De-duplicate TCP state in TCPEndpointState vs tcp.endpoint

This change replaces individual private members in tcp.endpoint with a single
private TCPEndpointState member.

Some internal substructures within endpoint (receiver, sender) have been broken
into a public substructure (which is then copied into the TCPEndpointState
returned from completeState()) alongside other private fields.

Fixes #4466

PiperOrigin-RevId: 369329514

21 files changed, 1268 insertions, 1419 deletions

diff --git a/pkg/tcpip/stack/BUILD b/pkg/tcpip/stack/BUILD
index d19b879dc..2bd6a67f5 100644
--- a/pkg/tcpip/stack/BUILD
+++ b/pkg/tcpip/stack/BUILD
@@ -67,6 +67,7 @@ go_library(
         "stack.go",
         "stack_global_state.go",
         "stack_options.go",
+        "tcp.go",
         "transport_demuxer.go",
         "tuple_list.go",
     ],
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index f23112410..8c8909acd 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -35,7 +35,6 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/ports"
-	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
@@ -56,306 +55,6 @@ type transportProtocolState struct {
 	defaultHandler func(id TransportEndpointID, pkt *PacketBuffer) bool
 }
 
-// TCPProbeFunc is the expected function type for a TCP probe function to be
-// passed to stack.AddTCPProbe.
-type TCPProbeFunc func(s TCPEndpointState)
-
-// TCPCubicState is used to hold a copy of the internal cubic state when the
-// TCPProbeFunc is invoked.
-type TCPCubicState struct {
-	WLastMax                float64
-	WMax                    float64
-	T                       time.Time
-	TimeSinceLastCongestion time.Duration
-	C                       float64
-	K                       float64
-	Beta                    float64
-	WC                      float64
-	WEst                    float64
-}
-
-// TCPRACKState is used to hold a copy of the internal RACK state when the
-// TCPProbeFunc is invoked.
-type TCPRACKState struct {
-	XmitTime      time.Time
-	EndSequence   seqnum.Value
-	FACK          seqnum.Value
-	RTT           time.Duration
-	Reord         bool
-	DSACKSeen     bool
-	ReoWnd        time.Duration
-	ReoWndIncr    uint8
-	ReoWndPersist int8
-	RTTSeq        seqnum.Value
-}
-
-// TCPEndpointID is the unique 4 tuple that identifies a given endpoint.
-type TCPEndpointID struct {
-	// LocalPort is the local port associated with the endpoint.
-	LocalPort uint16
-
-	// LocalAddress is the local [network layer] address associated with
-	// the endpoint.
-	LocalAddress tcpip.Address
-
-	// RemotePort is the remote port associated with the endpoint.
-	RemotePort uint16
-
-	// RemoteAddress it the remote [network layer] address associated with
-	// the endpoint.
-	RemoteAddress tcpip.Address
-}
-
-// TCPFastRecoveryState holds a copy of the internal fast recovery state of a
-// TCP endpoint.
-type TCPFastRecoveryState struct {
-	// Active if true indicates the endpoint is in fast recovery.
-	Active bool
-
-	// First is the first unacknowledged sequence number being recovered.
-	First seqnum.Value
-
-	// Last is the 'recover' sequence number that indicates the point at
-	// which we should exit recovery barring any timeouts etc.
-	Last seqnum.Value
-
-	// MaxCwnd is the maximum value we are permitted to grow the congestion
-	// window during recovery. This is set at the time we enter recovery.
-	MaxCwnd int
-
-	// HighRxt is the highest sequence number which has been retransmitted
-	// during the current loss recovery phase.
-	// See: RFC 6675 Section 2 for details.
-	HighRxt seqnum.Value
-
-	// RescueRxt is the highest sequence number which has been
-	// optimistically retransmitted to prevent stalling of the ACK clock
-	// when there is loss at the end of the window and no new data is
-	// available for transmission.
-	// See: RFC 6675 Section 2 for details.
-	RescueRxt seqnum.Value
-}
-
-// TCPReceiverState holds a copy of the internal state of the receiver for
-// a given TCP endpoint.
-type TCPReceiverState struct {
-	// RcvNxt is the TCP variable RCV.NXT.
-	RcvNxt seqnum.Value
-
-	// RcvAcc is the TCP variable RCV.ACC.
-	RcvAcc seqnum.Value
-
-	// RcvWndScale is the window scaling to use for inbound segments.
-	RcvWndScale uint8
-
-	// PendingBufUsed is the number of bytes pending in the receive
-	// queue.
-	PendingBufUsed int
-}
-
-// TCPSenderState holds a copy of the internal state of the sender for
-// a given TCP Endpoint.
-type TCPSenderState struct {
-	// LastSendTime is the time at which we sent the last segment.
-	LastSendTime time.Time
-
-	// DupAckCount is the number of Duplicate ACK's received.
-	DupAckCount int
-
-	// SndCwnd is the size of the sending congestion window in packets.
-	SndCwnd int
-
-	// Ssthresh is the slow start threshold in packets.
-	Ssthresh int
-
-	// SndCAAckCount is the number of packets consumed in congestion
-	// avoidance mode.
-	SndCAAckCount int
-
-	// Outstanding is the number of packets in flight.
-	Outstanding int
-
-	// SackedOut is the number of packets which have been selectively acked.
-	SackedOut int
-
-	// SndWnd is the send window size in bytes.
-	SndWnd seqnum.Size
-
-	// SndUna is the next unacknowledged sequence number.
-	SndUna seqnum.Value
-
-	// SndNxt is the sequence number of the next segment to be sent.
-	SndNxt seqnum.Value
-
-	// RTTMeasureSeqNum is the sequence number being used for the latest RTT
-	// measurement.
-	RTTMeasureSeqNum seqnum.Value
-
-	// RTTMeasureTime is the time when the RTTMeasureSeqNum was sent.
-	RTTMeasureTime time.Time
-
-	// Closed indicates that the caller has closed the endpoint for sending.
-	Closed bool
-
-	// SRTT is the smoothed round-trip time as defined in section 2 of
-	// RFC 6298.
-	SRTT time.Duration
-
-	// RTO is the retransmit timeout as defined in section of 2 of RFC 6298.
-	RTO time.Duration
-
-	// RTTVar is the round-trip time variation as defined in section 2 of
-	// RFC 6298.
-	RTTVar time.Duration
-
-	// SRTTInited if true indicates take a valid RTT measurement has been
-	// completed.
-	SRTTInited bool
-
-	// MaxPayloadSize is the maximum size of the payload of a given segment.
-	// It is initialized on demand.
-	MaxPayloadSize int
-
-	// SndWndScale is the number of bits to shift left when reading the send
-	// window size from a segment.
-	SndWndScale uint8
-
-	// MaxSentAck is the highest acknowledgement number sent till now.
-	MaxSentAck seqnum.Value
-
-	// FastRecovery holds the fast recovery state for the endpoint.
-	FastRecovery TCPFastRecoveryState
-
-	// Cubic holds the state related to CUBIC congestion control.
-	Cubic TCPCubicState
-
-	// RACKState holds the state related to RACK loss detection algorithm.
-	RACKState TCPRACKState
-}
-
-// TCPSACKInfo holds TCP SACK related information for a given TCP endpoint.
-type TCPSACKInfo struct {
-	// Blocks is the list of SACK Blocks that identify the out of order segments
-	// held by a given TCP endpoint.
-	Blocks []header.SACKBlock
-
-	// ReceivedBlocks are the SACK blocks received by this endpoint
-	// from the peer endpoint.
-	ReceivedBlocks []header.SACKBlock
-
-	// MaxSACKED is the highest sequence number that has been SACKED
-	// by the peer.
-	MaxSACKED seqnum.Value
-}
-
-// RcvBufAutoTuneParams holds state related to TCP receive buffer auto-tuning.
-type RcvBufAutoTuneParams struct {
-	// MeasureTime is the time at which the current measurement
-	// was started.
-	MeasureTime time.Time
-
-	// CopiedBytes is the number of bytes copied to user space since
-	// this measure began.
-	CopiedBytes int
-
-	// PrevCopiedBytes is the number of bytes copied to userspace in
-	// the previous RTT period.
-	PrevCopiedBytes int
-
-	// RcvBufSize is the auto tuned receive buffer size.
-	RcvBufSize int
-
-	// RTT is the smoothed RTT as measured 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.
-	RTT time.Duration
-
-	// RTTVar is the "round-trip time variation" as defined in section 2
-	// of RFC6298.
-	RTTVar time.Duration
-
-	// RTTMeasureSeqNumber is the highest acceptable sequence number at the
-	// time this RTT measurement period began.
-	RTTMeasureSeqNumber seqnum.Value
-
-	// RTTMeasureTime is the absolute time at which the current RTT
-	// measurement period began.
-	RTTMeasureTime time.Time
-
-	// Disabled is true if an explicit receive buffer is set for the
-	// endpoint.
-	Disabled bool
-}
-
-// TCPEndpointState is a copy of the internal state of a TCP endpoint.
-type TCPEndpointState struct {
-	// ID is a copy of the TransportEndpointID for the endpoint.
-	ID TCPEndpointID
-
-	// SegTime denotes the absolute time when this segment was received.
-	SegTime time.Time
-
-	// RcvBufSize is the size of the receive socket buffer for the endpoint.
-	RcvBufSize int
-
-	// RcvBufUsed is the amount of bytes actually held in the receive socket
-	// buffer for the endpoint.
-	RcvBufUsed int
-
-	// RcvBufAutoTuneParams is used to hold state variables to compute
-	// the auto tuned receive buffer size.
-	RcvAutoParams RcvBufAutoTuneParams
-
-	// RcvClosed if true, indicates the endpoint has been closed for reading.
-	RcvClosed bool
-
-	// SendTSOk is used to indicate when the TS Option has been negotiated.
-	// When sendTSOk is true every non-RST segment should carry a TS as per
-	// RFC7323#section-1.1.
-	SendTSOk bool
-
-	// RecentTS is the timestamp that should be sent in the TSEcr field of
-	// the timestamp for future segments sent by the endpoint. This field is
-	// updated if required when a new segment is received by this endpoint.
-	RecentTS uint32
-
-	// TSOffset is a randomized offset added to the value of the TSVal field
-	// in the timestamp option.
-	TSOffset uint32
-
-	// SACKPermitted is set to true if the peer sends the TCPSACKPermitted
-	// option in the SYN/SYN-ACK.
-	SACKPermitted bool
-
-	// SACK holds TCP SACK related information for this endpoint.
-	SACK TCPSACKInfo
-
-	// SndBufSize is the size of the socket send buffer.
-	SndBufSize int
-
-	// SndBufUsed is the number of bytes held in the socket send buffer.
-	SndBufUsed int
-
-	// SndClosed indicates that the endpoint has been closed for sends.
-	SndClosed bool
-
-	// SndBufInQueue is the number of bytes in the send queue.
-	SndBufInQueue seqnum.Size
-
-	// PacketTooBigCount is used to notify the main protocol routine how
-	// many times a "packet too big" control packet is received.
-	PacketTooBigCount int
-
-	// SndMTU is the smallest MTU seen in the control packets received.
-	SndMTU int
-
-	// Receiver holds variables related to the TCP receiver for the endpoint.
-	Receiver TCPReceiverState
-
-	// Sender holds state related to the TCP Sender for the endpoint.
-	Sender TCPSenderState
-}
-
 // ResumableEndpoint is an endpoint that needs to be resumed after restore.
 type ResumableEndpoint interface {
 	// Resume resumes an endpoint after restore. This can be used to restart
diff --git a/pkg/tcpip/stack/stack_global_state.go b/pkg/tcpip/stack/stack_global_state.go
index dfec4258a..33824afd0 100644
--- a/pkg/tcpip/stack/stack_global_state.go
+++ b/pkg/tcpip/stack/stack_global_state.go
@@ -14,6 +14,78 @@
 
 package stack
 
+import "time"
+
 // StackFromEnv is the global stack created in restore run.
 // FIXME(b/36201077)
 var StackFromEnv *Stack
+
+// saveT is invoked by stateify.
+func (t *TCPCubicState) saveT() unixTime {
+	return unixTime{t.T.Unix(), t.T.UnixNano()}
+}
+
+// loadT is invoked by stateify.
+func (t *TCPCubicState) loadT(unix unixTime) {
+	t.T = time.Unix(unix.second, unix.nano)
+}
+
+// saveXmitTime is invoked by stateify.
+func (t *TCPRACKState) saveXmitTime() unixTime {
+	return unixTime{t.XmitTime.Unix(), t.XmitTime.UnixNano()}
+}
+
+// loadXmitTime is invoked by stateify.
+func (t *TCPRACKState) loadXmitTime(unix unixTime) {
+	t.XmitTime = time.Unix(unix.second, unix.nano)
+}
+
+// saveLastSendTime is invoked by stateify.
+func (t *TCPSenderState) saveLastSendTime() unixTime {
+	return unixTime{t.LastSendTime.Unix(), t.LastSendTime.UnixNano()}
+}
+
+// loadLastSendTime is invoked by stateify.
+func (t *TCPSenderState) loadLastSendTime(unix unixTime) {
+	t.LastSendTime = time.Unix(unix.second, unix.nano)
+}
+
+// saveRTTMeasureTime is invoked by stateify.
+func (t *TCPSenderState) saveRTTMeasureTime() unixTime {
+	return unixTime{t.RTTMeasureTime.Unix(), t.RTTMeasureTime.UnixNano()}
+}
+
+// loadRTTMeasureTime is invoked by stateify.
+func (t *TCPSenderState) loadRTTMeasureTime(unix unixTime) {
+	t.RTTMeasureTime = time.Unix(unix.second, unix.nano)
+}
+
+// saveMeasureTime is invoked by stateify.
+func (r *RcvBufAutoTuneParams) saveMeasureTime() unixTime {
+	return unixTime{r.MeasureTime.Unix(), r.MeasureTime.UnixNano()}
+}
+
+// loadMeasureTime is invoked by stateify.
+func (r *RcvBufAutoTuneParams) loadMeasureTime(unix unixTime) {
+	r.MeasureTime = time.Unix(unix.second, unix.nano)
+}
+
+// saveRTTMeasureTime is invoked by stateify.
+func (r *RcvBufAutoTuneParams) saveRTTMeasureTime() unixTime {
+	return unixTime{r.RTTMeasureTime.Unix(), r.RTTMeasureTime.UnixNano()}
+}
+
+// loadRTTMeasureTime is invoked by stateify.
+func (r *RcvBufAutoTuneParams) loadRTTMeasureTime(unix unixTime) {
+	r.RTTMeasureTime = time.Unix(unix.second, unix.nano)
+}
+
+// saveSegTime is invoked by stateify.
+func (t *TCPEndpointState) saveSegTime() unixTime {
+	return unixTime{t.SegTime.Unix(), t.SegTime.UnixNano()}
+}
+
+// loadSegTime is invoked by stateify.
+func (t *TCPEndpointState) loadSegTime(unix unixTime) {
+	t.SegTime = time.Unix(unix.second, unix.nano)
+}
diff --git a/pkg/tcpip/stack/tcp.go b/pkg/tcpip/stack/tcp.go
new file mode 100644
index 000000000..2e32b8a8e
--- /dev/null
+++ b/pkg/tcpip/stack/tcp.go
@@ -0,0 +1,455 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package stack
+
+import (
+	"time"
+
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
+)
+
+// TCPProbeFunc is the expected function type for a TCP probe function to be
+// passed to stack.AddTCPProbe.
+type TCPProbeFunc func(s TCPEndpointState)
+
+// TCPCubicState is used to hold a copy of the internal cubic state when the
+// TCPProbeFunc is invoked.
+//
+// +stateify savable
+type TCPCubicState struct {
+	// WLastMax is the previous wMax value.
+	WLastMax float64
+
+	// WMax is the value of the congestion window at the time of the last
+	// congestion event.
+	WMax float64
+
+	// T is the time when the current congestion avoidance was entered.
+	T time.Time `state:".(unixTime)"`
+
+	// TimeSinceLastCongestion denotes the time since the current
+	// congestion avoidance was entered.
+	TimeSinceLastCongestion time.Duration
+
+	// C is the cubic constant as specified in RFC8312, page 11.
+	C float64
+
+	// K is the time period (in seconds) that the above function takes to
+	// increase the current window size to WMax if there are no further
+	// congestion events and is calculated using the following equation:
+	//
+	// K = cubic_root(WMax*(1-beta_cubic)/C) (Eq. 2, page 5)
+	K float64
+
+	// Beta is the CUBIC multiplication decrease factor. That is, when a
+	// congestion event is detected, CUBIC reduces its cwnd to
+	// WC(0)=WMax*beta_cubic.
+	Beta float64
+
+	// WC is window computed by CUBIC at time TimeSinceLastCongestion. It's
+	// calculated using the formula:
+	//
+	//  WC(TimeSinceLastCongestion) = C*(t-K)^3 + WMax (Eq. 1)
+	WC float64
+
+	// WEst is the window computed by CUBIC at time
+	// TimeSinceLastCongestion+RTT i.e WC(TimeSinceLastCongestion+RTT).
+	WEst float64
+}
+
+// TCPRACKState is used to hold a copy of the internal RACK state when the
+// TCPProbeFunc is invoked.
+//
+// +stateify savable
+type TCPRACKState struct {
+	// XmitTime is the transmission timestamp of the most recent
+	// acknowledged segment.
+	XmitTime time.Time `state:".(unixTime)"`
+
+	// EndSequence is the ending TCP sequence number of the most recent
+	// acknowledged segment.
+	EndSequence seqnum.Value
+
+	// FACK is the highest selectively or cumulatively acknowledged
+	// sequence.
+	FACK seqnum.Value
+
+	// RTT is the round trip time of the most recently delivered packet on
+	// the connection (either cumulatively acknowledged or selectively
+	// acknowledged) that was not marked invalid as a possible spurious
+	// retransmission.
+	RTT time.Duration
+
+	// Reord is true iff reordering has been detected on this connection.
+	Reord bool
+
+	// DSACKSeen is true iff the connection has seen a DSACK.
+	DSACKSeen bool
+
+	// ReoWnd is the reordering window time used for recording packet
+	// transmission times. It is used to defer the moment at which RACK
+	// marks a packet lost.
+	ReoWnd time.Duration
+
+	// ReoWndIncr is the multiplier applied to adjust reorder window.
+	ReoWndIncr uint8
+
+	// ReoWndPersist is the number of loss recoveries before resetting
+	// reorder window.
+	ReoWndPersist int8
+
+	// RTTSeq is the SND.NXT when RTT is updated.
+	RTTSeq seqnum.Value
+}
+
+// TCPEndpointID is the unique 4 tuple that identifies a given endpoint.
+//
+// +stateify savable
+type TCPEndpointID struct {
+	// LocalPort is the local port associated with the endpoint.
+	LocalPort uint16
+
+	// LocalAddress is the local [network layer] address associated with
+	// the endpoint.
+	LocalAddress tcpip.Address
+
+	// RemotePort is the remote port associated with the endpoint.
+	RemotePort uint16
+
+	// RemoteAddress it the remote [network layer] address associated with
+	// the endpoint.
+	RemoteAddress tcpip.Address
+}
+
+// TCPFastRecoveryState holds a copy of the internal fast recovery state of a
+// TCP endpoint.
+//
+// +stateify savable
+type TCPFastRecoveryState struct {
+	// Active if true indicates the endpoint is in fast recovery. The
+	// following fields are only meaningful when Active is true.
+	Active bool
+
+	// First is the first unacknowledged sequence number being recovered.
+	First seqnum.Value
+
+	// Last is the 'recover' sequence number that indicates the point at
+	// which we should exit recovery barring any timeouts etc.
+	Last seqnum.Value
+
+	// MaxCwnd is the maximum value we are permitted to grow the congestion
+	// window during recovery. This is set at the time we enter recovery.
+	// It exists to avoid attacks where the receiver intentionally sends
+	// duplicate acks to artificially inflate the sender's cwnd.
+	MaxCwnd int
+
+	// HighRxt is the highest sequence number which has been retransmitted
+	// during the current loss recovery phase.  See: RFC 6675 Section 2 for
+	// details.
+	HighRxt seqnum.Value
+
+	// RescueRxt is the highest sequence number which has been
+	// optimistically retransmitted to prevent stalling of the ACK clock
+	// when there is loss at the end of the window and no new data is
+	// available for transmission.  See: RFC 6675 Section 2 for details.
+	RescueRxt seqnum.Value
+}
+
+// TCPReceiverState holds a copy of the internal state of the receiver for a
+// given TCP endpoint.
+//
+// +stateify savable
+type TCPReceiverState struct {
+	// RcvNxt is the TCP variable RCV.NXT.
+	RcvNxt seqnum.Value
+
+	// RcvAcc is one beyond the last acceptable sequence number. That is,
+	// the "largest" sequence value that the receiver has announced to its
+	// peer that it's willing to accept. This may be different than RcvNxt
+	// + (last advertised receive window) if the receive window is reduced;
+	// in that case we have to reduce the window as we receive more data
+	// instead of shrinking it.
+	RcvAcc seqnum.Value
+
+	// RcvWndScale is the window scaling to use for inbound segments.
+	RcvWndScale uint8
+
+	// PendingBufUsed is the number of bytes pending in the receive queue.
+	PendingBufUsed int
+}
+
+// TCPRTTState holds a copy of information about the endpoint's round trip
+// time.
+//
+// +stateify savable
+type TCPRTTState struct {
+	// SRTT is the smoothed round trip time defined in section 2 of RFC
+	// 6298.
+	SRTT time.Duration
+
+	// RTTVar is the round-trip time variation as defined in section 2 of
+	// RFC 6298.
+	RTTVar time.Duration
+
+	// SRTTInited if true indicates that a valid RTT measurement has been
+	// completed.
+	SRTTInited bool
+}
+
+// TCPSenderState holds a copy of the internal state of the sender for a given
+// TCP Endpoint.
+//
+// +stateify savable
+type TCPSenderState struct {
+	// LastSendTime is the timestamp at which we sent the last segment.
+	LastSendTime time.Time `state:".(unixTime)"`
+
+	// DupAckCount is the number of Duplicate ACKs received. It is used for
+	// fast retransmit.
+	DupAckCount int
+
+	// SndCwnd is the size of the sending congestion window in packets.
+	SndCwnd int
+
+	// Ssthresh is the threshold between slow start and congestion
+	// avoidance.
+	Ssthresh int
+
+	// SndCAAckCount is the number of packets acknowledged during
+	// congestion avoidance. When enough packets have been ack'd (typically
+	// cwnd packets), the congestion window is incremented by one.
+	SndCAAckCount int
+
+	// Outstanding is the number of packets that have been sent but not yet
+	// acknowledged.
+	Outstanding int
+
+	// SackedOut is the number of packets which have been selectively
+	// acked.
+	SackedOut int
+
+	// SndWnd is the send window size in bytes.
+	SndWnd seqnum.Size
+
+	// SndUna is the next unacknowledged sequence number.
+	SndUna seqnum.Value
+
+	// SndNxt is the sequence number of the next segment to be sent.
+	SndNxt seqnum.Value
+
+	// RTTMeasureSeqNum is the sequence number being used for the latest
+	// RTT measurement.
+	RTTMeasureSeqNum seqnum.Value
+
+	// RTTMeasureTime is the time when the RTTMeasureSeqNum was sent.
+	RTTMeasureTime time.Time `state:".(unixTime)"`
+
+	// Closed indicates that the caller has closed the endpoint for
+	// sending.
+	Closed bool
+
+	// RTO is the retransmit timeout as defined in section of 2 of RFC
+	// 6298.
+	RTO time.Duration
+
+	// RTTState holds information about the endpoint's round trip time.
+	RTTState TCPRTTState
+
+	// MaxPayloadSize is the maximum size of the payload of a given
+	// segment.  It is initialized on demand.
+	MaxPayloadSize int
+
+	// SndWndScale is the number of bits to shift left when reading the
+	// send window size from a segment.
+	SndWndScale uint8
+
+	// MaxSentAck is the highest acknowledgement number sent till now.
+	MaxSentAck seqnum.Value
+
+	// FastRecovery holds the fast recovery state for the endpoint.
+	FastRecovery TCPFastRecoveryState
+
+	// Cubic holds the state related to CUBIC congestion control.
+	Cubic TCPCubicState
+
+	// RACKState holds the state related to RACK loss detection algorithm.
+	RACKState TCPRACKState
+}
+
+// TCPSACKInfo holds TCP SACK related information for a given TCP endpoint.
+//
+// +stateify savable
+type TCPSACKInfo struct {
+	// Blocks is the list of SACK Blocks that identify the out of order
+	// segments held by a given TCP endpoint.
+	Blocks []header.SACKBlock
+
+	// ReceivedBlocks are the SACK blocks received by this endpoint from
+	// the peer endpoint.
+	ReceivedBlocks []header.SACKBlock
+
+	// MaxSACKED is the highest sequence number that has been SACKED by the
+	// peer.
+	MaxSACKED seqnum.Value
+}
+
+// RcvBufAutoTuneParams holds state related to TCP receive buffer auto-tuning.
+//
+// +stateify savable
+type RcvBufAutoTuneParams struct {
+	// MeasureTime is the time at which the current measurement was
+	// started.
+	MeasureTime time.Time `state:".(unixTime)"`
+
+	// CopiedBytes is the number of bytes copied to user space since this
+	// measure began.
+	CopiedBytes int
+
+	// PrevCopiedBytes is the number of bytes copied to userspace in the
+	// previous RTT period.
+	PrevCopiedBytes int
+
+	// RcvBufSize is the auto tuned receive buffer size.
+	RcvBufSize int
+
+	// RTT is the smoothed RTT as measured 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.
+	RTT time.Duration
+
+	// RTTVar is the "round-trip time variation" as defined in section 2 of
+	// RFC6298.
+	RTTVar time.Duration
+
+	// RTTMeasureSeqNumber is the highest acceptable sequence number at the
+	// time this RTT measurement period began.
+	RTTMeasureSeqNumber seqnum.Value
+
+	// RTTMeasureTime is the absolute time at which the current RTT
+	// measurement period began.
+	RTTMeasureTime time.Time `state:".(unixTime)"`
+
+	// Disabled is true if an explicit receive buffer is set for the
+	// endpoint.
+	Disabled bool
+}
+
+// TCPRcvBufState contains information about the state of an endpoint's receive
+// socket buffer.
+//
+// +stateify savable
+type TCPRcvBufState struct {
+	// RcvBufSize is the size of the receive socket buffer for the
+	// endpoint.
+	RcvBufSize int
+
+	// RcvBufUsed is the amount of bytes actually held in the receive
+	// socket buffer for the endpoint.
+	RcvBufUsed int
+
+	// RcvBufAutoTuneParams is used to hold state variables to compute the
+	// auto tuned receive buffer size.
+	RcvAutoParams RcvBufAutoTuneParams
+
+	// RcvClosed if true, indicates the endpoint has been closed for
+	// reading.
+	RcvClosed bool
+}
+
+// TCPSndBufState contains information about the state of an endpoint's send
+// socket buffer.
+//
+// +stateify savable
+type TCPSndBufState struct {
+	// SndBufSize is the size of the socket send buffer.
+	SndBufSize int
+
+	// SndBufUsed is the number of bytes held in the socket send buffer.
+	SndBufUsed int
+
+	// SndClosed indicates that the endpoint has been closed for sends.
+	SndClosed bool
+
+	// SndBufInQueue is the number of bytes in the send queue.
+	SndBufInQueue seqnum.Size
+
+	// PacketTooBigCount is used to notify the main protocol routine how
+	// many times a "packet too big" control packet is received.
+	PacketTooBigCount int
+
+	// SndMTU is the smallest MTU seen in the control packets received.
+	SndMTU int
+}
+
+// TCPEndpointStateInner contains the members of TCPEndpointState used directly
+// (that is, not within another containing struct) within the endpoint's
+// internal implementation.
+//
+// +stateify savable
+type TCPEndpointStateInner struct {
+	// TSOffset is a randomized offset added to the value of the TSVal
+	// field in the timestamp option.
+	TSOffset uint32
+
+	// SACKPermitted is set to true if the peer sends the TCPSACKPermitted
+	// option in the SYN/SYN-ACK.
+	SACKPermitted bool
+
+	// SendTSOk is used to indicate when the TS Option has been negotiated.
+	// When sendTSOk is true every non-RST segment should carry a TS as per
+	// RFC7323#section-1.1.
+	SendTSOk bool
+
+	// RecentTS is the timestamp that should be sent in the TSEcr field of
+	// the timestamp for future segments sent by the endpoint. This field
+	// is updated if required when a new segment is received by this
+	// endpoint.
+	RecentTS uint32
+}
+
+// TCPEndpointState is a copy of the internal state of a TCP endpoint.
+//
+// +stateify savable
+type TCPEndpointState struct {
+	// TCPEndpointStateInner contains the members of TCPEndpointState used
+	// by the endpoint's internal implementation.
+	TCPEndpointStateInner
+
+	// ID is a copy of the TransportEndpointID for the endpoint.
+	ID TCPEndpointID
+
+	// SegTime denotes the absolute time when this segment was received.
+	SegTime time.Time `state:".(unixTime)"`
+
+	// RcvBufState contains information about the state of the endpoint's
+	// receive socket buffer.
+	RcvBufState TCPRcvBufState
+
+	// SndBufState contains information about the state of the endpoint's
+	// send socket buffer.
+	SndBufState TCPSndBufState
+
+	// SACK holds TCP SACK related information for this endpoint.
+	SACK TCPSACKInfo
+
+	// Receiver holds variables related to the TCP receiver for the
+	// endpoint.
+	Receiver TCPReceiverState
+
+	// Sender holds state related to the TCP Sender for the endpoint.
+	Sender TCPSenderState
+}
diff --git a/pkg/tcpip/transport/tcp/BUILD b/pkg/tcpip/transport/tcp/BUILD
index b09a0ebbc..48417f192 100644
--- a/pkg/tcpip/transport/tcp/BUILD
+++ b/pkg/tcpip/transport/tcp/BUILD
@@ -34,14 +34,12 @@ go_library(
         "connect.go",
         "connect_unsafe.go",
         "cubic.go",
-        "cubic_state.go",
         "dispatcher.go",
         "endpoint.go",
         "endpoint_state.go",
         "forwarder.go",
         "protocol.go",
         "rack.go",
-        "rack_state.go",
         "rcv.go",
         "rcv_state.go",
         "reno.go",
diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index 4be306434..664cb9420 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -215,11 +215,11 @@ func (l *listenContext) createConnectingEndpoint(s *segment, rcvdSynOpts *header
 
 	n := newEndpoint(l.stack, netProto, queue)
 	n.ops.SetV6Only(l.v6Only)
-	n.ID = s.id
+	n.TransportEndpointInfo.ID = s.id
 	n.boundNICID = s.nicID
 	n.route = route
 	n.effectiveNetProtos = []tcpip.NetworkProtocolNumber{s.netProto}
-	n.rcvBufSize = int(l.rcvWnd)
+	n.rcvQueueInfo.RcvBufSize = int(l.rcvWnd)
 	n.amss = calculateAdvertisedMSS(n.userMSS, n.route)
 	n.setEndpointState(StateConnecting)
 
@@ -231,7 +231,7 @@ func (l *listenContext) createConnectingEndpoint(s *segment, rcvdSynOpts *header
 	// Bootstrap the auto tuning algorithm. Starting at zero will result in
 	// a large step function on the first window adjustment causing the
 	// window to grow to a really large value.
-	n.rcvAutoParams.prevCopied = n.initialReceiveWindow()
+	n.rcvQueueInfo.RcvAutoParams.PrevCopiedBytes = n.initialReceiveWindow()
 
 	return n, nil
 }
@@ -290,7 +290,14 @@ func (l *listenContext) startHandshake(s *segment, opts *header.TCPSynOptions, q
 	}
 
 	// Register new endpoint so that packets are routed to it.
-	if err := ep.stack.RegisterTransportEndpoint(ep.effectiveNetProtos, ProtocolNumber, ep.ID, ep, ep.boundPortFlags, ep.boundBindToDevice); err != nil {
+	if err := ep.stack.RegisterTransportEndpoint(
+		ep.effectiveNetProtos,
+		ProtocolNumber,
+		ep.TransportEndpointInfo.ID,
+		ep,
+		ep.boundPortFlags,
+		ep.boundBindToDevice,
+	); err != nil {
 		ep.mu.Unlock()
 		ep.Close()
 
@@ -335,14 +342,14 @@ func (l *listenContext) performHandshake(s *segment, opts *header.TCPSynOptions,
 
 func (l *listenContext) addPendingEndpoint(n *endpoint) {
 	l.pendingMu.Lock()
-	l.pendingEndpoints[n.ID] = n
+	l.pendingEndpoints[n.TransportEndpointInfo.ID] = n
 	l.pending.Add(1)
 	l.pendingMu.Unlock()
 }
 
 func (l *listenContext) removePendingEndpoint(n *endpoint) {
 	l.pendingMu.Lock()
-	delete(l.pendingEndpoints, n.ID)
+	delete(l.pendingEndpoints, n.TransportEndpointInfo.ID)
 	l.pending.Done()
 	l.pendingMu.Unlock()
 }
@@ -383,7 +390,7 @@ func (l *listenContext) cleanupCompletedHandshake(h *handshake) {
 	// Update the receive window scaling. We can't do it before the
 	// handshake because it's possible that the peer doesn't support window
 	// scaling.
-	e.rcv.rcvWndScale = e.h.effectiveRcvWndScale()
+	e.rcv.RcvWndScale = e.h.effectiveRcvWndScale()
 
 	// Clean up handshake state stored in the endpoint so that it can be GCed.
 	e.h = nil
@@ -444,12 +451,15 @@ func (e *endpoint) propagateInheritableOptionsLocked(n *endpoint) {
 // * propagateInheritableOptionsLocked has been called.
 // * e.mu is held.
 func (e *endpoint) reserveTupleLocked() bool {
-	dest := tcpip.FullAddress{Addr: e.ID.RemoteAddress, Port: e.ID.RemotePort}
+	dest := tcpip.FullAddress{
+		Addr: e.TransportEndpointInfo.ID.RemoteAddress,
+		Port: e.TransportEndpointInfo.ID.RemotePort,
+	}
 	portRes := ports.Reservation{
 		Networks:     e.effectiveNetProtos,
 		Transport:    ProtocolNumber,
-		Addr:         e.ID.LocalAddress,
-		Port:         e.ID.LocalPort,
+		Addr:         e.TransportEndpointInfo.ID.LocalAddress,
+		Port:         e.TransportEndpointInfo.ID.LocalPort,
 		Flags:        e.boundPortFlags,
 		BindToDevice: e.boundBindToDevice,
 		Dest:         dest,
@@ -537,9 +547,9 @@ func (e *endpoint) acceptQueueIsFull() bool {
 //
 // Precondition: if ctx.listenEP != nil, ctx.listenEP.mu must be locked.
 func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) tcpip.Error {
-	e.rcvListMu.Lock()
-	rcvClosed := e.rcvClosed
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	rcvClosed := e.rcvQueueInfo.RcvClosed
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 	if rcvClosed || s.flagsAreSet(header.TCPFlagSyn|header.TCPFlagAck) {
 		// If the endpoint is shutdown, reply with reset.
 		//
@@ -689,7 +699,14 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) tcpip.Err
 		}
 
 		// Register new endpoint so that packets are routed to it.
-		if err := n.stack.RegisterTransportEndpoint(n.effectiveNetProtos, ProtocolNumber, n.ID, n, n.boundPortFlags, n.boundBindToDevice); err != nil {
+		if err := n.stack.RegisterTransportEndpoint(
+			n.effectiveNetProtos,
+			ProtocolNumber,
+			n.TransportEndpointInfo.ID,
+			n,
+			n.boundPortFlags,
+			n.boundBindToDevice,
+		); err != nil {
 			n.mu.Unlock()
 			n.Close()
 
@@ -704,7 +721,7 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) tcpip.Err
 		// endpoint as the Timestamp was already
 		// randomly offset when the original SYN-ACK was
 		// sent above.
-		n.tsOffset = 0
+		n.TSOffset = 0
 
 		// Switch state to connected.
 		n.isConnectNotified = true
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 8f0f0c3e9..7bc6b08f0 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -156,7 +156,7 @@ func (h *handshake) resetState() {
 	h.flags = header.TCPFlagSyn
 	h.ackNum = 0
 	h.mss = 0
-	h.iss = generateSecureISN(h.ep.ID, h.ep.stack.Seed())
+	h.iss = generateSecureISN(h.ep.TransportEndpointInfo.ID, h.ep.stack.Seed())
 }
 
 // generateSecureISN generates a secure Initial Sequence number based on the
@@ -302,7 +302,7 @@ func (h *handshake) synSentState(s *segment) tcpip.Error {
 		ttl = h.ep.route.DefaultTTL()
 	}
 	h.ep.sendSynTCP(h.ep.route, tcpFields{
-		id:     h.ep.ID,
+		id:     h.ep.TransportEndpointInfo.ID,
 		ttl:    ttl,
 		tos:    h.ep.sendTOS,
 		flags:  h.flags,
@@ -358,14 +358,14 @@ func (h *handshake) synRcvdState(s *segment) tcpip.Error {
 		h.resetState()
 		synOpts := header.TCPSynOptions{
 			WS:            h.rcvWndScale,
-			TS:            h.ep.sendTSOk,
+			TS:            h.ep.SendTSOk,
 			TSVal:         h.ep.timestamp(),
 			TSEcr:         h.ep.recentTimestamp(),
-			SACKPermitted: h.ep.sackPermitted,
+			SACKPermitted: h.ep.SACKPermitted,
 			MSS:           h.ep.amss,
 		}
 		h.ep.sendSynTCP(h.ep.route, tcpFields{
-			id:     h.ep.ID,
+			id:     h.ep.TransportEndpointInfo.ID,
 			ttl:    h.ep.ttl,
 			tos:    h.ep.sendTOS,
 			flags:  h.flags,
@@ -390,7 +390,7 @@ func (h *handshake) synRcvdState(s *segment) tcpip.Error {
 		// If the timestamp option is negotiated and the segment does
 		// not carry a timestamp option then the segment must be dropped
 		// as per https://tools.ietf.org/html/rfc7323#section-3.2.
-		if h.ep.sendTSOk && !s.parsedOptions.TS {
+		if h.ep.SendTSOk && !s.parsedOptions.TS {
 			h.ep.stack.Stats().DroppedPackets.Increment()
 			return nil
 		}
@@ -405,7 +405,7 @@ func (h *handshake) synRcvdState(s *segment) tcpip.Error {
 		}
 
 		// Update timestamp if required. See RFC7323, section-4.3.
-		if h.ep.sendTSOk && s.parsedOptions.TS {
+		if h.ep.SendTSOk && s.parsedOptions.TS {
 			h.ep.updateRecentTimestamp(s.parsedOptions.TSVal, h.ackNum, s.sequenceNumber)
 		}
 		h.state = handshakeCompleted
@@ -495,8 +495,8 @@ func (h *handshake) start() {
 	// start() is also called in a listen context so we want to make sure we only
 	// send the TS/SACK option when we received the TS/SACK in the initial SYN.
 	if h.state == handshakeSynRcvd {
-		synOpts.TS = h.ep.sendTSOk
-		synOpts.SACKPermitted = h.ep.sackPermitted && bool(sackEnabled)
+		synOpts.TS = h.ep.SendTSOk
+		synOpts.SACKPermitted = h.ep.SACKPermitted && bool(sackEnabled)
 		if h.sndWndScale < 0 {
 			// Disable window scaling if the peer did not send us
 			// the window scaling option.
@@ -506,7 +506,7 @@ func (h *handshake) start() {
 
 	h.sendSYNOpts = synOpts
 	h.ep.sendSynTCP(h.ep.route, tcpFields{
-		id:     h.ep.ID,
+		id:     h.ep.TransportEndpointInfo.ID,
 		ttl:    h.ep.ttl,
 		tos:    h.ep.sendTOS,
 		flags:  h.flags,
@@ -554,7 +554,7 @@ func (h *handshake) complete() tcpip.Error {
 			// retransmitted on their own).
 			if h.active || !h.acked || h.deferAccept != 0 && time.Since(h.startTime) > h.deferAccept {
 				h.ep.sendSynTCP(h.ep.route, tcpFields{
-					id:     h.ep.ID,
+					id:     h.ep.TransportEndpointInfo.ID,
 					ttl:    h.ep.ttl,
 					tos:    h.ep.sendTOS,
 					flags:  h.flags,
@@ -855,7 +855,7 @@ func (e *endpoint) makeOptions(sackBlocks []header.SACKBlock) []byte {
 	// N.B. the ordering here matches the ordering used by Linux internally
 	// and described in the raw makeOptions function. We don't include
 	// unnecessary cases here (post connection.)
-	if e.sendTSOk {
+	if e.SendTSOk {
 		// Embed the timestamp if timestamp has been enabled.
 		//
 		// We only use the lower 32 bits of the unix time in
@@ -872,7 +872,7 @@ func (e *endpoint) makeOptions(sackBlocks []header.SACKBlock) []byte {
 		offset += header.EncodeNOP(options[offset:])
 		offset += header.EncodeTSOption(e.timestamp(), e.recentTimestamp(), options[offset:])
 	}
-	if e.sackPermitted && len(sackBlocks) > 0 {
+	if e.SACKPermitted && len(sackBlocks) > 0 {
 		offset += header.EncodeNOP(options[offset:])
 		offset += header.EncodeNOP(options[offset:])
 		offset += header.EncodeSACKBlocks(sackBlocks, options[offset:])
@@ -894,7 +894,7 @@ func (e *endpoint) sendRaw(data buffer.VectorisedView, flags header.TCPFlags, se
 	}
 	options := e.makeOptions(sackBlocks)
 	err := e.sendTCP(e.route, tcpFields{
-		id:     e.ID,
+		id:     e.TransportEndpointInfo.ID,
 		ttl:    e.ttl,
 		tos:    e.sendTOS,
 		flags:  flags,
@@ -908,9 +908,9 @@ func (e *endpoint) sendRaw(data buffer.VectorisedView, flags header.TCPFlags, se
 }
 
 func (e *endpoint) handleWrite() {
-	e.sndBufMu.Lock()
+	e.sndQueueInfo.sndQueueMu.Lock()
 	next := e.drainSendQueueLocked()
-	e.sndBufMu.Unlock()
+	e.sndQueueInfo.sndQueueMu.Unlock()
 
 	e.sendData(next)
 }
@@ -919,10 +919,10 @@ func (e *endpoint) handleWrite() {
 //
 // Precondition: e.sndBufMu must be locked.
 func (e *endpoint) drainSendQueueLocked() *segment {
-	first := e.sndQueue.Front()
+	first := e.sndQueueInfo.sndQueue.Front()
 	if first != nil {
-		e.snd.writeList.PushBackList(&e.sndQueue)
-		e.sndBufInQueue = 0
+		e.snd.writeList.PushBackList(&e.sndQueueInfo.sndQueue)
+		e.sndQueueInfo.SndBufInQueue = 0
 	}
 	return first
 }
@@ -946,7 +946,7 @@ func (e *endpoint) handleClose() {
 	e.handleWrite()
 
 	// Mark send side as closed.
-	e.snd.closed = true
+	e.snd.Closed = true
 }
 
 // resetConnectionLocked puts the endpoint in an error state with the given
@@ -968,12 +968,12 @@ func (e *endpoint) resetConnectionLocked(err tcpip.Error) {
 		//
 		// See: https://www.snellman.net/blog/archive/2016-02-01-tcp-rst/ for more
 		// information.
-		sndWndEnd := e.snd.sndUna.Add(e.snd.sndWnd)
+		sndWndEnd := e.snd.SndUna.Add(e.snd.SndWnd)
 		resetSeqNum := sndWndEnd
-		if !sndWndEnd.LessThan(e.snd.sndNxt) || e.snd.sndNxt.Size(sndWndEnd) < (1<<e.snd.sndWndScale) {
-			resetSeqNum = e.snd.sndNxt
+		if !sndWndEnd.LessThan(e.snd.SndNxt) || e.snd.SndNxt.Size(sndWndEnd) < (1<<e.snd.SndWndScale) {
+			resetSeqNum = e.snd.SndNxt
 		}
-		e.sendRaw(buffer.VectorisedView{}, header.TCPFlagAck|header.TCPFlagRst, resetSeqNum, e.rcv.rcvNxt, 0)
+		e.sendRaw(buffer.VectorisedView{}, header.TCPFlagAck|header.TCPFlagRst, resetSeqNum, e.rcv.RcvNxt, 0)
 	}
 }
 
@@ -999,13 +999,13 @@ func (e *endpoint) transitionToStateEstablishedLocked(h *handshake) {
 	// (indicated by a negative send window scale).
 	e.snd = newSender(e, h.iss, h.ackNum-1, h.sndWnd, h.mss, h.sndWndScale)
 
-	e.rcvListMu.Lock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
 	e.rcv = newReceiver(e, h.ackNum-1, h.rcvWnd, h.effectiveRcvWndScale())
 	// Bootstrap the auto tuning algorithm. Starting at zero will
 	// result in a really large receive window after the first auto
 	// tuning adjustment.
-	e.rcvAutoParams.prevCopied = int(h.rcvWnd)
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.RcvAutoParams.PrevCopiedBytes = int(h.rcvWnd)
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 
 	e.setEndpointState(StateEstablished)
 }
@@ -1036,10 +1036,15 @@ func (e *endpoint) transitionToStateCloseLocked() {
 // only when the endpoint is in StateClose and we want to deliver the segment
 // to any other listening endpoint. We reply with RST if we cannot find one.
 func (e *endpoint) tryDeliverSegmentFromClosedEndpoint(s *segment) {
-	ep := e.stack.FindTransportEndpoint(e.NetProto, e.TransProto, e.ID, s.nicID)
+	ep := e.stack.FindTransportEndpoint(e.NetProto, e.TransProto, e.TransportEndpointInfo.ID, s.nicID)
 	if ep == nil && e.NetProto == header.IPv6ProtocolNumber && e.TransportEndpointInfo.ID.LocalAddress.To4() != "" {
 		// Dual-stack socket, try IPv4.
-		ep = e.stack.FindTransportEndpoint(header.IPv4ProtocolNumber, e.TransProto, e.ID, s.nicID)
+		ep = e.stack.FindTransportEndpoint(
+			header.IPv4ProtocolNumber,
+			e.TransProto,
+			e.TransportEndpointInfo.ID,
+			s.nicID,
+		)
 	}
 	if ep == nil {
 		replyWithReset(e.stack, s, stack.DefaultTOS, 0 /* ttl */)
@@ -1118,7 +1123,9 @@ func (e *endpoint) handleReset(s *segment) (ok bool, err tcpip.Error) {
 }
 
 // handleSegments processes all inbound segments.
-func (e *endpoint) handleSegments(fastPath bool) tcpip.Error {
+//
+// Precondition: e.mu must be held.
+func (e *endpoint) handleSegmentsLocked(fastPath bool) tcpip.Error {
 	checkRequeue := true
 	for i := 0; i < maxSegmentsPerWake; i++ {
 		if e.EndpointState().closed() {
@@ -1130,7 +1137,7 @@ func (e *endpoint) handleSegments(fastPath bool) tcpip.Error {
 			break
 		}
 
-		cont, err := e.handleSegment(s)
+		cont, err := e.handleSegmentLocked(s)
 		s.decRef()
 		if err != nil {
 			return err
@@ -1148,7 +1155,7 @@ func (e *endpoint) handleSegments(fastPath bool) tcpip.Error {
 	}
 
 	// Send an ACK for all processed packets if needed.
-	if e.rcv.rcvNxt != e.snd.maxSentAck {
+	if e.rcv.RcvNxt != e.snd.MaxSentAck {
 		e.snd.sendAck()
 	}
 
@@ -1157,18 +1164,21 @@ func (e *endpoint) handleSegments(fastPath bool) tcpip.Error {
 	return nil
 }
 
-func (e *endpoint) probeSegment() {
-	if e.probe != nil {
-		e.probe(e.completeState())
+// Precondition: e.mu must be held.
+func (e *endpoint) probeSegmentLocked() {
+	if fn := e.probe; fn != nil {
+		fn(e.completeStateLocked())
 	}
 }
 
 // handleSegment handles a given segment and notifies the worker goroutine if
 // if the connection should be terminated.
-func (e *endpoint) handleSegment(s *segment) (cont bool, err tcpip.Error) {
+//
+// Precondition: e.mu must be held.
+func (e *endpoint) handleSegmentLocked(s *segment) (cont bool, err tcpip.Error) {
 	// Invoke the tcp probe if installed. The tcp probe function will update
 	// the TCPEndpointState after the segment is processed.
-	defer e.probeSegment()
+	defer e.probeSegmentLocked()
 
 	if s.flagIsSet(header.TCPFlagRst) {
 		if ok, err := e.handleReset(s); !ok {
@@ -1201,7 +1211,7 @@ func (e *endpoint) handleSegment(s *segment) (cont bool, err tcpip.Error) {
 	} else if s.flagIsSet(header.TCPFlagAck) {
 		// Patch the window size in the segment according to the
 		// send window scale.
-		s.window <<= e.snd.sndWndScale
+		s.window <<= e.snd.SndWndScale
 
 		// RFC 793, page 41 states that "once in the ESTABLISHED
 		// state all segments must carry current acknowledgment
@@ -1265,7 +1275,7 @@ func (e *endpoint) keepaliveTimerExpired() tcpip.Error {
 	// seg.seq = snd.nxt-1.
 	e.keepalive.unacked++
 	e.keepalive.Unlock()
-	e.snd.sendSegmentFromView(buffer.VectorisedView{}, header.TCPFlagAck, e.snd.sndNxt-1)
+	e.snd.sendSegmentFromView(buffer.VectorisedView{}, header.TCPFlagAck, e.snd.SndNxt-1)
 	e.resetKeepaliveTimer(false)
 	return nil
 }
@@ -1279,7 +1289,7 @@ func (e *endpoint) resetKeepaliveTimer(receivedData bool) {
 	}
 	// Start the keepalive timer IFF it's enabled and there is no pending
 	// data to send.
-	if !e.SocketOptions().GetKeepAlive() || e.snd == nil || e.snd.sndUna != e.snd.sndNxt {
+	if !e.SocketOptions().GetKeepAlive() || e.snd == nil || e.snd.SndUna != e.snd.SndNxt {
 		e.keepalive.timer.disable()
 		e.keepalive.Unlock()
 		return
@@ -1372,14 +1382,14 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 		f func() tcpip.Error
 	}{
 		{
-			w: &e.sndWaker,
+			w: &e.sndQueueInfo.sndWaker,
 			f: func() tcpip.Error {
 				e.handleWrite()
 				return nil
 			},
 		},
 		{
-			w: &e.sndCloseWaker,
+			w: &e.sndQueueInfo.sndCloseWaker,
 			f: func() tcpip.Error {
 				e.handleClose()
 				return nil
@@ -1413,7 +1423,7 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 		{
 			w: &e.newSegmentWaker,
 			f: func() tcpip.Error {
-				return e.handleSegments(false /* fastPath */)
+				return e.handleSegmentsLocked(false /* fastPath */)
 			},
 		},
 		{
@@ -1429,11 +1439,11 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 				}
 
 				if n&notifyMTUChanged != 0 {
-					e.sndBufMu.Lock()
-					count := e.packetTooBigCount
-					e.packetTooBigCount = 0
-					mtu := e.sndMTU
-					e.sndBufMu.Unlock()
+					e.sndQueueInfo.sndQueueMu.Lock()
+					count := e.sndQueueInfo.PacketTooBigCount
+					e.sndQueueInfo.PacketTooBigCount = 0
+					mtu := e.sndQueueInfo.SndMTU
+					e.sndQueueInfo.sndQueueMu.Unlock()
 
 					e.snd.updateMaxPayloadSize(mtu, count)
 				}
@@ -1463,7 +1473,7 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 
 				if n&notifyDrain != 0 {
 					for !e.segmentQueue.empty() {
-						if err := e.handleSegments(false /* fastPath */); err != nil {
+						if err := e.handleSegmentsLocked(false /* fastPath */); err != nil {
 							return err
 						}
 					}
@@ -1514,11 +1524,11 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 		e.newSegmentWaker.Assert()
 	}
 
-	e.rcvListMu.Lock()
-	if !e.rcvList.Empty() {
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	if !e.rcvQueueInfo.rcvQueue.Empty() {
 		e.waiterQueue.Notify(waiter.ReadableEvents)
 	}
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 
 	if e.workerCleanup {
 		e.notifyProtocolGoroutine(notifyClose)
diff --git a/pkg/tcpip/transport/tcp/cubic.go b/pkg/tcpip/transport/tcp/cubic.go
index 1975f1a44..962f1d687 100644
--- a/pkg/tcpip/transport/tcp/cubic.go
+++ b/pkg/tcpip/transport/tcp/cubic.go
@@ -17,6 +17,8 @@ package tcp
 import (
 	"math"
 	"time"
+
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
 // cubicState stores the variables related to TCP CUBIC congestion
@@ -25,47 +27,12 @@ import (
 // See: https://tools.ietf.org/html/rfc8312.
 // +stateify savable
 type cubicState struct {
-	// wLastMax is the previous wMax value.
-	wLastMax float64
-
-	// wMax is the value of the congestion window at the
-	// time of last congestion event.
-	wMax float64
-
-	// t denotes the time when the current congestion avoidance
-	// was entered.
-	t time.Time `state:".(unixTime)"`
+	stack.TCPCubicState
 
 	// numCongestionEvents tracks the number of congestion events since last
 	// RTO.
 	numCongestionEvents int
 
-	// c is the cubic constant as specified in RFC8312. It's fixed at 0.4 as
-	// per RFC.
-	c float64
-
-	// k is the time period that the above function takes to increase the
-	// current window size to W_max if there are no further congestion
-	// events and is calculated using the following equation:
-	//
-	// K = cubic_root(W_max*(1-beta_cubic)/C) (Eq. 2)
-	k float64
-
-	// beta is the CUBIC multiplication decrease factor. that is, when a
-	// congestion event is detected, CUBIC reduces its cwnd to
-	// W_cubic(0)=W_max*beta_cubic.
-	beta float64
-
-	// wC is window computed by CUBIC at time t. It's calculated using the
-	// formula:
-	//
-	//  W_cubic(t) = C*(t-K)^3 + W_max (Eq. 1)
-	wC float64
-
-	// wEst is the window computed by CUBIC at time t+RTT i.e
-	// W_cubic(t+RTT).
-	wEst float64
-
 	s *sender
 }
 
@@ -73,10 +40,12 @@ type cubicState struct {
 // beta and c set and t set to current time.
 func newCubicCC(s *sender) *cubicState {
 	return &cubicState{
-		t:    time.Now(),
-		beta: 0.7,
-		c:    0.4,
-		s:    s,
+		TCPCubicState: stack.TCPCubicState{
+			T:    time.Now(),
+			Beta: 0.7,
+			C:    0.4,
+		},
+		s: s,
 	}
 }
 
@@ -90,10 +59,10 @@ func (c *cubicState) enterCongestionAvoidance() {
 	// See: https://tools.ietf.org/html/rfc8312#section-4.7 &
 	// https://tools.ietf.org/html/rfc8312#section-4.8
 	if c.numCongestionEvents == 0 {
-		c.k = 0
-		c.t = time.Now()
-		c.wLastMax = c.wMax
-		c.wMax = float64(c.s.sndCwnd)
+		c.K = 0
+		c.T = time.Now()
+		c.WLastMax = c.WMax
+		c.WMax = float64(c.s.SndCwnd)
 	}
 }
 
@@ -104,16 +73,16 @@ func (c *cubicState) enterCongestionAvoidance() {
 func (c *cubicState) updateSlowStart(packetsAcked int) int {
 	// Don't let the congestion window cross into the congestion
 	// avoidance range.
-	newcwnd := c.s.sndCwnd + packetsAcked
+	newcwnd := c.s.SndCwnd + packetsAcked
 	enterCA := false
-	if newcwnd >= c.s.sndSsthresh {
-		newcwnd = c.s.sndSsthresh
-		c.s.sndCAAckCount = 0
+	if newcwnd >= c.s.Ssthresh {
+		newcwnd = c.s.Ssthresh
+		c.s.SndCAAckCount = 0
 		enterCA = true
 	}
 
-	packetsAcked -= newcwnd - c.s.sndCwnd
-	c.s.sndCwnd = newcwnd
+	packetsAcked -= newcwnd - c.s.SndCwnd
+	c.s.SndCwnd = newcwnd
 	if enterCA {
 		c.enterCongestionAvoidance()
 	}
@@ -124,49 +93,49 @@ func (c *cubicState) updateSlowStart(packetsAcked int) int {
 // ACK received.
 // Refer: https://tools.ietf.org/html/rfc8312#section-4
 func (c *cubicState) Update(packetsAcked int) {
-	if c.s.sndCwnd < c.s.sndSsthresh {
+	if c.s.SndCwnd < c.s.Ssthresh {
 		packetsAcked = c.updateSlowStart(packetsAcked)
 		if packetsAcked == 0 {
 			return
 		}
 	} else {
 		c.s.rtt.Lock()
-		srtt := c.s.rtt.srtt
+		srtt := c.s.rtt.TCPRTTState.SRTT
 		c.s.rtt.Unlock()
-		c.s.sndCwnd = c.getCwnd(packetsAcked, c.s.sndCwnd, srtt)
+		c.s.SndCwnd = c.getCwnd(packetsAcked, c.s.SndCwnd, srtt)
 	}
 }
 
 // cubicCwnd computes the CUBIC congestion window after t seconds from last
 // congestion event.
 func (c *cubicState) cubicCwnd(t float64) float64 {
-	return c.c*math.Pow(t, 3.0) + c.wMax
+	return c.C*math.Pow(t, 3.0) + c.WMax
 }
 
 // getCwnd returns the current congestion window as computed by CUBIC.
 // Refer: https://tools.ietf.org/html/rfc8312#section-4
 func (c *cubicState) getCwnd(packetsAcked, sndCwnd int, srtt time.Duration) int {
-	elapsed := time.Since(c.t).Seconds()
+	elapsed := time.Since(c.T).Seconds()
 
 	// Compute the window as per Cubic after 'elapsed' time
 	// since last congestion event.
-	c.wC = c.cubicCwnd(elapsed - c.k)
+	c.WC = c.cubicCwnd(elapsed - c.K)
 
 	// Compute the TCP friendly estimate of the congestion window.
-	c.wEst = c.wMax*c.beta + (3.0*((1.0-c.beta)/(1.0+c.beta)))*(elapsed/srtt.Seconds())
+	c.WEst = c.WMax*c.Beta + (3.0*((1.0-c.Beta)/(1.0+c.Beta)))*(elapsed/srtt.Seconds())
 
 	// Make sure in the TCP friendly region CUBIC performs at least
 	// as well as Reno.
-	if c.wC < c.wEst && float64(sndCwnd) < c.wEst {
+	if c.WC < c.WEst && float64(sndCwnd) < c.WEst {
 		// TCP Friendly region of cubic.
-		return int(c.wEst)
+		return int(c.WEst)
 	}
 
 	// In Concave/Convex region of CUBIC, calculate what CUBIC window
 	// will be after 1 RTT and use that to grow congestion window
 	// for every ack.
-	tEst := (time.Since(c.t) + srtt).Seconds()
-	wtRtt := c.cubicCwnd(tEst - c.k)
+	tEst := (time.Since(c.T) + srtt).Seconds()
+	wtRtt := c.cubicCwnd(tEst - c.K)
 	// As per 4.3 for each received ACK cwnd must be incremented
 	// by (w_cubic(t+RTT) - cwnd/cwnd.
 	cwnd := float64(sndCwnd)
@@ -182,9 +151,9 @@ func (c *cubicState) getCwnd(packetsAcked, sndCwnd int, srtt time.Duration) int
 func (c *cubicState) HandleLossDetected() {
 	// See: https://tools.ietf.org/html/rfc8312#section-4.5
 	c.numCongestionEvents++
-	c.t = time.Now()
-	c.wLastMax = c.wMax
-	c.wMax = float64(c.s.sndCwnd)
+	c.T = time.Now()
+	c.WLastMax = c.WMax
+	c.WMax = float64(c.s.SndCwnd)
 
 	c.fastConvergence()
 	c.reduceSlowStartThreshold()
@@ -193,10 +162,10 @@ func (c *cubicState) HandleLossDetected() {
 // HandleRTOExpired implements congestionContrl.HandleRTOExpired.
 func (c *cubicState) HandleRTOExpired() {
 	// See: https://tools.ietf.org/html/rfc8312#section-4.6
-	c.t = time.Now()
+	c.T = time.Now()
 	c.numCongestionEvents = 0
-	c.wLastMax = c.wMax
-	c.wMax = float64(c.s.sndCwnd)
+	c.WLastMax = c.WMax
+	c.WMax = float64(c.s.SndCwnd)
 
 	c.fastConvergence()
 
@@ -206,29 +175,29 @@ func (c *cubicState) HandleRTOExpired() {
 	// Reduce the congestion window to 1, i.e., enter slow-start. Per
 	// RFC 5681, page 7, we must use 1 regardless of the value of the
 	// initial congestion window.
-	c.s.sndCwnd = 1
+	c.s.SndCwnd = 1
 }
 
 // fastConvergence implements the logic for Fast Convergence algorithm as
 // described in https://tools.ietf.org/html/rfc8312#section-4.6.
 func (c *cubicState) fastConvergence() {
-	if c.wMax < c.wLastMax {
-		c.wLastMax = c.wMax
-		c.wMax = c.wMax * (1.0 + c.beta) / 2.0
+	if c.WMax < c.WLastMax {
+		c.WLastMax = c.WMax
+		c.WMax = c.WMax * (1.0 + c.Beta) / 2.0
 	} else {
-		c.wLastMax = c.wMax
+		c.WLastMax = c.WMax
 	}
 	// Recompute k as wMax may have changed.
-	c.k = math.Cbrt(c.wMax * (1 - c.beta) / c.c)
+	c.K = math.Cbrt(c.WMax * (1 - c.Beta) / c.C)
 }
 
 // PostRecovery implemements congestionControl.PostRecovery.
 func (c *cubicState) PostRecovery() {
-	c.t = time.Now()
+	c.T = time.Now()
 }
 
 // reduceSlowStartThreshold returns new SsThresh as described in
 // https://tools.ietf.org/html/rfc8312#section-4.7.
 func (c *cubicState) reduceSlowStartThreshold() {
-	c.s.sndSsthresh = int(math.Max(float64(c.s.sndCwnd)*c.beta, 2.0))
+	c.s.Ssthresh = int(math.Max(float64(c.s.SndCwnd)*c.Beta, 2.0))
 }
diff --git a/pkg/tcpip/transport/tcp/cubic_state.go b/pkg/tcpip/transport/tcp/cubic_state.go
deleted file mode 100644
index d0f58cfaf..000000000
--- a/pkg/tcpip/transport/tcp/cubic_state.go
+++ /dev/null
@@ -1,29 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package tcp
-
-import (
-	"time"
-)
-
-// saveT is invoked by stateify.
-func (c *cubicState) saveT() unixTime {
-	return unixTime{c.t.Unix(), c.t.UnixNano()}
-}
-
-// loadT is invoked by stateify.
-func (c *cubicState) loadT(unix unixTime) {
-	c.t = time.Unix(unix.second, unix.nano)
-}
diff --git a/pkg/tcpip/transport/tcp/dispatcher.go b/pkg/tcpip/transport/tcp/dispatcher.go
index 21162f01a..512053a04 100644
--- a/pkg/tcpip/transport/tcp/dispatcher.go
+++ b/pkg/tcpip/transport/tcp/dispatcher.go
@@ -116,7 +116,7 @@ func (p *processor) start(wg *sync.WaitGroup) {
 			if ep.EndpointState() == StateEstablished && ep.mu.TryLock() {
 				// If the endpoint is in a connected state then we do direct delivery
 				// to ensure low latency and avoid scheduler interactions.
-				switch err := ep.handleSegments(true /* fastPath */); {
+				switch err := ep.handleSegmentsLocked(true /* fastPath */); {
 				case err != nil:
 					// Send any active resets if required.
 					ep.resetConnectionLocked(err)
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index bc88e48e9..884332828 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -191,42 +191,6 @@ type SACKInfo struct {
 	NumBlocks int
 }
 
-// rcvBufAutoTuneParams are used to hold state variables to compute
-// the auto tuned recv buffer size.
-//
-// +stateify savable
-type rcvBufAutoTuneParams struct {
-	// measureTime is the time at which the current measurement
-	// was started.
-	measureTime time.Time `state:".(unixTime)"`
-
-	// copied is the number of bytes copied out of the receive
-	// buffers since this measure began.
-	copied int
-
-	// prevCopied is the number of bytes copied out of the receive
-	// buffers in the previous RTT period.
-	prevCopied int
-
-	// rtt is the non-smoothed minimum RTT as measured 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.
-	rtt time.Duration
-
-	// rttMeasureSeqNumber is the highest acceptable sequence number at the
-	// time this RTT measurement period began.
-	rttMeasureSeqNumber seqnum.Value
-
-	// rttMeasureTime is the absolute time at which the current rtt
-	// measurement period began.
-	rttMeasureTime time.Time `state:".(unixTime)"`
-
-	// disabled is true if an explicit receive buffer is set for the
-	// endpoint.
-	disabled bool
-}
-
 // ReceiveErrors collect segment receive errors within transport layer.
 type ReceiveErrors struct {
 	tcpip.ReceiveErrors
@@ -247,7 +211,7 @@ type ReceiveErrors struct {
 	ListenOverflowAckDrop tcpip.StatCounter
 
 	// ZeroRcvWindowState is the number of times we advertised
-	// a zero receive window when rcvList is full.
+	// a zero receive window when rcvQueue is full.
 	ZeroRcvWindowState tcpip.StatCounter
 
 	// WantZeroWindow is the number of times we wanted to advertise a
@@ -310,18 +274,36 @@ type Stats struct {
 // marker interface.
 func (*Stats) IsEndpointStats() {}
 
-// EndpointInfo holds useful information about a transport endpoint which
-// can be queried by monitoring tools. This exists to allow tcp-only state to
-// be exposed.
+// sndQueueInfo implements a send queue.
 //
 // +stateify savable
-type EndpointInfo struct {
-	stack.TransportEndpointInfo
+type sndQueueInfo struct {
+	sndQueueMu sync.Mutex `state:"nosave"`
+	stack.TCPSndBufState
+
+	// sndQueue holds segments that are ready to be sent.
+	sndQueue segmentList `state:"wait"`
+
+	// sndWaker is used to signal the protocol goroutine when segments are
+	// added to the `sndQueue`.
+	sndWaker sleep.Waker `state:"manual"`
+
+	// sndCloseWaker is used to notify the protocol goroutine when the send
+	// side is closed.
+	sndCloseWaker sleep.Waker `state:"manual"`
 }
 
-// IsEndpointInfo is an empty method to implement the tcpip.EndpointInfo
-// marker interface.
-func (*EndpointInfo) IsEndpointInfo() {}
+// rcvQueueInfo contains the endpoint's rcvQueue and associated metadata.
+//
+// +stateify savable
+type rcvQueueInfo struct {
+	rcvQueueMu sync.Mutex `state:"nosave"`
+	stack.TCPRcvBufState
+
+	// rcvQueue is the queue for ready-for-delivery segments. This struct's
+	// mutex must be held in order append segments to list.
+	rcvQueue segmentList `state:"wait"`
+}
 
 // +stateify savable
 type accepted struct {
@@ -348,8 +330,8 @@ type accepted struct {
 // acquired with e.mu then e.mu must be acquired first.
 //
 // e.acceptMu -> protects accepted.
-// e.rcvListMu -> Protects the rcvList and associated fields.
-// e.sndBufMu -> Protects the sndQueue and associated fields.
+// e.rcvQueueMu -> Protects e.rcvQueue and associated fields.
+// e.sndQueueMu -> Protects the e.sndQueue and associated fields.
 // e.lastErrorMu -> Protects the lastError field.
 //
 // LOCKING/UNLOCKING of the endpoint.  The locking of an endpoint is different
@@ -372,7 +354,8 @@ type accepted struct {
 //
 // +stateify savable
 type endpoint struct {
-	EndpointInfo
+	stack.TCPEndpointStateInner
+	stack.TransportEndpointInfo
 	tcpip.DefaultSocketOptionsHandler
 
 	// endpointEntry is used to queue endpoints for processing to the
@@ -405,38 +388,23 @@ type endpoint struct {
 
 	// rcvReadMu synchronizes calls to Read.
 	//
-	// mu and rcvListMu are temporarily released during data copying. rcvReadMu
+	// mu and rcvQueueMu are temporarily released during data copying. rcvReadMu
 	// must be held during each read to ensure atomicity, so that multiple reads
 	// do not interleave.
 	//
 	// rcvReadMu should be held before holding mu.
 	rcvReadMu sync.Mutex `state:"nosave"`
 
-	// rcvListMu synchronizes access to rcvList.
-	//
-	// rcvListMu can be taken after the endpoint mu below.
-	rcvListMu sync.Mutex `state:"nosave"`
-
-	// rcvList is the queue for ready-for-delivery segments.
-	//
-	// rcvReadMu, mu and rcvListMu must be held, in the stated order, to read data
-	// and removing segments from list. A range of segment can be determined, then
-	// temporarily release mu and rcvListMu while processing the segment range.
-	// This allows new segments to be appended to the list while processing.
-	//
-	// rcvListMu must be held to append segments to list.
-	rcvList   segmentList `state:"wait"`
-	rcvClosed bool
-	// rcvBufSize is the total size of the receive buffer.
-	rcvBufSize int
-	// rcvBufUsed is the actual number of payload bytes held in the receive buffer
-	// not counting any overheads of the segments itself. NOTE: This will always
-	// be strictly <= rcvMemUsed below.
-	rcvBufUsed    int
-	rcvAutoParams rcvBufAutoTuneParams
+	// rcvQueueInfo holds the implementation of the endpoint's receive buffer.
+	// The data within rcvQueueInfo should only be accessed while rcvReadMu, mu,
+	// and rcvQueueMu are held, in that stated order. While processing the segment
+	// range, you can determine a range and then temporarily release mu and
+	// rcvQueueMu, which allows new segments to be appended to the queue while
+	// processing.
+	rcvQueueInfo rcvQueueInfo
 
 	// rcvMemUsed tracks the total amount of memory in use by received segments
-	// held in rcvList, pendingRcvdSegments and the segment queue. This is used to
+	// held in rcvQueue, pendingRcvdSegments and the segment queue. This is used to
 	// compute the window and the actual available buffer space. This is distinct
 	// from rcvBufUsed above which is the actual number of payload bytes held in
 	// the buffer not including any segment overheads.
@@ -498,33 +466,16 @@ type endpoint struct {
 	// also true, and they're both protected by the mutex.
 	workerCleanup bool
 
-	// sendTSOk is used to indicate when the TS Option has been negotiated.
-	// When sendTSOk is true every non-RST segment should carry a TS as per
-	// RFC7323#section-1.1
-	sendTSOk bool
-
-	// recentTS is the timestamp that should be sent in the TSEcr field of
-	// the timestamp for future segments sent by the endpoint. This field is
-	// updated if required when a new segment is received by this endpoint.
-	recentTS uint32
-
-	// recentTSTime is the unix time when we updated recentTS last.
+	// recentTSTime is the unix time when we last updated
+	// TCPEndpointStateInner.RecentTS.
 	recentTSTime time.Time `state:".(unixTime)"`
 
-	// tsOffset is a randomized offset added to the value of the
-	// TSVal field in the timestamp option.
-	tsOffset uint32
-
 	// shutdownFlags represent the current shutdown state of the endpoint.
 	shutdownFlags tcpip.ShutdownFlags
 
 	// tcpRecovery is the loss deteoction algorithm used by TCP.
 	tcpRecovery tcpip.TCPRecovery
 
-	// sackPermitted is set to true if the peer sends the TCPSACKPermitted
-	// option in the SYN/SYN-ACK.
-	sackPermitted bool
-
 	// sack holds TCP SACK related information for this endpoint.
 	sack SACKInfo
 
@@ -560,32 +511,13 @@ type endpoint struct {
 	// this value.
 	windowClamp uint32
 
-	// The following fields are used to manage the send buffer. When
-	// segments are ready to be sent, they are added to sndQueue and the
-	// protocol goroutine is signaled via sndWaker.
-	//
-	// When the send side is closed, the protocol goroutine is notified via
-	// sndCloseWaker, and sndClosed is set to true.
-	sndBufMu      sync.Mutex `state:"nosave"`
-	sndBufUsed    int
-	sndClosed     bool
-	sndBufInQueue seqnum.Size
-	sndQueue      segmentList `state:"wait"`
-	sndWaker      sleep.Waker `state:"manual"`
-	sndCloseWaker sleep.Waker `state:"manual"`
+	// sndQueueInfo contains the implementation of the endpoint's send queue.
+	sndQueueInfo sndQueueInfo
 
 	// cc stores the name of the Congestion Control algorithm to use for
 	// this endpoint.
 	cc tcpip.CongestionControlOption
 
-	// The following are used when a "packet too big" control packet is
-	// received. They are protected by sndBufMu. They are used to
-	// communicate to the main protocol goroutine how many such control
-	// messages have been received since the last notification was processed
-	// and what was the smallest MTU seen.
-	packetTooBigCount int
-	sndMTU            int
-
 	// newSegmentWaker is used to indicate to the protocol goroutine that
 	// it needs to wake up and handle new segments queued to it.
 	newSegmentWaker sleep.Waker `state:"manual"`
@@ -782,7 +714,7 @@ func (e *endpoint) UnlockUser() {
 
 		switch e.EndpointState() {
 		case StateEstablished:
-			if err := e.handleSegments(true /* fastPath */); err != nil {
+			if err := e.handleSegmentsLocked(true /* fastPath */); err != nil {
 				e.notifyProtocolGoroutine(notifyTickleWorker)
 			}
 		default:
@@ -842,13 +774,13 @@ func (e *endpoint) EndpointState() EndpointState {
 
 // setRecentTimestamp sets the recentTS field to the provided value.
 func (e *endpoint) setRecentTimestamp(recentTS uint32) {
-	e.recentTS = recentTS
+	e.RecentTS = recentTS
 	e.recentTSTime = time.Now()
 }
 
 // recentTimestamp returns the value of the recentTS field.
 func (e *endpoint) recentTimestamp() uint32 {
-	return e.recentTS
+	return e.RecentTS
 }
 
 // keepalive is a synchronization wrapper used to appease stateify. See the
@@ -868,16 +800,17 @@ type keepalive struct {
 func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) *endpoint {
 	e := &endpoint{
 		stack: s,
-		EndpointInfo: EndpointInfo{
-			TransportEndpointInfo: stack.TransportEndpointInfo{
-				NetProto:   netProto,
-				TransProto: header.TCPProtocolNumber,
+		TransportEndpointInfo: stack.TransportEndpointInfo{
+			NetProto:   netProto,
+			TransProto: header.TCPProtocolNumber,
+		},
+		sndQueueInfo: sndQueueInfo{
+			TCPSndBufState: stack.TCPSndBufState{
+				SndMTU: int(math.MaxInt32),
 			},
 		},
 		waiterQueue: waiterQueue,
 		state:       StateInitial,
-		rcvBufSize:  DefaultReceiveBufferSize,
-		sndMTU:      math.MaxInt32,
 		keepalive: keepalive{
 			// Linux defaults.
 			idle:     2 * time.Hour,
@@ -889,6 +822,7 @@ func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQue
 		windowClamp:   DefaultReceiveBufferSize,
 		maxSynRetries: DefaultSynRetries,
 	}
+	e.rcvQueueInfo.RcvBufSize = DefaultReceiveBufferSize
 	e.ops.InitHandler(e, e.stack, GetTCPSendBufferLimits)
 	e.ops.SetMulticastLoop(true)
 	e.ops.SetQuickAck(true)
@@ -901,7 +835,7 @@ func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQue
 
 	var rs tcpip.TCPReceiveBufferSizeRangeOption
 	if err := s.TransportProtocolOption(ProtocolNumber, &rs); err == nil {
-		e.rcvBufSize = rs.Default
+		e.rcvQueueInfo.RcvBufSize = rs.Default
 	}
 
 	var cs tcpip.CongestionControlOption
@@ -911,7 +845,7 @@ func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQue
 
 	var mrb tcpip.TCPModerateReceiveBufferOption
 	if err := s.TransportProtocolOption(ProtocolNumber, &mrb); err == nil {
-		e.rcvAutoParams.disabled = !bool(mrb)
+		e.rcvQueueInfo.RcvAutoParams.Disabled = !bool(mrb)
 	}
 
 	var de tcpip.TCPDelayEnabled
@@ -936,7 +870,7 @@ func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQue
 	}
 
 	e.segmentQueue.ep = e
-	e.tsOffset = timeStampOffset()
+	e.TSOffset = timeStampOffset()
 	e.acceptCond = sync.NewCond(&e.acceptMu)
 	e.keepalive.timer.init(&e.keepalive.waker)
 
@@ -974,21 +908,21 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 	if e.EndpointState().connected() {
 		// Determine if the endpoint is writable if requested.
 		if (mask & waiter.WritableEvents) != 0 {
-			e.sndBufMu.Lock()
+			e.sndQueueInfo.sndQueueMu.Lock()
 			sndBufSize := e.getSendBufferSize()
-			if e.sndClosed || e.sndBufUsed < sndBufSize {
+			if e.sndQueueInfo.SndClosed || e.sndQueueInfo.SndBufUsed < sndBufSize {
 				result |= waiter.WritableEvents
 			}
-			e.sndBufMu.Unlock()
+			e.sndQueueInfo.sndQueueMu.Unlock()
 		}
 
 		// Determine if the endpoint is readable if requested.
 		if (mask & waiter.ReadableEvents) != 0 {
-			e.rcvListMu.Lock()
-			if e.rcvBufUsed > 0 || e.rcvClosed {
+			e.rcvQueueInfo.rcvQueueMu.Lock()
+			if e.rcvQueueInfo.RcvBufUsed > 0 || e.rcvQueueInfo.RcvClosed {
 				result |= waiter.ReadableEvents
 			}
-			e.rcvListMu.Unlock()
+			e.rcvQueueInfo.rcvQueueMu.Unlock()
 		}
 	}
 
@@ -1096,15 +1030,15 @@ func (e *endpoint) closeNoShutdownLocked() {
 	// in Listen() when trying to register.
 	if e.EndpointState() == StateListen && e.isPortReserved {
 		if e.isRegistered {
-			e.stack.StartTransportEndpointCleanup(e.effectiveNetProtos, ProtocolNumber, e.ID, e, e.boundPortFlags, e.boundBindToDevice)
+			e.stack.StartTransportEndpointCleanup(e.effectiveNetProtos, ProtocolNumber, e.TransportEndpointInfo.ID, e, e.boundPortFlags, e.boundBindToDevice)
 			e.isRegistered = false
 		}
 
 		portRes := ports.Reservation{
 			Networks:     e.effectiveNetProtos,
 			Transport:    ProtocolNumber,
-			Addr:         e.ID.LocalAddress,
-			Port:         e.ID.LocalPort,
+			Addr:         e.TransportEndpointInfo.ID.LocalAddress,
+			Port:         e.TransportEndpointInfo.ID.LocalPort,
 			Flags:        e.boundPortFlags,
 			BindToDevice: e.boundBindToDevice,
 			Dest:         e.boundDest,
@@ -1179,7 +1113,7 @@ func (e *endpoint) cleanupLocked() {
 	e.workerCleanup = false
 
 	if e.isRegistered {
-		e.stack.StartTransportEndpointCleanup(e.effectiveNetProtos, ProtocolNumber, e.ID, e, e.boundPortFlags, e.boundBindToDevice)
+		e.stack.StartTransportEndpointCleanup(e.effectiveNetProtos, ProtocolNumber, e.TransportEndpointInfo.ID, e, e.boundPortFlags, e.boundBindToDevice)
 		e.isRegistered = false
 	}
 
@@ -1187,8 +1121,8 @@ func (e *endpoint) cleanupLocked() {
 		portRes := ports.Reservation{
 			Networks:     e.effectiveNetProtos,
 			Transport:    ProtocolNumber,
-			Addr:         e.ID.LocalAddress,
-			Port:         e.ID.LocalPort,
+			Addr:         e.TransportEndpointInfo.ID.LocalAddress,
+			Port:         e.TransportEndpointInfo.ID.LocalPort,
 			Flags:        e.boundPortFlags,
 			BindToDevice: e.boundBindToDevice,
 			Dest:         e.boundDest,
@@ -1250,19 +1184,19 @@ func (e *endpoint) ModerateRecvBuf(copied int) {
 	e.LockUser()
 	defer e.UnlockUser()
 
-	e.rcvListMu.Lock()
-	if e.rcvAutoParams.disabled {
-		e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	if e.rcvQueueInfo.RcvAutoParams.Disabled {
+		e.rcvQueueInfo.rcvQueueMu.Unlock()
 		return
 	}
 	now := time.Now()
-	if rtt := e.rcvAutoParams.rtt; rtt == 0 || now.Sub(e.rcvAutoParams.measureTime) < rtt {
-		e.rcvAutoParams.copied += copied
-		e.rcvListMu.Unlock()
+	if rtt := e.rcvQueueInfo.RcvAutoParams.RTT; rtt == 0 || now.Sub(e.rcvQueueInfo.RcvAutoParams.MeasureTime) < rtt {
+		e.rcvQueueInfo.RcvAutoParams.CopiedBytes += copied
+		e.rcvQueueInfo.rcvQueueMu.Unlock()
 		return
 	}
-	prevRTTCopied := e.rcvAutoParams.copied + copied
-	prevCopied := e.rcvAutoParams.prevCopied
+	prevRTTCopied := e.rcvQueueInfo.RcvAutoParams.CopiedBytes + copied
+	prevCopied := e.rcvQueueInfo.RcvAutoParams.PrevCopiedBytes
 	rcvWnd := 0
 	if prevRTTCopied > prevCopied {
 		// The minimal receive window based on what was copied by the app
@@ -1294,24 +1228,24 @@ func (e *endpoint) ModerateRecvBuf(copied int) {
 		// We do not adjust downwards as that can cause the receiver to
 		// reject valid data that might already be in flight as the
 		// acceptable window will shrink.
-		if rcvWnd > e.rcvBufSize {
+		if rcvWnd > e.rcvQueueInfo.RcvBufSize {
 			availBefore := wndFromSpace(e.receiveBufferAvailableLocked())
-			e.rcvBufSize = rcvWnd
+			e.rcvQueueInfo.RcvBufSize = rcvWnd
 			availAfter := wndFromSpace(e.receiveBufferAvailableLocked())
 			if crossed, above := e.windowCrossedACKThresholdLocked(availAfter - availBefore); crossed && above {
 				e.notifyProtocolGoroutine(notifyNonZeroReceiveWindow)
 			}
 		}
 
-		// We only update prevCopied when we grow the buffer because in cases
-		// where prevCopied > prevRTTCopied the existing buffer is already big
+		// We only update PrevCopiedBytes when we grow the buffer because in cases
+		// where PrevCopiedBytes > prevRTTCopied the existing buffer is already big
 		// enough to handle the current rate and we don't need to do any
 		// adjustments.
-		e.rcvAutoParams.prevCopied = prevRTTCopied
+		e.rcvQueueInfo.RcvAutoParams.PrevCopiedBytes = prevRTTCopied
 	}
-	e.rcvAutoParams.measureTime = now
-	e.rcvAutoParams.copied = 0
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.RcvAutoParams.MeasureTime = now
+	e.rcvQueueInfo.RcvAutoParams.CopiedBytes = 0
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 }
 
 // SetOwner implements tcpip.Endpoint.SetOwner.
@@ -1360,7 +1294,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 	defer e.rcvReadMu.Unlock()
 
 	// N.B. Here we get a range of segments to be processed. It is safe to not
-	// hold rcvListMu when processing, since we hold rcvReadMu to ensure only we
+	// hold rcvQueueMu when processing, since we hold rcvReadMu to ensure only we
 	// can remove segments from the list through commitRead().
 	first, last, serr := e.startRead()
 	if serr != nil {
@@ -1432,10 +1366,10 @@ func (e *endpoint) startRead() (first, last *segment, err tcpip.Error) {
 	// but has some pending unread data. Also note that a RST being received
 	// would cause the state to become StateError so we should allow the
 	// reads to proceed before returning a ECONNRESET.
-	e.rcvListMu.Lock()
-	defer e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	defer e.rcvQueueInfo.rcvQueueMu.Unlock()
 
-	bufUsed := e.rcvBufUsed
+	bufUsed := e.rcvQueueInfo.RcvBufUsed
 	if s := e.EndpointState(); !s.connected() && s != StateClose && bufUsed == 0 {
 		if s == StateError {
 			if err := e.hardErrorLocked(); err != nil {
@@ -1447,14 +1381,14 @@ func (e *endpoint) startRead() (first, last *segment, err tcpip.Error) {
 		return nil, nil, &tcpip.ErrNotConnected{}
 	}
 
-	if e.rcvBufUsed == 0 {
-		if e.rcvClosed || !e.EndpointState().connected() {
+	if e.rcvQueueInfo.RcvBufUsed == 0 {
+		if e.rcvQueueInfo.RcvClosed || !e.EndpointState().connected() {
 			return nil, nil, &tcpip.ErrClosedForReceive{}
 		}
 		return nil, nil, &tcpip.ErrWouldBlock{}
 	}
 
-	return e.rcvList.Front(), e.rcvList.Back(), nil
+	return e.rcvQueueInfo.rcvQueue.Front(), e.rcvQueueInfo.rcvQueue.Back(), nil
 }
 
 // commitRead commits a read of done bytes and returns the next non-empty
@@ -1470,20 +1404,20 @@ func (e *endpoint) startRead() (first, last *segment, err tcpip.Error) {
 func (e *endpoint) commitRead(done int) *segment {
 	e.LockUser()
 	defer e.UnlockUser()
-	e.rcvListMu.Lock()
-	defer e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	defer e.rcvQueueInfo.rcvQueueMu.Unlock()
 
 	memDelta := 0
-	s := e.rcvList.Front()
+	s := e.rcvQueueInfo.rcvQueue.Front()
 	for s != nil && s.data.Size() == 0 {
-		e.rcvList.Remove(s)
+		e.rcvQueueInfo.rcvQueue.Remove(s)
 		// Memory is only considered released when the whole segment has been
 		// read.
 		memDelta += s.segMemSize()
 		s.decRef()
-		s = e.rcvList.Front()
+		s = e.rcvQueueInfo.rcvQueue.Front()
 	}
-	e.rcvBufUsed -= done
+	e.rcvQueueInfo.RcvBufUsed -= done
 
 	if memDelta > 0 {
 		// If the window was small before this read and if the read freed up
@@ -1495,14 +1429,14 @@ func (e *endpoint) commitRead(done int) *segment {
 		}
 	}
 
-	return e.rcvList.Front()
+	return e.rcvQueueInfo.rcvQueue.Front()
 }
 
 // isEndpointWritableLocked checks if a given endpoint is writable
 // and also returns the number of bytes that can be written at this
 // moment. If the endpoint is not writable then it returns an error
 // indicating the reason why it's not writable.
-// Caller must hold e.mu and e.sndBufMu
+// Caller must hold e.mu and e.sndQueueMu
 func (e *endpoint) isEndpointWritableLocked() (int, tcpip.Error) {
 	// The endpoint cannot be written to if it's not connected.
 	switch s := e.EndpointState(); {
@@ -1522,12 +1456,12 @@ func (e *endpoint) isEndpointWritableLocked() (int, tcpip.Error) {
 	}
 
 	// Check if the connection has already been closed for sends.
-	if e.sndClosed {
+	if e.sndQueueInfo.SndClosed {
 		return 0, &tcpip.ErrClosedForSend{}
 	}
 
 	sndBufSize := e.getSendBufferSize()
-	avail := sndBufSize - e.sndBufUsed
+	avail := sndBufSize - e.sndQueueInfo.SndBufUsed
 	if avail <= 0 {
 		return 0, &tcpip.ErrWouldBlock{}
 	}
@@ -1544,8 +1478,8 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 	defer e.UnlockUser()
 
 	nextSeg, n, err := func() (*segment, int, tcpip.Error) {
-		e.sndBufMu.Lock()
-		defer e.sndBufMu.Unlock()
+		e.sndQueueInfo.sndQueueMu.Lock()
+		defer e.sndQueueInfo.sndQueueMu.Unlock()
 
 		avail, err := e.isEndpointWritableLocked()
 		if err != nil {
@@ -1560,8 +1494,8 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 			// available buffer space to be consumed by some other caller while we
 			// are copying data in.
 			if !opts.Atomic {
-				e.sndBufMu.Unlock()
-				defer e.sndBufMu.Lock()
+				e.sndQueueInfo.sndQueueMu.Unlock()
+				defer e.sndQueueInfo.sndQueueMu.Lock()
 
 				e.UnlockUser()
 				defer e.LockUser()
@@ -1603,10 +1537,10 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 		}
 
 		// Add data to the send queue.
-		s := newOutgoingSegment(e.ID, v)
-		e.sndBufUsed += len(v)
-		e.sndBufInQueue += seqnum.Size(len(v))
-		e.sndQueue.PushBack(s)
+		s := newOutgoingSegment(e.TransportEndpointInfo.ID, v)
+		e.sndQueueInfo.SndBufUsed += len(v)
+		e.sndQueueInfo.SndBufInQueue += seqnum.Size(len(v))
+		e.sndQueueInfo.sndQueue.PushBack(s)
 
 		return e.drainSendQueueLocked(), len(v), nil
 	}()
@@ -1621,11 +1555,11 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 
 // selectWindowLocked returns the new window without checking for shrinking or scaling
 // applied.
-// Precondition: e.mu and e.rcvListMu must be held.
+// Precondition: e.mu and e.rcvQueueMu must be held.
 func (e *endpoint) selectWindowLocked() (wnd seqnum.Size) {
 	wndFromAvailable := wndFromSpace(e.receiveBufferAvailableLocked())
-	maxWindow := wndFromSpace(e.rcvBufSize)
-	wndFromUsedBytes := maxWindow - e.rcvBufUsed
+	maxWindow := wndFromSpace(e.rcvQueueInfo.RcvBufSize)
+	wndFromUsedBytes := maxWindow - e.rcvQueueInfo.RcvBufUsed
 
 	// We take the lesser of the wndFromAvailable and wndFromUsedBytes because in
 	// cases where we receive a lot of small segments the segment overhead is a
@@ -1643,11 +1577,11 @@ func (e *endpoint) selectWindowLocked() (wnd seqnum.Size) {
 	return seqnum.Size(newWnd)
 }
 
-// selectWindow invokes selectWindowLocked after acquiring e.rcvListMu.
+// selectWindow invokes selectWindowLocked after acquiring e.rcvQueueMu.
 func (e *endpoint) selectWindow() (wnd seqnum.Size) {
-	e.rcvListMu.Lock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
 	wnd = e.selectWindowLocked()
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 	return wnd
 }
 
@@ -1665,7 +1599,7 @@ func (e *endpoint) selectWindow() (wnd seqnum.Size) {
 // above will be true if the new window is >= ACK threshold and false
 // otherwise.
 //
-// Precondition: e.mu and e.rcvListMu must be held.
+// Precondition: e.mu and e.rcvQueueMu must be held.
 func (e *endpoint) windowCrossedACKThresholdLocked(deltaBefore int) (crossed bool, above bool) {
 	newAvail := int(e.selectWindowLocked())
 	oldAvail := newAvail - deltaBefore
@@ -1676,7 +1610,7 @@ func (e *endpoint) windowCrossedACKThresholdLocked(deltaBefore int) (crossed boo
 	// rcvBufFraction is the inverse of the fraction of receive buffer size that
 	// is used to decide if the available buffer space is now above it.
 	const rcvBufFraction = 2
-	if wndThreshold := wndFromSpace(e.rcvBufSize / rcvBufFraction); threshold > wndThreshold {
+	if wndThreshold := wndFromSpace(e.rcvQueueInfo.RcvBufSize / rcvBufFraction); threshold > wndThreshold {
 		threshold = wndThreshold
 	}
 	switch {
@@ -1711,7 +1645,7 @@ func (e *endpoint) OnKeepAliveSet(bool) {
 func (e *endpoint) OnDelayOptionSet(v bool) {
 	if !v {
 		// Handle delayed data.
-		e.sndWaker.Assert()
+		e.sndQueueInfo.sndWaker.Assert()
 	}
 }
 
@@ -1719,7 +1653,7 @@ func (e *endpoint) OnDelayOptionSet(v bool) {
 func (e *endpoint) OnCorkOptionSet(v bool) {
 	if !v {
 		// Handle the corked data.
-		e.sndWaker.Assert()
+		e.sndQueueInfo.sndWaker.Assert()
 	}
 }
 
@@ -1792,23 +1726,23 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) tcpip.Error {
 		}
 
 		e.LockUser()
-		e.rcvListMu.Lock()
+		e.rcvQueueInfo.rcvQueueMu.Lock()
 
 		// Make sure the receive buffer size allows us to send a
 		// non-zero window size.
 		scale := uint8(0)
 		if e.rcv != nil {
-			scale = e.rcv.rcvWndScale
+			scale = e.rcv.RcvWndScale
 		}
 		if v>>scale == 0 {
 			v = 1 << scale
 		}
 
 		availBefore := wndFromSpace(e.receiveBufferAvailableLocked())
-		e.rcvBufSize = v
+		e.rcvQueueInfo.RcvBufSize = v
 		availAfter := wndFromSpace(e.receiveBufferAvailableLocked())
 
-		e.rcvAutoParams.disabled = true
+		e.rcvQueueInfo.RcvAutoParams.Disabled = true
 
 		// Immediately send an ACK to uncork the sender silly window
 		// syndrome prevetion, when our available space grows above aMSS
@@ -1817,7 +1751,7 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) tcpip.Error {
 			e.notifyProtocolGoroutine(notifyNonZeroReceiveWindow)
 		}
 
-		e.rcvListMu.Unlock()
+		e.rcvQueueInfo.rcvQueueMu.Unlock()
 		e.UnlockUser()
 
 	case tcpip.TTLOption:
@@ -1962,10 +1896,10 @@ func (e *endpoint) readyReceiveSize() (int, tcpip.Error) {
 		return 0, &tcpip.ErrInvalidEndpointState{}
 	}
 
-	e.rcvListMu.Lock()
-	defer e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	defer e.rcvQueueInfo.rcvQueueMu.Unlock()
 
-	return e.rcvBufUsed, nil
+	return e.rcvQueueInfo.RcvBufUsed, nil
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
@@ -2006,9 +1940,9 @@ func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, tcpip.Error) {
 		return e.readyReceiveSize()
 
 	case tcpip.ReceiveBufferSizeOption:
-		e.rcvListMu.Lock()
-		v := e.rcvBufSize
-		e.rcvListMu.Unlock()
+		e.rcvQueueInfo.rcvQueueMu.Lock()
+		v := e.rcvQueueInfo.RcvBufSize
+		e.rcvQueueInfo.rcvQueueMu.Unlock()
 		return v, nil
 
 	case tcpip.TTLOption:
@@ -2046,15 +1980,15 @@ func (e *endpoint) getTCPInfo() tcpip.TCPInfoOption {
 		// 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
+		info.RTT = snd.rtt.TCPRTTState.SRTT
+		info.RTTVar = snd.rtt.TCPRTTState.RTTVar
 		snd.rtt.Unlock()
 
-		info.RTO = snd.rto
+		info.RTO = snd.RTO
 		info.CcState = snd.state
-		info.SndSsthresh = uint32(snd.sndSsthresh)
-		info.SndCwnd = uint32(snd.sndCwnd)
-		info.ReorderSeen = snd.rc.reorderSeen
+		info.SndSsthresh = uint32(snd.Ssthresh)
+		info.SndCwnd = uint32(snd.SndCwnd)
+		info.ReorderSeen = snd.rc.Reord
 	}
 	e.UnlockUser()
 	return info
@@ -2099,7 +2033,7 @@ func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) tcpip.Error {
 	case *tcpip.OriginalDestinationOption:
 		e.LockUser()
 		ipt := e.stack.IPTables()
-		addr, port, err := ipt.OriginalDst(e.ID, e.NetProto)
+		addr, port, err := ipt.OriginalDst(e.TransportEndpointInfo.ID, e.NetProto)
 		e.UnlockUser()
 		if err != nil {
 			return err
@@ -2207,20 +2141,20 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) tcp
 	}
 
 	// Find a route to the desired destination.
-	r, err := e.stack.FindRoute(nicID, e.ID.LocalAddress, addr.Addr, netProto, false /* multicastLoop */)
+	r, err := e.stack.FindRoute(nicID, e.TransportEndpointInfo.ID.LocalAddress, addr.Addr, netProto, false /* multicastLoop */)
 	if err != nil {
 		return err
 	}
 	defer r.Release()
 
 	netProtos := []tcpip.NetworkProtocolNumber{netProto}
-	e.ID.LocalAddress = r.LocalAddress()
-	e.ID.RemoteAddress = r.RemoteAddress()
-	e.ID.RemotePort = addr.Port
+	e.TransportEndpointInfo.ID.LocalAddress = r.LocalAddress()
+	e.TransportEndpointInfo.ID.RemoteAddress = r.RemoteAddress()
+	e.TransportEndpointInfo.ID.RemotePort = addr.Port
 
-	if e.ID.LocalPort != 0 {
+	if e.TransportEndpointInfo.ID.LocalPort != 0 {
 		// The endpoint is bound to a port, attempt to register it.
-		err := e.stack.RegisterTransportEndpoint(netProtos, ProtocolNumber, e.ID, e, e.boundPortFlags, e.boundBindToDevice)
+		err := e.stack.RegisterTransportEndpoint(netProtos, ProtocolNumber, e.TransportEndpointInfo.ID, e, e.boundPortFlags, e.boundBindToDevice)
 		if err != nil {
 			return err
 		}
@@ -2229,7 +2163,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) tcp
 		// one. Make sure that it isn't one that will result in the same
 		// address/port for both local and remote (otherwise this
 		// endpoint would be trying to connect to itself).
-		sameAddr := e.ID.LocalAddress == e.ID.RemoteAddress
+		sameAddr := e.TransportEndpointInfo.ID.LocalAddress == e.TransportEndpointInfo.ID.RemoteAddress
 
 		// Calculate a port offset based on the destination IP/port and
 		// src IP to ensure that for a given tuple (srcIP, destIP,
@@ -2262,21 +2196,21 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) tcp
 		if twReuse == tcpip.TCPTimeWaitReuseLoopbackOnly {
 			switch netProto {
 			case header.IPv4ProtocolNumber:
-				reuse = header.IsV4LoopbackAddress(e.ID.LocalAddress) && header.IsV4LoopbackAddress(e.ID.RemoteAddress)
+				reuse = header.IsV4LoopbackAddress(e.TransportEndpointInfo.ID.LocalAddress) && header.IsV4LoopbackAddress(e.TransportEndpointInfo.ID.RemoteAddress)
 			case header.IPv6ProtocolNumber:
-				reuse = e.ID.LocalAddress == header.IPv6Loopback && e.ID.RemoteAddress == header.IPv6Loopback
+				reuse = e.TransportEndpointInfo.ID.LocalAddress == header.IPv6Loopback && e.TransportEndpointInfo.ID.RemoteAddress == header.IPv6Loopback
 			}
 		}
 
 		bindToDevice := tcpip.NICID(e.ops.GetBindToDevice())
 		if _, err := e.stack.PickEphemeralPortStable(portOffset, func(p uint16) (bool, tcpip.Error) {
-			if sameAddr && p == e.ID.RemotePort {
+			if sameAddr && p == e.TransportEndpointInfo.ID.RemotePort {
 				return false, nil
 			}
 			portRes := ports.Reservation{
 				Networks:     netProtos,
 				Transport:    ProtocolNumber,
-				Addr:         e.ID.LocalAddress,
+				Addr:         e.TransportEndpointInfo.ID.LocalAddress,
 				Port:         p,
 				Flags:        e.portFlags,
 				BindToDevice: bindToDevice,
@@ -2286,7 +2220,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) tcp
 				if _, ok := err.(*tcpip.ErrPortInUse); !ok || !reuse {
 					return false, nil
 				}
-				transEPID := e.ID
+				transEPID := e.TransportEndpointInfo.ID
 				transEPID.LocalPort = p
 				// Check if an endpoint is registered with demuxer in TIME-WAIT and if
 				// we can reuse it. If we can't find a transport endpoint then we just
@@ -2323,7 +2257,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) tcp
 				portRes := ports.Reservation{
 					Networks:     netProtos,
 					Transport:    ProtocolNumber,
-					Addr:         e.ID.LocalAddress,
+					Addr:         e.TransportEndpointInfo.ID.LocalAddress,
 					Port:         p,
 					Flags:        e.portFlags,
 					BindToDevice: bindToDevice,
@@ -2334,13 +2268,13 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) tcp
 				}
 			}
 
-			id := e.ID
+			id := e.TransportEndpointInfo.ID
 			id.LocalPort = p
 			if err := e.stack.RegisterTransportEndpoint(netProtos, ProtocolNumber, id, e, e.portFlags, bindToDevice); err != nil {
 				portRes := ports.Reservation{
 					Networks:     netProtos,
 					Transport:    ProtocolNumber,
-					Addr:         e.ID.LocalAddress,
+					Addr:         e.TransportEndpointInfo.ID.LocalAddress,
 					Port:         p,
 					Flags:        e.portFlags,
 					BindToDevice: bindToDevice,
@@ -2355,7 +2289,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) tcp
 
 			// Port picking successful. Save the details of
 			// the selected port.
-			e.ID = id
+			e.TransportEndpointInfo.ID = id
 			e.isPortReserved = true
 			e.boundBindToDevice = bindToDevice
 			e.boundPortFlags = e.portFlags
@@ -2381,10 +2315,10 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) tcp
 	// connection setting here.
 	if !handshake {
 		e.segmentQueue.mu.Lock()
-		for _, l := range []segmentList{e.segmentQueue.list, e.sndQueue, e.snd.writeList} {
+		for _, l := range []segmentList{e.segmentQueue.list, e.sndQueueInfo.sndQueue, e.snd.writeList} {
 			for s := l.Front(); s != nil; s = s.Next() {
-				s.id = e.ID
-				e.sndWaker.Assert()
+				s.id = e.TransportEndpointInfo.ID
+				e.sndQueueInfo.sndWaker.Assert()
 			}
 		}
 		e.segmentQueue.mu.Unlock()
@@ -2426,10 +2360,10 @@ func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) tcpip.Error {
 		// Close for read.
 		if e.shutdownFlags&tcpip.ShutdownRead != 0 {
 			// Mark read side as closed.
-			e.rcvListMu.Lock()
-			e.rcvClosed = true
-			rcvBufUsed := e.rcvBufUsed
-			e.rcvListMu.Unlock()
+			e.rcvQueueInfo.rcvQueueMu.Lock()
+			e.rcvQueueInfo.RcvClosed = true
+			rcvBufUsed := e.rcvQueueInfo.RcvBufUsed
+			e.rcvQueueInfo.rcvQueueMu.Unlock()
 
 			// If we're fully closed and we have unread data we need to abort
 			// the connection with a RST.
@@ -2443,10 +2377,10 @@ func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) tcpip.Error {
 
 		// Close for write.
 		if e.shutdownFlags&tcpip.ShutdownWrite != 0 {
-			e.sndBufMu.Lock()
-			if e.sndClosed {
+			e.sndQueueInfo.sndQueueMu.Lock()
+			if e.sndQueueInfo.SndClosed {
 				// Already closed.
-				e.sndBufMu.Unlock()
+				e.sndQueueInfo.sndQueueMu.Unlock()
 				if e.EndpointState() == StateTimeWait {
 					return &tcpip.ErrNotConnected{}
 				}
@@ -2454,12 +2388,12 @@ func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) tcpip.Error {
 			}
 
 			// Queue fin segment.
-			s := newOutgoingSegment(e.ID, nil)
-			e.sndQueue.PushBack(s)
-			e.sndBufInQueue++
+			s := newOutgoingSegment(e.TransportEndpointInfo.ID, nil)
+			e.sndQueueInfo.sndQueue.PushBack(s)
+			e.sndQueueInfo.SndBufInQueue++
 			// Mark endpoint as closed.
-			e.sndClosed = true
-			e.sndBufMu.Unlock()
+			e.sndQueueInfo.SndClosed = true
+			e.sndQueueInfo.sndQueueMu.Unlock()
 			e.handleClose()
 		}
 
@@ -2472,9 +2406,9 @@ func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) tcpip.Error {
 			//
 			// By not removing this endpoint from the demuxer mapping, we
 			// ensure that any other bind to the same port fails, as on Linux.
-			e.rcvListMu.Lock()
-			e.rcvClosed = true
-			e.rcvListMu.Unlock()
+			e.rcvQueueInfo.rcvQueueMu.Lock()
+			e.rcvQueueInfo.RcvClosed = true
+			e.rcvQueueInfo.rcvQueueMu.Unlock()
 			e.closePendingAcceptableConnectionsLocked()
 			// Notify waiters that the endpoint is shutdown.
 			e.waiterQueue.Notify(waiter.ReadableEvents | waiter.WritableEvents | waiter.EventHUp | waiter.EventErr)
@@ -2513,9 +2447,9 @@ func (e *endpoint) listen(backlog int) tcpip.Error {
 			// listen is called after shutdown.
 			e.accepted.cap = backlog
 			e.shutdownFlags = 0
-			e.rcvListMu.Lock()
-			e.rcvClosed = false
-			e.rcvListMu.Unlock()
+			e.rcvQueueInfo.rcvQueueMu.Lock()
+			e.rcvQueueInfo.RcvClosed = false
+			e.rcvQueueInfo.rcvQueueMu.Unlock()
 		} else {
 			// Adjust the size of the backlog iff we can fit
 			// existing pending connections into the new one.
@@ -2548,7 +2482,7 @@ func (e *endpoint) listen(backlog int) tcpip.Error {
 	}
 
 	// Register the endpoint.
-	if err := e.stack.RegisterTransportEndpoint(e.effectiveNetProtos, ProtocolNumber, e.ID, e, e.boundPortFlags, e.boundBindToDevice); err != nil {
+	if err := e.stack.RegisterTransportEndpoint(e.effectiveNetProtos, ProtocolNumber, e.TransportEndpointInfo.ID, e, e.boundPortFlags, e.boundBindToDevice); err != nil {
 		return err
 	}
 
@@ -2588,9 +2522,9 @@ func (e *endpoint) Accept(peerAddr *tcpip.FullAddress) (tcpip.Endpoint, *waiter.
 	e.LockUser()
 	defer e.UnlockUser()
 
-	e.rcvListMu.Lock()
-	rcvClosed := e.rcvClosed
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	rcvClosed := e.rcvQueueInfo.RcvClosed
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 	// Endpoint must be in listen state before it can accept connections.
 	if rcvClosed || e.EndpointState() != StateListen {
 		return nil, nil, &tcpip.ErrInvalidEndpointState{}
@@ -2656,7 +2590,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) (err tcpip.Error) {
 		if nic == 0 {
 			return &tcpip.ErrBadLocalAddress{}
 		}
-		e.ID.LocalAddress = addr.Addr
+		e.TransportEndpointInfo.ID.LocalAddress = addr.Addr
 	}
 
 	bindToDevice := tcpip.NICID(e.ops.GetBindToDevice())
@@ -2670,7 +2604,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) (err tcpip.Error) {
 		Dest:         tcpip.FullAddress{},
 	}
 	port, err := e.stack.ReservePort(portRes, func(p uint16) (bool, tcpip.Error) {
-		id := e.ID
+		id := e.TransportEndpointInfo.ID
 		id.LocalPort = p
 		// CheckRegisterTransportEndpoint should only return an error if there is a
 		// listening endpoint bound with the same id and portFlags and bindToDevice
@@ -2696,7 +2630,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) (err tcpip.Error) {
 	e.boundNICID = nic
 	e.isPortReserved = true
 	e.effectiveNetProtos = netProtos
-	e.ID.LocalPort = port
+	e.TransportEndpointInfo.ID.LocalPort = port
 
 	// Mark endpoint as bound.
 	e.setEndpointState(StateBound)
@@ -2710,8 +2644,8 @@ func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, tcpip.Error) {
 	defer e.UnlockUser()
 
 	return tcpip.FullAddress{
-		Addr: e.ID.LocalAddress,
-		Port: e.ID.LocalPort,
+		Addr: e.TransportEndpointInfo.ID.LocalAddress,
+		Port: e.TransportEndpointInfo.ID.LocalPort,
 		NIC:  e.boundNICID,
 	}, nil
 }
@@ -2730,8 +2664,8 @@ func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 
 func (e *endpoint) getRemoteAddress() tcpip.FullAddress {
 	return tcpip.FullAddress{
-		Addr: e.ID.RemoteAddress,
-		Port: e.ID.RemotePort,
+		Addr: e.TransportEndpointInfo.ID.RemoteAddress,
+		Port: e.TransportEndpointInfo.ID.RemotePort,
 		NIC:  e.boundNICID,
 	}
 }
@@ -2770,13 +2704,13 @@ func (e *endpoint) onICMPError(err tcpip.Error, transErr stack.TransportError, p
 			Payload: pkt.Data().AsRange().ToOwnedView(),
 			Dst: tcpip.FullAddress{
 				NIC:  pkt.NICID,
-				Addr: e.ID.RemoteAddress,
-				Port: e.ID.RemotePort,
+				Addr: e.TransportEndpointInfo.ID.RemoteAddress,
+				Port: e.TransportEndpointInfo.ID.RemotePort,
 			},
 			Offender: tcpip.FullAddress{
 				NIC:  pkt.NICID,
-				Addr: e.ID.LocalAddress,
-				Port: e.ID.LocalPort,
+				Addr: e.TransportEndpointInfo.ID.LocalAddress,
+				Port: e.TransportEndpointInfo.ID.LocalPort,
 			},
 			NetProto: pkt.NetworkProtocolNumber,
 		})
@@ -2789,12 +2723,12 @@ func (e *endpoint) onICMPError(err tcpip.Error, transErr stack.TransportError, p
 // HandleError implements stack.TransportEndpoint.
 func (e *endpoint) HandleError(transErr stack.TransportError, pkt *stack.PacketBuffer) {
 	handlePacketTooBig := func(mtu uint32) {
-		e.sndBufMu.Lock()
-		e.packetTooBigCount++
-		if v := int(mtu); v < e.sndMTU {
-			e.sndMTU = v
+		e.sndQueueInfo.sndQueueMu.Lock()
+		e.sndQueueInfo.PacketTooBigCount++
+		if v := int(mtu); v < e.sndQueueInfo.SndMTU {
+			e.sndQueueInfo.SndMTU = v
 		}
-		e.sndBufMu.Unlock()
+		e.sndQueueInfo.sndQueueMu.Unlock()
 		e.notifyProtocolGoroutine(notifyMTUChanged)
 	}
 
@@ -2813,14 +2747,14 @@ func (e *endpoint) HandleError(transErr stack.TransportError, pkt *stack.PacketB
 // in the send buffer. The number of newly available bytes is v.
 func (e *endpoint) updateSndBufferUsage(v int) {
 	sendBufferSize := e.getSendBufferSize()
-	e.sndBufMu.Lock()
-	notify := e.sndBufUsed >= sendBufferSize>>1
-	e.sndBufUsed -= v
+	e.sndQueueInfo.sndQueueMu.Lock()
+	notify := e.sndQueueInfo.SndBufUsed >= sendBufferSize>>1
+	e.sndQueueInfo.SndBufUsed -= v
 	// We only notify when there is half the sendBufferSize available after
 	// a full buffer event occurs. This ensures that we don't wake up
 	// writers to queue just 1-2 segments and go back to sleep.
-	notify = notify && e.sndBufUsed < sendBufferSize>>1
-	e.sndBufMu.Unlock()
+	notify = notify && e.sndQueueInfo.SndBufUsed < int(sendBufferSize)>>1
+	e.sndQueueInfo.sndQueueMu.Unlock()
 
 	if notify {
 		e.waiterQueue.Notify(waiter.WritableEvents)
@@ -2831,55 +2765,55 @@ func (e *endpoint) updateSndBufferUsage(v int) {
 // to be read, or when the connection is closed for receiving (in which case
 // s will be nil).
 func (e *endpoint) readyToRead(s *segment) {
-	e.rcvListMu.Lock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
 	if s != nil {
-		e.rcvBufUsed += s.payloadSize()
+		e.rcvQueueInfo.RcvBufUsed += s.payloadSize()
 		s.incRef()
-		e.rcvList.PushBack(s)
+		e.rcvQueueInfo.rcvQueue.PushBack(s)
 	} else {
-		e.rcvClosed = true
+		e.rcvQueueInfo.RcvClosed = true
 	}
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 	e.waiterQueue.Notify(waiter.ReadableEvents)
 }
 
 // receiveBufferAvailableLocked calculates how many bytes are still available
 // in the receive buffer.
-// rcvListMu must be held when this function is called.
+// rcvQueueMu must be held when this function is called.
 func (e *endpoint) receiveBufferAvailableLocked() int {
 	// We may use more bytes than the buffer size when the receive buffer
 	// shrinks.
 	memUsed := e.receiveMemUsed()
-	if memUsed >= e.rcvBufSize {
+	if memUsed >= e.rcvQueueInfo.RcvBufSize {
 		return 0
 	}
 
-	return e.rcvBufSize - memUsed
+	return e.rcvQueueInfo.RcvBufSize - memUsed
 }
 
 // receiveBufferAvailable calculates how many bytes are still available in the
 // receive buffer based on the actual memory used by all segments held in
 // receive buffer/pending and segment queue.
 func (e *endpoint) receiveBufferAvailable() int {
-	e.rcvListMu.Lock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
 	available := e.receiveBufferAvailableLocked()
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 	return available
 }
 
 // receiveBufferUsed returns the amount of in-use receive buffer.
 func (e *endpoint) receiveBufferUsed() int {
-	e.rcvListMu.Lock()
-	used := e.rcvBufUsed
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	used := e.rcvQueueInfo.RcvBufUsed
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 	return used
 }
 
 // receiveBufferSize returns the current size of the receive buffer.
 func (e *endpoint) receiveBufferSize() int {
-	e.rcvListMu.Lock()
-	size := e.rcvBufSize
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	size := e.rcvQueueInfo.RcvBufSize
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 	return size
 }
 
@@ -2913,9 +2847,9 @@ func (e *endpoint) maxReceiveBufferSize() int {
 func (e *endpoint) rcvWndScaleForHandshake() int {
 	bufSizeForScale := e.receiveBufferSize()
 
-	e.rcvListMu.Lock()
-	autoTuningDisabled := e.rcvAutoParams.disabled
-	e.rcvListMu.Unlock()
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	autoTuningDisabled := e.rcvQueueInfo.RcvAutoParams.Disabled
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
 	if autoTuningDisabled {
 		return FindWndScale(seqnum.Size(bufSizeForScale))
 	}
@@ -2926,7 +2860,7 @@ func (e *endpoint) rcvWndScaleForHandshake() int {
 // updateRecentTimestamp updates the recent timestamp using the algorithm
 // described in https://tools.ietf.org/html/rfc7323#section-4.3
 func (e *endpoint) updateRecentTimestamp(tsVal uint32, maxSentAck seqnum.Value, segSeq seqnum.Value) {
-	if e.sendTSOk && seqnum.Value(e.recentTimestamp()).LessThan(seqnum.Value(tsVal)) && segSeq.LessThanEq(maxSentAck) {
+	if e.SendTSOk && seqnum.Value(e.recentTimestamp()).LessThan(seqnum.Value(tsVal)) && segSeq.LessThanEq(maxSentAck) {
 		e.setRecentTimestamp(tsVal)
 	}
 }
@@ -2936,7 +2870,7 @@ func (e *endpoint) updateRecentTimestamp(tsVal uint32, maxSentAck seqnum.Value,
 // initializes the recentTS with the value provided in synOpts.TSval.
 func (e *endpoint) maybeEnableTimestamp(synOpts *header.TCPSynOptions) {
 	if synOpts.TS {
-		e.sendTSOk = true
+		e.SendTSOk = true
 		e.setRecentTimestamp(synOpts.TSVal)
 	}
 }
@@ -2944,7 +2878,7 @@ func (e *endpoint) maybeEnableTimestamp(synOpts *header.TCPSynOptions) {
 // timestamp returns the timestamp value to be used in the TSVal field of the
 // timestamp option for outgoing TCP segments for a given endpoint.
 func (e *endpoint) timestamp() uint32 {
-	return tcpTimeStamp(time.Now(), e.tsOffset)
+	return tcpTimeStamp(time.Now(), e.TSOffset)
 }
 
 // tcpTimeStamp returns a timestamp offset by the provided offset. This is
@@ -2983,7 +2917,7 @@ func (e *endpoint) maybeEnableSACKPermitted(synOpts *header.TCPSynOptions) {
 		return
 	}
 	if bool(v) && synOpts.SACKPermitted {
-		e.sackPermitted = true
+		e.SACKPermitted = true
 	}
 }
 
@@ -2997,118 +2931,46 @@ func (e *endpoint) maxOptionSize() (size int) {
 	return size
 }
 
-// completeState makes a full copy of the endpoint and returns it. This is used
-// before invoking the probe. The state returned may not be fully consistent if
-// there are intervening syscalls when the state is being copied.
-func (e *endpoint) completeState() stack.TCPEndpointState {
-	var s stack.TCPEndpointState
-	s.SegTime = time.Now()
-
-	// Copy EndpointID.
-	s.ID = stack.TCPEndpointID(e.ID)
-
-	// Copy endpoint rcv state.
-	e.rcvListMu.Lock()
-	s.RcvBufSize = e.rcvBufSize
-	s.RcvBufUsed = e.rcvBufUsed
-	s.RcvClosed = e.rcvClosed
-	s.RcvAutoParams.MeasureTime = e.rcvAutoParams.measureTime
-	s.RcvAutoParams.CopiedBytes = e.rcvAutoParams.copied
-	s.RcvAutoParams.PrevCopiedBytes = e.rcvAutoParams.prevCopied
-	s.RcvAutoParams.RTT = e.rcvAutoParams.rtt
-	s.RcvAutoParams.RTTMeasureSeqNumber = e.rcvAutoParams.rttMeasureSeqNumber
-	s.RcvAutoParams.RTTMeasureTime = e.rcvAutoParams.rttMeasureTime
-	s.RcvAutoParams.Disabled = e.rcvAutoParams.disabled
-	e.rcvListMu.Unlock()
-
-	// Endpoint TCP Option state.
-	s.SendTSOk = e.sendTSOk
-	s.RecentTS = e.recentTimestamp()
-	s.TSOffset = e.tsOffset
-	s.SACKPermitted = e.sackPermitted
+// completeStateLocked makes a full copy of the endpoint and returns it. This is
+// used before invoking the probe.
+//
+// Precondition: e.mu must be held.
+func (e *endpoint) completeStateLocked() stack.TCPEndpointState {
+	s := stack.TCPEndpointState{
+		TCPEndpointStateInner: e.TCPEndpointStateInner,
+		ID:                    stack.TCPEndpointID(e.TransportEndpointInfo.ID),
+		SegTime:               time.Now(),
+		Receiver:              e.rcv.TCPReceiverState,
+		Sender:                e.snd.TCPSenderState,
+	}
+
+	sndBufSize := e.getSendBufferSize()
+	// Copy the send buffer atomically.
+	e.sndQueueInfo.sndQueueMu.Lock()
+	s.SndBufState = e.sndQueueInfo.TCPSndBufState
+	s.SndBufState.SndBufSize = sndBufSize
+	e.sndQueueInfo.sndQueueMu.Unlock()
+
+	// Copy the receive buffer atomically.
+	e.rcvQueueInfo.rcvQueueMu.Lock()
+	s.RcvBufState = e.rcvQueueInfo.TCPRcvBufState
+	e.rcvQueueInfo.rcvQueueMu.Unlock()
+
+	// Copy the endpoint TCP Option state.
 	s.SACK.Blocks = make([]header.SACKBlock, e.sack.NumBlocks)
 	copy(s.SACK.Blocks, e.sack.Blocks[:e.sack.NumBlocks])
 	s.SACK.ReceivedBlocks, s.SACK.MaxSACKED = e.scoreboard.Copy()
 
-	// Copy endpoint send state.
-	sndBufSize := e.getSendBufferSize()
-	e.sndBufMu.Lock()
-	s.SndBufSize = sndBufSize
-	s.SndBufUsed = e.sndBufUsed
-	s.SndClosed = e.sndClosed
-	s.SndBufInQueue = e.sndBufInQueue
-	s.PacketTooBigCount = e.packetTooBigCount
-	s.SndMTU = e.sndMTU
-	e.sndBufMu.Unlock()
-
-	// Copy receiver state.
-	s.Receiver = stack.TCPReceiverState{
-		RcvNxt:         e.rcv.rcvNxt,
-		RcvAcc:         e.rcv.rcvAcc,
-		RcvWndScale:    e.rcv.rcvWndScale,
-		PendingBufUsed: e.rcv.pendingBufUsed,
-	}
-
-	// Copy sender state.
-	s.Sender = stack.TCPSenderState{
-		LastSendTime: e.snd.lastSendTime,
-		DupAckCount:  e.snd.dupAckCount,
-		FastRecovery: stack.TCPFastRecoveryState{
-			Active:    e.snd.fr.active,
-			First:     e.snd.fr.first,
-			Last:      e.snd.fr.last,
-			MaxCwnd:   e.snd.fr.maxCwnd,
-			HighRxt:   e.snd.fr.highRxt,
-			RescueRxt: e.snd.fr.rescueRxt,
-		},
-		SndCwnd:          e.snd.sndCwnd,
-		Ssthresh:         e.snd.sndSsthresh,
-		SndCAAckCount:    e.snd.sndCAAckCount,
-		Outstanding:      e.snd.outstanding,
-		SackedOut:        e.snd.sackedOut,
-		SndWnd:           e.snd.sndWnd,
-		SndUna:           e.snd.sndUna,
-		SndNxt:           e.snd.sndNxt,
-		RTTMeasureSeqNum: e.snd.rttMeasureSeqNum,
-		RTTMeasureTime:   e.snd.rttMeasureTime,
-		Closed:           e.snd.closed,
-		RTO:              e.snd.rto,
-		MaxPayloadSize:   e.snd.maxPayloadSize,
-		SndWndScale:      e.snd.sndWndScale,
-		MaxSentAck:       e.snd.maxSentAck,
-	}
 	e.snd.rtt.Lock()
-	s.Sender.SRTT = e.snd.rtt.srtt
-	s.Sender.SRTTInited = e.snd.rtt.srttInited
+	s.Sender.RTTState = e.snd.rtt.TCPRTTState
 	e.snd.rtt.Unlock()
 
 	if cubic, ok := e.snd.cc.(*cubicState); ok {
-		s.Sender.Cubic = stack.TCPCubicState{
-			WMax:                    cubic.wMax,
-			WLastMax:                cubic.wLastMax,
-			T:                       cubic.t,
-			TimeSinceLastCongestion: time.Since(cubic.t),
-			C:                       cubic.c,
-			K:                       cubic.k,
-			Beta:                    cubic.beta,
-			WC:                      cubic.wC,
-			WEst:                    cubic.wEst,
-		}
-	}
-
-	rc := &e.snd.rc
-	s.Sender.RACKState = stack.TCPRACKState{
-		XmitTime:      rc.xmitTime,
-		EndSequence:   rc.endSequence,
-		FACK:          rc.fack,
-		RTT:           rc.rtt,
-		Reord:         rc.reorderSeen,
-		DSACKSeen:     rc.dsackSeen,
-		ReoWnd:        rc.reoWnd,
-		ReoWndIncr:    rc.reoWndIncr,
-		ReoWndPersist: rc.reoWndPersist,
-		RTTSeq:        rc.rttSeq,
+		s.Sender.Cubic = cubic.TCPCubicState
+		s.Sender.Cubic.TimeSinceLastCongestion = time.Since(s.Sender.Cubic.T)
 	}
+
+	s.Sender.RACKState = e.snd.rc.TCPRACKState
 	return s
 }
 
diff --git a/pkg/tcpip/transport/tcp/endpoint_state.go b/pkg/tcpip/transport/tcp/endpoint_state.go
index 590775434..034eacd72 100644
--- a/pkg/tcpip/transport/tcp/endpoint_state.go
+++ b/pkg/tcpip/transport/tcp/endpoint_state.go
@@ -58,7 +58,7 @@ func (e *endpoint) beforeSave() {
 		if !e.route.HasSaveRestoreCapability() {
 			if !e.route.HasDisconncetOkCapability() {
 				panic(&tcpip.ErrSaveRejection{
-					Err: fmt.Errorf("endpoint cannot be saved in connected state: local %s:%d, remote %s:%d", e.ID.LocalAddress, e.ID.LocalPort, e.ID.RemoteAddress, e.ID.RemotePort),
+					Err: fmt.Errorf("endpoint cannot be saved in connected state: local %s:%d, remote %s:%d", e.TransportEndpointInfo.ID.LocalAddress, e.TransportEndpointInfo.ID.LocalPort, e.TransportEndpointInfo.ID.RemoteAddress, e.TransportEndpointInfo.ID.RemotePort),
 				})
 			}
 			e.resetConnectionLocked(&tcpip.ErrConnectionAborted{})
@@ -88,7 +88,7 @@ func (e *endpoint) beforeSave() {
 			e.mu.Lock()
 		}
 		if e.workerRunning {
-			panic(fmt.Sprintf("endpoint: %+v still has worker running in closed or error state", e.ID))
+			panic(fmt.Sprintf("endpoint: %+v still has worker running in closed or error state", e.TransportEndpointInfo.ID))
 		}
 	default:
 		panic(fmt.Sprintf("endpoint in unknown state %v", e.EndpointState()))
@@ -180,14 +180,14 @@ func (e *endpoint) Resume(s *stack.Stack) {
 
 		var rs tcpip.TCPReceiveBufferSizeRangeOption
 		if err := e.stack.TransportProtocolOption(ProtocolNumber, &rs); err == nil {
-			if e.rcvBufSize < rs.Min || e.rcvBufSize > rs.Max {
-				panic(fmt.Sprintf("endpoint.rcvBufSize %d is outside the min and max allowed [%d, %d]", e.rcvBufSize, rs.Min, rs.Max))
+			if e.rcvQueueInfo.RcvBufSize < rs.Min || e.rcvQueueInfo.RcvBufSize > rs.Max {
+				panic(fmt.Sprintf("endpoint.rcvQueueInfo.RcvBufSize %d is outside the min and max allowed [%d, %d]", e.rcvQueueInfo.RcvBufSize, rs.Min, rs.Max))
 			}
 		}
 	}
 
 	bind := func() {
-		addr, _, err := e.checkV4MappedLocked(tcpip.FullAddress{Addr: e.BindAddr, Port: e.ID.LocalPort})
+		addr, _, err := e.checkV4MappedLocked(tcpip.FullAddress{Addr: e.BindAddr, Port: e.TransportEndpointInfo.ID.LocalPort})
 		if err != nil {
 			panic("unable to parse BindAddr: " + err.String())
 		}
@@ -213,19 +213,19 @@ func (e *endpoint) Resume(s *stack.Stack) {
 	case epState.connected():
 		bind()
 		if len(e.connectingAddress) == 0 {
-			e.connectingAddress = e.ID.RemoteAddress
+			e.connectingAddress = e.TransportEndpointInfo.ID.RemoteAddress
 			// This endpoint is accepted by netstack but not yet by
 			// the app. If the endpoint is IPv6 but the remote
 			// address is IPv4, we need to connect as IPv6 so that
 			// dual-stack mode can be properly activated.
-			if e.NetProto == header.IPv6ProtocolNumber && len(e.ID.RemoteAddress) != header.IPv6AddressSize {
-				e.connectingAddress = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff" + e.ID.RemoteAddress
+			if e.NetProto == header.IPv6ProtocolNumber && len(e.TransportEndpointInfo.ID.RemoteAddress) != header.IPv6AddressSize {
+				e.connectingAddress = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff" + e.TransportEndpointInfo.ID.RemoteAddress
 			}
 		}
 		// Reset the scoreboard to reinitialize the sack information as
 		// we do not restore SACK information.
 		e.scoreboard.Reset()
-		err := e.connect(tcpip.FullAddress{NIC: e.boundNICID, Addr: e.connectingAddress, Port: e.ID.RemotePort}, false, e.workerRunning)
+		err := e.connect(tcpip.FullAddress{NIC: e.boundNICID, Addr: e.connectingAddress, Port: e.TransportEndpointInfo.ID.RemotePort}, false, e.workerRunning)
 		if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
 			panic("endpoint connecting failed: " + err.String())
 		}
@@ -263,7 +263,7 @@ func (e *endpoint) Resume(s *stack.Stack) {
 			connectedLoading.Wait()
 			listenLoading.Wait()
 			bind()
-			err := e.Connect(tcpip.FullAddress{NIC: e.boundNICID, Addr: e.connectingAddress, Port: e.ID.RemotePort})
+			err := e.Connect(tcpip.FullAddress{NIC: e.boundNICID, Addr: e.connectingAddress, Port: e.TransportEndpointInfo.ID.RemotePort})
 			if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
 				panic("endpoint connecting failed: " + err.String())
 			}
@@ -310,23 +310,3 @@ func (e *endpoint) saveLastOutOfWindowAckTime() unixTime {
 func (e *endpoint) loadLastOutOfWindowAckTime(unix unixTime) {
 	e.lastOutOfWindowAckTime = time.Unix(unix.second, unix.nano)
 }
-
-// saveMeasureTime is invoked by stateify.
-func (r *rcvBufAutoTuneParams) saveMeasureTime() unixTime {
-	return unixTime{r.measureTime.Unix(), r.measureTime.UnixNano()}
-}
-
-// loadMeasureTime is invoked by stateify.
-func (r *rcvBufAutoTuneParams) loadMeasureTime(unix unixTime) {
-	r.measureTime = time.Unix(unix.second, unix.nano)
-}
-
-// saveRttMeasureTime is invoked by stateify.
-func (r *rcvBufAutoTuneParams) saveRttMeasureTime() unixTime {
-	return unixTime{r.rttMeasureTime.Unix(), r.rttMeasureTime.UnixNano()}
-}
-
-// loadRttMeasureTime is invoked by stateify.
-func (r *rcvBufAutoTuneParams) loadRttMeasureTime(unix unixTime) {
-	r.rttMeasureTime = time.Unix(unix.second, unix.nano)
-}
diff --git a/pkg/tcpip/transport/tcp/rack.go b/pkg/tcpip/transport/tcp/rack.go
index 0a0d5f7a1..9e332dcf7 100644
--- a/pkg/tcpip/transport/tcp/rack.go
+++ b/pkg/tcpip/transport/tcp/rack.go
@@ -19,6 +19,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
 const (
@@ -46,54 +47,16 @@ const (
 //
 // +stateify savable
 type rackControl struct {
-	// dsackSeen indicates if the connection has seen a DSACK.
-	dsackSeen bool
-
-	// endSequence is the ending TCP sequence number of the most recent
-	// acknowledged segment.
-	endSequence seqnum.Value
+	stack.TCPRACKState
 
 	// exitedRecovery indicates if the connection is exiting loss recovery.
 	// This flag is set if the sender is leaving the recovery after
 	// receiving an ACK and is reset during updating of reorder window.
 	exitedRecovery bool
 
-	// fack is the highest selectively or cumulatively acknowledged
-	// sequence.
-	fack seqnum.Value
-
 	// minRTT is the estimated minimum RTT of the connection.
 	minRTT time.Duration
 
-	// reorderSeen indicates if reordering has been detected on this
-	// connection.
-	reorderSeen bool
-
-	// reoWnd is the reordering window time used for recording packet
-	// transmission times. It is used to defer the moment at which RACK
-	// marks a packet lost.
-	reoWnd time.Duration
-
-	// reoWndIncr is the multiplier applied to adjust reorder window.
-	reoWndIncr uint8
-
-	// reoWndPersist is the number of loss recoveries before resetting
-	// reorder window.
-	reoWndPersist int8
-
-	// rtt is the RTT of the most recently delivered packet on the
-	// connection (either cumulatively acknowledged or selectively
-	// acknowledged) that was not marked invalid as a possible spurious
-	// retransmission.
-	rtt time.Duration
-
-	// rttSeq is the SND.NXT when rtt is updated.
-	rttSeq seqnum.Value
-
-	// xmitTime is the latest transmission timestamp of the most recent
-	// acknowledged segment.
-	xmitTime time.Time `state:".(unixTime)"`
-
 	// tlpRxtOut indicates whether there is an unacknowledged
 	// TLP retransmission.
 	tlpRxtOut bool
@@ -108,8 +71,8 @@ type rackControl struct {
 
 // init initializes RACK specific fields.
 func (rc *rackControl) init(snd *sender, iss seqnum.Value) {
-	rc.fack = iss
-	rc.reoWndIncr = 1
+	rc.FACK = iss
+	rc.ReoWndIncr = 1
 	rc.snd = snd
 }
 
@@ -117,7 +80,7 @@ func (rc *rackControl) init(snd *sender, iss seqnum.Value) {
 // See: https://tools.ietf.org/html/draft-ietf-tcpm-rack-09#section-6.2
 func (rc *rackControl) update(seg *segment, ackSeg *segment) {
 	rtt := time.Now().Sub(seg.xmitTime)
-	tsOffset := rc.snd.ep.tsOffset
+	tsOffset := rc.snd.ep.TSOffset
 
 	// If the ACK is for a retransmitted packet, do not update if it is a
 	// spurious inference which is determined by below checks:
@@ -138,7 +101,7 @@ func (rc *rackControl) update(seg *segment, ackSeg *segment) {
 		}
 	}
 
-	rc.rtt = rtt
+	rc.RTT = rtt
 
 	// The sender can either track a simple global minimum of all RTT
 	// measurements from the connection, or a windowed min-filtered value
@@ -152,9 +115,9 @@ func (rc *rackControl) update(seg *segment, ackSeg *segment) {
 	// ending sequence number of the packet which has been acknowledged
 	// most recently.
 	endSeq := seg.sequenceNumber.Add(seqnum.Size(seg.data.Size()))
-	if rc.xmitTime.Before(seg.xmitTime) || (seg.xmitTime.Equal(rc.xmitTime) && rc.endSequence.LessThan(endSeq)) {
-		rc.xmitTime = seg.xmitTime
-		rc.endSequence = endSeq
+	if rc.XmitTime.Before(seg.xmitTime) || (seg.xmitTime.Equal(rc.XmitTime) && rc.EndSequence.LessThan(endSeq)) {
+		rc.XmitTime = seg.xmitTime
+		rc.EndSequence = endSeq
 	}
 }
 
@@ -171,18 +134,18 @@ func (rc *rackControl) update(seg *segment, ackSeg *segment) {
 //   is identified.
 func (rc *rackControl) detectReorder(seg *segment) {
 	endSeq := seg.sequenceNumber.Add(seqnum.Size(seg.data.Size()))
-	if rc.fack.LessThan(endSeq) {
-		rc.fack = endSeq
+	if rc.FACK.LessThan(endSeq) {
+		rc.FACK = endSeq
 		return
 	}
 
-	if endSeq.LessThan(rc.fack) && seg.xmitCount == 1 {
-		rc.reorderSeen = true
+	if endSeq.LessThan(rc.FACK) && seg.xmitCount == 1 {
+		rc.Reord = true
 	}
 }
 
 func (rc *rackControl) setDSACKSeen(dsackSeen bool) {
-	rc.dsackSeen = dsackSeen
+	rc.DSACKSeen = dsackSeen
 }
 
 // shouldSchedulePTO dictates whether we should schedule a PTO or not.
@@ -191,7 +154,7 @@ func (s *sender) shouldSchedulePTO() bool {
 	// Schedule PTO only if RACK loss detection is enabled.
 	return s.ep.tcpRecovery&tcpip.TCPRACKLossDetection != 0 &&
 		// The connection supports SACK.
-		s.ep.sackPermitted &&
+		s.ep.SACKPermitted &&
 		// The connection is not in loss recovery.
 		(s.state != tcpip.RTORecovery && s.state != tcpip.SACKRecovery) &&
 		// The connection has no SACKed sequences in the SACK scoreboard.
@@ -203,9 +166,9 @@ func (s *sender) shouldSchedulePTO() bool {
 func (s *sender) schedulePTO() {
 	pto := time.Second
 	s.rtt.Lock()
-	if s.rtt.srttInited && s.rtt.srtt > 0 {
-		pto = s.rtt.srtt * 2
-		if s.outstanding == 1 {
+	if s.rtt.TCPRTTState.SRTTInited && s.rtt.TCPRTTState.SRTT > 0 {
+		pto = s.rtt.TCPRTTState.SRTT * 2
+		if s.Outstanding == 1 {
 			pto += wcDelayedACKTimeout
 		}
 	}
@@ -230,10 +193,10 @@ func (s *sender) probeTimerExpired() tcpip.Error {
 	}
 
 	var dataSent bool
-	if s.writeNext != nil && s.writeNext.xmitCount == 0 && s.outstanding < s.sndCwnd {
-		dataSent = s.maybeSendSegment(s.writeNext, int(s.ep.scoreboard.SMSS()), s.sndUna.Add(s.sndWnd))
+	if s.writeNext != nil && s.writeNext.xmitCount == 0 && s.Outstanding < s.SndCwnd {
+		dataSent = s.maybeSendSegment(s.writeNext, int(s.ep.scoreboard.SMSS()), s.SndUna.Add(s.SndWnd))
 		if dataSent {
-			s.outstanding += s.pCount(s.writeNext, s.maxPayloadSize)
+			s.Outstanding += s.pCount(s.writeNext, s.MaxPayloadSize)
 			s.writeNext = s.writeNext.Next()
 		}
 	}
@@ -255,10 +218,10 @@ func (s *sender) probeTimerExpired() tcpip.Error {
 		}
 
 		if highestSeqXmit != nil {
-			dataSent = s.maybeSendSegment(highestSeqXmit, int(s.ep.scoreboard.SMSS()), s.sndUna.Add(s.sndWnd))
+			dataSent = s.maybeSendSegment(highestSeqXmit, int(s.ep.scoreboard.SMSS()), s.SndUna.Add(s.SndWnd))
 			if dataSent {
 				s.rc.tlpRxtOut = true
-				s.rc.tlpHighRxt = s.sndNxt
+				s.rc.tlpHighRxt = s.SndNxt
 			}
 		}
 	}
@@ -274,7 +237,7 @@ func (s *sender) probeTimerExpired() tcpip.Error {
 // and updates TLP state accordingly.
 // See https://tools.ietf.org/html/draft-ietf-tcpm-rack-08#section-7.6.3.
 func (s *sender) detectTLPRecovery(ack seqnum.Value, rcvdSeg *segment) {
-	if !(s.ep.sackPermitted && s.rc.tlpRxtOut) {
+	if !(s.ep.SACKPermitted && s.rc.tlpRxtOut) {
 		return
 	}
 
@@ -317,13 +280,13 @@ func (s *sender) detectTLPRecovery(ack seqnum.Value, rcvdSeg *segment) {
 //   retransmit quickly, or when the number of DUPACKs exceeds the classic
 //   DUPACKthreshold.
 func (rc *rackControl) updateRACKReorderWindow(ackSeg *segment) {
-	dsackSeen := rc.dsackSeen
+	dsackSeen := rc.DSACKSeen
 	snd := rc.snd
 
 	// React to DSACK once per round trip.
 	// If SND.UNA < RACK.rtt_seq:
 	//   RACK.dsack = false
-	if snd.sndUna.LessThan(rc.rttSeq) {
+	if snd.SndUna.LessThan(rc.RTTSeq) {
 		dsackSeen = false
 	}
 
@@ -333,18 +296,18 @@ func (rc *rackControl) updateRACKReorderWindow(ackSeg *segment) {
 	//   RACK.rtt_seq = SND.NXT
 	//   RACK.reo_wnd_persist = 16
 	if dsackSeen {
-		rc.reoWndIncr++
+		rc.ReoWndIncr++
 		dsackSeen = false
-		rc.rttSeq = snd.sndNxt
-		rc.reoWndPersist = tcpRACKRecoveryThreshold
+		rc.RTTSeq = snd.SndNxt
+		rc.ReoWndPersist = tcpRACKRecoveryThreshold
 	} else if rc.exitedRecovery {
 		// Else if exiting loss recovery:
 		//   RACK.reo_wnd_persist -= 1
 		//   If RACK.reo_wnd_persist <= 0:
 		//      RACK.reo_wnd_incr = 1
-		rc.reoWndPersist--
-		if rc.reoWndPersist <= 0 {
-			rc.reoWndIncr = 1
+		rc.ReoWndPersist--
+		if rc.ReoWndPersist <= 0 {
+			rc.ReoWndIncr = 1
 		}
 		rc.exitedRecovery = false
 	}
@@ -358,14 +321,14 @@ func (rc *rackControl) updateRACKReorderWindow(ackSeg *segment) {
 	//   Else if RACK.pkts_sacked >= RACK.dupthresh:
 	//     RACK.reo_wnd = 0
 	//     return
-	if !rc.reorderSeen {
+	if !rc.Reord {
 		if snd.state == tcpip.RTORecovery || snd.state == tcpip.SACKRecovery {
-			rc.reoWnd = 0
+			rc.ReoWnd = 0
 			return
 		}
 
-		if snd.sackedOut >= nDupAckThreshold {
-			rc.reoWnd = 0
+		if snd.SackedOut >= nDupAckThreshold {
+			rc.ReoWnd = 0
 			return
 		}
 	}
@@ -374,11 +337,11 @@ func (rc *rackControl) updateRACKReorderWindow(ackSeg *segment) {
 	// RACK.reo_wnd = RACK.min_RTT / 4 * RACK.reo_wnd_incr
 	// RACK.reo_wnd = min(RACK.reo_wnd, SRTT)
 	snd.rtt.Lock()
-	srtt := snd.rtt.srtt
+	srtt := snd.rtt.TCPRTTState.SRTT
 	snd.rtt.Unlock()
-	rc.reoWnd = time.Duration((int64(rc.minRTT) / 4) * int64(rc.reoWndIncr))
-	if srtt < rc.reoWnd {
-		rc.reoWnd = srtt
+	rc.ReoWnd = time.Duration((int64(rc.minRTT) / 4) * int64(rc.ReoWndIncr))
+	if srtt < rc.ReoWnd {
+		rc.ReoWnd = srtt
 	}
 }
 
@@ -403,8 +366,8 @@ func (rc *rackControl) detectLoss(rcvTime time.Time) int {
 		}
 
 		endSeq := seg.sequenceNumber.Add(seqnum.Size(seg.data.Size()))
-		if seg.xmitTime.Before(rc.xmitTime) || (seg.xmitTime.Equal(rc.xmitTime) && rc.endSequence.LessThan(endSeq)) {
-			timeRemaining := seg.xmitTime.Sub(rcvTime) + rc.rtt + rc.reoWnd
+		if seg.xmitTime.Before(rc.XmitTime) || (seg.xmitTime.Equal(rc.XmitTime) && rc.EndSequence.LessThan(endSeq)) {
+			timeRemaining := seg.xmitTime.Sub(rcvTime) + rc.RTT + rc.ReoWnd
 			if timeRemaining <= 0 {
 				seg.lost = true
 				numLost++
@@ -435,7 +398,7 @@ func (rc *rackControl) reorderTimerExpired() tcpip.Error {
 	}
 
 	fastRetransmit := false
-	if !rc.snd.fr.active {
+	if !rc.snd.FastRecovery.Active {
 		rc.snd.cc.HandleLossDetected()
 		rc.snd.enterRecovery()
 		fastRetransmit = true
@@ -471,15 +434,15 @@ func (rc *rackControl) DoRecovery(_ *segment, fastRetransmit bool) {
 		}
 
 		// Check the congestion window after entering recovery.
-		if snd.outstanding >= snd.sndCwnd {
+		if snd.Outstanding >= snd.SndCwnd {
 			break
 		}
 
-		if sent := snd.maybeSendSegment(seg, int(snd.ep.scoreboard.SMSS()), snd.sndUna.Add(snd.sndWnd)); !sent {
+		if sent := snd.maybeSendSegment(seg, int(snd.ep.scoreboard.SMSS()), snd.SndUna.Add(snd.SndWnd)); !sent {
 			break
 		}
 		dataSent = true
-		snd.outstanding += snd.pCount(seg, snd.maxPayloadSize)
+		snd.Outstanding += snd.pCount(seg, snd.MaxPayloadSize)
 	}
 
 	snd.postXmit(dataSent, true /* shouldScheduleProbe */)
diff --git a/pkg/tcpip/transport/tcp/rack_state.go b/pkg/tcpip/transport/tcp/rack_state.go
deleted file mode 100644
index c9dc7e773..000000000
--- a/pkg/tcpip/transport/tcp/rack_state.go
+++ /dev/null
@@ -1,29 +0,0 @@
-// Copyright 2020 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package tcp
-
-import (
-	"time"
-)
-
-// saveXmitTime is invoked by stateify.
-func (rc *rackControl) saveXmitTime() unixTime {
-	return unixTime{rc.xmitTime.Unix(), rc.xmitTime.UnixNano()}
-}
-
-// loadXmitTime is invoked by stateify.
-func (rc *rackControl) loadXmitTime(unix unixTime) {
-	rc.xmitTime = time.Unix(unix.second, unix.nano)
-}
diff --git a/pkg/tcpip/transport/tcp/rcv.go b/pkg/tcpip/transport/tcp/rcv.go
index bc6793fc6..fc11b4ba9 100644
--- a/pkg/tcpip/transport/tcp/rcv.go
+++ b/pkg/tcpip/transport/tcp/rcv.go
@@ -22,6 +22,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
 // receiver holds the state necessary to receive TCP segments and turn them
@@ -29,26 +30,15 @@ import (
 //
 // +stateify savable
 type receiver struct {
+	stack.TCPReceiverState
 	ep *endpoint
 
-	rcvNxt seqnum.Value
-
-	// rcvAcc is one beyond the last acceptable sequence number. That is,
-	// the "largest" sequence value that the receiver has announced to the
-	// its peer that it's willing to accept. This may be different than
-	// rcvNxt + rcvWnd if the receive window is reduced; in that case we
-	// have to reduce the window as we receive more data instead of
-	// shrinking it.
-	rcvAcc seqnum.Value
-
 	// rcvWnd is the non-scaled receive window last advertised to the peer.
 	rcvWnd seqnum.Size
 
-	// rcvWUP is the rcvNxt value at the last window update sent.
+	// rcvWUP is the RcvNxt value at the last window update sent.
 	rcvWUP seqnum.Value
 
-	rcvWndScale uint8
-
 	// prevBufused is the snapshot of endpoint rcvBufUsed taken when we
 	// advertise a receive window.
 	prevBufUsed int
@@ -58,9 +48,6 @@ type receiver struct {
 	// pendingRcvdSegments is bounded by the receive buffer size of the
 	// endpoint.
 	pendingRcvdSegments segmentHeap
-	// pendingBufUsed tracks the total number of bytes (including segment
-	// overhead) currently queued in pendingRcvdSegments.
-	pendingBufUsed int
 
 	// Time when the last ack was received.
 	lastRcvdAckTime time.Time `state:".(unixTime)"`
@@ -68,12 +55,14 @@ type receiver struct {
 
 func newReceiver(ep *endpoint, irs seqnum.Value, rcvWnd seqnum.Size, rcvWndScale uint8) *receiver {
 	return &receiver{
-		ep:              ep,
-		rcvNxt:          irs + 1,
-		rcvAcc:          irs.Add(rcvWnd + 1),
+		ep: ep,
+		TCPReceiverState: stack.TCPReceiverState{
+			RcvNxt:      irs + 1,
+			RcvAcc:      irs.Add(rcvWnd + 1),
+			RcvWndScale: rcvWndScale,
+		},
 		rcvWnd:          rcvWnd,
 		rcvWUP:          irs + 1,
-		rcvWndScale:     rcvWndScale,
 		lastRcvdAckTime: time.Now(),
 	}
 }
@@ -84,34 +73,34 @@ func (r *receiver) acceptable(segSeq seqnum.Value, segLen seqnum.Size) bool {
 	// r.rcvWnd could be much larger than the window size we advertised in our
 	// outgoing packets, we should use what we have advertised for acceptability
 	// test.
-	scaledWindowSize := r.rcvWnd >> r.rcvWndScale
+	scaledWindowSize := r.rcvWnd >> r.RcvWndScale
 	if scaledWindowSize > math.MaxUint16 {
 		// This is what we actually put in the Window field.
 		scaledWindowSize = math.MaxUint16
 	}
-	advertisedWindowSize := scaledWindowSize << r.rcvWndScale
-	return header.Acceptable(segSeq, segLen, r.rcvNxt, r.rcvNxt.Add(advertisedWindowSize))
+	advertisedWindowSize := scaledWindowSize << r.RcvWndScale
+	return header.Acceptable(segSeq, segLen, r.RcvNxt, r.RcvNxt.Add(advertisedWindowSize))
 }
 
 // currentWindow returns the available space in the window that was advertised
 // last to our peer.
 func (r *receiver) currentWindow() (curWnd seqnum.Size) {
 	endOfWnd := r.rcvWUP.Add(r.rcvWnd)
-	if endOfWnd.LessThan(r.rcvNxt) {
-		// return 0 if r.rcvNxt is past the end of the previously advertised window.
+	if endOfWnd.LessThan(r.RcvNxt) {
+		// return 0 if r.RcvNxt is past the end of the previously advertised window.
 		// This can happen because we accept a large segment completely even if
 		// accepting it causes it to partially exceed the advertised window.
 		return 0
 	}
-	return r.rcvNxt.Size(endOfWnd)
+	return r.RcvNxt.Size(endOfWnd)
 }
 
 // getSendParams returns the parameters needed by the sender when building
 // segments to send.
-func (r *receiver) getSendParams() (rcvNxt seqnum.Value, rcvWnd seqnum.Size) {
+func (r *receiver) getSendParams() (RcvNxt seqnum.Value, rcvWnd seqnum.Size) {
 	newWnd := r.ep.selectWindow()
 	curWnd := r.currentWindow()
-	unackLen := int(r.ep.snd.maxSentAck.Size(r.rcvNxt))
+	unackLen := int(r.ep.snd.MaxSentAck.Size(r.RcvNxt))
 	bufUsed := r.ep.receiveBufferUsed()
 
 	// Grow the right edge of the window only for payloads larger than the
@@ -139,18 +128,18 @@ func (r *receiver) getSendParams() (rcvNxt seqnum.Value, rcvWnd seqnum.Size) {
 	// edge, as we are still advertising a window that we think can be serviced.
 	toGrow := unackLen >= SegSize || bufUsed <= r.prevBufUsed
 
-	// Update rcvAcc only if new window is > previously advertised window. We
+	// Update RcvAcc only if new window is > previously advertised window. We
 	// should never shrink the acceptable sequence space once it has been
 	// advertised the peer. If we shrink the acceptable sequence space then we
 	// would end up dropping bytes that might already be in flight.
 	// ====================================================  sequence space.
 	// ^             ^               ^                   ^
-	// rcvWUP       rcvNxt         rcvAcc          new rcvAcc
+	// rcvWUP       RcvNxt         RcvAcc          new RcvAcc
 	//               <=====curWnd ===>
 	//               <========= newWnd > curWnd ========= >
-	if r.rcvNxt.Add(seqnum.Size(curWnd)).LessThan(r.rcvNxt.Add(seqnum.Size(newWnd))) && toGrow {
-		// If the new window moves the right edge, then update rcvAcc.
-		r.rcvAcc = r.rcvNxt.Add(seqnum.Size(newWnd))
+	if r.RcvNxt.Add(seqnum.Size(curWnd)).LessThan(r.RcvNxt.Add(seqnum.Size(newWnd))) && toGrow {
+		// If the new window moves the right edge, then update RcvAcc.
+		r.RcvAcc = r.RcvNxt.Add(seqnum.Size(newWnd))
 	} else {
 		if newWnd == 0 {
 			// newWnd is zero but we can't advertise a zero as it would cause window
@@ -162,9 +151,9 @@ func (r *receiver) getSendParams() (rcvNxt seqnum.Value, rcvWnd seqnum.Size) {
 	// Stash away the non-scaled receive window as we use it for measuring
 	// receiver's estimated RTT.
 	r.rcvWnd = newWnd
-	r.rcvWUP = r.rcvNxt
+	r.rcvWUP = r.RcvNxt
 	r.prevBufUsed = bufUsed
-	scaledWnd := r.rcvWnd >> r.rcvWndScale
+	scaledWnd := r.rcvWnd >> r.RcvWndScale
 	if scaledWnd == 0 {
 		// Increment a metric if we are advertising an actual zero window.
 		r.ep.stats.ReceiveErrors.ZeroRcvWindowState.Increment()
@@ -177,9 +166,9 @@ func (r *receiver) getSendParams() (rcvNxt seqnum.Value, rcvWnd seqnum.Size) {
 
 		// Ensure that the stashed receive window always reflects what
 		// is being advertised.
-		r.rcvWnd = scaledWnd << r.rcvWndScale
+		r.rcvWnd = scaledWnd << r.RcvWndScale
 	}
-	return r.rcvNxt, scaledWnd
+	return r.RcvNxt, scaledWnd
 }
 
 // nonZeroWindow is called when the receive window grows from zero to nonzero;
@@ -201,13 +190,13 @@ func (r *receiver) consumeSegment(s *segment, segSeq seqnum.Value, segLen seqnum
 		// If the segment doesn't include the seqnum we're expecting to
 		// consume now, we're missing a segment. We cannot proceed until
 		// we receive that segment though.
-		if !r.rcvNxt.InWindow(segSeq, segLen) {
+		if !r.RcvNxt.InWindow(segSeq, segLen) {
 			return false
 		}
 
 		// Trim segment to eliminate already acknowledged data.
-		if segSeq.LessThan(r.rcvNxt) {
-			diff := segSeq.Size(r.rcvNxt)
+		if segSeq.LessThan(r.RcvNxt) {
+			diff := segSeq.Size(r.RcvNxt)
 			segLen -= diff
 			segSeq.UpdateForward(diff)
 			s.sequenceNumber.UpdateForward(diff)
@@ -217,35 +206,35 @@ func (r *receiver) consumeSegment(s *segment, segSeq seqnum.Value, segLen seqnum
 		// Move segment to ready-to-deliver list. Wakeup any waiters.
 		r.ep.readyToRead(s)
 
-	} else if segSeq != r.rcvNxt {
+	} else if segSeq != r.RcvNxt {
 		return false
 	}
 
 	// Update the segment that we're expecting to consume.
-	r.rcvNxt = segSeq.Add(segLen)
+	r.RcvNxt = segSeq.Add(segLen)
 
 	// In cases of a misbehaving sender which could send more than the
 	// advertised window, we could end up in a situation where we get a
 	// segment that exceeds the window advertised. Instead of partially
 	// accepting the segment and discarding bytes beyond the advertised
-	// window, we accept the whole segment and make sure r.rcvAcc is moved
-	// forward to match r.rcvNxt to indicate that the window is now closed.
+	// window, we accept the whole segment and make sure r.RcvAcc is moved
+	// forward to match r.RcvNxt to indicate that the window is now closed.
 	//
 	// In absence of this check the r.acceptable() check fails and accepts
 	// segments that should be dropped because rcvWnd is calculated as
-	// the size of the interval (rcvNxt, rcvAcc] which becomes extremely
-	// large if rcvAcc is ever less than rcvNxt.
-	if r.rcvAcc.LessThan(r.rcvNxt) {
-		r.rcvAcc = r.rcvNxt
+	// the size of the interval (RcvNxt, RcvAcc] which becomes extremely
+	// large if RcvAcc is ever less than RcvNxt.
+	if r.RcvAcc.LessThan(r.RcvNxt) {
+		r.RcvAcc = r.RcvNxt
 	}
 
 	// Trim SACK Blocks to remove any SACK information that covers
 	// sequence numbers that have been consumed.
-	TrimSACKBlockList(&r.ep.sack, r.rcvNxt)
+	TrimSACKBlockList(&r.ep.sack, r.RcvNxt)
 
 	// Handle FIN or FIN-ACK.
 	if s.flagIsSet(header.TCPFlagFin) {
-		r.rcvNxt++
+		r.RcvNxt++
 
 		// Send ACK immediately.
 		r.ep.snd.sendAck()
@@ -260,7 +249,7 @@ func (r *receiver) consumeSegment(s *segment, segSeq seqnum.Value, segLen seqnum
 		case StateEstablished:
 			r.ep.setEndpointState(StateCloseWait)
 		case StateFinWait1:
-			if s.flagIsSet(header.TCPFlagAck) && s.ackNumber == r.ep.snd.sndNxt {
+			if s.flagIsSet(header.TCPFlagAck) && s.ackNumber == r.ep.snd.SndNxt {
 				// FIN-ACK, transition to TIME-WAIT.
 				r.ep.setEndpointState(StateTimeWait)
 			} else {
@@ -280,7 +269,7 @@ func (r *receiver) consumeSegment(s *segment, segSeq seqnum.Value, segLen seqnum
 		}
 
 		for i := first; i < len(r.pendingRcvdSegments); i++ {
-			r.pendingBufUsed -= r.pendingRcvdSegments[i].segMemSize()
+			r.PendingBufUsed -= r.pendingRcvdSegments[i].segMemSize()
 			r.pendingRcvdSegments[i].decRef()
 
 			// Note that slice truncation does not allow garbage collection of
@@ -295,7 +284,7 @@ func (r *receiver) consumeSegment(s *segment, segSeq seqnum.Value, segLen seqnum
 
 	// Handle ACK (not FIN-ACK, which we handled above) during one of the
 	// shutdown states.
-	if s.flagIsSet(header.TCPFlagAck) && s.ackNumber == r.ep.snd.sndNxt {
+	if s.flagIsSet(header.TCPFlagAck) && s.ackNumber == r.ep.snd.SndNxt {
 		switch r.ep.EndpointState() {
 		case StateFinWait1:
 			r.ep.setEndpointState(StateFinWait2)
@@ -323,40 +312,40 @@ func (r *receiver) updateRTT() {
 	// 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() {
+	r.ep.rcvQueueInfo.rcvQueueMu.Lock()
+	if r.ep.rcvQueueInfo.RcvAutoParams.RTTMeasureTime.IsZero() {
 		// New measurement.
-		r.ep.rcvAutoParams.rttMeasureTime = time.Now()
-		r.ep.rcvAutoParams.rttMeasureSeqNumber = r.rcvNxt.Add(r.rcvWnd)
-		r.ep.rcvListMu.Unlock()
+		r.ep.rcvQueueInfo.RcvAutoParams.RTTMeasureTime = time.Now()
+		r.ep.rcvQueueInfo.RcvAutoParams.RTTMeasureSeqNumber = r.RcvNxt.Add(r.rcvWnd)
+		r.ep.rcvQueueInfo.rcvQueueMu.Unlock()
 		return
 	}
-	if r.rcvNxt.LessThan(r.ep.rcvAutoParams.rttMeasureSeqNumber) {
-		r.ep.rcvListMu.Unlock()
+	if r.RcvNxt.LessThan(r.ep.rcvQueueInfo.RcvAutoParams.RTTMeasureSeqNumber) {
+		r.ep.rcvQueueInfo.rcvQueueMu.Unlock()
 		return
 	}
-	rtt := time.Since(r.ep.rcvAutoParams.rttMeasureTime)
+	rtt := time.Since(r.ep.rcvQueueInfo.RcvAutoParams.RTTMeasureTime)
 	// We only store the minimum observed RTT here as this is only used in
 	// absence of a SRTT available from either timestamps or a sender
 	// measurement of RTT.
-	if r.ep.rcvAutoParams.rtt == 0 || rtt < r.ep.rcvAutoParams.rtt {
-		r.ep.rcvAutoParams.rtt = rtt
+	if r.ep.rcvQueueInfo.RcvAutoParams.RTT == 0 || rtt < r.ep.rcvQueueInfo.RcvAutoParams.RTT {
+		r.ep.rcvQueueInfo.RcvAutoParams.RTT = rtt
 	}
-	r.ep.rcvAutoParams.rttMeasureTime = time.Now()
-	r.ep.rcvAutoParams.rttMeasureSeqNumber = r.rcvNxt.Add(r.rcvWnd)
-	r.ep.rcvListMu.Unlock()
+	r.ep.rcvQueueInfo.RcvAutoParams.RTTMeasureTime = time.Now()
+	r.ep.rcvQueueInfo.RcvAutoParams.RTTMeasureSeqNumber = r.RcvNxt.Add(r.rcvWnd)
+	r.ep.rcvQueueInfo.rcvQueueMu.Unlock()
 }
 
 func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, closed bool) (drop bool, err tcpip.Error) {
-	r.ep.rcvListMu.Lock()
-	rcvClosed := r.ep.rcvClosed || r.closed
-	r.ep.rcvListMu.Unlock()
+	r.ep.rcvQueueInfo.rcvQueueMu.Lock()
+	rcvClosed := r.ep.rcvQueueInfo.RcvClosed || r.closed
+	r.ep.rcvQueueInfo.rcvQueueMu.Unlock()
 
 	// If we are in one of the shutdown states then we need to do
 	// additional checks before we try and process the segment.
 	switch state {
 	case StateCloseWait, StateClosing, StateLastAck:
-		if !s.sequenceNumber.LessThanEq(r.rcvNxt) {
+		if !s.sequenceNumber.LessThanEq(r.RcvNxt) {
 			// Just drop the segment as we have
 			// already received a FIN and this
 			// segment is after the sequence number
@@ -384,17 +373,17 @@ func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, clo
 		// The ESTABLISHED state processing is here where if the ACK check
 		// fails, we ignore the packet:
 		// https://github.com/torvalds/linux/blob/v5.8/net/ipv4/tcp_input.c#L5591
-		if r.ep.snd.sndNxt.LessThan(s.ackNumber) {
+		if r.ep.snd.SndNxt.LessThan(s.ackNumber) {
 			r.ep.snd.maybeSendOutOfWindowAck(s)
 			return true, nil
 		}
 
 		// If we are closed for reads (either due to an
 		// incoming FIN or the user calling shutdown(..,
-		// SHUT_RD) then any data past the rcvNxt should
+		// SHUT_RD) then any data past the RcvNxt should
 		// trigger a RST.
 		endDataSeq := s.sequenceNumber.Add(seqnum.Size(s.data.Size()))
-		if state != StateCloseWait && rcvClosed && r.rcvNxt.LessThan(endDataSeq) {
+		if state != StateCloseWait && rcvClosed && r.RcvNxt.LessThan(endDataSeq) {
 			return true, &tcpip.ErrConnectionAborted{}
 		}
 		if state == StateFinWait1 {
@@ -403,7 +392,7 @@ func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, clo
 
 		// If it's a retransmission of an old data segment
 		// or a pure ACK then allow it.
-		if s.sequenceNumber.Add(s.logicalLen()).LessThanEq(r.rcvNxt) ||
+		if s.sequenceNumber.Add(s.logicalLen()).LessThanEq(r.RcvNxt) ||
 			s.logicalLen() == 0 {
 			break
 		}
@@ -413,7 +402,7 @@ func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, clo
 		// then the only acceptable segment is a
 		// FIN. Since FIN can technically also carry
 		// data we verify that the segment carrying a
-		// FIN ends at exactly e.rcvNxt+1.
+		// FIN ends at exactly e.RcvNxt+1.
 		//
 		// From RFC793 page 25.
 		//
@@ -423,7 +412,7 @@ func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, clo
 		// while the FIN is considered to occur after
 		// the last actual data octet in a segment in
 		// which it occurs.
-		if closed && (!s.flagIsSet(header.TCPFlagFin) || s.sequenceNumber.Add(s.logicalLen()) != r.rcvNxt+1) {
+		if closed && (!s.flagIsSet(header.TCPFlagFin) || s.sequenceNumber.Add(s.logicalLen()) != r.RcvNxt+1) {
 			return true, &tcpip.ErrConnectionAborted{}
 		}
 	}
@@ -435,7 +424,7 @@ func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, clo
 	// end has closed and the peer is yet to send a FIN. Hence we
 	// compare only the payload.
 	segEnd := s.sequenceNumber.Add(seqnum.Size(s.data.Size()))
-	if rcvClosed && !segEnd.LessThanEq(r.rcvNxt) {
+	if rcvClosed && !segEnd.LessThanEq(r.RcvNxt) {
 		return true, nil
 	}
 	return false, nil
@@ -477,13 +466,13 @@ func (r *receiver) handleRcvdSegment(s *segment) (drop bool, err tcpip.Error) {
 			// segments. This ensures that we always leave some space for the inorder
 			// segments to arrive allowing pending segments to be processed and
 			// delivered to the user.
-			if r.ep.receiveBufferAvailable() > 0 && r.pendingBufUsed < r.ep.receiveBufferSize()>>2 {
-				r.ep.rcvListMu.Lock()
-				r.pendingBufUsed += s.segMemSize()
-				r.ep.rcvListMu.Unlock()
+			if r.ep.receiveBufferAvailable() > 0 && r.PendingBufUsed < r.ep.receiveBufferSize()>>2 {
+				r.ep.rcvQueueInfo.rcvQueueMu.Lock()
+				r.PendingBufUsed += s.segMemSize()
+				r.ep.rcvQueueInfo.rcvQueueMu.Unlock()
 				s.incRef()
 				heap.Push(&r.pendingRcvdSegments, s)
-				UpdateSACKBlocks(&r.ep.sack, segSeq, segSeq.Add(segLen), r.rcvNxt)
+				UpdateSACKBlocks(&r.ep.sack, segSeq, segSeq.Add(segLen), r.RcvNxt)
 			}
 
 			// Immediately send an ack so that the peer knows it may
@@ -508,15 +497,15 @@ func (r *receiver) handleRcvdSegment(s *segment) (drop bool, err tcpip.Error) {
 		segSeq := s.sequenceNumber
 
 		// Skip segment altogether if it has already been acknowledged.
-		if !segSeq.Add(segLen-1).LessThan(r.rcvNxt) &&
+		if !segSeq.Add(segLen-1).LessThan(r.RcvNxt) &&
 			!r.consumeSegment(s, segSeq, segLen) {
 			break
 		}
 
 		heap.Pop(&r.pendingRcvdSegments)
-		r.ep.rcvListMu.Lock()
-		r.pendingBufUsed -= s.segMemSize()
-		r.ep.rcvListMu.Unlock()
+		r.ep.rcvQueueInfo.rcvQueueMu.Lock()
+		r.PendingBufUsed -= s.segMemSize()
+		r.ep.rcvQueueInfo.rcvQueueMu.Unlock()
 		s.decRef()
 	}
 	return false, nil
@@ -558,7 +547,7 @@ func (r *receiver) handleTimeWaitSegment(s *segment) (resetTimeWait bool, newSyn
 
 	//    (2) returns to TIME-WAIT state if the SYN turns out
 	//      to be an old duplicate".
-	if s.flagIsSet(header.TCPFlagSyn) && r.rcvNxt.LessThan(segSeq) {
+	if s.flagIsSet(header.TCPFlagSyn) && r.RcvNxt.LessThan(segSeq) {
 
 		return false, true
 	}
@@ -569,11 +558,11 @@ func (r *receiver) handleTimeWaitSegment(s *segment) (resetTimeWait bool, newSyn
 	}
 
 	// Update Timestamp if required. See RFC7323, section-4.3.
-	if r.ep.sendTSOk && s.parsedOptions.TS {
-		r.ep.updateRecentTimestamp(s.parsedOptions.TSVal, r.ep.snd.maxSentAck, segSeq)
+	if r.ep.SendTSOk && s.parsedOptions.TS {
+		r.ep.updateRecentTimestamp(s.parsedOptions.TSVal, r.ep.snd.MaxSentAck, segSeq)
 	}
 
-	if segSeq.Add(1) == r.rcvNxt && s.flagIsSet(header.TCPFlagFin) {
+	if segSeq.Add(1) == r.RcvNxt && s.flagIsSet(header.TCPFlagFin) {
 		// If it's a FIN-ACK then resetTimeWait and send an ACK, as it
 		// indicates our final ACK could have been lost.
 		r.ep.snd.sendAck()
@@ -584,8 +573,8 @@ func (r *receiver) handleTimeWaitSegment(s *segment) (resetTimeWait bool, newSyn
 	// carries data then just send an ACK. This is according to RFC 793,
 	// page 37.
 	//
-	// NOTE: In TIME_WAIT the only acceptable sequence number is rcvNxt.
-	if segSeq != r.rcvNxt || segLen != 0 {
+	// NOTE: In TIME_WAIT the only acceptable sequence number is RcvNxt.
+	if segSeq != r.RcvNxt || segLen != 0 {
 		r.ep.snd.sendAck()
 	}
 	return false, false
diff --git a/pkg/tcpip/transport/tcp/reno.go b/pkg/tcpip/transport/tcp/reno.go
index ff39780a5..063552c7f 100644
--- a/pkg/tcpip/transport/tcp/reno.go
+++ b/pkg/tcpip/transport/tcp/reno.go
@@ -34,14 +34,14 @@ func newRenoCC(s *sender) *renoState {
 func (r *renoState) updateSlowStart(packetsAcked int) int {
 	// Don't let the congestion window cross into the congestion
 	// avoidance range.
-	newcwnd := r.s.sndCwnd + packetsAcked
-	if newcwnd >= r.s.sndSsthresh {
-		newcwnd = r.s.sndSsthresh
-		r.s.sndCAAckCount = 0
+	newcwnd := r.s.SndCwnd + packetsAcked
+	if newcwnd >= r.s.Ssthresh {
+		newcwnd = r.s.Ssthresh
+		r.s.SndCAAckCount = 0
 	}
 
-	packetsAcked -= newcwnd - r.s.sndCwnd
-	r.s.sndCwnd = newcwnd
+	packetsAcked -= newcwnd - r.s.SndCwnd
+	r.s.SndCwnd = newcwnd
 	return packetsAcked
 }
 
@@ -49,19 +49,19 @@ func (r *renoState) updateSlowStart(packetsAcked int) int {
 // avoidance mode as described in RFC5681 section 3.1
 func (r *renoState) updateCongestionAvoidance(packetsAcked int) {
 	// Consume the packets in congestion avoidance mode.
-	r.s.sndCAAckCount += packetsAcked
-	if r.s.sndCAAckCount >= r.s.sndCwnd {
-		r.s.sndCwnd += r.s.sndCAAckCount / r.s.sndCwnd
-		r.s.sndCAAckCount = r.s.sndCAAckCount % r.s.sndCwnd
+	r.s.SndCAAckCount += packetsAcked
+	if r.s.SndCAAckCount >= r.s.SndCwnd {
+		r.s.SndCwnd += r.s.SndCAAckCount / r.s.SndCwnd
+		r.s.SndCAAckCount = r.s.SndCAAckCount % r.s.SndCwnd
 	}
 }
 
 // reduceSlowStartThreshold reduces the slow-start threshold per RFC 5681,
 // page 6, eq. 4. It is called when we detect congestion in the network.
 func (r *renoState) reduceSlowStartThreshold() {
-	r.s.sndSsthresh = r.s.outstanding / 2
-	if r.s.sndSsthresh < 2 {
-		r.s.sndSsthresh = 2
+	r.s.Ssthresh = r.s.Outstanding / 2
+	if r.s.Ssthresh < 2 {
+		r.s.Ssthresh = 2
 	}
 
 }
@@ -70,7 +70,7 @@ func (r *renoState) reduceSlowStartThreshold() {
 // were acknowledged.
 // Update implements congestionControl.Update.
 func (r *renoState) Update(packetsAcked int) {
-	if r.s.sndCwnd < r.s.sndSsthresh {
+	if r.s.SndCwnd < r.s.Ssthresh {
 		packetsAcked = r.updateSlowStart(packetsAcked)
 		if packetsAcked == 0 {
 			return
@@ -94,7 +94,7 @@ func (r *renoState) HandleRTOExpired() {
 	// Reduce the congestion window to 1, i.e., enter slow-start. Per
 	// RFC 5681, page 7, we must use 1 regardless of the value of the
 	// initial congestion window.
-	r.s.sndCwnd = 1
+	r.s.SndCwnd = 1
 }
 
 // PostRecovery implements congestionControl.PostRecovery.
diff --git a/pkg/tcpip/transport/tcp/reno_recovery.go b/pkg/tcpip/transport/tcp/reno_recovery.go
index 2aa708e97..d368a29fc 100644
--- a/pkg/tcpip/transport/tcp/reno_recovery.go
+++ b/pkg/tcpip/transport/tcp/reno_recovery.go
@@ -31,25 +31,25 @@ func (rr *renoRecovery) DoRecovery(rcvdSeg *segment, fastRetransmit bool) {
 	snd := rr.s
 
 	// We are in fast recovery mode. Ignore the ack if it's out of range.
-	if !ack.InRange(snd.sndUna, snd.sndNxt+1) {
+	if !ack.InRange(snd.SndUna, snd.SndNxt+1) {
 		return
 	}
 
 	// Don't count this as a duplicate if it is carrying data or
 	// updating the window.
-	if rcvdSeg.logicalLen() != 0 || snd.sndWnd != rcvdSeg.window {
+	if rcvdSeg.logicalLen() != 0 || snd.SndWnd != rcvdSeg.window {
 		return
 	}
 
 	// Inflate the congestion window if we're getting duplicate acks
 	// for the packet we retransmitted.
-	if !fastRetransmit && ack == snd.fr.first {
+	if !fastRetransmit && ack == snd.FastRecovery.First {
 		// We received a dup, inflate the congestion window by 1 packet
 		// if we're not at the max yet. Only inflate the window if
 		// regular FastRecovery is in use, RFC6675 does not require
 		// inflating cwnd on duplicate ACKs.
-		if snd.sndCwnd < snd.fr.maxCwnd {
-			snd.sndCwnd++
+		if snd.SndCwnd < snd.FastRecovery.MaxCwnd {
+			snd.SndCwnd++
 		}
 		return
 	}
@@ -61,7 +61,7 @@ func (rr *renoRecovery) DoRecovery(rcvdSeg *segment, fastRetransmit bool) {
 	// back onto the wire.
 	//
 	// N.B. The retransmit timer will be reset by the caller.
-	snd.fr.first = ack
-	snd.dupAckCount = 0
+	snd.FastRecovery.First = ack
+	snd.DupAckCount = 0
 	snd.resendSegment()
 }
diff --git a/pkg/tcpip/transport/tcp/sack_recovery.go b/pkg/tcpip/transport/tcp/sack_recovery.go
index 9d406b0bc..cd860b5e8 100644
--- a/pkg/tcpip/transport/tcp/sack_recovery.go
+++ b/pkg/tcpip/transport/tcp/sack_recovery.go
@@ -42,14 +42,14 @@ func (sr *sackRecovery) handleSACKRecovery(limit int, end seqnum.Value) (dataSen
 	}
 
 	nextSegHint := snd.writeList.Front()
-	for snd.outstanding < snd.sndCwnd {
+	for snd.Outstanding < snd.SndCwnd {
 		var nextSeg *segment
 		var rescueRtx bool
 		nextSeg, nextSegHint, rescueRtx = snd.NextSeg(nextSegHint)
 		if nextSeg == nil {
 			return dataSent
 		}
-		if !snd.isAssignedSequenceNumber(nextSeg) || snd.sndNxt.LessThanEq(nextSeg.sequenceNumber) {
+		if !snd.isAssignedSequenceNumber(nextSeg) || snd.SndNxt.LessThanEq(nextSeg.sequenceNumber) {
 			// New data being sent.
 
 			// Step C.3 described below is handled by
@@ -67,7 +67,7 @@ func (sr *sackRecovery) handleSACKRecovery(limit int, end seqnum.Value) (dataSen
 				return dataSent
 			}
 			dataSent = true
-			snd.outstanding++
+			snd.Outstanding++
 			snd.writeNext = nextSeg.Next()
 			continue
 		}
@@ -79,7 +79,7 @@ func (sr *sackRecovery) handleSACKRecovery(limit int, end seqnum.Value) (dataSen
 		// "The estimate of the amount of data outstanding in the network
 		// must be updated by incrementing pipe by the number of octets
 		// transmitted in (C.1)."
-		snd.outstanding++
+		snd.Outstanding++
 		dataSent = true
 		snd.sendSegment(nextSeg)
 
@@ -88,7 +88,7 @@ func (sr *sackRecovery) handleSACKRecovery(limit int, end seqnum.Value) (dataSen
 			// We do the last part of rule (4) of NextSeg here to update
 			// RescueRxt as until this point we don't know if we are going
 			// to use the rescue transmission.
-			snd.fr.rescueRxt = snd.fr.last
+			snd.FastRecovery.RescueRxt = snd.FastRecovery.Last
 		} else {
 			// RFC 6675, Step C.2
 			//
@@ -96,7 +96,7 @@ func (sr *sackRecovery) handleSACKRecovery(limit int, end seqnum.Value) (dataSen
 			// HighData, HighRxt MUST be set to the highest sequence
 			// number of the retransmitted segment unless NextSeg ()
 			// rule (4) was invoked for this retransmission."
-			snd.fr.highRxt = segEnd - 1
+			snd.FastRecovery.HighRxt = segEnd - 1
 		}
 	}
 	return dataSent
@@ -109,12 +109,12 @@ func (sr *sackRecovery) DoRecovery(rcvdSeg *segment, fastRetransmit bool) {
 	}
 
 	// We are in fast recovery mode. Ignore the ack if it's out of range.
-	if ack := rcvdSeg.ackNumber; !ack.InRange(snd.sndUna, snd.sndNxt+1) {
+	if ack := rcvdSeg.ackNumber; !ack.InRange(snd.SndUna, snd.SndNxt+1) {
 		return
 	}
 
 	// RFC 6675 recovery algorithm step C 1-5.
-	end := snd.sndUna.Add(snd.sndWnd)
-	dataSent := sr.handleSACKRecovery(snd.maxPayloadSize, end)
+	end := snd.SndUna.Add(snd.SndWnd)
+	dataSent := sr.handleSACKRecovery(snd.MaxPayloadSize, end)
 	snd.postXmit(dataSent, true /* shouldScheduleProbe */)
 }
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index faca35892..cf2e8dcd8 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -26,6 +26,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
 const (
@@ -85,56 +86,12 @@ type lossRecovery interface {
 //
 // +stateify savable
 type sender struct {
+	stack.TCPSenderState
 	ep *endpoint
 
-	// lastSendTime is the timestamp when the last packet was sent.
-	lastSendTime time.Time `state:".(unixTime)"`
-
-	// dupAckCount is the number of duplicated acks received. It is used for
-	// fast retransmit.
-	dupAckCount int
-
-	// fr holds state related to fast recovery.
-	fr fastRecovery
-
 	// lr is the loss recovery algorithm used by the sender.
 	lr lossRecovery
 
-	// sndCwnd is the congestion window, in packets.
-	sndCwnd int
-
-	// sndSsthresh is the threshold between slow start and congestion
-	// avoidance.
-	sndSsthresh int
-
-	// sndCAAckCount is the number of packets acknowledged during congestion
-	// avoidance. When enough packets have been ack'd (typically cwnd
-	// packets), the congestion window is incremented by one.
-	sndCAAckCount int
-
-	// outstanding is the number of outstanding packets, that is, packets
-	// that have been sent but not yet acknowledged.
-	outstanding int
-
-	// sackedOut is the number of packets which are selectively acked.
-	sackedOut int
-
-	// sndWnd is the send window size.
-	sndWnd seqnum.Size
-
-	// sndUna is the next unacknowledged sequence number.
-	sndUna seqnum.Value
-
-	// sndNxt is the sequence number of the next segment to be sent.
-	sndNxt seqnum.Value
-
-	// rttMeasureSeqNum is the sequence number being used for the latest RTT
-	// measurement.
-	rttMeasureSeqNum seqnum.Value
-
-	// rttMeasureTime is the time when the rttMeasureSeqNum was sent.
-	rttMeasureTime time.Time `state:".(unixTime)"`
-
 	// firstRetransmittedSegXmitTime is the original transmit time of
 	// the first segment that was retransmitted due to RTO expiration.
 	firstRetransmittedSegXmitTime time.Time `state:".(unixTime)"`
@@ -147,17 +104,15 @@ type sender struct {
 	// window probes.
 	unackZeroWindowProbes uint32 `state:"nosave"`
 
-	closed      bool
 	writeNext   *segment
 	writeList   segmentList
 	resendTimer timer       `state:"nosave"`
 	resendWaker sleep.Waker `state:"nosave"`
 
-	// rtt.srtt, rtt.rttvar, and rto are the "smoothed round-trip time",
-	// "round-trip time variation" and "retransmit timeout", as defined in
+	// rtt.TCPRTTState.SRTT and rtt.TCPRTTState.RTTVar are the "smoothed
+	// round-trip time", and "round-trip time variation", as defined in
 	// section 2 of RFC 6298.
 	rtt rtt
-	rto time.Duration
 
 	// minRTO is the minimum permitted value for sender.rto.
 	minRTO time.Duration
@@ -168,20 +123,9 @@ type sender struct {
 	// maxRetries is the maximum permitted retransmissions.
 	maxRetries uint32
 
-	// maxPayloadSize is the maximum size of the payload of a given segment.
-	// It is initialized on demand.
-	maxPayloadSize int
-
 	// gso is set if generic segmentation offload is enabled.
 	gso bool
 
-	// sndWndScale is the number of bits to shift left when reading the send
-	// window size from a segment.
-	sndWndScale uint8
-
-	// maxSentAck is the maxium acknowledgement actually sent.
-	maxSentAck seqnum.Value
-
 	// state is the current state of congestion control for this endpoint.
 	state tcpip.CongestionControlState
 
@@ -209,41 +153,7 @@ type sender struct {
 type rtt struct {
 	sync.Mutex `state:"nosave"`
 
-	srtt       time.Duration
-	rttvar     time.Duration
-	srttInited bool
-}
-
-// fastRecovery holds information related to fast recovery from a packet loss.
-//
-// +stateify savable
-type fastRecovery struct {
-	// active whether the endpoint is in fast recovery. The following fields
-	// are only meaningful when active is true.
-	active bool
-
-	// first and last represent the inclusive sequence number range being
-	// recovered.
-	first seqnum.Value
-	last  seqnum.Value
-
-	// maxCwnd is the maximum value the congestion window may be inflated to
-	// due to duplicate acks. This exists to avoid attacks where the
-	// receiver intentionally sends duplicate acks to artificially inflate
-	// the sender's cwnd.
-	maxCwnd int
-
-	// highRxt is the highest sequence number which has been retransmitted
-	// during the current loss recovery phase.
-	// See: RFC 6675 Section 2 for details.
-	highRxt seqnum.Value
-
-	// rescueRxt is the highest sequence number which has been
-	// optimistically retransmitted to prevent stalling of the ACK clock
-	// when there is loss at the end of the window and no new data is
-	// available for transmission.
-	// See: RFC 6675 Section 2 for details.
-	rescueRxt seqnum.Value
+	stack.TCPRTTState
 }
 
 func newSender(ep *endpoint, iss, irs seqnum.Value, sndWnd seqnum.Size, mss uint16, sndWndScale int) *sender {
@@ -253,20 +163,22 @@ func newSender(ep *endpoint, iss, irs seqnum.Value, sndWnd seqnum.Size, mss uint
 	maxPayloadSize := int(mss) - ep.maxOptionSize()
 
 	s := &sender{
-		ep:               ep,
-		sndWnd:           sndWnd,
-		sndUna:           iss + 1,
-		sndNxt:           iss + 1,
-		rto:              1 * time.Second,
-		rttMeasureSeqNum: iss + 1,
-		lastSendTime:     time.Now(),
-		maxPayloadSize:   maxPayloadSize,
-		maxSentAck:       irs + 1,
-		fr: fastRecovery{
-			// See: https://tools.ietf.org/html/rfc6582#section-3.2 Step 1.
-			last:      iss,
-			highRxt:   iss,
-			rescueRxt: iss,
+		ep: ep,
+		TCPSenderState: stack.TCPSenderState{
+			SndWnd:           sndWnd,
+			SndUna:           iss + 1,
+			SndNxt:           iss + 1,
+			RTTMeasureSeqNum: iss + 1,
+			LastSendTime:     time.Now(),
+			MaxPayloadSize:   maxPayloadSize,
+			MaxSentAck:       irs + 1,
+			FastRecovery: stack.TCPFastRecoveryState{
+				// See: https://tools.ietf.org/html/rfc6582#section-3.2 Step 1.
+				Last:      iss,
+				HighRxt:   iss,
+				RescueRxt: iss,
+			},
+			RTO: 1 * time.Second,
 		},
 		gso: ep.gso != nil,
 	}
@@ -282,7 +194,7 @@ func newSender(ep *endpoint, iss, irs seqnum.Value, sndWnd seqnum.Size, mss uint
 	// A negative sndWndScale means that no scaling is in use, otherwise we
 	// store the scaling value.
 	if sndWndScale > 0 {
-		s.sndWndScale = uint8(sndWndScale)
+		s.SndWndScale = uint8(sndWndScale)
 	}
 
 	s.resendTimer.init(&s.resendWaker)
@@ -294,7 +206,7 @@ func newSender(ep *endpoint, iss, irs seqnum.Value, sndWnd seqnum.Size, mss uint
 	// Initialize SACK Scoreboard after updating max payload size as we use
 	// the maxPayloadSize as the smss when determining if a segment is lost
 	// etc.
-	s.ep.scoreboard = NewSACKScoreboard(uint16(s.maxPayloadSize), iss)
+	s.ep.scoreboard = NewSACKScoreboard(uint16(s.MaxPayloadSize), iss)
 
 	// Get Stack wide config.
 	var minRTO tcpip.TCPMinRTOOption
@@ -322,10 +234,10 @@ func newSender(ep *endpoint, iss, irs seqnum.Value, sndWnd seqnum.Size, mss uint
 // returns a handle to it. It also initializes the sndCwnd and sndSsThresh to
 // their initial values.
 func (s *sender) initCongestionControl(congestionControlName tcpip.CongestionControlOption) congestionControl {
-	s.sndCwnd = InitialCwnd
+	s.SndCwnd = InitialCwnd
 	// Set sndSsthresh to the maximum int value, which depends on the
 	// platform.
-	s.sndSsthresh = int(^uint(0) >> 1)
+	s.Ssthresh = int(^uint(0) >> 1)
 
 	switch congestionControlName {
 	case ccCubic:
@@ -339,7 +251,7 @@ func (s *sender) initCongestionControl(congestionControlName tcpip.CongestionCon
 
 // initLossRecovery initiates the loss recovery algorithm for the sender.
 func (s *sender) initLossRecovery() lossRecovery {
-	if s.ep.sackPermitted {
+	if s.ep.SACKPermitted {
 		return newSACKRecovery(s)
 	}
 	return newRenoRecovery(s)
@@ -355,7 +267,7 @@ func (s *sender) updateMaxPayloadSize(mtu, count int) {
 	m -= s.ep.maxOptionSize()
 
 	// We don't adjust up for now.
-	if m >= s.maxPayloadSize {
+	if m >= s.MaxPayloadSize {
 		return
 	}
 
@@ -364,8 +276,8 @@ func (s *sender) updateMaxPayloadSize(mtu, count int) {
 		m = 1
 	}
 
-	oldMSS := s.maxPayloadSize
-	s.maxPayloadSize = m
+	oldMSS := s.MaxPayloadSize
+	s.MaxPayloadSize = m
 	if s.gso {
 		s.ep.gso.MSS = uint16(m)
 	}
@@ -380,9 +292,9 @@ func (s *sender) updateMaxPayloadSize(mtu, count int) {
 	// maxPayloadSize.
 	s.ep.scoreboard.smss = uint16(m)
 
-	s.outstanding -= count
-	if s.outstanding < 0 {
-		s.outstanding = 0
+	s.Outstanding -= count
+	if s.Outstanding < 0 {
+		s.Outstanding = 0
 	}
 
 	// Rewind writeNext to the first segment exceeding the MTU. Do nothing
@@ -401,10 +313,10 @@ func (s *sender) updateMaxPayloadSize(mtu, count int) {
 			nextSeg = seg
 		}
 
-		if s.ep.sackPermitted && s.ep.scoreboard.IsSACKED(seg.sackBlock()) {
+		if s.ep.SACKPermitted && s.ep.scoreboard.IsSACKED(seg.sackBlock()) {
 			// Update sackedOut for new maximum payload size.
-			s.sackedOut -= s.pCount(seg, oldMSS)
-			s.sackedOut += s.pCount(seg, s.maxPayloadSize)
+			s.SackedOut -= s.pCount(seg, oldMSS)
+			s.SackedOut += s.pCount(seg, s.MaxPayloadSize)
 		}
 	}
 
@@ -416,32 +328,32 @@ func (s *sender) updateMaxPayloadSize(mtu, count int) {
 
 // sendAck sends an ACK segment.
 func (s *sender) sendAck() {
-	s.sendSegmentFromView(buffer.VectorisedView{}, header.TCPFlagAck, s.sndNxt)
+	s.sendSegmentFromView(buffer.VectorisedView{}, header.TCPFlagAck, s.SndNxt)
 }
 
 // updateRTO updates the retransmit timeout when a new roud-trip time is
 // available. This is done in accordance with section 2 of RFC 6298.
 func (s *sender) updateRTO(rtt time.Duration) {
 	s.rtt.Lock()
-	if !s.rtt.srttInited {
-		s.rtt.rttvar = rtt / 2
-		s.rtt.srtt = rtt
-		s.rtt.srttInited = true
+	if !s.rtt.TCPRTTState.SRTTInited {
+		s.rtt.TCPRTTState.RTTVar = rtt / 2
+		s.rtt.TCPRTTState.SRTT = rtt
+		s.rtt.TCPRTTState.SRTTInited = true
 	} else {
-		diff := s.rtt.srtt - rtt
+		diff := s.rtt.TCPRTTState.SRTT - rtt
 		if diff < 0 {
 			diff = -diff
 		}
-		// Use RFC6298 standard algorithm to update rttvar and srtt when
+		// Use RFC6298 standard algorithm to update TCPRTTState.RTTVar and TCPRTTState.SRTT when
 		// no timestamps are available.
-		if !s.ep.sendTSOk {
-			s.rtt.rttvar = (3*s.rtt.rttvar + diff) / 4
-			s.rtt.srtt = (7*s.rtt.srtt + rtt) / 8
+		if !s.ep.SendTSOk {
+			s.rtt.TCPRTTState.RTTVar = (3*s.rtt.TCPRTTState.RTTVar + diff) / 4
+			s.rtt.TCPRTTState.SRTT = (7*s.rtt.TCPRTTState.SRTT + rtt) / 8
 		} else {
 			// When we are taking RTT measurements of every ACK then
 			// we need to use a modified method as specified in
 			// https://tools.ietf.org/html/rfc7323#appendix-G
-			if s.outstanding == 0 {
+			if s.Outstanding == 0 {
 				s.rtt.Unlock()
 				return
 			}
@@ -449,7 +361,7 @@ func (s *sender) updateRTO(rtt time.Duration) {
 			// terms of packets and not bytes. This is similar to
 			// how linux also does cwnd and inflight. In practice
 			// this approximation works as expected.
-			expectedSamples := math.Ceil(float64(s.outstanding) / 2)
+			expectedSamples := math.Ceil(float64(s.Outstanding) / 2)
 
 			// alpha & beta values are the original values as recommended in
 			// https://tools.ietf.org/html/rfc6298#section-2.3.
@@ -458,17 +370,17 @@ func (s *sender) updateRTO(rtt time.Duration) {
 
 			alphaPrime := alpha / expectedSamples
 			betaPrime := beta / expectedSamples
-			rttVar := (1-betaPrime)*s.rtt.rttvar.Seconds() + betaPrime*diff.Seconds()
-			srtt := (1-alphaPrime)*s.rtt.srtt.Seconds() + alphaPrime*rtt.Seconds()
-			s.rtt.rttvar = time.Duration(rttVar * float64(time.Second))
-			s.rtt.srtt = time.Duration(srtt * float64(time.Second))
+			rttVar := (1-betaPrime)*s.rtt.TCPRTTState.RTTVar.Seconds() + betaPrime*diff.Seconds()
+			srtt := (1-alphaPrime)*s.rtt.TCPRTTState.SRTT.Seconds() + alphaPrime*rtt.Seconds()
+			s.rtt.TCPRTTState.RTTVar = time.Duration(rttVar * float64(time.Second))
+			s.rtt.TCPRTTState.SRTT = time.Duration(srtt * float64(time.Second))
 		}
 	}
 
-	s.rto = s.rtt.srtt + 4*s.rtt.rttvar
+	s.RTO = s.rtt.TCPRTTState.SRTT + 4*s.rtt.TCPRTTState.RTTVar
 	s.rtt.Unlock()
-	if s.rto < s.minRTO {
-		s.rto = s.minRTO
+	if s.RTO < s.minRTO {
+		s.RTO = s.minRTO
 	}
 }
 
@@ -476,20 +388,20 @@ func (s *sender) updateRTO(rtt time.Duration) {
 func (s *sender) resendSegment() {
 	// Don't use any segments we already sent to measure RTT as they may
 	// have been affected by packets being lost.
-	s.rttMeasureSeqNum = s.sndNxt
+	s.RTTMeasureSeqNum = s.SndNxt
 
 	// Resend the segment.
 	if seg := s.writeList.Front(); seg != nil {
-		if seg.data.Size() > s.maxPayloadSize {
-			s.splitSeg(seg, s.maxPayloadSize)
+		if seg.data.Size() > s.MaxPayloadSize {
+			s.splitSeg(seg, s.MaxPayloadSize)
 		}
 
 		// See: RFC 6675 section 5 Step 4.3
 		//
 		// To prevent retransmission, set both the HighRXT and RescueRXT
 		// to the highest sequence number in the retransmitted segment.
-		s.fr.highRxt = seg.sequenceNumber.Add(seqnum.Size(seg.data.Size())) - 1
-		s.fr.rescueRxt = seg.sequenceNumber.Add(seqnum.Size(seg.data.Size())) - 1
+		s.FastRecovery.HighRxt = seg.sequenceNumber.Add(seqnum.Size(seg.data.Size())) - 1
+		s.FastRecovery.RescueRxt = seg.sequenceNumber.Add(seqnum.Size(seg.data.Size())) - 1
 		s.sendSegment(seg)
 		s.ep.stack.Stats().TCP.FastRetransmit.Increment()
 		s.ep.stats.SendErrors.FastRetransmit.Increment()
@@ -554,15 +466,15 @@ func (s *sender) retransmitTimerExpired() bool {
 
 	// Set new timeout. The timer will be restarted by the call to sendData
 	// below.
-	s.rto *= 2
+	s.RTO *= 2
 	// Cap the RTO as per RFC 1122 4.2.3.1, RFC 6298 5.5
-	if s.rto > s.maxRTO {
-		s.rto = s.maxRTO
+	if s.RTO > s.maxRTO {
+		s.RTO = s.maxRTO
 	}
 
 	// Cap RTO to remaining time.
-	if s.rto > remaining {
-		s.rto = remaining
+	if s.RTO > remaining {
+		s.RTO = remaining
 	}
 
 	// See: https://tools.ietf.org/html/rfc6582#section-3.2 Step 4.
@@ -571,9 +483,9 @@ func (s *sender) retransmitTimerExpired() bool {
 	//     After a retransmit timeout, record the highest sequence number
 	//     transmitted in the variable recover, and exit the fast recovery
 	//     procedure if applicable.
-	s.fr.last = s.sndNxt - 1
+	s.FastRecovery.Last = s.SndNxt - 1
 
-	if s.fr.active {
+	if s.FastRecovery.Active {
 		// We were attempting fast recovery but were not successful.
 		// Leave the state. We don't need to update ssthresh because it
 		// has already been updated when entered fast-recovery.
@@ -589,7 +501,7 @@ func (s *sender) retransmitTimerExpired() bool {
 	//
 	// We'll keep on transmitting (or retransmitting) as we get acks for
 	// the data we transmit.
-	s.outstanding = 0
+	s.Outstanding = 0
 
 	// Expunge all SACK information as per https://tools.ietf.org/html/rfc6675#section-5.1
 	//
@@ -663,7 +575,7 @@ func (s *sender) splitSeg(seg *segment, size int) {
 	// window space.
 	// ref: net/ipv4/tcp_output.c::tcp_write_xmit(), tcp_mss_split_point()
 	// ref: net/ipv4/tcp_output.c::tcp_write_wakeup(), tcp_snd_wnd_test()
-	if seg.data.Size() > s.maxPayloadSize {
+	if seg.data.Size() > s.MaxPayloadSize {
 		seg.flags ^= header.TCPFlagPsh
 	}
 
@@ -689,7 +601,7 @@ func (s *sender) NextSeg(nextSegHint *segment) (nextSeg, hint *segment, rescueRt
 		// transmitted (i.e. either it has no assigned sequence number
 		// or if it does have one, it's >= the next sequence number
 		// to be sent [i.e. >= s.sndNxt]).
-		if !s.isAssignedSequenceNumber(seg) || s.sndNxt.LessThanEq(seg.sequenceNumber) {
+		if !s.isAssignedSequenceNumber(seg) || s.SndNxt.LessThanEq(seg.sequenceNumber) {
 			hint = nil
 			break
 		}
@@ -710,7 +622,7 @@ func (s *sender) NextSeg(nextSegHint *segment) (nextSeg, hint *segment, rescueRt
 			//    (1.a) S2 is greater than HighRxt
 			//    (1.b) S2 is less than highest octect covered by
 			//    any received SACK.
-			if s.fr.highRxt.LessThan(segSeq) && segSeq.LessThan(s.ep.scoreboard.maxSACKED) {
+			if s.FastRecovery.HighRxt.LessThan(segSeq) && segSeq.LessThan(s.ep.scoreboard.maxSACKED) {
 				// NextSeg():
 				//     (1.c) IsLost(S2) returns true.
 				if s.ep.scoreboard.IsLost(segSeq) {
@@ -743,7 +655,7 @@ func (s *sender) NextSeg(nextSegHint *segment) (nextSeg, hint *segment, rescueRt
 			//     unSACKed sequence number SHOULD be returned, and
 			//     RescueRxt set to RecoveryPoint. HighRxt MUST NOT
 			//     be updated.
-			if s.fr.rescueRxt.LessThan(s.sndUna - 1) {
+			if s.FastRecovery.RescueRxt.LessThan(s.SndUna - 1) {
 				if s4 != nil {
 					if s4.sequenceNumber.LessThan(segSeq) {
 						s4 = seg
@@ -763,7 +675,7 @@ func (s *sender) NextSeg(nextSegHint *segment) (nextSeg, hint *segment, rescueRt
 	// previously unsent data starting with sequence number
 	// HighData+1 MUST be returned."
 	for seg := s.writeNext; seg != nil; seg = seg.Next() {
-		if s.isAssignedSequenceNumber(seg) && seg.sequenceNumber.LessThan(s.sndNxt) {
+		if s.isAssignedSequenceNumber(seg) && seg.sequenceNumber.LessThan(s.SndNxt) {
 			continue
 		}
 		// We do not split the segment here to <= smss as it has
@@ -788,7 +700,7 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se
 	if !s.isAssignedSequenceNumber(seg) {
 		// Merge segments if allowed.
 		if seg.data.Size() != 0 {
-			available := int(s.sndNxt.Size(end))
+			available := int(s.SndNxt.Size(end))
 			if available > limit {
 				available = limit
 			}
@@ -816,7 +728,7 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se
 			}
 			if !nextTooBig && seg.data.Size() < available {
 				// Segment is not full.
-				if s.outstanding > 0 && s.ep.ops.GetDelayOption() {
+				if s.Outstanding > 0 && s.ep.ops.GetDelayOption() {
 					// Nagle's algorithm. From Wikipedia:
 					//   Nagle's algorithm works by
 					//   combining a number of small
@@ -835,7 +747,7 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se
 				// send space and MSS.
 				// TODO(gvisor.dev/issue/2833): Drain the held segments after a
 				// timeout.
-				if seg.data.Size() < s.maxPayloadSize && s.ep.ops.GetCorkOption() {
+				if seg.data.Size() < s.MaxPayloadSize && s.ep.ops.GetCorkOption() {
 					return false
 				}
 			}
@@ -843,7 +755,7 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se
 
 		// Assign flags. We don't do it above so that we can merge
 		// additional data if Nagle holds the segment.
-		seg.sequenceNumber = s.sndNxt
+		seg.sequenceNumber = s.SndNxt
 		seg.flags = header.TCPFlagAck | header.TCPFlagPsh
 	}
 
@@ -893,12 +805,12 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se
 		// the segment right here if there are no pending segments. If
 		// there are pending segments, segment transmits are deferred to
 		// the retransmit timer handler.
-		if s.sndUna != s.sndNxt {
+		if s.SndUna != s.SndNxt {
 			switch {
 			case available >= seg.data.Size():
 				// OK to send, the whole segments fits in the
 				// receiver's advertised window.
-			case available >= s.maxPayloadSize:
+			case available >= s.MaxPayloadSize:
 				// OK to send, at least 1 MSS sized segment fits
 				// in the receiver's advertised window.
 			default:
@@ -918,8 +830,8 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se
 		// If GSO is not in use then cap available to
 		// maxPayloadSize. When GSO is in use the gVisor GSO logic or
 		// the host GSO logic will cap the segment to the correct size.
-		if s.ep.gso == nil && available > s.maxPayloadSize {
-			available = s.maxPayloadSize
+		if s.ep.gso == nil && available > s.MaxPayloadSize {
+			available = s.MaxPayloadSize
 		}
 
 		if seg.data.Size() > available {
@@ -933,8 +845,8 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se
 
 	// Update sndNxt if we actually sent new data (as opposed to
 	// retransmitting some previously sent data).
-	if s.sndNxt.LessThan(segEnd) {
-		s.sndNxt = segEnd
+	if s.SndNxt.LessThan(segEnd) {
+		s.SndNxt = segEnd
 	}
 
 	return true
@@ -945,9 +857,9 @@ func (s *sender) sendZeroWindowProbe() {
 	s.unackZeroWindowProbes++
 	// Send a zero window probe with sequence number pointing to
 	// the last acknowledged byte.
-	s.ep.sendRaw(buffer.VectorisedView{}, header.TCPFlagAck, s.sndUna-1, ack, win)
+	s.ep.sendRaw(buffer.VectorisedView{}, header.TCPFlagAck, s.SndUna-1, ack, win)
 	// Rearm the timer to continue probing.
-	s.resendTimer.enable(s.rto)
+	s.resendTimer.enable(s.RTO)
 }
 
 func (s *sender) enableZeroWindowProbing() {
@@ -958,7 +870,7 @@ func (s *sender) enableZeroWindowProbing() {
 	if s.firstRetransmittedSegXmitTime.IsZero() {
 		s.firstRetransmittedSegXmitTime = time.Now()
 	}
-	s.resendTimer.enable(s.rto)
+	s.resendTimer.enable(s.RTO)
 }
 
 func (s *sender) disableZeroWindowProbing() {
@@ -978,12 +890,12 @@ func (s *sender) postXmit(dataSent bool, shouldScheduleProbe bool) {
 	// If the sender has advertized zero receive window and we have
 	// data to be sent out, start zero window probing to query the
 	// the remote for it's receive window size.
-	if s.writeNext != nil && s.sndWnd == 0 {
+	if s.writeNext != nil && s.SndWnd == 0 {
 		s.enableZeroWindowProbing()
 	}
 
 	// If we have no more pending data, start the keepalive timer.
-	if s.sndUna == s.sndNxt {
+	if s.SndUna == s.SndNxt {
 		s.ep.resetKeepaliveTimer(false)
 	} else {
 		// Enable timers if we have pending data.
@@ -992,10 +904,10 @@ func (s *sender) postXmit(dataSent bool, shouldScheduleProbe bool) {
 			s.schedulePTO()
 		} else if !s.resendTimer.enabled() {
 			s.probeTimer.disable()
-			if s.outstanding > 0 {
+			if s.Outstanding > 0 {
 				// Enable the resend timer if it's not enabled yet and there is
 				// outstanding data.
-				s.resendTimer.enable(s.rto)
+				s.resendTimer.enable(s.RTO)
 			}
 		}
 	}
@@ -1004,29 +916,29 @@ func (s *sender) postXmit(dataSent bool, shouldScheduleProbe bool) {
 // sendData sends new data segments. It is called when data becomes available or
 // when the send window opens up.
 func (s *sender) sendData() {
-	limit := s.maxPayloadSize
+	limit := s.MaxPayloadSize
 	if s.gso {
 		limit = int(s.ep.gso.MaxSize - header.TCPHeaderMaximumSize)
 	}
-	end := s.sndUna.Add(s.sndWnd)
+	end := s.SndUna.Add(s.SndWnd)
 
 	// Reduce the congestion window to min(IW, cwnd) per RFC 5681, page 10.
 	// "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 != tcpip.RTORecovery && time.Now().Sub(s.lastSendTime) > s.rto {
-		if s.sndCwnd > InitialCwnd {
-			s.sndCwnd = InitialCwnd
+	if !s.FastRecovery.Active && s.state != tcpip.RTORecovery && time.Now().Sub(s.LastSendTime) > s.RTO {
+		if s.SndCwnd > InitialCwnd {
+			s.SndCwnd = InitialCwnd
 		}
 	}
 
 	var dataSent bool
-	for seg := s.writeNext; seg != nil && s.outstanding < s.sndCwnd; seg = seg.Next() {
-		cwndLimit := (s.sndCwnd - s.outstanding) * s.maxPayloadSize
+	for seg := s.writeNext; seg != nil && s.Outstanding < s.SndCwnd; seg = seg.Next() {
+		cwndLimit := (s.SndCwnd - s.Outstanding) * s.MaxPayloadSize
 		if cwndLimit < limit {
 			limit = cwndLimit
 		}
-		if s.isAssignedSequenceNumber(seg) && s.ep.sackPermitted && s.ep.scoreboard.IsSACKED(seg.sackBlock()) {
+		if s.isAssignedSequenceNumber(seg) && s.ep.SACKPermitted && s.ep.scoreboard.IsSACKED(seg.sackBlock()) {
 			// Move writeNext along so that we don't try and scan data that
 			// has already been SACKED.
 			s.writeNext = seg.Next()
@@ -1036,7 +948,7 @@ func (s *sender) sendData() {
 			break
 		}
 		dataSent = true
-		s.outstanding += s.pCount(seg, s.maxPayloadSize)
+		s.Outstanding += s.pCount(seg, s.MaxPayloadSize)
 		s.writeNext = seg.Next()
 	}
 
@@ -1044,21 +956,21 @@ func (s *sender) sendData() {
 }
 
 func (s *sender) enterRecovery() {
-	s.fr.active = true
+	s.FastRecovery.Active = true
 	// Save state to reflect we're now in fast recovery.
 	//
 	// See : https://tools.ietf.org/html/rfc5681#section-3.2 Step 3.
 	// We inflate the cwnd by 3 to account for the 3 packets which triggered
 	// the 3 duplicate ACKs and are now not in flight.
-	s.sndCwnd = s.sndSsthresh + 3
-	s.sackedOut = 0
-	s.dupAckCount = 0
-	s.fr.first = s.sndUna
-	s.fr.last = s.sndNxt - 1
-	s.fr.maxCwnd = s.sndCwnd + s.outstanding
-	s.fr.highRxt = s.sndUna
-	s.fr.rescueRxt = s.sndUna
-	if s.ep.sackPermitted {
+	s.SndCwnd = s.Ssthresh + 3
+	s.SackedOut = 0
+	s.DupAckCount = 0
+	s.FastRecovery.First = s.SndUna
+	s.FastRecovery.Last = s.SndNxt - 1
+	s.FastRecovery.MaxCwnd = s.SndCwnd + s.Outstanding
+	s.FastRecovery.HighRxt = s.SndUna
+	s.FastRecovery.RescueRxt = s.SndUna
+	if s.ep.SACKPermitted {
 		s.state = tcpip.SACKRecovery
 		s.ep.stack.Stats().TCP.SACKRecovery.Increment()
 		// Set TLPRxtOut to false according to
@@ -1075,12 +987,12 @@ func (s *sender) enterRecovery() {
 }
 
 func (s *sender) leaveRecovery() {
-	s.fr.active = false
-	s.fr.maxCwnd = 0
-	s.dupAckCount = 0
+	s.FastRecovery.Active = false
+	s.FastRecovery.MaxCwnd = 0
+	s.DupAckCount = 0
 
 	// Deflate cwnd. It had been artificially inflated when new dups arrived.
-	s.sndCwnd = s.sndSsthresh
+	s.SndCwnd = s.Ssthresh
 	s.cc.PostRecovery()
 }
 
@@ -1099,7 +1011,7 @@ func (s *sender) isAssignedSequenceNumber(seg *segment) bool {
 func (s *sender) SetPipe() {
 	// If SACK isn't permitted or it is permitted but recovery is not active
 	// then ignore pipe calculations.
-	if !s.ep.sackPermitted || !s.fr.active {
+	if !s.ep.SACKPermitted || !s.FastRecovery.Active {
 		return
 	}
 	pipe := 0
@@ -1119,7 +1031,7 @@ func (s *sender) SetPipe() {
 			// After initializing pipe to zero, the following steps are
 			// taken for each octet 'S1' in the sequence space between
 			// HighACK and HighData that has not been SACKed:
-			if !s1.sequenceNumber.LessThan(s.sndNxt) {
+			if !s1.sequenceNumber.LessThan(s.SndNxt) {
 				break
 			}
 			if s.ep.scoreboard.IsSACKED(sb) {
@@ -1138,20 +1050,20 @@ func (s *sender) SetPipe() {
 			}
 			// SetPipe():
 			//    (b) If S1 <= HighRxt, Pipe is incremented by 1.
-			if s1.sequenceNumber.LessThanEq(s.fr.highRxt) {
+			if s1.sequenceNumber.LessThanEq(s.FastRecovery.HighRxt) {
 				pipe++
 			}
 		}
 	}
-	s.outstanding = pipe
+	s.Outstanding = pipe
 }
 
 // shouldEnterRecovery returns true if the sender should enter fast recovery
 // based on dupAck count and sack scoreboard.
 // See RFC 6675 section 5.
 func (s *sender) shouldEnterRecovery() bool {
-	return s.dupAckCount >= nDupAckThreshold ||
-		(s.ep.sackPermitted && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection == 0 && s.ep.scoreboard.IsLost(s.sndUna))
+	return s.DupAckCount >= nDupAckThreshold ||
+		(s.ep.SACKPermitted && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection == 0 && s.ep.scoreboard.IsLost(s.SndUna))
 }
 
 // detectLoss is called when an ack is received and returns whether a loss is
@@ -1163,24 +1075,24 @@ func (s *sender) detectLoss(seg *segment) (fastRetransmit bool) {
 	// If RACK is enabled and there is no reordering we should honor the
 	// three duplicate ACK rule to enter recovery.
 	// See: https://tools.ietf.org/html/draft-ietf-tcpm-rack-08#section-4
-	if s.ep.sackPermitted && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection != 0 {
-		if s.rc.reorderSeen {
+	if s.ep.SACKPermitted && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection != 0 {
+		if s.rc.Reord {
 			return false
 		}
 	}
 
 	if !s.isDupAck(seg) {
-		s.dupAckCount = 0
+		s.DupAckCount = 0
 		return false
 	}
 
-	s.dupAckCount++
+	s.DupAckCount++
 
 	// Do not enter fast recovery until we reach nDupAckThreshold or the
 	// first unacknowledged byte is considered lost as per SACK scoreboard.
 	if !s.shouldEnterRecovery() {
 		// RFC 6675 Step 3.
-		s.fr.highRxt = s.sndUna - 1
+		s.FastRecovery.HighRxt = s.SndUna - 1
 		// Do run SetPipe() to calculate the outstanding segments.
 		s.SetPipe()
 		s.state = tcpip.Disorder
@@ -1196,8 +1108,8 @@ func (s *sender) detectLoss(seg *segment) (fastRetransmit bool) {
 	// Note that we only enter recovery when at least one more byte of data
 	// beyond s.fr.last (the highest byte that was outstanding when fast
 	// retransmit was last entered) is acked.
-	if !s.fr.last.LessThan(seg.ackNumber - 1) {
-		s.dupAckCount = 0
+	if !s.FastRecovery.Last.LessThan(seg.ackNumber - 1) {
+		s.DupAckCount = 0
 		return false
 	}
 	s.cc.HandleLossDetected()
@@ -1212,22 +1124,22 @@ func (s *sender) isDupAck(seg *segment) bool {
 	// can leverage the SACK information to determine when an incoming ACK is a
 	// "duplicate" (e.g., if the ACK contains previously unknown SACK
 	// information).
-	if s.ep.sackPermitted && !seg.hasNewSACKInfo {
+	if s.ep.SACKPermitted && !seg.hasNewSACKInfo {
 		return false
 	}
 
 	// (a) The receiver of the ACK has outstanding data.
-	return s.sndUna != s.sndNxt &&
+	return s.SndUna != s.SndNxt &&
 		// (b) The incoming acknowledgment carries no data.
 		seg.logicalLen() == 0 &&
 		// (c) The SYN and FIN bits are both off.
 		!seg.flagIsSet(header.TCPFlagFin) && !seg.flagIsSet(header.TCPFlagSyn) &&
 		// (d) the ACK number is equal to the greatest acknowledgment received on
 		// the given connection (TCP.UNA from RFC793).
-		seg.ackNumber == s.sndUna &&
+		seg.ackNumber == s.SndUna &&
 		// (e) the advertised window in the incoming acknowledgment equals the
 		// advertised window in the last incoming acknowledgment.
-		s.sndWnd == seg.window
+		s.SndWnd == seg.window
 }
 
 // Iterate the writeList and update RACK for each segment which is newly acked
@@ -1267,7 +1179,7 @@ func (s *sender) walkSACK(rcvdSeg *segment) {
 				s.rc.update(seg, rcvdSeg)
 				s.rc.detectReorder(seg)
 				seg.acked = true
-				s.sackedOut += s.pCount(seg, s.maxPayloadSize)
+				s.SackedOut += s.pCount(seg, s.MaxPayloadSize)
 			}
 			seg = seg.Next()
 		}
@@ -1322,18 +1234,18 @@ func checkDSACK(rcvdSeg *segment) bool {
 // updating the send-related state.
 func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 	// Check if we can extract an RTT measurement from this ack.
-	if !rcvdSeg.parsedOptions.TS && s.rttMeasureSeqNum.LessThan(rcvdSeg.ackNumber) {
-		s.updateRTO(time.Now().Sub(s.rttMeasureTime))
-		s.rttMeasureSeqNum = s.sndNxt
+	if !rcvdSeg.parsedOptions.TS && s.RTTMeasureSeqNum.LessThan(rcvdSeg.ackNumber) {
+		s.updateRTO(time.Now().Sub(s.RTTMeasureTime))
+		s.RTTMeasureSeqNum = s.SndNxt
 	}
 
 	// Update Timestamp if required. See RFC7323, section-4.3.
-	if s.ep.sendTSOk && rcvdSeg.parsedOptions.TS {
-		s.ep.updateRecentTimestamp(rcvdSeg.parsedOptions.TSVal, s.maxSentAck, rcvdSeg.sequenceNumber)
+	if s.ep.SendTSOk && rcvdSeg.parsedOptions.TS {
+		s.ep.updateRecentTimestamp(rcvdSeg.parsedOptions.TSVal, s.MaxSentAck, rcvdSeg.sequenceNumber)
 	}
 
 	// Insert SACKBlock information into our scoreboard.
-	if s.ep.sackPermitted {
+	if s.ep.SACKPermitted {
 		for _, sb := range rcvdSeg.parsedOptions.SACKBlocks {
 			// Only insert the SACK block if the following holds
 			// true:
@@ -1347,7 +1259,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 			// NOTE: This check specifically excludes DSACK blocks
 			// which have start/end before sndUna and are used to
 			// indicate spurious retransmissions.
-			if rcvdSeg.ackNumber.LessThan(sb.Start) && s.sndUna.LessThan(sb.Start) && sb.End.LessThanEq(s.sndNxt) && !s.ep.scoreboard.IsSACKED(sb) {
+			if rcvdSeg.ackNumber.LessThan(sb.Start) && s.SndUna.LessThan(sb.Start) && sb.End.LessThanEq(s.SndNxt) && !s.ep.scoreboard.IsSACKED(sb) {
 				s.ep.scoreboard.Insert(sb)
 				rcvdSeg.hasNewSACKInfo = true
 			}
@@ -1375,10 +1287,10 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 	ack := rcvdSeg.ackNumber
 	fastRetransmit := false
 	// Do not leave fast recovery, if the ACK is out of range.
-	if s.fr.active {
+	if s.FastRecovery.Active {
 		// Leave fast recovery if it acknowledges all the data covered by
 		// this fast recovery session.
-		if (ack-1).InRange(s.sndUna, s.sndNxt) && s.fr.last.LessThan(ack) {
+		if (ack-1).InRange(s.SndUna, s.SndNxt) && s.FastRecovery.Last.LessThan(ack) {
 			s.leaveRecovery()
 		}
 	} else {
@@ -1392,28 +1304,28 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 	}
 
 	// Stash away the current window size.
-	s.sndWnd = rcvdSeg.window
+	s.SndWnd = rcvdSeg.window
 
 	// Disable zero window probing if remote advertizes a non-zero receive
 	// window. This can be with an ACK to the zero window probe (where the
 	// acknumber refers to the already acknowledged byte) OR to any previously
 	// unacknowledged segment.
 	if s.zeroWindowProbing && rcvdSeg.window > 0 &&
-		(ack == s.sndUna || (ack-1).InRange(s.sndUna, s.sndNxt)) {
+		(ack == s.SndUna || (ack-1).InRange(s.SndUna, s.SndNxt)) {
 		s.disableZeroWindowProbing()
 	}
 
 	// On receiving the ACK for the zero window probe, account for it and
 	// skip trying to send any segment as we are still probing for
 	// receive window to become non-zero.
-	if s.zeroWindowProbing && s.unackZeroWindowProbes > 0 && ack == s.sndUna {
+	if s.zeroWindowProbing && s.unackZeroWindowProbes > 0 && ack == s.SndUna {
 		s.unackZeroWindowProbes--
 		return
 	}
 
 	// Ignore ack if it doesn't acknowledge any new data.
-	if (ack - 1).InRange(s.sndUna, s.sndNxt) {
-		s.dupAckCount = 0
+	if (ack - 1).InRange(s.SndUna, s.SndNxt) {
+		s.DupAckCount = 0
 
 		// See : https://tools.ietf.org/html/rfc1323#section-3.3.
 		// Specifically we should only update the RTO using TSEcr if the
@@ -1423,7 +1335,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 		//    averaged RTT measurement only if the segment acknowledges
 		//    some new data, i.e., only if it advances the left edge of
 		//    the send window.
-		if s.ep.sendTSOk && rcvdSeg.parsedOptions.TSEcr != 0 {
+		if s.ep.SendTSOk && rcvdSeg.parsedOptions.TSEcr != 0 {
 			// TSVal/Ecr values sent by Netstack are at a millisecond
 			// granularity.
 			elapsed := time.Duration(s.ep.timestamp()-rcvdSeg.parsedOptions.TSEcr) * time.Millisecond
@@ -1438,12 +1350,12 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 			// When an ack is received we must rearm the timer.
 			// RFC 6298 5.3
 			s.probeTimer.disable()
-			s.resendTimer.enable(s.rto)
+			s.resendTimer.enable(s.RTO)
 		}
 
 		// Remove all acknowledged data from the write list.
-		acked := s.sndUna.Size(ack)
-		s.sndUna = ack
+		acked := s.SndUna.Size(ack)
+		s.SndUna = ack
 
 		// The remote ACK-ing at least 1 byte is an indication that we have a
 		// full-duplex connection to the remote as the only way we will receive an
@@ -1457,7 +1369,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 		}
 
 		ackLeft := acked
-		originalOutstanding := s.outstanding
+		originalOutstanding := s.Outstanding
 		for ackLeft > 0 {
 			// We use logicalLen here because we can have FIN
 			// segments (which are always at the end of list) that
@@ -1466,10 +1378,10 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 			datalen := seg.logicalLen()
 
 			if datalen > ackLeft {
-				prevCount := s.pCount(seg, s.maxPayloadSize)
+				prevCount := s.pCount(seg, s.MaxPayloadSize)
 				seg.data.TrimFront(int(ackLeft))
 				seg.sequenceNumber.UpdateForward(ackLeft)
-				s.outstanding -= prevCount - s.pCount(seg, s.maxPayloadSize)
+				s.Outstanding -= prevCount - s.pCount(seg, s.MaxPayloadSize)
 				break
 			}
 
@@ -1478,7 +1390,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 			}
 
 			// Update the RACK fields if SACK is enabled.
-			if s.ep.sackPermitted && !seg.acked && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection != 0 {
+			if s.ep.SACKPermitted && !seg.acked && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection != 0 {
 				s.rc.update(seg, rcvdSeg)
 				s.rc.detectReorder(seg)
 			}
@@ -1488,10 +1400,10 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 			// If SACK is enabled then only reduce outstanding if
 			// the segment was not previously SACKED as these have
 			// already been accounted for in SetPipe().
-			if !s.ep.sackPermitted || !s.ep.scoreboard.IsSACKED(seg.sackBlock()) {
-				s.outstanding -= s.pCount(seg, s.maxPayloadSize)
+			if !s.ep.SACKPermitted || !s.ep.scoreboard.IsSACKED(seg.sackBlock()) {
+				s.Outstanding -= s.pCount(seg, s.MaxPayloadSize)
 			} else {
-				s.sackedOut -= s.pCount(seg, s.maxPayloadSize)
+				s.SackedOut -= s.pCount(seg, s.MaxPayloadSize)
 			}
 			seg.decRef()
 			ackLeft -= datalen
@@ -1501,13 +1413,13 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 		s.ep.updateSndBufferUsage(int(acked))
 
 		// Clear SACK information for all acked data.
-		s.ep.scoreboard.Delete(s.sndUna)
+		s.ep.scoreboard.Delete(s.SndUna)
 
 		// If we are not in fast recovery then update the congestion
 		// window based on the number of acknowledged packets.
-		if !s.fr.active {
-			s.cc.Update(originalOutstanding - s.outstanding)
-			if s.fr.last.LessThan(s.sndUna) {
+		if !s.FastRecovery.Active {
+			s.cc.Update(originalOutstanding - s.Outstanding)
+			if s.FastRecovery.Last.LessThan(s.SndUna) {
 				s.state = tcpip.Open
 				// Update RACK when we are exiting fast or RTO
 				// recovery as described in the RFC
@@ -1522,16 +1434,16 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 		// It is possible for s.outstanding to drop below zero if we get
 		// a retransmit timeout, reset outstanding to zero but later
 		// get an ack that cover previously sent data.
-		if s.outstanding < 0 {
-			s.outstanding = 0
+		if s.Outstanding < 0 {
+			s.Outstanding = 0
 		}
 
 		s.SetPipe()
 
 		// If all outstanding data was acknowledged the disable the timer.
 		// RFC 6298 Rule 5.3
-		if s.sndUna == s.sndNxt {
-			s.outstanding = 0
+		if s.SndUna == s.SndNxt {
+			s.Outstanding = 0
 			// Reset firstRetransmittedSegXmitTime to the zero value.
 			s.firstRetransmittedSegXmitTime = time.Time{}
 			s.resendTimer.disable()
@@ -1539,7 +1451,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 		}
 	}
 
-	if s.ep.sackPermitted && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection != 0 {
+	if s.ep.SACKPermitted && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection != 0 {
 		// Update RACK reorder window.
 		// See: https://tools.ietf.org/html/draft-ietf-tcpm-rack-08#section-7.2
 		// * Upon receiving an ACK:
@@ -1549,7 +1461,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 		// After the reorder window is calculated, detect any loss by checking
 		// if the time elapsed after the segments are sent is greater than the
 		// reorder window.
-		if numLost := s.rc.detectLoss(rcvdSeg.rcvdTime); numLost > 0 && !s.fr.active {
+		if numLost := s.rc.detectLoss(rcvdSeg.rcvdTime); numLost > 0 && !s.FastRecovery.Active {
 			// If any segment is marked as lost by
 			// RACK, enter recovery and retransmit
 			// the lost segments.
@@ -1558,19 +1470,19 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 			fastRetransmit = true
 		}
 
-		if s.fr.active {
+		if s.FastRecovery.Active {
 			s.rc.DoRecovery(nil, fastRetransmit)
 		}
 	}
 
 	// Now that we've popped all acknowledged data from the retransmit
 	// queue, retransmit if needed.
-	if s.fr.active && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection == 0 {
+	if s.FastRecovery.Active && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection == 0 {
 		s.lr.DoRecovery(rcvdSeg, fastRetransmit)
 		// When SACK is enabled data sending is governed by steps in
 		// RFC 6675 Section 5 recovery steps  A-C.
 		// See: https://tools.ietf.org/html/rfc6675#section-5.
-		if s.ep.sackPermitted {
+		if s.ep.SACKPermitted {
 			return
 		}
 	}
@@ -1587,7 +1499,7 @@ func (s *sender) sendSegment(seg *segment) tcpip.Error {
 	if seg.xmitCount > 0 {
 		s.ep.stack.Stats().TCP.Retransmits.Increment()
 		s.ep.stats.SendErrors.Retransmits.Increment()
-		if s.sndCwnd < s.sndSsthresh {
+		if s.SndCwnd < s.Ssthresh {
 			s.ep.stack.Stats().TCP.SlowStartRetransmits.Increment()
 		}
 	}
@@ -1601,11 +1513,11 @@ func (s *sender) sendSegment(seg *segment) tcpip.Error {
 	// then use the conservative timer described in RFC6675 Section 6.0,
 	// otherwise follow the standard time described in RFC6298 Section 5.1.
 	if err != nil && seg.data.Size() != 0 {
-		if s.fr.active && seg.xmitCount > 1 && s.ep.sackPermitted {
-			s.resendTimer.enable(s.rto)
+		if s.FastRecovery.Active && seg.xmitCount > 1 && s.ep.SACKPermitted {
+			s.resendTimer.enable(s.RTO)
 		} else {
 			if !s.resendTimer.enabled() {
-				s.resendTimer.enable(s.rto)
+				s.resendTimer.enable(s.RTO)
 			}
 		}
 	}
@@ -1616,15 +1528,15 @@ func (s *sender) sendSegment(seg *segment) tcpip.Error {
 // sendSegmentFromView sends a new segment containing the given payload, flags
 // and sequence number.
 func (s *sender) sendSegmentFromView(data buffer.VectorisedView, flags header.TCPFlags, seq seqnum.Value) tcpip.Error {
-	s.lastSendTime = time.Now()
-	if seq == s.rttMeasureSeqNum {
-		s.rttMeasureTime = s.lastSendTime
+	s.LastSendTime = time.Now()
+	if seq == s.RTTMeasureSeqNum {
+		s.RTTMeasureTime = s.LastSendTime
 	}
 
 	rcvNxt, rcvWnd := s.ep.rcv.getSendParams()
 
 	// Remember the max sent ack.
-	s.maxSentAck = rcvNxt
+	s.MaxSentAck = rcvNxt
 
 	return s.ep.sendRaw(data, flags, seq, rcvNxt, rcvWnd)
 }
diff --git a/pkg/tcpip/transport/tcp/snd_state.go b/pkg/tcpip/transport/tcp/snd_state.go
index ba41cff6d..2f805d8ce 100644
--- a/pkg/tcpip/transport/tcp/snd_state.go
+++ b/pkg/tcpip/transport/tcp/snd_state.go
@@ -24,26 +24,6 @@ type unixTime struct {
 	nano   int64
 }
 
-// saveLastSendTime is invoked by stateify.
-func (s *sender) saveLastSendTime() unixTime {
-	return unixTime{s.lastSendTime.Unix(), s.lastSendTime.UnixNano()}
-}
-
-// loadLastSendTime is invoked by stateify.
-func (s *sender) loadLastSendTime(unix unixTime) {
-	s.lastSendTime = time.Unix(unix.second, unix.nano)
-}
-
-// saveRttMeasureTime is invoked by stateify.
-func (s *sender) saveRttMeasureTime() unixTime {
-	return unixTime{s.rttMeasureTime.Unix(), s.rttMeasureTime.UnixNano()}
-}
-
-// loadRttMeasureTime is invoked by stateify.
-func (s *sender) loadRttMeasureTime(unix unixTime) {
-	s.rttMeasureTime = time.Unix(unix.second, unix.nano)
-}
-
 // afterLoad is invoked by stateify.
 func (s *sender) afterLoad() {
 	s.resendTimer.init(&s.resendWaker)
diff --git a/pkg/tcpip/transport/tcp/tcp_rack_test.go b/pkg/tcpip/transport/tcp/tcp_rack_test.go
index 81e7dc36e..c58361bc1 100644
--- a/pkg/tcpip/transport/tcp/tcp_rack_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_rack_test.go
@@ -856,8 +856,8 @@ func addReorderWindowCheckerProbe(c *context.Context, numACK int, probeDone chan
 			return
 		}
 
-		if state.Sender.RACKState.ReoWnd == 0 || state.Sender.RACKState.ReoWnd > state.Sender.SRTT {
-			probeDone <- fmt.Errorf("got RACKState.ReoWnd: %v, expected it to be greater than 0 and less than %v", state.Sender.RACKState.ReoWnd, state.Sender.SRTT)
+		if state.Sender.RACKState.ReoWnd == 0 || state.Sender.RACKState.ReoWnd > state.Sender.RTTState.SRTT {
+			probeDone <- fmt.Errorf("got RACKState.ReoWnd: %d, expected it to be greater than 0 and less than %d", state.Sender.RACKState.ReoWnd, state.Sender.RTTState.SRTT)
 			return
 		}