| // Copyright 2016 The Netstack Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package tcp contains the implementation of the TCP transport protocol. To use |
| // it in the networking stack, this package must be added to the project, and |
| // activated on the stack by passing tcp.ProtocolName (or "tcp") as one of the |
| // transport protocols when calling stack.New(). Then endpoints can be created |
| // by passing tcp.ProtocolNumber as the transport protocol number when calling |
| // Stack.NewEndpoint(). |
| package tcp |
| |
| import ( |
| "github.com/google/netstack/tcpip" |
| "github.com/google/netstack/tcpip/buffer" |
| "github.com/google/netstack/tcpip/header" |
| "github.com/google/netstack/tcpip/seqnum" |
| "github.com/google/netstack/tcpip/stack" |
| "github.com/google/netstack/waiter" |
| ) |
| |
| const ( |
| // ProtocolName is the string representation of the tcp protocol name. |
| ProtocolName = "tcp" |
| |
| // ProtocolNumber is the tcp protocol number. |
| ProtocolNumber = header.TCPProtocolNumber |
| ) |
| |
| type protocol struct{} |
| |
| // Number returns the tcp protocol number. |
| func (*protocol) Number() tcpip.TransportProtocolNumber { |
| return ProtocolNumber |
| } |
| |
| // NewEndpoint creates a new tcp endpoint. |
| func (*protocol) NewEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) { |
| return newEndpoint(stack, netProto, waiterQueue), nil |
| } |
| |
| // MinimumPacketSize returns the minimum valid tcp packet size. |
| func (*protocol) MinimumPacketSize() int { |
| return header.TCPMinimumSize |
| } |
| |
| // ParsePorts returns the source and destination ports stored in the given tcp |
| // packet. |
| func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) { |
| h := header.TCP(v) |
| return h.SourcePort(), h.DestinationPort(), nil |
| } |
| |
| // HandleUnknownDestinationPacket handles packets targeted at this protocol but |
| // that don't match any existing endpoint. |
| // |
| // RFC 793, page 36, states that "If the connection does not exist (CLOSED) then |
| // a reset is sent in response to any incoming segment except another reset. In |
| // particular, SYNs addressed to a non-existent connection are rejected by this |
| // means." |
| func (*protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, vv *buffer.VectorisedView) bool { |
| s := newSegment(r, id, vv) |
| defer s.decRef() |
| |
| if !s.parse() { |
| return false |
| } |
| |
| // There's nothing to do if this is already a reset packet. |
| if s.flagIsSet(flagRst) { |
| return true |
| } |
| |
| replyWithReset(s) |
| return true |
| } |
| |
| // replyWithReset replies to the given segment with a reset segment. |
| func replyWithReset(s *segment) { |
| // Get the seqnum from the packet if the ack flag is set. |
| seq := seqnum.Value(0) |
| if s.flagIsSet(flagAck) { |
| seq = s.ackNumber |
| } |
| |
| ack := s.sequenceNumber.Add(s.logicalLen()) |
| |
| sendTCP(&s.route, s.id, nil, s.route.DefaultTTL(), flagRst|flagAck, seq, ack, 0) |
| } |
| |
| // SetOption implements TransportProtocol.SetOption. |
| func (p *protocol) SetOption(option interface{}) *tcpip.Error { |
| return tcpip.ErrUnknownProtocolOption |
| } |
| |
| func init() { |
| stack.RegisterTransportProtocolFactory(ProtocolName, func() stack.TransportProtocol { |
| return &protocol{} |
| }) |
| } |