Add support for TCP_USER_TIMEOUT option.

The implementation follows the linux behavior where specifying
a TCP_USER_TIMEOUT will cause the resend timer to honor the
user specified timeout rather than the default rto based timeout.

Further it alters when connections are timedout due to keepalive
failures. It does not alter the behavior of when keepalives are
sent. This is as per the linux behavior.

PiperOrigin-RevId: 285099795

1 files changed, 19 insertions, 0 deletions

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 4861ab513..dd8b47cbe 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -341,6 +341,7 @@ type endpoint struct {
 	// TCP should never broadcast but Linux nevertheless supports enabling/
 	// disabling SO_BROADCAST, albeit as a NOOP.
 	broadcast bool
+
 	// Values used to reserve a port or register a transport endpoint
 	// (which ever happens first).
 	boundBindToDevice tcpip.NICID
@@ -474,6 +475,12 @@ type endpoint struct {
 	// without hearing a response, the connection is closed.
 	keepalive keepalive
 
+	// userTimeout if non-zero specifies a user specified timeout for
+	// a connection w/ pending data to send. A connection that has pending
+	// unacked data will be forcibily aborted if the timeout is reached
+	// without any data being acked.
+	userTimeout time.Duration
+
 	// pendingAccepted is a synchronization primitive used to track number
 	// of connections that are queued up to be delivered to the accepted
 	// channel. We use this to ensure that all goroutines blocked on writing
@@ -1333,6 +1340,12 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 		e.notifyProtocolGoroutine(notifyKeepaliveChanged)
 		return nil
 
+	case tcpip.TCPUserTimeoutOption:
+		e.mu.Lock()
+		e.userTimeout = time.Duration(v)
+		e.mu.Unlock()
+		return nil
+
 	case tcpip.BroadcastOption:
 		e.mu.Lock()
 		e.broadcast = v != 0
@@ -1591,6 +1604,12 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 		e.keepalive.Unlock()
 		return nil
 
+	case *tcpip.TCPUserTimeoutOption:
+		e.mu.Lock()
+		*o = tcpip.TCPUserTimeoutOption(e.userTimeout)
+		e.mu.Unlock()
+		return nil
+
 	case *tcpip.OutOfBandInlineOption:
 		// We don't currently support disabling this option.
 		*o = 1