Add support for TCP receive buffer auto tuning.

The implementation is similar to linux where we track the number of bytes
consumed by the application to grow the receive buffer of a given TCP endpoint.

This ensures that the advertised window grows at a reasonable rate to accomodate
for the sender's rate and prevents large amounts of data being held in stack
buffers if the application is not actively reading or not reading fast enough.

The original paper that was used to implement the linux receive buffer auto-
tuning is available @ https://public.lanl.gov/radiant/pubs/drs/lacsi2001.pdf

NOTE: Linux does not implement DRS as defined in that paper, it's just a good
reference to understand the solution space.

Updates #230

PiperOrigin-RevId: 253168283

1 files changed, 29 insertions, 7 deletions

diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
index 919e4ce24..ee04dcfcc 100644
--- a/pkg/tcpip/transport/tcp/protocol.go
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -41,13 +41,18 @@ const (
 	ProtocolNumber = header.TCPProtocolNumber
 
 	// MinBufferSize is the smallest size of a receive or send buffer.
-	minBufferSize = 4 << 10 // 4096 bytes.
+	MinBufferSize = 4 << 10 // 4096 bytes.
 
-	// DefaultBufferSize is the default size of the receive and send buffers.
-	DefaultBufferSize = 1 << 20 // 1MB
+	// DefaultSendBufferSize is the default size of the send buffer for
+	// an endpoint.
+	DefaultSendBufferSize = 1 << 20 // 1MB
 
-	// MaxBufferSize is the largest size a receive and send buffer can grow to.
-	maxBufferSize = 4 << 20 // 4MB
+	// DefaultReceiveBufferSize is the default size of the receive buffer
+	// for an endpoint.
+	DefaultReceiveBufferSize = 1 << 20 // 1MB
+
+	// MaxBufferSize is the largest size a receive/send buffer can grow to.
+	MaxBufferSize = 4 << 20 // 4MB
 
 	// MaxUnprocessedSegments is the maximum number of unprocessed segments
 	// that can be queued for a given endpoint.
@@ -86,6 +91,7 @@ type protocol struct {
 	recvBufferSize             ReceiveBufferSizeOption
 	congestionControl          string
 	availableCongestionControl []string
+	moderateReceiveBuffer      bool
 }
 
 // Number returns the tcp protocol number.
@@ -192,6 +198,13 @@ func (p *protocol) SetOption(option interface{}) *tcpip.Error {
 		// linux returns ENOENT when an invalid congestion control
 		// is specified.
 		return tcpip.ErrNoSuchFile
+
+	case tcpip.ModerateReceiveBufferOption:
+		p.mu.Lock()
+		p.moderateReceiveBuffer = bool(v)
+		p.mu.Unlock()
+		return nil
+
 	default:
 		return tcpip.ErrUnknownProtocolOption
 	}
@@ -217,16 +230,25 @@ func (p *protocol) Option(option interface{}) *tcpip.Error {
 		*v = p.recvBufferSize
 		p.mu.Unlock()
 		return nil
+
 	case *tcpip.CongestionControlOption:
 		p.mu.Lock()
 		*v = tcpip.CongestionControlOption(p.congestionControl)
 		p.mu.Unlock()
 		return nil
+
 	case *tcpip.AvailableCongestionControlOption:
 		p.mu.Lock()
 		*v = tcpip.AvailableCongestionControlOption(strings.Join(p.availableCongestionControl, " "))
 		p.mu.Unlock()
 		return nil
+
+	case *tcpip.ModerateReceiveBufferOption:
+		p.mu.Lock()
+		*v = tcpip.ModerateReceiveBufferOption(p.moderateReceiveBuffer)
+		p.mu.Unlock()
+		return nil
+
 	default:
 		return tcpip.ErrUnknownProtocolOption
 	}
@@ -235,8 +257,8 @@ func (p *protocol) Option(option interface{}) *tcpip.Error {
 func init() {
 	stack.RegisterTransportProtocolFactory(ProtocolName, func() stack.TransportProtocol {
 		return &protocol{
-			sendBufferSize:             SendBufferSizeOption{minBufferSize, DefaultBufferSize, maxBufferSize},
-			recvBufferSize:             ReceiveBufferSizeOption{minBufferSize, DefaultBufferSize, maxBufferSize},
+			sendBufferSize:             SendBufferSizeOption{MinBufferSize, DefaultSendBufferSize, MaxBufferSize},
+			recvBufferSize:             ReceiveBufferSizeOption{MinBufferSize, DefaultReceiveBufferSize, MaxBufferSize},
 			congestionControl:          ccReno,
 			availableCongestionControl: []string{ccReno, ccCubic},
 		}