2018-10-19 23:34:09 +00:00
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// Copyright 2018 Google LLC
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2018-07-09 21:03:03 +00:00
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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2018-04-27 17:37:02 +00:00
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// Package tcp contains the implementation of the TCP transport protocol. To use
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// it in the networking stack, this package must be added to the project, and
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// activated on the stack by passing tcp.ProtocolName (or "tcp") as one of the
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// transport protocols when calling stack.New(). Then endpoints can be created
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// by passing tcp.ProtocolNumber as the transport protocol number when calling
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// Stack.NewEndpoint().
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package tcp
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import (
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2018-06-08 18:45:30 +00:00
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"strings"
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2018-04-27 17:37:02 +00:00
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"sync"
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"gvisor.googlesource.com/gvisor/pkg/tcpip"
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"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
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"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
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"gvisor.googlesource.com/gvisor/pkg/tcpip/seqnum"
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"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
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"gvisor.googlesource.com/gvisor/pkg/waiter"
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)
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const (
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// ProtocolName is the string representation of the tcp protocol name.
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ProtocolName = "tcp"
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// ProtocolNumber is the tcp protocol number.
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ProtocolNumber = header.TCPProtocolNumber
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// MinBufferSize is the smallest size of a receive or send buffer.
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minBufferSize = 4 << 10 // 4096 bytes.
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// DefaultBufferSize is the default size of the receive and send buffers.
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DefaultBufferSize = 1 << 20 // 1MB
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// MaxBufferSize is the largest size a receive and send buffer can grow to.
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maxBufferSize = 4 << 20 // 4MB
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)
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// SACKEnabled option can be used to enable SACK support in the TCP
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// protocol. See: https://tools.ietf.org/html/rfc2018.
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type SACKEnabled bool
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// SendBufferSizeOption allows the default, min and max send buffer sizes for
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// TCP endpoints to be queried or configured.
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type SendBufferSizeOption struct {
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Min int
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Default int
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Max int
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}
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// ReceiveBufferSizeOption allows the default, min and max receive buffer size
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// for TCP endpoints to be queried or configured.
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type ReceiveBufferSizeOption struct {
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Min int
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Default int
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Max int
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}
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2018-08-04 00:53:24 +00:00
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const (
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ccReno = "reno"
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ccCubic = "cubic"
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)
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2018-06-08 18:45:30 +00:00
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// CongestionControlOption sets the current congestion control algorithm.
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type CongestionControlOption string
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// AvailableCongestionControlOption returns the supported congestion control
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// algorithms.
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type AvailableCongestionControlOption string
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type protocol struct {
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mu sync.Mutex
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sackEnabled bool
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sendBufferSize SendBufferSizeOption
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recvBufferSize ReceiveBufferSizeOption
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congestionControl string
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availableCongestionControl []string
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allowedCongestionControl []string
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}
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// Number returns the tcp protocol number.
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func (*protocol) Number() tcpip.TransportProtocolNumber {
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return ProtocolNumber
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}
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// NewEndpoint creates a new tcp endpoint.
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func (*protocol) NewEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
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return newEndpoint(stack, netProto, waiterQueue), nil
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}
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// MinimumPacketSize returns the minimum valid tcp packet size.
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func (*protocol) MinimumPacketSize() int {
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return header.TCPMinimumSize
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}
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// ParsePorts returns the source and destination ports stored in the given tcp
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// packet.
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func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
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h := header.TCP(v)
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return h.SourcePort(), h.DestinationPort(), nil
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}
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// HandleUnknownDestinationPacket handles packets targeted at this protocol but
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// that don't match any existing endpoint.
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//
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// RFC 793, page 36, states that "If the connection does not exist (CLOSED) then
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// a reset is sent in response to any incoming segment except another reset. In
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// particular, SYNs addressed to a non-existent connection are rejected by this
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// means."
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2018-09-13 04:57:04 +00:00
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func (*protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, vv buffer.VectorisedView) bool {
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s := newSegment(r, id, vv)
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defer s.decRef()
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if !s.parse() {
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return false
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}
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// There's nothing to do if this is already a reset packet.
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if s.flagIsSet(flagRst) {
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return true
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}
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replyWithReset(s)
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return true
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}
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// replyWithReset replies to the given segment with a reset segment.
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func replyWithReset(s *segment) {
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// Get the seqnum from the packet if the ack flag is set.
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seq := seqnum.Value(0)
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if s.flagIsSet(flagAck) {
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seq = s.ackNumber
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}
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ack := s.sequenceNumber.Add(s.logicalLen())
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2018-09-13 03:38:27 +00:00
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sendTCP(&s.route, s.id, buffer.VectorisedView{}, s.route.DefaultTTL(), flagRst|flagAck, seq, ack, 0, nil)
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}
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// SetOption implements TransportProtocol.SetOption.
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func (p *protocol) SetOption(option interface{}) *tcpip.Error {
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switch v := option.(type) {
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case SACKEnabled:
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p.mu.Lock()
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p.sackEnabled = bool(v)
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p.mu.Unlock()
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return nil
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case SendBufferSizeOption:
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if v.Min <= 0 || v.Default < v.Min || v.Default > v.Max {
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return tcpip.ErrInvalidOptionValue
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}
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p.mu.Lock()
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p.sendBufferSize = v
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p.mu.Unlock()
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return nil
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case ReceiveBufferSizeOption:
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if v.Min <= 0 || v.Default < v.Min || v.Default > v.Max {
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return tcpip.ErrInvalidOptionValue
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}
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p.mu.Lock()
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p.recvBufferSize = v
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p.mu.Unlock()
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return nil
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2018-06-08 18:45:30 +00:00
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case CongestionControlOption:
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for _, c := range p.availableCongestionControl {
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if string(v) == c {
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p.mu.Lock()
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p.congestionControl = string(v)
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p.mu.Unlock()
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return nil
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}
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}
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return tcpip.ErrInvalidOptionValue
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default:
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return tcpip.ErrUnknownProtocolOption
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}
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}
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// Option implements TransportProtocol.Option.
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func (p *protocol) Option(option interface{}) *tcpip.Error {
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switch v := option.(type) {
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case *SACKEnabled:
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p.mu.Lock()
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*v = SACKEnabled(p.sackEnabled)
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p.mu.Unlock()
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return nil
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case *SendBufferSizeOption:
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p.mu.Lock()
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*v = p.sendBufferSize
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p.mu.Unlock()
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return nil
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case *ReceiveBufferSizeOption:
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p.mu.Lock()
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*v = p.recvBufferSize
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p.mu.Unlock()
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return nil
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case *CongestionControlOption:
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p.mu.Lock()
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*v = CongestionControlOption(p.congestionControl)
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p.mu.Unlock()
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return nil
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case *AvailableCongestionControlOption:
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p.mu.Lock()
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*v = AvailableCongestionControlOption(strings.Join(p.availableCongestionControl, " "))
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p.mu.Unlock()
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return nil
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default:
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return tcpip.ErrUnknownProtocolOption
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}
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}
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func init() {
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stack.RegisterTransportProtocolFactory(ProtocolName, func() stack.TransportProtocol {
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return &protocol{
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sendBufferSize: SendBufferSizeOption{minBufferSize, DefaultBufferSize, maxBufferSize},
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recvBufferSize: ReceiveBufferSizeOption{minBufferSize, DefaultBufferSize, maxBufferSize},
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2018-08-04 00:53:24 +00:00
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congestionControl: ccReno,
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availableCongestionControl: []string{ccReno, ccCubic},
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}
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})
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}
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