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, 11 insertions, 0 deletions

diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 2f931a5a3..4aafb51ab 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -381,6 +381,13 @@ type Endpoint interface {
 	// State returns a socket's lifecycle state. The returned value is
 	// protocol-specific and is primarily used for diagnostics.
 	State() uint32
+
+	// ModerateRecvBuf should be called everytime data is copied to the user
+	// space. This allows for dynamic tuning of recv buffer space for a
+	// given socket.
+	//
+	// NOTE: This method is a no-op for sockets other than TCP.
+	ModerateRecvBuf(copied int)
 }
 
 // WriteOptions contains options for Endpoint.Write.
@@ -480,6 +487,10 @@ type CongestionControlOption string
 // control algorithms.
 type AvailableCongestionControlOption string
 
+// ModerateReceiveBufferOption allows the caller to enable/disable TCP receive
+// buffer moderation.
+type ModerateReceiveBufferOption bool
+
 // MulticastTTLOption is used by SetSockOpt/GetSockOpt to control the default
 // TTL value for multicast messages. The default is 1.
 type MulticastTTLOption uint8