Add support for more fields in netstack for TCP_INFO

This CL adds support for the following fields:
- RTT, RTTVar, RTO
- send congestion window (sndCwnd) and send slow start threshold (sndSsthresh)
- congestion control state(CaState)
- ReorderSeen

PiperOrigin-RevId: 354195361

4 files changed, 75 insertions, 41 deletions

diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 812ee36ed..e70ae69ef 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -993,12 +993,54 @@ type SettableSocketOption interface {
 	isSettableSocketOption()
 }
 
+// CongestionControlState indicates the current congestion control state for
+// TCP sender.
+type CongestionControlState int
+
+const (
+	// Open indicates that the sender is receiving acks in order and
+	// no loss or dupACK's etc have been detected.
+	Open CongestionControlState = iota
+	// RTORecovery indicates that an RTO has occurred and the sender
+	// has entered an RTO based recovery phase.
+	RTORecovery
+	// FastRecovery indicates that the sender has entered FastRecovery
+	// based on receiving nDupAck's. This state is entered only when
+	// SACK is not in use.
+	FastRecovery
+	// SACKRecovery indicates that the sender has entered SACK based
+	// recovery.
+	SACKRecovery
+	// Disorder indicates the sender either received some SACK blocks
+	// or dupACK's.
+	Disorder
+)
+
 // TCPInfoOption is used by GetSockOpt to expose TCP statistics.
 //
 // TODO(b/64800844): Add and populate stat fields.
 type TCPInfoOption struct {
-	RTT    time.Duration
+	// RTT is the smoothed round trip time.
+	RTT time.Duration
+
+	// RTTVar is the round trip time variation.
 	RTTVar time.Duration
+
+	// RTO is the retransmission timeout for the endpoint.
+	RTO time.Duration
+
+	// CcState is the congestion control state.
+	CcState CongestionControlState
+
+	// SndCwnd is the congestion window, in packets.
+	SndCwnd uint32
+
+	// SndSsthresh is the threshold between slow start and congestion
+	// avoidance.
+	SndSsthresh uint32
+
+	// ReorderSeen indicates if reordering is seen in the endpoint.
+	ReorderSeen bool
 }
 
 func (*TCPInfoOption) isGettableSocketOption() {}
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index b6bd6d455..bfa5b01fb 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -2011,20 +2011,34 @@ func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 	}
 }
 
+func (e *endpoint) getTCPInfo() tcpip.TCPInfoOption {
+	info := tcpip.TCPInfoOption{}
+	e.LockUser()
+	snd := e.snd
+	if snd != nil {
+		// We do not calculate RTT before sending the data packets. If
+		// the connection did not send and receive data, then RTT will
+		// be zero.
+		snd.rtt.Lock()
+		info.RTT = snd.rtt.srtt
+		info.RTTVar = snd.rtt.rttvar
+		snd.rtt.Unlock()
+
+		info.RTO = snd.rto
+		info.CcState = snd.state
+		info.SndSsthresh = uint32(snd.sndSsthresh)
+		info.SndCwnd = uint32(snd.sndCwnd)
+		info.ReorderSeen = snd.rc.reorderSeen
+	}
+	e.UnlockUser()
+	return info
+}
+
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
 func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error {
 	switch o := opt.(type) {
 	case *tcpip.TCPInfoOption:
-		*o = tcpip.TCPInfoOption{}
-		e.LockUser()
-		snd := e.snd
-		e.UnlockUser()
-		if snd != nil {
-			snd.rtt.Lock()
-			o.RTT = snd.rtt.srtt
-			o.RTTVar = snd.rtt.rttvar
-			snd.rtt.Unlock()
-		}
+		*o = e.getTCPInfo()
 
 	case *tcpip.KeepaliveIdleOption:
 		e.keepalive.Lock()
diff --git a/pkg/tcpip/transport/tcp/rack.go b/pkg/tcpip/transport/tcp/rack.go
index 307bacca5..fdb7e3dc6 100644
--- a/pkg/tcpip/transport/tcp/rack.go
+++ b/pkg/tcpip/transport/tcp/rack.go
@@ -162,7 +162,7 @@ func (s *sender) shouldSchedulePTO() bool {
 		// The connection supports SACK.
 		s.ep.sackPermitted &&
 		// The connection is not in loss recovery.
-		(s.state != RTORecovery && s.state != SACKRecovery) &&
+		(s.state != tcpip.RTORecovery && s.state != tcpip.SACKRecovery) &&
 		// The connection has no SACKed sequences in the SACK scoreboard.
 		s.ep.scoreboard.Sacked() == 0
 }
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index 079d90848..28ef9f899 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -48,28 +48,6 @@ const (
 	MaxRetries = 15
 )
 
-// ccState indicates the current congestion control state for this sender.
-type ccState int
-
-const (
-	// Open indicates that the sender is receiving acks in order and
-	// no loss or dupACK's etc have been detected.
-	Open ccState = iota
-	// RTORecovery indicates that an RTO has occurred and the sender
-	// has entered an RTO based recovery phase.
-	RTORecovery
-	// FastRecovery indicates that the sender has entered FastRecovery
-	// based on receiving nDupAck's. This state is entered only when
-	// SACK is not in use.
-	FastRecovery
-	// SACKRecovery indicates that the sender has entered SACK based
-	// recovery.
-	SACKRecovery
-	// Disorder indicates the sender either received some SACK blocks
-	// or dupACK's.
-	Disorder
-)
-
 // congestionControl is an interface that must be implemented by any supported
 // congestion control algorithm.
 type congestionControl interface {
@@ -204,7 +182,7 @@ type sender struct {
 	maxSentAck seqnum.Value
 
 	// state is the current state of congestion control for this endpoint.
-	state ccState
+	state tcpip.CongestionControlState
 
 	// cc is the congestion control algorithm in use for this sender.
 	cc congestionControl
@@ -593,7 +571,7 @@ func (s *sender) retransmitTimerExpired() bool {
 		s.leaveRecovery()
 	}
 
-	s.state = RTORecovery
+	s.state = tcpip.RTORecovery
 	s.cc.HandleRTOExpired()
 
 	// Mark the next segment to be sent as the first unacknowledged one and
@@ -1018,7 +996,7 @@ func (s *sender) sendData() {
 	// "A TCP SHOULD set cwnd to no more than RW before beginning
 	// transmission if the TCP has not sent data in the interval exceeding
 	// the retrasmission timeout."
-	if !s.fr.active && s.state != RTORecovery && time.Now().Sub(s.lastSendTime) > s.rto {
+	if !s.fr.active && s.state != tcpip.RTORecovery && time.Now().Sub(s.lastSendTime) > s.rto {
 		if s.sndCwnd > InitialCwnd {
 			s.sndCwnd = InitialCwnd
 		}
@@ -1062,14 +1040,14 @@ func (s *sender) enterRecovery() {
 	s.fr.highRxt = s.sndUna
 	s.fr.rescueRxt = s.sndUna
 	if s.ep.sackPermitted {
-		s.state = SACKRecovery
+		s.state = tcpip.SACKRecovery
 		s.ep.stack.Stats().TCP.SACKRecovery.Increment()
 		// Set TLPRxtOut to false according to
 		// https://tools.ietf.org/html/draft-ietf-tcpm-rack-08#section-7.6.1.
 		s.rc.tlpRxtOut = false
 		return
 	}
-	s.state = FastRecovery
+	s.state = tcpip.FastRecovery
 	s.ep.stack.Stats().TCP.FastRecovery.Increment()
 }
 
@@ -1166,7 +1144,7 @@ func (s *sender) detectLoss(seg *segment) (fastRetransmit bool) {
 		s.fr.highRxt = s.sndUna - 1
 		// Do run SetPipe() to calculate the outstanding segments.
 		s.SetPipe()
-		s.state = Disorder
+		s.state = tcpip.Disorder
 		return false
 	}
 
@@ -1464,7 +1442,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 		if !s.fr.active {
 			s.cc.Update(originalOutstanding - s.outstanding)
 			if s.fr.last.LessThan(s.sndUna) {
-				s.state = Open
+				s.state = tcpip.Open
 			}
 		}