Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 192 insertions, 0 deletions

diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
new file mode 100644
index 000000000..d81a1dd9b
--- /dev/null
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -0,0 +1,192 @@
+// 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 (
+	"sync"
+
+	"gvisor.googlesource.com/gvisor/pkg/tcpip"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/seqnum"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+const (
+	// ProtocolName is the string representation of the tcp protocol name.
+	ProtocolName = "tcp"
+
+	// ProtocolNumber is the tcp protocol number.
+	ProtocolNumber = header.TCPProtocolNumber
+
+	// MinBufferSize is the smallest size of a receive or send buffer.
+	minBufferSize = 4 << 10 // 4096 bytes.
+
+	// DefaultBufferSize is the default size of the receive and send buffers.
+	DefaultBufferSize = 1 << 20 // 1MB
+
+	// MaxBufferSize is the largest size a receive and send buffer can grow to.
+	maxBufferSize = 4 << 20 // 4MB
+)
+
+// SACKEnabled option can be used to enable SACK support in the TCP
+// protocol. See: https://tools.ietf.org/html/rfc2018.
+type SACKEnabled bool
+
+// SendBufferSizeOption allows the default, min and max send buffer sizes for
+// TCP endpoints to be queried or configured.
+type SendBufferSizeOption struct {
+	Min     int
+	Default int
+	Max     int
+}
+
+// ReceiveBufferSizeOption allows the default, min and max receive buffer size
+// for TCP endpoints to be queried or configured.
+type ReceiveBufferSizeOption struct {
+	Min     int
+	Default int
+	Max     int
+}
+
+type protocol struct {
+	mu             sync.Mutex
+	sackEnabled    bool
+	sendBufferSize SendBufferSizeOption
+	recvBufferSize ReceiveBufferSizeOption
+}
+
+// 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, flagRst|flagAck, seq, ack, 0)
+}
+
+// SetOption implements TransportProtocol.SetOption.
+func (p *protocol) SetOption(option interface{}) *tcpip.Error {
+	switch v := option.(type) {
+	case SACKEnabled:
+		p.mu.Lock()
+		p.sackEnabled = bool(v)
+		p.mu.Unlock()
+		return nil
+
+	case SendBufferSizeOption:
+		if v.Min <= 0 || v.Default < v.Min || v.Default > v.Max {
+			return tcpip.ErrInvalidOptionValue
+		}
+		p.mu.Lock()
+		p.sendBufferSize = v
+		p.mu.Unlock()
+		return nil
+
+	case ReceiveBufferSizeOption:
+		if v.Min <= 0 || v.Default < v.Min || v.Default > v.Max {
+			return tcpip.ErrInvalidOptionValue
+		}
+		p.mu.Lock()
+		p.recvBufferSize = v
+		p.mu.Unlock()
+		return nil
+
+	default:
+		return tcpip.ErrUnknownProtocolOption
+	}
+}
+
+// Option implements TransportProtocol.Option.
+func (p *protocol) Option(option interface{}) *tcpip.Error {
+	switch v := option.(type) {
+	case *SACKEnabled:
+		p.mu.Lock()
+		*v = SACKEnabled(p.sackEnabled)
+		p.mu.Unlock()
+		return nil
+
+	case *SendBufferSizeOption:
+		p.mu.Lock()
+		*v = p.sendBufferSize
+		p.mu.Unlock()
+		return nil
+
+	case *ReceiveBufferSizeOption:
+		p.mu.Lock()
+		*v = p.recvBufferSize
+		p.mu.Unlock()
+		return nil
+
+	default:
+		return tcpip.ErrUnknownProtocolOption
+	}
+}
+
+func init() {
+	stack.RegisterTransportProtocolFactory(ProtocolName, func() stack.TransportProtocol {
+		return &protocol{
+			sendBufferSize: SendBufferSizeOption{minBufferSize, DefaultBufferSize, maxBufferSize},
+			recvBufferSize: ReceiveBufferSizeOption{minBufferSize, DefaultBufferSize, maxBufferSize},
+		}
+	})
+}