Implement getsockopt(TCP_INFO).

Export some readily-available fields for TCP_INFO and stub out the rest.

PiperOrigin-RevId: 261191548

1 files changed, 17 insertions, 10 deletions

diff --git a/pkg/tcpip/transport/tcp/rcv.go b/pkg/tcpip/transport/tcp/rcv.go
index e90f9a7d9..a8f490c4a 100644
--- a/pkg/tcpip/transport/tcp/rcv.go
+++ b/pkg/tcpip/transport/tcp/rcv.go
@@ -220,25 +220,24 @@ func (r *receiver) consumeSegment(s *segment, segSeq seqnum.Value, segLen seqnum
 	return true
 }
 
-// updateRTT updates the receiver RTT measurement based on the sequence number
-// of the received segment.
-func (r *receiver) updateRTT() {
+// updateRTTLocked updates the receiver RTT measurement based on the sequence
+// number of the received segment.
+//
+// Precondition: Caller must hold r.ep.rcvListMu.
+func (r *receiver) updateRTTLocked() {
 	// From: https://public.lanl.gov/radiant/pubs/drs/sc2001-poster.pdf
 	//
 	// A system that is only transmitting acknowledgements can still
 	// estimate the round-trip time by observing the time between when a byte
 	// is first acknowledged and the receipt of data that is at least one
 	// window beyond the sequence number that was acknowledged.
-	r.ep.rcvListMu.Lock()
 	if r.ep.rcvAutoParams.rttMeasureTime.IsZero() {
 		// New measurement.
 		r.ep.rcvAutoParams.rttMeasureTime = time.Now()
 		r.ep.rcvAutoParams.rttMeasureSeqNumber = r.rcvNxt.Add(r.rcvWnd)
-		r.ep.rcvListMu.Unlock()
 		return
 	}
 	if r.rcvNxt.LessThan(r.ep.rcvAutoParams.rttMeasureSeqNumber) {
-		r.ep.rcvListMu.Unlock()
 		return
 	}
 	rtt := time.Since(r.ep.rcvAutoParams.rttMeasureTime)
@@ -250,7 +249,6 @@ func (r *receiver) updateRTT() {
 	}
 	r.ep.rcvAutoParams.rttMeasureTime = time.Now()
 	r.ep.rcvAutoParams.rttMeasureSeqNumber = r.rcvNxt.Add(r.rcvWnd)
-	r.ep.rcvListMu.Unlock()
 }
 
 // handleRcvdSegment handles TCP segments directed at the connection managed by
@@ -291,11 +289,20 @@ func (r *receiver) handleRcvdSegment(s *segment) {
 		return
 	}
 
-	// Since we consumed a segment update the receiver's RTT estimate
-	// if required.
+	r.ep.rcvListMu.Lock()
+	// FIXME(b/137581805): Using the runtime clock here is incorrect as it
+	// doesn't account for potentially virtualized time.
+	now := time.Now().UnixNano()
+	if s.flagIsSet(header.TCPFlagAck) {
+		r.ep.rcvLastAckNanos = now
+	}
 	if segLen > 0 {
-		r.updateRTT()
+		// Since we consumed a segment update the receiver's RTT estimate if
+		// required.
+		r.ep.rcvLastDataNanos = now
+		r.updateRTTLocked()
 	}
+	r.ep.rcvListMu.Unlock()
 
 	// By consuming the current segment, we may have filled a gap in the
 	// sequence number domain that allows pending segments to be consumed