK { - return true - } - case TCPStateLastAck: - if tcp.RST { - t.state = TCPStateReset - return true - } - - if tcp.ACK && t.dir == dir { - t.state = TCPStateClosed - return true - } - } - return false -} |