Only carry GSO options in the packet buffer

With this change, GSO options no longer needs to be passed around as
a function argument in the write path.

This change is done in preparation for a later change that defers
segmentation, and may change GSO options for a packet as it flows
down the stack.

Updates #170.

PiperOrigin-RevId: 369774872

56 files changed, 279 insertions, 325 deletions

diff --git a/pkg/sentry/socket/netfilter/targets.go b/pkg/sentry/socket/netfilter/targets.go
index 38b6491e2..4ae1592b2 100644
--- a/pkg/sentry/socket/netfilter/targets.go
+++ b/pkg/sentry/socket/netfilter/targets.go
@@ -658,7 +658,7 @@ func (jt *JumpTarget) id() targetID {
 }
 
 // Action implements stack.Target.Action.
-func (jt *JumpTarget) Action(*stack.PacketBuffer, *stack.ConnTrack, stack.Hook, *stack.GSO, *stack.Route, tcpip.Address) (stack.RuleVerdict, int) {
+func (jt *JumpTarget) Action(*stack.PacketBuffer, *stack.ConnTrack, stack.Hook, *stack.Route, tcpip.Address) (stack.RuleVerdict, int) {
 	return stack.RuleJump, jt.RuleNum
 }
 
diff --git a/pkg/tcpip/link/channel/channel.go b/pkg/tcpip/link/channel/channel.go
index cd76272de..f75ee34ab 100644
--- a/pkg/tcpip/link/channel/channel.go
+++ b/pkg/tcpip/link/channel/channel.go
@@ -30,7 +30,6 @@ import (
 type PacketInfo struct {
 	Pkt   *stack.PacketBuffer
 	Proto tcpip.NetworkProtocolNumber
-	GSO   *stack.GSO
 	Route stack.RouteInfo
 }
 
@@ -229,11 +228,10 @@ func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
 }
 
 // WritePacket stores outbound packets into the channel.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *Endpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	p := PacketInfo{
 		Pkt:   pkt,
 		Proto: protocol,
-		GSO:   gso,
 		Route: r,
 	}
 
@@ -243,13 +241,12 @@ func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 }
 
 // WritePackets stores outbound packets into the channel.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *Endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	n := 0
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		p := PacketInfo{
 			Pkt:   pkt,
 			Proto: protocol,
-			GSO:   gso,
 			Route: r,
 		}
 
diff --git a/pkg/tcpip/link/ethernet/ethernet.go b/pkg/tcpip/link/ethernet/ethernet.go
index d873766a6..b427c6170 100644
--- a/pkg/tcpip/link/ethernet/ethernet.go
+++ b/pkg/tcpip/link/ethernet/ethernet.go
@@ -61,20 +61,20 @@ func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
 }
 
 // WritePacket implements stack.LinkEndpoint.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *Endpoint) WritePacket(r stack.RouteInfo, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	e.AddHeader(e.Endpoint.LinkAddress(), r.RemoteLinkAddress, proto, pkt)
-	return e.Endpoint.WritePacket(r, gso, proto, pkt)
+	return e.Endpoint.WritePacket(r, proto, pkt)
 }
 
 // WritePackets implements stack.LinkEndpoint.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *Endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	linkAddr := e.Endpoint.LinkAddress()
 
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		e.AddHeader(linkAddr, r.RemoteLinkAddress, proto, pkt)
 	}
 
-	return e.Endpoint.WritePackets(r, gso, pkts, proto)
+	return e.Endpoint.WritePackets(r, pkts, proto)
 }
 
 // MaxHeaderLength implements stack.LinkEndpoint.
diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index 6be945116..feb79fe0e 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -433,7 +433,7 @@ func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.Net
 
 // WritePacket writes outbound packets to the file descriptor. If it is not
 // currently writable, the packet is dropped.
-func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *endpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if e.hdrSize > 0 {
 		e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress, protocol, pkt)
 	}
@@ -443,23 +443,23 @@ func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 	fd := e.fds[pkt.Hash%uint32(len(e.fds))]
 	if e.Capabilities()&stack.CapabilityHardwareGSO != 0 {
 		vnetHdr := virtioNetHdr{}
-		if gso != nil {
+		if pkt.GSOOptions.Type != stack.GSONone {
 			vnetHdr.hdrLen = uint16(pkt.HeaderSize())
-			if gso.NeedsCsum {
+			if pkt.GSOOptions.NeedsCsum {
 				vnetHdr.flags = _VIRTIO_NET_HDR_F_NEEDS_CSUM
-				vnetHdr.csumStart = header.EthernetMinimumSize + gso.L3HdrLen
-				vnetHdr.csumOffset = gso.CsumOffset
+				vnetHdr.csumStart = header.EthernetMinimumSize + pkt.GSOOptions.L3HdrLen
+				vnetHdr.csumOffset = pkt.GSOOptions.CsumOffset
 			}
-			if gso.Type != stack.GSONone && uint16(pkt.Data().Size()) > gso.MSS {
-				switch gso.Type {
+			if pkt.GSOOptions.Type != stack.GSONone && uint16(pkt.Data().Size()) > pkt.GSOOptions.MSS {
+				switch pkt.GSOOptions.Type {
 				case stack.GSOTCPv4:
 					vnetHdr.gsoType = _VIRTIO_NET_HDR_GSO_TCPV4
 				case stack.GSOTCPv6:
 					vnetHdr.gsoType = _VIRTIO_NET_HDR_GSO_TCPV6
 				default:
-					panic(fmt.Sprintf("Unknown gso type: %v", gso.Type))
+					panic(fmt.Sprintf("Unknown gso type: %v", pkt.GSOOptions.Type))
 				}
-				vnetHdr.gsoSize = gso.MSS
+				vnetHdr.gsoSize = pkt.GSOOptions.MSS
 			}
 		}
 
@@ -484,7 +484,7 @@ func (e *endpoint) sendBatch(batchFD int, batch []*stack.PacketBuffer) (int, tcp
 		var vnetHdrBuf []byte
 		if e.Capabilities()&stack.CapabilityHardwareGSO != 0 {
 			vnetHdr := virtioNetHdr{}
-			if pkt.GSOOptions != nil {
+			if pkt.GSOOptions.Type != stack.GSONone {
 				vnetHdr.hdrLen = uint16(pkt.HeaderSize())
 				if pkt.GSOOptions.NeedsCsum {
 					vnetHdr.flags = _VIRTIO_NET_HDR_F_NEEDS_CSUM
@@ -540,7 +540,7 @@ func (e *endpoint) sendBatch(batchFD int, batch []*stack.PacketBuffer) (int, tcp
 //  - pkt.EgressRoute
 //  - pkt.GSOOptions
 //  - pkt.NetworkProtocolNumber
-func (e *endpoint) WritePackets(_ stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, _ tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *endpoint) WritePackets(_ stack.RouteInfo, pkts stack.PacketBufferList, _ tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	// Preallocate to avoid repeated reallocation as we append to batch.
 	// batchSz is 47 because when SWGSO is in use then a single 65KB TCP
 	// segment can get split into 46 segments of 1420 bytes and a single 216
diff --git a/pkg/tcpip/link/fdbased/endpoint_test.go b/pkg/tcpip/link/fdbased/endpoint_test.go
index 1e40f3fef..8aad338b6 100644
--- a/pkg/tcpip/link/fdbased/endpoint_test.go
+++ b/pkg/tcpip/link/fdbased/endpoint_test.go
@@ -207,18 +207,17 @@ func testWritePacket(t *testing.T, plen int, eth bool, gsoMaxSize uint32, hash u
 
 	// Write.
 	want := append(append(buffer.View(nil), b...), payload...)
-	var gso *stack.GSO
+	const l3HdrLen = header.IPv6MinimumSize
 	if gsoMaxSize != 0 {
-		gso = &stack.GSO{
+		pkt.GSOOptions = stack.GSO{
 			Type:       stack.GSOTCPv6,
 			NeedsCsum:  true,
 			CsumOffset: csumOffset,
 			MSS:        gsoMSS,
-			MaxSize:    gsoMaxSize,
-			L3HdrLen:   header.IPv4MaximumHeaderSize,
+			L3HdrLen:   l3HdrLen,
 		}
 	}
-	if err := c.ep.WritePacket(r, gso, proto, pkt); err != nil {
+	if err := c.ep.WritePacket(r, proto, pkt); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 
@@ -235,7 +234,7 @@ func testWritePacket(t *testing.T, plen int, eth bool, gsoMaxSize uint32, hash u
 		if vnetHdr.flags&_VIRTIO_NET_HDR_F_NEEDS_CSUM == 0 {
 			t.Fatalf("virtioNetHdr.flags %v  doesn't contain %v", vnetHdr.flags, _VIRTIO_NET_HDR_F_NEEDS_CSUM)
 		}
-		csumStart := header.EthernetMinimumSize + gso.L3HdrLen
+		const csumStart = header.EthernetMinimumSize + l3HdrLen
 		if vnetHdr.csumStart != csumStart {
 			t.Fatalf("vnetHdr.csumStart = %v, want %v", vnetHdr.csumStart, csumStart)
 		}
@@ -243,7 +242,7 @@ func testWritePacket(t *testing.T, plen int, eth bool, gsoMaxSize uint32, hash u
 			t.Fatalf("vnetHdr.csumOffset = %v, want %v", vnetHdr.csumOffset, csumOffset)
 		}
 		gsoType := uint8(0)
-		if int(gso.MSS) < plen {
+		if plen > gsoMSS {
 			gsoType = _VIRTIO_NET_HDR_GSO_TCPV6
 		}
 		if vnetHdr.gsoType != gsoType {
@@ -333,7 +332,7 @@ func TestPreserveSrcAddress(t *testing.T) {
 		ReserveHeaderBytes: header.EthernetMinimumSize,
 		Data:               buffer.VectorisedView{},
 	})
-	if err := c.ep.WritePacket(r, nil /* gso */, proto, pkt); err != nil {
+	if err := c.ep.WritePacket(r, proto, pkt); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 
diff --git a/pkg/tcpip/link/loopback/loopback.go b/pkg/tcpip/link/loopback/loopback.go
index 691467870..7012d8829 100644
--- a/pkg/tcpip/link/loopback/loopback.go
+++ b/pkg/tcpip/link/loopback/loopback.go
@@ -76,7 +76,7 @@ func (*endpoint) Wait() {}
 
 // WritePacket implements stack.LinkEndpoint.WritePacket. It delivers outbound
 // packets to the network-layer dispatcher.
-func (e *endpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *endpoint) WritePacket(_ stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	// Construct data as the unparsed portion for the loopback packet.
 	data := buffer.NewVectorisedView(pkt.Size(), pkt.Views())
 
@@ -92,7 +92,7 @@ func (e *endpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, protocol tcpip.N
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (e *endpoint) WritePackets(stack.RouteInfo, *stack.GSO, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *endpoint) WritePackets(stack.RouteInfo, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
diff --git a/pkg/tcpip/link/muxed/injectable.go b/pkg/tcpip/link/muxed/injectable.go
index 668f72eee..3e2a1aa94 100644
--- a/pkg/tcpip/link/muxed/injectable.go
+++ b/pkg/tcpip/link/muxed/injectable.go
@@ -87,20 +87,20 @@ func (m *InjectableEndpoint) InjectInbound(protocol tcpip.NetworkProtocolNumber,
 // WritePackets writes outbound packets to the appropriate
 // LinkInjectableEndpoint based on the RemoteAddress. HandleLocal only works if
 // r.RemoteAddress has a route registered in this endpoint.
-func (m *InjectableEndpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (m *InjectableEndpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	endpoint, ok := m.routes[r.RemoteAddress]
 	if !ok {
 		return 0, &tcpip.ErrNoRoute{}
 	}
-	return endpoint.WritePackets(r, gso, pkts, protocol)
+	return endpoint.WritePackets(r, pkts, protocol)
 }
 
 // WritePacket writes outbound packets to the appropriate LinkInjectableEndpoint
 // based on the RemoteAddress. HandleLocal only works if r.RemoteAddress has a
 // route registered in this endpoint.
-func (m *InjectableEndpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (m *InjectableEndpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if endpoint, ok := m.routes[r.RemoteAddress]; ok {
-		return endpoint.WritePacket(r, gso, protocol, pkt)
+		return endpoint.WritePacket(r, protocol, pkt)
 	}
 	return &tcpip.ErrNoRoute{}
 }
diff --git a/pkg/tcpip/link/muxed/injectable_test.go b/pkg/tcpip/link/muxed/injectable_test.go
index 5806f7fdf..040e3a35b 100644
--- a/pkg/tcpip/link/muxed/injectable_test.go
+++ b/pkg/tcpip/link/muxed/injectable_test.go
@@ -54,7 +54,7 @@ func TestInjectableEndpointDispatch(t *testing.T) {
 	var packetRoute stack.RouteInfo
 	packetRoute.RemoteAddress = dstIP
 
-	endpoint.WritePacket(packetRoute, nil /* gso */, ipv4.ProtocolNumber, pkt)
+	endpoint.WritePacket(packetRoute, ipv4.ProtocolNumber, pkt)
 
 	buf := make([]byte, 6500)
 	bytesRead, err := sock.Read(buf)
@@ -76,7 +76,7 @@ func TestInjectableEndpointDispatchHdrOnly(t *testing.T) {
 	pkt.TransportHeader().Push(1)[0] = 0xFA
 	var packetRoute stack.RouteInfo
 	packetRoute.RemoteAddress = dstIP
-	endpoint.WritePacket(packetRoute, nil /* gso */, ipv4.ProtocolNumber, pkt)
+	endpoint.WritePacket(packetRoute, ipv4.ProtocolNumber, pkt)
 	buf := make([]byte, 6500)
 	bytesRead, err := sock.Read(buf)
 	if err != nil {
diff --git a/pkg/tcpip/link/nested/nested.go b/pkg/tcpip/link/nested/nested.go
index 97ad9fdd5..89df35822 100644
--- a/pkg/tcpip/link/nested/nested.go
+++ b/pkg/tcpip/link/nested/nested.go
@@ -113,13 +113,13 @@ func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
 }
 
 // WritePacket implements stack.LinkEndpoint.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
-	return e.child.WritePacket(r, gso, protocol, pkt)
+func (e *Endpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+	return e.child.WritePacket(r, protocol, pkt)
 }
 
 // WritePackets implements stack.LinkEndpoint.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
-	return e.child.WritePackets(r, gso, pkts, protocol)
+func (e *Endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+	return e.child.WritePackets(r, pkts, protocol)
 }
 
 // Wait implements stack.LinkEndpoint.
diff --git a/pkg/tcpip/link/packetsocket/endpoint.go b/pkg/tcpip/link/packetsocket/endpoint.go
index 6cbe18a56..e01837e2d 100644
--- a/pkg/tcpip/link/packetsocket/endpoint.go
+++ b/pkg/tcpip/link/packetsocket/endpoint.go
@@ -35,16 +35,16 @@ func New(lower stack.LinkEndpoint) stack.LinkEndpoint {
 }
 
 // WritePacket implements stack.LinkEndpoint.WritePacket.
-func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *endpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	e.Endpoint.DeliverOutboundPacket(r.RemoteLinkAddress, r.LocalLinkAddress, protocol, pkt)
-	return e.Endpoint.WritePacket(r, gso, protocol, pkt)
+	return e.Endpoint.WritePacket(r, protocol, pkt)
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		e.Endpoint.DeliverOutboundPacket(r.RemoteLinkAddress, r.LocalLinkAddress, pkt.NetworkProtocolNumber, pkt)
 	}
 
-	return e.Endpoint.WritePackets(r, gso, pkts, proto)
+	return e.Endpoint.WritePackets(r, pkts, proto)
 }
diff --git a/pkg/tcpip/link/pipe/pipe.go b/pkg/tcpip/link/pipe/pipe.go
index 21fb87757..5030b6ba1 100644
--- a/pkg/tcpip/link/pipe/pipe.go
+++ b/pkg/tcpip/link/pipe/pipe.go
@@ -66,7 +66,7 @@ func (e *Endpoint) deliverPackets(r stack.RouteInfo, proto tcpip.NetworkProtocol
 }
 
 // WritePacket implements stack.LinkEndpoint.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *Endpoint) WritePacket(r stack.RouteInfo, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	var pkts stack.PacketBufferList
 	pkts.PushBack(pkt)
 	e.deliverPackets(r, proto, pkts)
@@ -74,7 +74,7 @@ func (e *Endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, proto tcpip.Netw
 }
 
 // WritePackets implements stack.LinkEndpoint.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *Endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	n := pkts.Len()
 	e.deliverPackets(r, proto, pkts)
 	return n, nil
diff --git a/pkg/tcpip/link/qdisc/fifo/endpoint.go b/pkg/tcpip/link/qdisc/fifo/endpoint.go
index 128ef6e87..bba6a6973 100644
--- a/pkg/tcpip/link/qdisc/fifo/endpoint.go
+++ b/pkg/tcpip/link/qdisc/fifo/endpoint.go
@@ -91,7 +91,7 @@ func (q *queueDispatcher) dispatchLoop() {
 			}
 			// We pass a protocol of zero here because each packet carries its
 			// NetworkProtocol.
-			q.lower.WritePackets(stack.RouteInfo{}, nil /* gso */, batch, 0 /* protocol */)
+			q.lower.WritePackets(stack.RouteInfo{}, batch, 0 /* protocol */)
 			for pkt := batch.Front(); pkt != nil; pkt = pkt.Next() {
 				batch.Remove(pkt)
 			}
@@ -150,12 +150,12 @@ func (e *endpoint) GSOMaxSize() uint32 {
 }
 
 // WritePacket implements stack.LinkEndpoint.WritePacket.
-func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
-	// WritePacket caller's do not set the following fields in PacketBuffer
-	// so we populate them here.
-	pkt.EgressRoute = r
-	pkt.GSOOptions = gso
-	pkt.NetworkProtocolNumber = protocol
+//
+// The packet must have the following fields populated:
+//  - pkt.EgressRoute
+//  - pkt.GSOOptions
+//  - pkt.NetworkProtocolNumber
+func (e *endpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	d := e.dispatchers[int(pkt.Hash)%len(e.dispatchers)]
 	if !d.q.enqueue(pkt) {
 		return &tcpip.ErrNoBufferSpace{}
@@ -166,12 +166,12 @@ func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
 //
-// Being a batch API, each packet in pkts should have the following
-// fields populated:
+// Each packet in the packet buffer list must have the following fields
+// populated:
 //  - pkt.EgressRoute
 //  - pkt.GSOOptions
 //  - pkt.NetworkProtocolNumber
-func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	enqueued := 0
 	for pkt := pkts.Front(); pkt != nil; {
 		d := e.dispatchers[int(pkt.Hash)%len(e.dispatchers)]
diff --git a/pkg/tcpip/link/sharedmem/sharedmem.go b/pkg/tcpip/link/sharedmem/sharedmem.go
index d8d0b16b2..df9a0b90a 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem.go
@@ -203,7 +203,7 @@ func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.Net
 
 // WritePacket writes outbound packets to the file descriptor. If it is not
 // currently writable, the packet is dropped.
-func (e *endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *endpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress, protocol, pkt)
 
 	views := pkt.Views()
@@ -220,7 +220,7 @@ func (e *endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, protocol tcpip.N
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (*endpoint) WritePackets(stack.RouteInfo, *stack.GSO, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (*endpoint) WritePackets(stack.RouteInfo, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
diff --git a/pkg/tcpip/link/sharedmem/sharedmem_test.go b/pkg/tcpip/link/sharedmem/sharedmem_test.go
index d4b3ddd5c..0f72d4e95 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem_test.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem_test.go
@@ -281,7 +281,7 @@ func TestSimpleSend(t *testing.T) {
 			copy(pkt.NetworkHeader().Push(hdrLen), hdrBuf)
 
 			proto := tcpip.NetworkProtocolNumber(rand.Intn(0x10000))
-			if err := c.ep.WritePacket(r, nil /* gso */, proto, pkt); err != nil {
+			if err := c.ep.WritePacket(r, proto, pkt); err != nil {
 				t.Fatalf("WritePacket failed: %v", err)
 			}
 
@@ -351,7 +351,7 @@ func TestPreserveSrcAddressInSend(t *testing.T) {
 	})
 
 	proto := tcpip.NetworkProtocolNumber(rand.Intn(0x10000))
-	if err := c.ep.WritePacket(r, nil /* gso */, proto, pkt); err != nil {
+	if err := c.ep.WritePacket(r, proto, pkt); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 
@@ -407,7 +407,7 @@ func TestFillTxQueue(t *testing.T) {
 			Data:               buf.ToVectorisedView(),
 		})
 
-		if err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt); err != nil {
+		if err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 
@@ -425,7 +425,7 @@ func TestFillTxQueue(t *testing.T) {
 		ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 		Data:               buf.ToVectorisedView(),
 	})
-	err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt)
+	err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt)
 	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 		t.Fatalf("got WritePacket(...) = %v, want %s", err, &tcpip.ErrWouldBlock{})
 	}
@@ -453,7 +453,7 @@ func TestFillTxQueueAfterBadCompletion(t *testing.T) {
 			ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 			Data:               buf.ToVectorisedView(),
 		})
-		if err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt); err != nil {
+		if err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 	}
@@ -476,7 +476,7 @@ func TestFillTxQueueAfterBadCompletion(t *testing.T) {
 			ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 			Data:               buf.ToVectorisedView(),
 		})
-		if err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt); err != nil {
+		if err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 
@@ -494,7 +494,7 @@ func TestFillTxQueueAfterBadCompletion(t *testing.T) {
 		ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 		Data:               buf.ToVectorisedView(),
 	})
-	err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt)
+	err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt)
 	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 		t.Fatalf("got WritePacket(...) = %v, want %s", err, &tcpip.ErrWouldBlock{})
 	}
@@ -520,7 +520,7 @@ func TestFillTxMemory(t *testing.T) {
 			ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 			Data:               buf.ToVectorisedView(),
 		})
-		if err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt); err != nil {
+		if err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 
@@ -539,7 +539,7 @@ func TestFillTxMemory(t *testing.T) {
 		ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 		Data:               buf.ToVectorisedView(),
 	})
-	err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt)
+	err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt)
 	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 		t.Fatalf("got WritePacket(...) = %v, want %s", err, &tcpip.ErrWouldBlock{})
 	}
@@ -566,7 +566,7 @@ func TestFillTxMemoryWithMultiBuffer(t *testing.T) {
 			ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 			Data:               buf.ToVectorisedView(),
 		})
-		if err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt); err != nil {
+		if err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 
@@ -581,7 +581,7 @@ func TestFillTxMemoryWithMultiBuffer(t *testing.T) {
 			ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 			Data:               buffer.NewView(bufferSize).ToVectorisedView(),
 		})
-		err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt)
+		err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt)
 		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 			t.Fatalf("got WritePacket(...) = %v, want %s", err, &tcpip.ErrWouldBlock{})
 		}
@@ -593,7 +593,7 @@ func TestFillTxMemoryWithMultiBuffer(t *testing.T) {
 			ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 			Data:               buf.ToVectorisedView(),
 		})
-		if err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt); err != nil {
+		if err := c.ep.WritePacket(r, header.IPv4ProtocolNumber, pkt); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 	}
diff --git a/pkg/tcpip/link/sniffer/sniffer.go b/pkg/tcpip/link/sniffer/sniffer.go
index 7aaee3d13..2d6a3a833 100644
--- a/pkg/tcpip/link/sniffer/sniffer.go
+++ b/pkg/tcpip/link/sniffer/sniffer.go
@@ -139,7 +139,7 @@ func NewWithWriter(lower stack.LinkEndpoint, writer io.Writer, snapLen uint32) (
 // called by the link-layer endpoint being wrapped when a packet arrives, and
 // logs the packet before forwarding to the actual dispatcher.
 func (e *endpoint) DeliverNetworkPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
-	e.dumpPacket(directionRecv, nil, protocol, pkt)
+	e.dumpPacket(directionRecv, protocol, pkt)
 	e.Endpoint.DeliverNetworkPacket(remote, local, protocol, pkt)
 }
 
@@ -148,10 +148,10 @@ func (e *endpoint) DeliverOutboundPacket(remote, local tcpip.LinkAddress, protoc
 	e.Endpoint.DeliverOutboundPacket(remote, local, protocol, pkt)
 }
 
-func (e *endpoint) dumpPacket(dir direction, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+func (e *endpoint) dumpPacket(dir direction, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
 	writer := e.writer
 	if writer == nil && atomic.LoadUint32(&LogPackets) == 1 {
-		logPacket(e.logPrefix, dir, protocol, pkt, gso)
+		logPacket(e.logPrefix, dir, protocol, pkt)
 	}
 	if writer != nil && atomic.LoadUint32(&LogPacketsToPCAP) == 1 {
 		totalLength := pkt.Size()
@@ -187,22 +187,22 @@ func (e *endpoint) dumpPacket(dir direction, gso *stack.GSO, protocol tcpip.Netw
 // WritePacket implements the stack.LinkEndpoint interface. It is called by
 // higher-level protocols to write packets; it just logs the packet and
 // forwards the request to the lower endpoint.
-func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
-	e.dumpPacket(directionSend, gso, protocol, pkt)
-	return e.Endpoint.WritePacket(r, gso, protocol, pkt)
+func (e *endpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+	e.dumpPacket(directionSend, protocol, pkt)
+	return e.Endpoint.WritePacket(r, protocol, pkt)
 }
 
 // WritePackets implements the stack.LinkEndpoint interface. It is called by
 // higher-level protocols to write packets; it just logs the packet and
 // forwards the request to the lower endpoint.
-func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
-		e.dumpPacket(directionSend, gso, protocol, pkt)
+		e.dumpPacket(directionSend, protocol, pkt)
 	}
-	return e.Endpoint.WritePackets(r, gso, pkts, protocol)
+	return e.Endpoint.WritePackets(r, pkts, protocol)
 }
 
-func logPacket(prefix string, dir direction, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer, gso *stack.GSO) {
+func logPacket(prefix string, dir direction, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
 	// Figure out the network layer info.
 	var transProto uint8
 	src := tcpip.Address("unknown")
@@ -411,8 +411,8 @@ func logPacket(prefix string, dir direction, protocol tcpip.NetworkProtocolNumbe
 		return
 	}
 
-	if gso != nil {
-		details += fmt.Sprintf(" gso: %+v", gso)
+	if pkt.GSOOptions.Type != stack.GSONone {
+		details += fmt.Sprintf(" gso: %#v", pkt.GSOOptions)
 	}
 
 	log.Infof("%s%s %s %s:%d -> %s:%d len:%d id:%04x %s", prefix, directionPrefix, transName, src, srcPort, dst, dstPort, size, id, details)
diff --git a/pkg/tcpip/link/waitable/waitable.go b/pkg/tcpip/link/waitable/waitable.go
index ce5113746..a95602aa5 100644
--- a/pkg/tcpip/link/waitable/waitable.go
+++ b/pkg/tcpip/link/waitable/waitable.go
@@ -108,12 +108,12 @@ func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
 // WritePacket implements stack.LinkEndpoint.WritePacket. It is called by
 // higher-level protocols to write packets. It only forwards packets to the
 // lower endpoint if Wait or WaitWrite haven't been called.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *Endpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if !e.writeGate.Enter() {
 		return nil
 	}
 
-	err := e.lower.WritePacket(r, gso, protocol, pkt)
+	err := e.lower.WritePacket(r, protocol, pkt)
 	e.writeGate.Leave()
 	return err
 }
@@ -121,12 +121,12 @@ func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 // WritePackets implements stack.LinkEndpoint.WritePackets. It is called by
 // higher-level protocols to write packets. It only forwards packets to the
 // lower endpoint if Wait or WaitWrite haven't been called.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *Endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	if !e.writeGate.Enter() {
 		return pkts.Len(), nil
 	}
 
-	n, err := e.lower.WritePackets(r, gso, pkts, protocol)
+	n, err := e.lower.WritePackets(r, pkts, protocol)
 	e.writeGate.Leave()
 	return n, err
 }
diff --git a/pkg/tcpip/link/waitable/waitable_test.go b/pkg/tcpip/link/waitable/waitable_test.go
index e368a9eaa..a71400ee9 100644
--- a/pkg/tcpip/link/waitable/waitable_test.go
+++ b/pkg/tcpip/link/waitable/waitable_test.go
@@ -69,13 +69,13 @@ func (e *countedEndpoint) LinkAddress() tcpip.LinkAddress {
 	return e.linkAddr
 }
 
-func (e *countedEndpoint) WritePacket(stack.RouteInfo, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
+func (e *countedEndpoint) WritePacket(stack.RouteInfo, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
 	e.writeCount++
 	return nil
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (e *countedEndpoint) WritePackets(_ stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, _ tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *countedEndpoint) WritePackets(_ stack.RouteInfo, pkts stack.PacketBufferList, _ tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	e.writeCount += pkts.Len()
 	return pkts.Len(), nil
 }
@@ -98,21 +98,21 @@ func TestWaitWrite(t *testing.T) {
 	wep := New(ep)
 
 	// Write and check that it goes through.
-	wep.WritePacket(stack.RouteInfo{}, nil /* gso */, 0, stack.NewPacketBuffer(stack.PacketBufferOptions{}))
+	wep.WritePacket(stack.RouteInfo{}, 0, stack.NewPacketBuffer(stack.PacketBufferOptions{}))
 	if want := 1; ep.writeCount != want {
 		t.Fatalf("Unexpected writeCount: got=%v, want=%v", ep.writeCount, want)
 	}
 
 	// Wait on dispatches, then try to write. It must go through.
 	wep.WaitDispatch()
-	wep.WritePacket(stack.RouteInfo{}, nil /* gso */, 0, stack.NewPacketBuffer(stack.PacketBufferOptions{}))
+	wep.WritePacket(stack.RouteInfo{}, 0, stack.NewPacketBuffer(stack.PacketBufferOptions{}))
 	if want := 2; ep.writeCount != want {
 		t.Fatalf("Unexpected writeCount: got=%v, want=%v", ep.writeCount, want)
 	}
 
 	// Wait on writes, then try to write. It must not go through.
 	wep.WaitWrite()
-	wep.WritePacket(stack.RouteInfo{}, nil /* gso */, 0, stack.NewPacketBuffer(stack.PacketBufferOptions{}))
+	wep.WritePacket(stack.RouteInfo{}, 0, stack.NewPacketBuffer(stack.PacketBufferOptions{}))
 	if want := 2; ep.writeCount != want {
 		t.Fatalf("Unexpected writeCount: got=%v, want=%v", ep.writeCount, want)
 	}
diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go
index 7ae38d684..0efa3a926 100644
--- a/pkg/tcpip/network/arp/arp.go
+++ b/pkg/tcpip/network/arp/arp.go
@@ -136,7 +136,7 @@ func (e *endpoint) MaxHeaderLength() uint16 {
 
 func (*endpoint) Close() {}
 
-func (*endpoint) WritePacket(*stack.Route, *stack.GSO, stack.NetworkHeaderParams, *stack.PacketBuffer) tcpip.Error {
+func (*endpoint) WritePacket(*stack.Route, stack.NetworkHeaderParams, *stack.PacketBuffer) tcpip.Error {
 	return &tcpip.ErrNotSupported{}
 }
 
@@ -146,7 +146,7 @@ func (*endpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumber {
 }
 
 // WritePackets implements stack.NetworkEndpoint.WritePackets.
-func (*endpoint) WritePackets(*stack.Route, *stack.GSO, stack.PacketBufferList, stack.NetworkHeaderParams) (int, tcpip.Error) {
+func (*endpoint) WritePackets(*stack.Route, stack.PacketBufferList, stack.NetworkHeaderParams) (int, tcpip.Error) {
 	return 0, &tcpip.ErrNotSupported{}
 }
 
@@ -222,7 +222,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 		//
 		//   Send the packet to the (new) target hardware address on the same
 		//   hardware on which the request was received.
-		if err := e.nic.WritePacketToRemote(tcpip.LinkAddress(origSender), nil /* gso */, ProtocolNumber, respPkt); err != nil {
+		if err := e.nic.WritePacketToRemote(tcpip.LinkAddress(origSender), ProtocolNumber, respPkt); err != nil {
 			stats.outgoingRepliesDropped.Increment()
 		} else {
 			stats.outgoingRepliesSent.Increment()
@@ -355,7 +355,7 @@ func (e *endpoint) sendARPRequest(localAddr, targetAddr tcpip.Address, remoteLin
 	}
 
 	stats := e.stats.arp
-	if err := e.nic.WritePacketToRemote(remoteLinkAddr, nil /* gso */, ProtocolNumber, pkt); err != nil {
+	if err := e.nic.WritePacketToRemote(remoteLinkAddr, ProtocolNumber, pkt); err != nil {
 		stats.outgoingRequestsDropped.Increment()
 		return err
 	}
diff --git a/pkg/tcpip/network/arp/arp_test.go b/pkg/tcpip/network/arp/arp_test.go
index 9b3714f9e..94209b026 100644
--- a/pkg/tcpip/network/arp/arp_test.go
+++ b/pkg/tcpip/network/arp/arp_test.go
@@ -451,12 +451,12 @@ type testLinkEndpoint struct {
 	writeErr tcpip.Error
 }
 
-func (t *testLinkEndpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (t *testLinkEndpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if t.writeErr != nil {
 		return t.writeErr
 	}
 
-	return t.LinkEndpoint.WritePacket(r, gso, protocol, pkt)
+	return t.LinkEndpoint.WritePacket(r, protocol, pkt)
 }
 
 func TestLinkAddressRequest(t *testing.T) {
diff --git a/pkg/tcpip/network/internal/testutil/testutil.go b/pkg/tcpip/network/internal/testutil/testutil.go
index f5fa77b65..e2cf24b67 100644
--- a/pkg/tcpip/network/internal/testutil/testutil.go
+++ b/pkg/tcpip/network/internal/testutil/testutil.go
@@ -64,7 +64,7 @@ func (*MockLinkEndpoint) MaxHeaderLength() uint16 { return 0 }
 func (*MockLinkEndpoint) LinkAddress() tcpip.LinkAddress { return "" }
 
 // WritePacket implements LinkEndpoint.WritePacket.
-func (ep *MockLinkEndpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, _ tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (ep *MockLinkEndpoint) WritePacket(_ stack.RouteInfo, _ tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if ep.allowPackets == 0 {
 		return ep.err
 	}
@@ -74,11 +74,11 @@ func (ep *MockLinkEndpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, _ tcpip
 }
 
 // WritePackets implements LinkEndpoint.WritePackets.
-func (ep *MockLinkEndpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (ep *MockLinkEndpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	var n int
 
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
-		if err := ep.WritePacket(r, gso, protocol, pkt); err != nil {
+		if err := ep.WritePacket(r, protocol, pkt); err != nil {
 			return n, err
 		}
 		n++
diff --git a/pkg/tcpip/network/ip_test.go b/pkg/tcpip/network/ip_test.go
index dbd674634..74aad126c 100644
--- a/pkg/tcpip/network/ip_test.go
+++ b/pkg/tcpip/network/ip_test.go
@@ -183,7 +183,7 @@ func (*testObject) Wait() {}
 // WritePacket is called by network endpoints after producing a packet and
 // writing it to the link endpoint. This is used by the test object to verify
 // that the produced packet is as expected.
-func (t *testObject) WritePacket(_ *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (t *testObject) WritePacket(_ *stack.Route, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	var prot tcpip.TransportProtocolNumber
 	var srcAddr tcpip.Address
 	var dstAddr tcpip.Address
@@ -205,7 +205,7 @@ func (t *testObject) WritePacket(_ *stack.Route, _ *stack.GSO, protocol tcpip.Ne
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (*testObject) WritePackets(_ *stack.Route, _ *stack.GSO, pkt stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (*testObject) WritePackets(_ *stack.Route, pkt stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
@@ -326,7 +326,7 @@ func (t *testInterface) setEnabled(v bool) {
 	t.mu.disabled = !v
 }
 
-func (*testInterface) WritePacketToRemote(tcpip.LinkAddress, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
+func (*testInterface) WritePacketToRemote(tcpip.LinkAddress, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
 	return &tcpip.ErrNotSupported{}
 }
 
@@ -591,7 +591,7 @@ func TestIPv4Send(t *testing.T) {
 	if err != nil {
 		t.Fatalf("could not find route: %v", err)
 	}
-	if err := ep.WritePacket(r, nil /* gso */, stack.NetworkHeaderParams{
+	if err := ep.WritePacket(r, stack.NetworkHeaderParams{
 		Protocol: 123,
 		TTL:      123,
 		TOS:      stack.DefaultTOS,
@@ -1018,7 +1018,7 @@ func TestIPv6Send(t *testing.T) {
 	if err != nil {
 		t.Fatalf("could not find route: %v", err)
 	}
-	if err := ep.WritePacket(r, nil /* gso */, stack.NetworkHeaderParams{
+	if err := ep.WritePacket(r, stack.NetworkHeaderParams{
 		Protocol: 123,
 		TTL:      123,
 		TOS:      stack.DefaultTOS,
diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go
index 1525f15db..f663fdc0b 100644
--- a/pkg/tcpip/network/ipv4/icmp.go
+++ b/pkg/tcpip/network/ipv4/icmp.go
@@ -629,7 +629,6 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) tcpip
 	icmpHdr.SetChecksum(header.ICMPv4Checksum(icmpHdr, icmpPkt.Data().AsRange().Checksum()))
 
 	if err := route.WritePacket(
-		nil, /* gso */
 		stack.NetworkHeaderParams{
 			Protocol: header.ICMPv4ProtocolNumber,
 			TTL:      route.DefaultTTL(),
diff --git a/pkg/tcpip/network/ipv4/igmp.go b/pkg/tcpip/network/ipv4/igmp.go
index b1ac29294..3ce499298 100644
--- a/pkg/tcpip/network/ipv4/igmp.go
+++ b/pkg/tcpip/network/ipv4/igmp.go
@@ -341,7 +341,7 @@ func (igmp *igmpState) writePacket(destAddress tcpip.Address, groupAddress tcpip
 	}
 
 	sentStats := igmp.ep.stats.igmp.packetsSent
-	if err := igmp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv4Address(destAddress), nil /* gso */, ProtocolNumber, pkt); err != nil {
+	if err := igmp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv4Address(destAddress), ProtocolNumber, pkt); err != nil {
 		sentStats.dropped.Increment()
 		return false, err
 	}
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index a82a5790d..a0bc06465 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -350,7 +350,7 @@ func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.Packet
 // fragment. It returns the number of fragments handled and the number of
 // fragments left to be processed. The IP header must already be present in the
 // original packet.
-func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU uint32, pkt *stack.PacketBuffer, handler func(*stack.PacketBuffer) tcpip.Error) (int, int, tcpip.Error) {
+func (e *endpoint) handleFragments(r *stack.Route, networkMTU uint32, pkt *stack.PacketBuffer, handler func(*stack.PacketBuffer) tcpip.Error) (int, int, tcpip.Error) {
 	// Round the MTU down to align to 8 bytes.
 	fragmentPayloadSize := networkMTU &^ 7
 	networkHeader := header.IPv4(pkt.NetworkHeader().View())
@@ -370,7 +370,7 @@ func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU ui
 }
 
 // WritePacket writes a packet to the given destination address and protocol.
-func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *endpoint) WritePacket(r *stack.Route, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
 	if err := e.addIPHeader(r.LocalAddress(), r.RemoteAddress(), pkt, params, nil /* options */); err != nil {
 		return err
 	}
@@ -378,7 +378,7 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 	// iptables filtering. All packets that reach here are locally
 	// generated.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Output, pkt, gso, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
+	if ok := e.protocol.stack.IPTables().Check(stack.Output, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesOutputDropped.Increment()
 		return nil
@@ -401,10 +401,10 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 		}
 	}
 
-	return e.writePacket(r, gso, pkt, false /* headerIncluded */)
+	return e.writePacket(r, pkt, false /* headerIncluded */)
 }
 
-func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.PacketBuffer, headerIncluded bool) tcpip.Error {
+func (e *endpoint) writePacket(r *stack.Route, pkt *stack.PacketBuffer, headerIncluded bool) tcpip.Error {
 	if r.Loop()&stack.PacketLoop != 0 {
 		// If the packet was generated by the stack (not a raw/packet endpoint
 		// where a packet may be written with the header included), then we can
@@ -418,7 +418,7 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 	// Postrouting NAT can only change the source address, and does not alter the
 	// route or outgoing interface of the packet.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Postrouting, pkt, gso, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
+	if ok := e.protocol.stack.IPTables().Check(stack.Postrouting, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesPostroutingDropped.Increment()
 		return nil
@@ -432,20 +432,20 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 		return err
 	}
 
-	if packetMustBeFragmented(pkt, networkMTU, gso) {
-		sent, remain, err := e.handleFragments(r, gso, networkMTU, pkt, func(fragPkt *stack.PacketBuffer) tcpip.Error {
+	if packetMustBeFragmented(pkt, networkMTU) {
+		sent, remain, err := e.handleFragments(r, networkMTU, pkt, func(fragPkt *stack.PacketBuffer) tcpip.Error {
 			// TODO(gvisor.dev/issue/3884): Evaluate whether we want to send each
 			// fragment one by one using WritePacket() (current strategy) or if we
 			// want to create a PacketBufferList from the fragments and feed it to
 			// WritePackets(). It'll be faster but cost more memory.
-			return e.nic.WritePacket(r, gso, ProtocolNumber, fragPkt)
+			return e.nic.WritePacket(r, ProtocolNumber, fragPkt)
 		})
 		stats.PacketsSent.IncrementBy(uint64(sent))
 		stats.OutgoingPacketErrors.IncrementBy(uint64(remain))
 		return err
 	}
 
-	if err := e.nic.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
+	if err := e.nic.WritePacket(r, ProtocolNumber, pkt); err != nil {
 		stats.OutgoingPacketErrors.Increment()
 		return err
 	}
@@ -454,7 +454,7 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 }
 
 // WritePackets implements stack.NetworkEndpoint.WritePackets.
-func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
+func (e *endpoint) WritePackets(r *stack.Route, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
 	if r.Loop()&stack.PacketLoop != 0 {
 		panic("multiple packets in local loop")
 	}
@@ -475,11 +475,11 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 			return 0, err
 		}
 
-		if packetMustBeFragmented(pkt, networkMTU, gso) {
+		if packetMustBeFragmented(pkt, networkMTU) {
 			// Keep track of the packet that is about to be fragmented so it can be
 			// removed once the fragmentation is done.
 			originalPkt := pkt
-			if _, _, err := e.handleFragments(r, gso, networkMTU, pkt, func(fragPkt *stack.PacketBuffer) tcpip.Error {
+			if _, _, err := e.handleFragments(r, networkMTU, pkt, func(fragPkt *stack.PacketBuffer) tcpip.Error {
 				// Modify the packet list in place with the new fragments.
 				pkts.InsertAfter(pkt, fragPkt)
 				pkt = fragPkt
@@ -495,7 +495,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
 	// iptables filtering. All packets that reach here are locally
 	// generated.
-	outputDropped, natPkts := e.protocol.stack.IPTables().CheckPackets(stack.Output, pkts, gso, r, "" /* inNicName */, outNicName)
+	outputDropped, natPkts := e.protocol.stack.IPTables().CheckPackets(stack.Output, pkts, r, "" /* inNicName */, outNicName)
 	stats.IPTablesOutputDropped.IncrementBy(uint64(len(outputDropped)))
 	for pkt := range outputDropped {
 		pkts.Remove(pkt)
@@ -522,7 +522,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	// We ignore the list of NAT-ed packets here because Postrouting NAT can only
 	// change the source address, and does not alter the route or outgoing
 	// interface of the packet.
-	postroutingDropped, _ := e.protocol.stack.IPTables().CheckPackets(stack.Postrouting, pkts, gso, r, "" /* inNicName */, outNicName)
+	postroutingDropped, _ := e.protocol.stack.IPTables().CheckPackets(stack.Postrouting, pkts, r, "" /* inNicName */, outNicName)
 	stats.IPTablesPostroutingDropped.IncrementBy(uint64(len(postroutingDropped)))
 	for pkt := range postroutingDropped {
 		pkts.Remove(pkt)
@@ -530,7 +530,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 
 	// The rest of the packets can be delivered to the NIC as a batch.
 	pktsLen := pkts.Len()
-	written, err := e.nic.WritePackets(r, gso, pkts, ProtocolNumber)
+	written, err := e.nic.WritePackets(r, pkts, ProtocolNumber)
 	stats.PacketsSent.IncrementBy(uint64(written))
 	stats.OutgoingPacketErrors.IncrementBy(uint64(pktsLen - written))
 
@@ -595,7 +595,7 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu
 		return &tcpip.ErrMalformedHeader{}
 	}
 
-	return e.writePacket(r, nil /* gso */, pkt, true /* headerIncluded */)
+	return e.writePacket(r, pkt, true /* headerIncluded */)
 }
 
 // forwardPacket attempts to forward a packet to its final destination.
@@ -732,7 +732,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 
 		// Loopback traffic skips the prerouting chain.
 		inNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-		if ok := e.protocol.stack.IPTables().Check(stack.Prerouting, pkt, nil, nil, e.MainAddress().Address, inNicName, "" /* outNicName */); !ok {
+		if ok := e.protocol.stack.IPTables().Check(stack.Prerouting, pkt, nil, e.MainAddress().Address, inNicName, "" /* outNicName */); !ok {
 			// iptables is telling us to drop the packet.
 			stats.IPTablesPreroutingDropped.Increment()
 			return
@@ -805,7 +805,7 @@ func (e *endpoint) handleValidatedPacket(h header.IPv4, pkt *stack.PacketBuffer)
 	// iptables filtering. All packets that reach here are intended for
 	// this machine and will not be forwarded.
 	inNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Input, pkt, nil, nil, "" /* preroutingAddr */, inNicName, "" /* outNicName */); !ok {
+	if ok := e.protocol.stack.IPTables().Check(stack.Input, pkt, nil, "" /* preroutingAddr */, inNicName, "" /* outNicName */); !ok {
 		// iptables is telling us to drop the packet.
 		stats.ip.IPTablesInputDropped.Increment()
 		return
@@ -1258,9 +1258,9 @@ func calculateNetworkMTU(linkMTU, networkHeaderSize uint32) (uint32, tcpip.Error
 	return networkMTU - uint32(networkHeaderSize), nil
 }
 
-func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32, gso *stack.GSO) bool {
+func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32) bool {
 	payload := pkt.TransportHeader().View().Size() + pkt.Data().Size()
-	return (gso == nil || gso.Type == stack.GSONone) && uint32(payload) > networkMTU
+	return pkt.GSOOptions.Type == stack.GSONone && uint32(payload) > networkMTU
 }
 
 // addressToUint32 translates an IPv4 address into its little endian uint32
diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go
index d49dff4d5..7d413c455 100644
--- a/pkg/tcpip/network/ipv4/ipv4_test.go
+++ b/pkg/tcpip/network/ipv4/ipv4_test.go
@@ -1242,7 +1242,6 @@ type fragmentInfo struct {
 var fragmentationTests = []struct {
 	description           string
 	mtu                   uint32
-	gso                   *stack.GSO
 	transportHeaderLength int
 	payloadSize           int
 	wantFragments         []fragmentInfo
@@ -1250,7 +1249,6 @@ var fragmentationTests = []struct {
 	{
 		description:           "No fragmentation",
 		mtu:                   1280,
-		gso:                   nil,
 		transportHeaderLength: 0,
 		payloadSize:           1000,
 		wantFragments: []fragmentInfo{
@@ -1260,7 +1258,6 @@ var fragmentationTests = []struct {
 	{
 		description:           "Fragmented",
 		mtu:                   1280,
-		gso:                   nil,
 		transportHeaderLength: 0,
 		payloadSize:           2000,
 		wantFragments: []fragmentInfo{
@@ -1271,7 +1268,6 @@ var fragmentationTests = []struct {
 	{
 		description:           "Fragmented with the minimum mtu",
 		mtu:                   header.IPv4MinimumMTU,
-		gso:                   nil,
 		transportHeaderLength: 0,
 		payloadSize:           100,
 		wantFragments: []fragmentInfo{
@@ -1283,7 +1279,6 @@ var fragmentationTests = []struct {
 	{
 		description:           "Fragmented with mtu not a multiple of 8",
 		mtu:                   header.IPv4MinimumMTU + 1,
-		gso:                   nil,
 		transportHeaderLength: 0,
 		payloadSize:           100,
 		wantFragments: []fragmentInfo{
@@ -1295,7 +1290,6 @@ var fragmentationTests = []struct {
 	{
 		description:           "No fragmentation with big header",
 		mtu:                   2000,
-		gso:                   nil,
 		transportHeaderLength: 100,
 		payloadSize:           1000,
 		wantFragments: []fragmentInfo{
@@ -1303,20 +1297,8 @@ var fragmentationTests = []struct {
 		},
 	},
 	{
-		description:           "Fragmented with gso none",
-		mtu:                   1280,
-		gso:                   &stack.GSO{Type: stack.GSONone},
-		transportHeaderLength: 0,
-		payloadSize:           1400,
-		wantFragments: []fragmentInfo{
-			{offset: 0, payloadSize: 1256, more: true},
-			{offset: 1256, payloadSize: 144, more: false},
-		},
-	},
-	{
 		description:           "Fragmented with big header",
 		mtu:                   1280,
-		gso:                   nil,
 		transportHeaderLength: 100,
 		payloadSize:           1200,
 		wantFragments: []fragmentInfo{
@@ -1327,7 +1309,6 @@ var fragmentationTests = []struct {
 	{
 		description:           "Fragmented with MTU smaller than header",
 		mtu:                   300,
-		gso:                   nil,
 		transportHeaderLength: 1000,
 		payloadSize:           500,
 		wantFragments: []fragmentInfo{
@@ -1350,13 +1331,13 @@ func TestFragmentationWritePacket(t *testing.T) {
 			r := buildRoute(t, ep)
 			pkt := testutil.MakeRandPkt(ft.transportHeaderLength, extraHeaderReserve+header.IPv4MinimumSize, []int{ft.payloadSize}, header.IPv4ProtocolNumber)
 			source := pkt.Clone()
-			err := r.WritePacket(ft.gso, stack.NetworkHeaderParams{
+			err := r.WritePacket(stack.NetworkHeaderParams{
 				Protocol: tcp.ProtocolNumber,
 				TTL:      ttl,
 				TOS:      stack.DefaultTOS,
 			}, pkt)
 			if err != nil {
-				t.Fatalf("r.WritePacket(_, _, _) = %s", err)
+				t.Fatalf("r.WritePacket(...): %s", err)
 			}
 			if got := len(ep.WrittenPackets); got != len(ft.wantFragments) {
 				t.Errorf("got len(ep.WrittenPackets) = %d, want = %d", got, len(ft.wantFragments))
@@ -1422,7 +1403,7 @@ func TestFragmentationWritePackets(t *testing.T) {
 					r := buildRoute(t, ep)
 
 					wantTotalPackets := len(ft.wantFragments) + test.insertBefore + test.insertAfter
-					n, err := r.WritePackets(ft.gso, pkts, stack.NetworkHeaderParams{
+					n, err := r.WritePackets(pkts, stack.NetworkHeaderParams{
 						Protocol: tcp.ProtocolNumber,
 						TTL:      ttl,
 						TOS:      stack.DefaultTOS,
@@ -1529,7 +1510,7 @@ func TestFragmentationErrors(t *testing.T) {
 			pkt := testutil.MakeRandPkt(ft.transportHeaderLength, extraHeaderReserve+header.IPv4MinimumSize, []int{ft.payloadSize}, header.IPv4ProtocolNumber)
 			ep := testutil.NewMockLinkEndpoint(ft.mtu, ft.mockError, ft.allowPackets)
 			r := buildRoute(t, ep)
-			err := r.WritePacket(&stack.GSO{}, stack.NetworkHeaderParams{
+			err := r.WritePacket(stack.NetworkHeaderParams{
 				Protocol: tcp.ProtocolNumber,
 				TTL:      ttl,
 				TOS:      stack.DefaultTOS,
@@ -2729,7 +2710,7 @@ func TestWriteStats(t *testing.T) {
 			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, tcpip.Error) {
 				nWritten := 0
 				for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
-					if err := rt.WritePacket(nil, stack.NetworkHeaderParams{}, pkt); err != nil {
+					if err := rt.WritePacket(stack.NetworkHeaderParams{}, pkt); err != nil {
 						return nWritten, err
 					}
 					nWritten++
@@ -2739,7 +2720,7 @@ func TestWriteStats(t *testing.T) {
 		}, {
 			name: "WritePackets",
 			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, tcpip.Error) {
-				return rt.WritePackets(nil, pkts, stack.NetworkHeaderParams{})
+				return rt.WritePackets(pkts, stack.NetworkHeaderParams{})
 			},
 		},
 	}
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index b2a80e1e9..1319db32b 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -564,7 +564,7 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer, hasFragmentHeader bool, r
 		//
 		// The IP Hop Limit field has a value of 255, i.e., the packet
 		// could not possibly have been forwarded by a router.
-		if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: header.NDPHopLimit, TOS: stack.DefaultTOS}, pkt); err != nil {
+		if err := r.WritePacket(stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: header.NDPHopLimit, TOS: stack.DefaultTOS}, pkt); err != nil {
 			sent.dropped.Increment()
 			return
 		}
@@ -704,7 +704,7 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer, hasFragmentHeader bool, r
 			PayloadCsum: dataRange.Checksum(),
 			PayloadLen:  dataRange.Size(),
 		}))
-		if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
+		if err := r.WritePacket(stack.NetworkHeaderParams{
 			Protocol: header.ICMPv6ProtocolNumber,
 			TTL:      r.DefaultTTL(),
 			TOS:      stack.DefaultTOS,
@@ -1167,7 +1167,6 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) tcpip
 		PayloadLen:  dataRange.Size(),
 	}))
 	if err := route.WritePacket(
-		nil, /* gso */
 		stack.NetworkHeaderParams{
 			Protocol: header.ICMPv6ProtocolNumber,
 			TTL:      route.DefaultTTL(),
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index 6a7705ed1..e457be3cf 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -81,7 +81,7 @@ func (*stubLinkEndpoint) LinkAddress() tcpip.LinkAddress {
 	return ""
 }
 
-func (*stubLinkEndpoint) WritePacket(stack.RouteInfo, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
+func (*stubLinkEndpoint) WritePacket(stack.RouteInfo, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
 	return nil
 }
 
@@ -130,19 +130,19 @@ func (*testInterface) Spoofing() bool {
 	return false
 }
 
-func (t *testInterface) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
-	return t.LinkEndpoint.WritePacket(r.Fields(), gso, protocol, pkt)
+func (t *testInterface) WritePacket(r *stack.Route, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+	return t.LinkEndpoint.WritePacket(r.Fields(), protocol, pkt)
 }
 
-func (t *testInterface) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
-	return t.LinkEndpoint.WritePackets(r.Fields(), gso, pkts, protocol)
+func (t *testInterface) WritePackets(r *stack.Route, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+	return t.LinkEndpoint.WritePackets(r.Fields(), pkts, protocol)
 }
 
-func (t *testInterface) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+func (t *testInterface) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	var r stack.RouteInfo
 	r.NetProto = protocol
 	r.RemoteLinkAddress = remoteLinkAddr
-	return t.LinkEndpoint.WritePacket(r, gso, protocol, pkt)
+	return t.LinkEndpoint.WritePacket(r, protocol, pkt)
 }
 
 func (t *testInterface) HandleNeighborProbe(tcpip.NetworkProtocolNumber, tcpip.Address, tcpip.LinkAddress) tcpip.Error {
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 2e515379c..f7510c243 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -675,9 +675,9 @@ func addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params
 	return nil
 }
 
-func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32, gso *stack.GSO) bool {
+func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32) bool {
 	payload := pkt.TransportHeader().View().Size() + pkt.Data().Size()
-	return (gso == nil || gso.Type == stack.GSONone) && uint32(payload) > networkMTU
+	return pkt.GSOOptions.Type == stack.GSONone && uint32(payload) > networkMTU
 }
 
 // handleFragments fragments pkt and calls the handler function on each
@@ -685,7 +685,7 @@ func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32, gso *sta
 // fragments left to be processed. The IP header must already be present in the
 // original packet. The transport header protocol number is required to avoid
 // parsing the IPv6 extension headers.
-func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU uint32, pkt *stack.PacketBuffer, transProto tcpip.TransportProtocolNumber, handler func(*stack.PacketBuffer) tcpip.Error) (int, int, tcpip.Error) {
+func (e *endpoint) handleFragments(r *stack.Route, networkMTU uint32, pkt *stack.PacketBuffer, transProto tcpip.TransportProtocolNumber, handler func(*stack.PacketBuffer) tcpip.Error) (int, int, tcpip.Error) {
 	networkHeader := header.IPv6(pkt.NetworkHeader().View())
 
 	// TODO(gvisor.dev/issue/3912): Once the Authentication or ESP Headers are
@@ -724,7 +724,7 @@ func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU ui
 }
 
 // WritePacket writes a packet to the given destination address and protocol.
-func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
+func (e *endpoint) WritePacket(r *stack.Route, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
 	if err := addIPHeader(r.LocalAddress(), r.RemoteAddress(), pkt, params, nil /* extensionHeaders */); err != nil {
 		return err
 	}
@@ -732,7 +732,7 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 	// iptables filtering. All packets that reach here are locally
 	// generated.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Output, pkt, gso, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
+	if ok := e.protocol.stack.IPTables().Check(stack.Output, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesOutputDropped.Increment()
 		return nil
@@ -755,10 +755,10 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 		}
 	}
 
-	return e.writePacket(r, gso, pkt, params.Protocol, false /* headerIncluded */)
+	return e.writePacket(r, pkt, params.Protocol, false /* headerIncluded */)
 }
 
-func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.PacketBuffer, protocol tcpip.TransportProtocolNumber, headerIncluded bool) tcpip.Error {
+func (e *endpoint) writePacket(r *stack.Route, pkt *stack.PacketBuffer, protocol tcpip.TransportProtocolNumber, headerIncluded bool) tcpip.Error {
 	if r.Loop()&stack.PacketLoop != 0 {
 		// If the packet was generated by the stack (not a raw/packet endpoint
 		// where a packet may be written with the header included), then we can
@@ -772,7 +772,7 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 	// Postrouting NAT can only change the source address, and does not alter the
 	// route or outgoing interface of the packet.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Postrouting, pkt, gso, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
+	if ok := e.protocol.stack.IPTables().Check(stack.Postrouting, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesPostroutingDropped.Increment()
 		return nil
@@ -785,20 +785,20 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 		return err
 	}
 
-	if packetMustBeFragmented(pkt, networkMTU, gso) {
-		sent, remain, err := e.handleFragments(r, gso, networkMTU, pkt, protocol, func(fragPkt *stack.PacketBuffer) tcpip.Error {
+	if packetMustBeFragmented(pkt, networkMTU) {
+		sent, remain, err := e.handleFragments(r, networkMTU, pkt, protocol, func(fragPkt *stack.PacketBuffer) tcpip.Error {
 			// TODO(gvisor.dev/issue/3884): Evaluate whether we want to send each
 			// fragment one by one using WritePacket() (current strategy) or if we
 			// want to create a PacketBufferList from the fragments and feed it to
 			// WritePackets(). It'll be faster but cost more memory.
-			return e.nic.WritePacket(r, gso, ProtocolNumber, fragPkt)
+			return e.nic.WritePacket(r, ProtocolNumber, fragPkt)
 		})
 		stats.PacketsSent.IncrementBy(uint64(sent))
 		stats.OutgoingPacketErrors.IncrementBy(uint64(remain))
 		return err
 	}
 
-	if err := e.nic.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
+	if err := e.nic.WritePacket(r, ProtocolNumber, pkt); err != nil {
 		stats.OutgoingPacketErrors.Increment()
 		return err
 	}
@@ -808,7 +808,7 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 }
 
 // WritePackets implements stack.NetworkEndpoint.WritePackets.
-func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
+func (e *endpoint) WritePackets(r *stack.Route, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
 	if r.Loop()&stack.PacketLoop != 0 {
 		panic("not implemented")
 	}
@@ -828,11 +828,11 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 			stats.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len()))
 			return 0, err
 		}
-		if packetMustBeFragmented(pb, networkMTU, gso) {
+		if packetMustBeFragmented(pb, networkMTU) {
 			// Keep track of the packet that is about to be fragmented so it can be
 			// removed once the fragmentation is done.
 			originalPkt := pb
-			if _, _, err := e.handleFragments(r, gso, networkMTU, pb, params.Protocol, func(fragPkt *stack.PacketBuffer) tcpip.Error {
+			if _, _, err := e.handleFragments(r, networkMTU, pb, params.Protocol, func(fragPkt *stack.PacketBuffer) tcpip.Error {
 				// Modify the packet list in place with the new fragments.
 				pkts.InsertAfter(pb, fragPkt)
 				pb = fragPkt
@@ -849,7 +849,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	// iptables filtering. All packets that reach here are locally
 	// generated.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	outputDropped, natPkts := e.protocol.stack.IPTables().CheckPackets(stack.Output, pkts, gso, r, "" /* inNicName */, outNicName)
+	outputDropped, natPkts := e.protocol.stack.IPTables().CheckPackets(stack.Output, pkts, r, "" /* inNicName */, outNicName)
 	stats.IPTablesOutputDropped.IncrementBy(uint64(len(outputDropped)))
 	for pkt := range outputDropped {
 		pkts.Remove(pkt)
@@ -875,7 +875,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 	// We ignore the list of NAT-ed packets here because Postrouting NAT can only
 	// change the source address, and does not alter the route or outgoing
 	// interface of the packet.
-	postroutingDropped, _ := e.protocol.stack.IPTables().CheckPackets(stack.Postrouting, pkts, gso, r, "" /* inNicName */, outNicName)
+	postroutingDropped, _ := e.protocol.stack.IPTables().CheckPackets(stack.Postrouting, pkts, r, "" /* inNicName */, outNicName)
 	stats.IPTablesPostroutingDropped.IncrementBy(uint64(len(postroutingDropped)))
 	for pkt := range postroutingDropped {
 		pkts.Remove(pkt)
@@ -883,7 +883,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 
 	// The rest of the packets can be delivered to the NIC as a batch.
 	pktsLen := pkts.Len()
-	written, err := e.nic.WritePackets(r, gso, pkts, ProtocolNumber)
+	written, err := e.nic.WritePackets(r, pkts, ProtocolNumber)
 	stats.PacketsSent.IncrementBy(uint64(written))
 	stats.OutgoingPacketErrors.IncrementBy(uint64(pktsLen - written))
 
@@ -924,7 +924,7 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu
 		return &tcpip.ErrMalformedHeader{}
 	}
 
-	return e.writePacket(r, nil /* gso */, pkt, proto, true /* headerIncluded */)
+	return e.writePacket(r, pkt, proto, true /* headerIncluded */)
 }
 
 // forwardPacket attempts to forward a packet to its final destination.
@@ -1027,7 +1027,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 
 		// Loopback traffic skips the prerouting chain.
 		inNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-		if ok := e.protocol.stack.IPTables().Check(stack.Prerouting, pkt, nil, nil, e.MainAddress().Address, inNicName, "" /* outNicName */); !ok {
+		if ok := e.protocol.stack.IPTables().Check(stack.Prerouting, pkt, nil, e.MainAddress().Address, inNicName, "" /* outNicName */); !ok {
 			// iptables is telling us to drop the packet.
 			stats.IPTablesPreroutingDropped.Increment()
 			return
@@ -1097,7 +1097,7 @@ func (e *endpoint) handleValidatedPacket(h header.IPv6, pkt *stack.PacketBuffer)
 	// iptables filtering. All packets that reach here are intended for
 	// this machine and need not be forwarded.
 	inNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Input, pkt, nil, nil, "" /* preroutingAddr */, inNicName, "" /* outNicName */); !ok {
+	if ok := e.protocol.stack.IPTables().Check(stack.Input, pkt, nil, "" /* preroutingAddr */, inNicName, "" /* outNicName */); !ok {
 		// iptables is telling us to drop the packet.
 		stats.IPTablesInputDropped.Increment()
 		return
diff --git a/pkg/tcpip/network/ipv6/ipv6_test.go b/pkg/tcpip/network/ipv6/ipv6_test.go
index a620e9ad9..40a793d6b 100644
--- a/pkg/tcpip/network/ipv6/ipv6_test.go
+++ b/pkg/tcpip/network/ipv6/ipv6_test.go
@@ -2584,7 +2584,7 @@ func TestWriteStats(t *testing.T) {
 			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, tcpip.Error) {
 				nWritten := 0
 				for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
-					if err := rt.WritePacket(nil, stack.NetworkHeaderParams{}, pkt); err != nil {
+					if err := rt.WritePacket(stack.NetworkHeaderParams{}, pkt); err != nil {
 						return nWritten, err
 					}
 					nWritten++
@@ -2594,7 +2594,7 @@ func TestWriteStats(t *testing.T) {
 		}, {
 			name: "WritePackets",
 			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, tcpip.Error) {
-				return rt.WritePackets(nil, pkts, stack.NetworkHeaderParams{})
+				return rt.WritePackets(pkts, stack.NetworkHeaderParams{})
 			},
 		},
 	}
@@ -2739,7 +2739,6 @@ type fragmentInfo struct {
 var fragmentationTests = []struct {
 	description   string
 	mtu           uint32
-	gso           *stack.GSO
 	transHdrLen   int
 	payloadSize   int
 	wantFragments []fragmentInfo
@@ -2747,7 +2746,6 @@ var fragmentationTests = []struct {
 	{
 		description: "No fragmentation",
 		mtu:         header.IPv6MinimumMTU,
-		gso:         nil,
 		transHdrLen: 0,
 		payloadSize: 1000,
 		wantFragments: []fragmentInfo{
@@ -2757,7 +2755,6 @@ var fragmentationTests = []struct {
 	{
 		description: "Fragmented",
 		mtu:         header.IPv6MinimumMTU,
-		gso:         nil,
 		transHdrLen: 0,
 		payloadSize: 2000,
 		wantFragments: []fragmentInfo{
@@ -2768,7 +2765,6 @@ var fragmentationTests = []struct {
 	{
 		description: "Fragmented with mtu not a multiple of 8",
 		mtu:         header.IPv6MinimumMTU + 1,
-		gso:         nil,
 		transHdrLen: 0,
 		payloadSize: 2000,
 		wantFragments: []fragmentInfo{
@@ -2779,7 +2775,6 @@ var fragmentationTests = []struct {
 	{
 		description: "No fragmentation with big header",
 		mtu:         2000,
-		gso:         nil,
 		transHdrLen: 100,
 		payloadSize: 1000,
 		wantFragments: []fragmentInfo{
@@ -2787,20 +2782,8 @@ var fragmentationTests = []struct {
 		},
 	},
 	{
-		description: "Fragmented with gso none",
-		mtu:         header.IPv6MinimumMTU,
-		gso:         &stack.GSO{Type: stack.GSONone},
-		transHdrLen: 0,
-		payloadSize: 1400,
-		wantFragments: []fragmentInfo{
-			{offset: 0, payloadSize: 1240, more: true},
-			{offset: 154, payloadSize: 176, more: false},
-		},
-	},
-	{
 		description: "Fragmented with big header",
 		mtu:         header.IPv6MinimumMTU,
-		gso:         nil,
 		transHdrLen: 100,
 		payloadSize: 1200,
 		wantFragments: []fragmentInfo{
@@ -2823,7 +2806,7 @@ func TestFragmentationWritePacket(t *testing.T) {
 			source := pkt.Clone()
 			ep := testutil.NewMockLinkEndpoint(ft.mtu, nil, math.MaxInt32)
 			r := buildRoute(t, ep)
-			err := r.WritePacket(ft.gso, stack.NetworkHeaderParams{
+			err := r.WritePacket(stack.NetworkHeaderParams{
 				Protocol: tcp.ProtocolNumber,
 				TTL:      ttl,
 				TOS:      stack.DefaultTOS,
@@ -2896,7 +2879,7 @@ func TestFragmentationWritePackets(t *testing.T) {
 					r := buildRoute(t, ep)
 
 					wantTotalPackets := len(ft.wantFragments) + test.insertBefore + test.insertAfter
-					n, err := r.WritePackets(ft.gso, pkts, stack.NetworkHeaderParams{
+					n, err := r.WritePackets(pkts, stack.NetworkHeaderParams{
 						Protocol: tcp.ProtocolNumber,
 						TTL:      ttl,
 						TOS:      stack.DefaultTOS,
@@ -3000,7 +2983,7 @@ func TestFragmentationErrors(t *testing.T) {
 			pkt := testutil.MakeRandPkt(ft.transHdrLen, extraHeaderReserve+header.IPv6MinimumSize, []int{ft.payloadSize}, header.IPv6ProtocolNumber)
 			ep := testutil.NewMockLinkEndpoint(ft.mtu, ft.mockError, ft.allowPackets)
 			r := buildRoute(t, ep)
-			err := r.WritePacket(&stack.GSO{}, stack.NetworkHeaderParams{
+			err := r.WritePacket(stack.NetworkHeaderParams{
 				Protocol: tcp.ProtocolNumber,
 				TTL:      ttl,
 				TOS:      stack.DefaultTOS,
diff --git a/pkg/tcpip/network/ipv6/mld.go b/pkg/tcpip/network/ipv6/mld.go
index 165b7d2d2..bc1af193c 100644
--- a/pkg/tcpip/network/ipv6/mld.go
+++ b/pkg/tcpip/network/ipv6/mld.go
@@ -277,7 +277,7 @@ func (mld *mldState) writePacket(destAddress, groupAddress tcpip.Address, mldTyp
 	}, extensionHeaders); err != nil {
 		panic(fmt.Sprintf("failed to add IP header: %s", err))
 	}
-	if err := mld.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv6Address(destAddress), nil /* gso */, ProtocolNumber, pkt); err != nil {
+	if err := mld.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv6Address(destAddress), ProtocolNumber, pkt); err != nil {
 		sentStats.dropped.Increment()
 		return false, err
 	}
diff --git a/pkg/tcpip/network/ipv6/ndp.go b/pkg/tcpip/network/ipv6/ndp.go
index a110faa54..d6e0a81a6 100644
--- a/pkg/tcpip/network/ipv6/ndp.go
+++ b/pkg/tcpip/network/ipv6/ndp.go
@@ -1746,7 +1746,7 @@ func (ndp *ndpState) startSolicitingRouters() {
 				panic(fmt.Sprintf("failed to add IP header: %s", err))
 			}
 
-			if err := ndp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv6Address(header.IPv6AllRoutersLinkLocalMulticastAddress), nil /* gso */, ProtocolNumber, pkt); err != nil {
+			if err := ndp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv6Address(header.IPv6AllRoutersLinkLocalMulticastAddress), ProtocolNumber, pkt); err != nil {
 				sent.dropped.Increment()
 				// Don't send any more messages if we had an error.
 				remaining = 0
@@ -1839,7 +1839,7 @@ func (e *endpoint) sendNDPNS(srcAddr, dstAddr, targetAddr tcpip.Address, remoteL
 	}
 
 	sent := e.stats.icmp.packetsSent
-	err := e.nic.WritePacketToRemote(remoteLinkAddr, nil /* gso */, ProtocolNumber, pkt)
+	err := e.nic.WritePacketToRemote(remoteLinkAddr, ProtocolNumber, pkt)
 	if err != nil {
 		sent.dropped.Increment()
 	} else {
diff --git a/pkg/tcpip/stack/conntrack.go b/pkg/tcpip/stack/conntrack.go
index 41e964cf3..5720e7543 100644
--- a/pkg/tcpip/stack/conntrack.go
+++ b/pkg/tcpip/stack/conntrack.go
@@ -372,7 +372,7 @@ func (ct *ConnTrack) insertConn(conn *conn) {
 // handlePacket will manipulate the port and address of the packet if the
 // connection exists. Returns whether, after the packet traverses the tables,
 // it should create a new entry in the table.
-func (ct *ConnTrack) handlePacket(pkt *PacketBuffer, hook Hook, gso *GSO, r *Route) bool {
+func (ct *ConnTrack) handlePacket(pkt *PacketBuffer, hook Hook, r *Route) bool {
 	if pkt.NatDone {
 		return false
 	}
@@ -446,7 +446,7 @@ func (ct *ConnTrack) handlePacket(pkt *PacketBuffer, hook Hook, gso *GSO, r *Rou
 		tcpHeader.SetChecksum(0)
 		length := uint16(len(tcpHeader) + pkt.Data().Size())
 		xsum := header.PseudoHeaderChecksum(header.TCPProtocolNumber, netHeader.SourceAddress(), netHeader.DestinationAddress(), length)
-		if gso != nil && gso.NeedsCsum {
+		if pkt.GSOOptions.Type != GSONone && pkt.GSOOptions.NeedsCsum {
 			tcpHeader.SetChecksum(xsum)
 		} else if r.RequiresTXTransportChecksum() {
 			xsum = header.ChecksumCombine(xsum, pkt.Data().AsRange().Checksum())
diff --git a/pkg/tcpip/stack/forwarding_test.go b/pkg/tcpip/stack/forwarding_test.go
index 16ee75bc4..2d74e0abc 100644
--- a/pkg/tcpip/stack/forwarding_test.go
+++ b/pkg/tcpip/stack/forwarding_test.go
@@ -117,7 +117,7 @@ func (f *fwdTestNetworkEndpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNu
 	return f.proto.Number()
 }
 
-func (f *fwdTestNetworkEndpoint) WritePacket(r *Route, gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
+func (f *fwdTestNetworkEndpoint) WritePacket(r *Route, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
 	// Add the protocol's header to the packet and send it to the link
 	// endpoint.
 	b := pkt.NetworkHeader().Push(fwdTestNetHeaderLen)
@@ -125,11 +125,11 @@ func (f *fwdTestNetworkEndpoint) WritePacket(r *Route, gso *GSO, params NetworkH
 	b[srcAddrOffset] = r.LocalAddress()[0]
 	b[protocolNumberOffset] = byte(params.Protocol)
 
-	return f.nic.WritePacket(r, gso, fwdTestNetNumber, pkt)
+	return f.nic.WritePacket(r, fwdTestNetNumber, pkt)
 }
 
 // WritePackets implements LinkEndpoint.WritePackets.
-func (*fwdTestNetworkEndpoint) WritePackets(r *Route, gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
+func (*fwdTestNetworkEndpoint) WritePackets(r *Route, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
@@ -139,7 +139,7 @@ func (f *fwdTestNetworkEndpoint) WriteHeaderIncludedPacket(r *Route, pkt *Packet
 		return &tcpip.ErrMalformedHeader{}
 	}
 
-	return f.nic.WritePacket(r, nil /* gso */, fwdTestNetNumber, pkt)
+	return f.nic.WritePacket(r, fwdTestNetNumber, pkt)
 }
 
 func (f *fwdTestNetworkEndpoint) Close() {
@@ -322,7 +322,7 @@ func (e *fwdTestLinkEndpoint) LinkAddress() tcpip.LinkAddress {
 	return e.linkAddr
 }
 
-func (e fwdTestLinkEndpoint) WritePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
+func (e fwdTestLinkEndpoint) WritePacket(r RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	p := fwdTestPacketInfo{
 		RemoteLinkAddress: r.RemoteLinkAddress,
 		LocalLinkAddress:  r.LocalLinkAddress,
@@ -338,10 +338,10 @@ func (e fwdTestLinkEndpoint) WritePacket(r RouteInfo, gso *GSO, protocol tcpip.N
 }
 
 // WritePackets stores outbound packets into the channel.
-func (e *fwdTestLinkEndpoint) WritePackets(r RouteInfo, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+func (e *fwdTestLinkEndpoint) WritePackets(r RouteInfo, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	n := 0
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
-		e.WritePacket(r, gso, protocol, pkt)
+		e.WritePacket(r, protocol, pkt)
 		n++
 	}
 
diff --git a/pkg/tcpip/stack/iptables.go b/pkg/tcpip/stack/iptables.go
index 7ea87d325..e2894c548 100644
--- a/pkg/tcpip/stack/iptables.go
+++ b/pkg/tcpip/stack/iptables.go
@@ -267,12 +267,12 @@ const (
 // should continue traversing the network stack and false when it should be
 // dropped.
 //
-// TODO(gvisor.dev/issue/170): PacketBuffer should hold the GSO and route, from
+// TODO(gvisor.dev/issue/170): PacketBuffer should hold the route, from
 // which address can be gathered. Currently, address is only needed for
 // prerouting.
 //
 // Precondition: pkt.NetworkHeader is set.
-func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) bool {
+func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) bool {
 	if pkt.NetworkProtocolNumber != header.IPv4ProtocolNumber && pkt.NetworkProtocolNumber != header.IPv6ProtocolNumber {
 		return true
 	}
@@ -286,7 +286,7 @@ func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, prer
 
 	// Packets are manipulated only if connection and matching
 	// NAT rule exists.
-	shouldTrack := it.connections.handlePacket(pkt, hook, gso, r)
+	shouldTrack := it.connections.handlePacket(pkt, hook, r)
 
 	// Go through each table containing the hook.
 	priorities := it.priorities[hook]
@@ -303,7 +303,7 @@ func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, prer
 			table = it.v4Tables[tableID]
 		}
 		ruleIdx := table.BuiltinChains[hook]
-		switch verdict := it.checkChain(hook, pkt, table, ruleIdx, gso, r, preroutingAddr, inNicName, outNicName); verdict {
+		switch verdict := it.checkChain(hook, pkt, table, ruleIdx, r, preroutingAddr, inNicName, outNicName); verdict {
 		// If the table returns Accept, move on to the next table.
 		case chainAccept:
 			continue
@@ -314,7 +314,7 @@ func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, gso *GSO, r *Route, prer
 			// Any Return from a built-in chain means we have to
 			// call the underflow.
 			underflow := table.Rules[table.Underflows[hook]]
-			switch v, _ := underflow.Target.Action(pkt, &it.connections, hook, gso, r, preroutingAddr); v {
+			switch v, _ := underflow.Target.Action(pkt, &it.connections, hook, r, preroutingAddr); v {
 			case RuleAccept:
 				continue
 			case RuleDrop:
@@ -386,10 +386,10 @@ func (it *IPTables) startReaper(interval time.Duration) {
 //
 // NOTE: unlike the Check API the returned map contains packets that should be
 // dropped.
-func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList, gso *GSO, r *Route, inNicName, outNicName string) (drop map[*PacketBuffer]struct{}, natPkts map[*PacketBuffer]struct{}) {
+func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList, r *Route, inNicName, outNicName string) (drop map[*PacketBuffer]struct{}, natPkts map[*PacketBuffer]struct{}) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		if !pkt.NatDone {
-			if ok := it.Check(hook, pkt, gso, r, "", inNicName, outNicName); !ok {
+			if ok := it.Check(hook, pkt, r, "", inNicName, outNicName); !ok {
 				if drop == nil {
 					drop = make(map[*PacketBuffer]struct{})
 				}
@@ -409,11 +409,11 @@ func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList, gso *GSO, r *
 // Preconditions:
 // * pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
 // * pkt.NetworkHeader is not nil.
-func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, gso *GSO, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) chainVerdict {
+func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) chainVerdict {
 	// Start from ruleIdx and walk the list of rules until a rule gives us
 	// a verdict.
 	for ruleIdx < len(table.Rules) {
-		switch verdict, jumpTo := it.checkRule(hook, pkt, table, ruleIdx, gso, r, preroutingAddr, inNicName, outNicName); verdict {
+		switch verdict, jumpTo := it.checkRule(hook, pkt, table, ruleIdx, r, preroutingAddr, inNicName, outNicName); verdict {
 		case RuleAccept:
 			return chainAccept
 
@@ -430,7 +430,7 @@ func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleId
 				ruleIdx++
 				continue
 			}
-			switch verdict := it.checkChain(hook, pkt, table, jumpTo, gso, r, preroutingAddr, inNicName, outNicName); verdict {
+			switch verdict := it.checkChain(hook, pkt, table, jumpTo, r, preroutingAddr, inNicName, outNicName); verdict {
 			case chainAccept:
 				return chainAccept
 			case chainDrop:
@@ -456,7 +456,7 @@ func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleId
 // Preconditions:
 // * pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
 // * pkt.NetworkHeader is not nil.
-func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, gso *GSO, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) (RuleVerdict, int) {
+func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) (RuleVerdict, int) {
 	rule := table.Rules[ruleIdx]
 
 	// Check whether the packet matches the IP header filter.
@@ -479,7 +479,7 @@ func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx
 	}
 
 	// All the matchers matched, so run the target.
-	return rule.Target.Action(pkt, &it.connections, hook, gso, r, preroutingAddr)
+	return rule.Target.Action(pkt, &it.connections, hook, r, preroutingAddr)
 }
 
 // OriginalDst returns the original destination of redirected connections. It
diff --git a/pkg/tcpip/stack/iptables_targets.go b/pkg/tcpip/stack/iptables_targets.go
index 317efe754..2812c89aa 100644
--- a/pkg/tcpip/stack/iptables_targets.go
+++ b/pkg/tcpip/stack/iptables_targets.go
@@ -29,7 +29,7 @@ type AcceptTarget struct {
 }
 
 // Action implements Target.Action.
-func (*AcceptTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*AcceptTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	return RuleAccept, 0
 }
 
@@ -40,7 +40,7 @@ type DropTarget struct {
 }
 
 // Action implements Target.Action.
-func (*DropTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*DropTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	return RuleDrop, 0
 }
 
@@ -52,7 +52,7 @@ type ErrorTarget struct {
 }
 
 // Action implements Target.Action.
-func (*ErrorTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*ErrorTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	log.Debugf("ErrorTarget triggered.")
 	return RuleDrop, 0
 }
@@ -67,7 +67,7 @@ type UserChainTarget struct {
 }
 
 // Action implements Target.Action.
-func (*UserChainTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*UserChainTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	panic("UserChainTarget should never be called.")
 }
 
@@ -79,7 +79,7 @@ type ReturnTarget struct {
 }
 
 // Action implements Target.Action.
-func (*ReturnTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*ReturnTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
 	return RuleReturn, 0
 }
 
@@ -103,7 +103,7 @@ type RedirectTarget struct {
 // TODO(gvisor.dev/issue/170): Parse headers without copying. The current
 // implementation only works for Prerouting and calls pkt.Clone(), neither
 // of which should be the case.
-func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gso *GSO, r *Route, address tcpip.Address) (RuleVerdict, int) {
+func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r *Route, address tcpip.Address) (RuleVerdict, int) {
 	// Sanity check.
 	if rt.NetworkProtocol != pkt.NetworkProtocolNumber {
 		panic(fmt.Sprintf(
@@ -174,7 +174,7 @@ func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gs
 		// packet of the connection comes here. Other packets will be
 		// manipulated in connection tracking.
 		if conn := ct.insertRedirectConn(pkt, hook, rt.Port, address); conn != nil {
-			ct.handlePacket(pkt, hook, gso, r)
+			ct.handlePacket(pkt, hook, r)
 		}
 	default:
 		return RuleDrop, 0
@@ -194,7 +194,7 @@ type SNATTarget struct {
 }
 
 // Action implements Target.Action.
-func (st *SNATTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gso *GSO, r *Route, address tcpip.Address) (RuleVerdict, int) {
+func (st *SNATTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r *Route, address tcpip.Address) (RuleVerdict, int) {
 	// Sanity check.
 	if st.NetworkProtocol != pkt.NetworkProtocolNumber {
 		panic(fmt.Sprintf(
@@ -252,7 +252,7 @@ func (st *SNATTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gso *G
 		// packet of the connection comes here. Other packets will be
 		// manipulated in connection tracking.
 		if conn := ct.insertSNATConn(pkt, hook, st.Port, st.Addr); conn != nil {
-			ct.handlePacket(pkt, hook, gso, r)
+			ct.handlePacket(pkt, hook, r)
 		}
 	default:
 		return RuleDrop, 0
diff --git a/pkg/tcpip/stack/iptables_types.go b/pkg/tcpip/stack/iptables_types.go
index b0d84befb..4631ab93f 100644
--- a/pkg/tcpip/stack/iptables_types.go
+++ b/pkg/tcpip/stack/iptables_types.go
@@ -345,5 +345,5 @@ type Target interface {
 	// Action takes an action on the packet and returns a verdict on how
 	// traversal should (or should not) continue. If the return value is
 	// Jump, it also returns the index of the rule to jump to.
-	Action(packet *PacketBuffer, connections *ConnTrack, hook Hook, gso *GSO, r *Route, address tcpip.Address) (RuleVerdict, int)
+	Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int)
 }
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index ca15c0691..8d615500f 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -316,30 +316,30 @@ func (n *nic) IsLoopback() bool {
 }
 
 // WritePacket implements NetworkLinkEndpoint.
-func (n *nic) WritePacket(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
-	_, err := n.enqueuePacketBuffer(r, gso, protocol, pkt)
+func (n *nic) WritePacket(r *Route, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
+	_, err := n.enqueuePacketBuffer(r, protocol, pkt)
 	return err
 }
 
-func (n *nic) writePacketBuffer(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
+func (n *nic) writePacketBuffer(r RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
 	switch pkt := pkt.(type) {
 	case *PacketBuffer:
-		if err := n.writePacket(r, gso, protocol, pkt); err != nil {
+		if err := n.writePacket(r, protocol, pkt); err != nil {
 			return 0, err
 		}
 		return 1, nil
 	case *PacketBufferList:
-		return n.writePackets(r, gso, protocol, *pkt)
+		return n.writePackets(r, protocol, *pkt)
 	default:
 		panic(fmt.Sprintf("unrecognized pending packet buffer type = %T", pkt))
 	}
 }
 
-func (n *nic) enqueuePacketBuffer(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
+func (n *nic) enqueuePacketBuffer(r *Route, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
 	routeInfo, _, err := r.resolvedFields(nil)
 	switch err.(type) {
 	case nil:
-		return n.writePacketBuffer(routeInfo, gso, protocol, pkt)
+		return n.writePacketBuffer(routeInfo, protocol, pkt)
 	case *tcpip.ErrWouldBlock:
 		// As per relevant RFCs, we should queue packets while we wait for link
 		// resolution to complete.
@@ -358,28 +358,27 @@ func (n *nic) enqueuePacketBuffer(r *Route, gso *GSO, protocol tcpip.NetworkProt
 		//   SHOULD be limited to some small value. When a queue overflows, the new
 		//   arrival SHOULD replace the oldest entry. Once address resolution
 		//   completes, the node transmits any queued packets.
-		return n.linkResQueue.enqueue(r, gso, protocol, pkt)
+		return n.linkResQueue.enqueue(r, protocol, pkt)
 	default:
 		return 0, err
 	}
 }
 
 // WritePacketToRemote implements NetworkInterface.
-func (n *nic) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
+func (n *nic) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	var r RouteInfo
 	r.NetProto = protocol
 	r.RemoteLinkAddress = remoteLinkAddr
-	return n.writePacket(r, gso, protocol, pkt)
+	return n.writePacket(r, protocol, pkt)
 }
 
-func (n *nic) writePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
+func (n *nic) writePacket(r RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	// WritePacket takes ownership of pkt, calculate numBytes first.
 	numBytes := pkt.Size()
 
 	pkt.EgressRoute = r
-	pkt.GSOOptions = gso
 	pkt.NetworkProtocolNumber = protocol
-	if err := n.LinkEndpoint.WritePacket(r, gso, protocol, pkt); err != nil {
+	if err := n.LinkEndpoint.WritePacket(r, protocol, pkt); err != nil {
 		return err
 	}
 
@@ -389,18 +388,17 @@ func (n *nic) writePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolN
 }
 
 // WritePackets implements NetworkLinkEndpoint.
-func (n *nic) WritePackets(r *Route, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
-	return n.enqueuePacketBuffer(r, gso, protocol, &pkts)
+func (n *nic) WritePackets(r *Route, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+	return n.enqueuePacketBuffer(r, protocol, &pkts)
 }
 
-func (n *nic) writePackets(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkts PacketBufferList) (int, tcpip.Error) {
+func (n *nic) writePackets(r RouteInfo, protocol tcpip.NetworkProtocolNumber, pkts PacketBufferList) (int, tcpip.Error) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		pkt.EgressRoute = r
-		pkt.GSOOptions = gso
 		pkt.NetworkProtocolNumber = protocol
 	}
 
-	writtenPackets, err := n.LinkEndpoint.WritePackets(r, gso, pkts, protocol)
+	writtenPackets, err := n.LinkEndpoint.WritePackets(r, pkts, protocol)
 	n.stats.Tx.Packets.IncrementBy(uint64(writtenPackets))
 	writtenBytes := 0
 	for i, pb := 0, pkts.Front(); i < writtenPackets && pb != nil; i, pb = i+1, pb.Next() {
diff --git a/pkg/tcpip/stack/nic_test.go b/pkg/tcpip/stack/nic_test.go
index c0f956e53..8a3005295 100644
--- a/pkg/tcpip/stack/nic_test.go
+++ b/pkg/tcpip/stack/nic_test.go
@@ -65,12 +65,12 @@ func (e *testIPv6Endpoint) MaxHeaderLength() uint16 {
 }
 
 // WritePacket implements NetworkEndpoint.WritePacket.
-func (*testIPv6Endpoint) WritePacket(*Route, *GSO, NetworkHeaderParams, *PacketBuffer) tcpip.Error {
+func (*testIPv6Endpoint) WritePacket(*Route, NetworkHeaderParams, *PacketBuffer) tcpip.Error {
 	return nil
 }
 
 // WritePackets implements NetworkEndpoint.WritePackets.
-func (*testIPv6Endpoint) WritePackets(*Route, *GSO, PacketBufferList, NetworkHeaderParams) (int, tcpip.Error) {
+func (*testIPv6Endpoint) WritePackets(*Route, PacketBufferList, NetworkHeaderParams) (int, tcpip.Error) {
 	// Our tests don't use this so we don't support it.
 	return 0, &tcpip.ErrNotSupported{}
 }
diff --git a/pkg/tcpip/stack/packet_buffer.go b/pkg/tcpip/stack/packet_buffer.go
index c10304d5f..646979d1e 100644
--- a/pkg/tcpip/stack/packet_buffer.go
+++ b/pkg/tcpip/stack/packet_buffer.go
@@ -103,7 +103,7 @@ type PacketBuffer struct {
 	// The following fields are only set by the qdisc layer when the packet
 	// is added to a queue.
 	EgressRoute RouteInfo
-	GSOOptions  *GSO
+	GSOOptions  GSO
 
 	// NatDone indicates if the packet has been manipulated as per NAT
 	// iptables rule.
diff --git a/pkg/tcpip/stack/pending_packets.go b/pkg/tcpip/stack/pending_packets.go
index e936aa728..13e8907ec 100644
--- a/pkg/tcpip/stack/pending_packets.go
+++ b/pkg/tcpip/stack/pending_packets.go
@@ -46,7 +46,6 @@ func (p *PacketBufferList) len() int {
 
 type pendingPacket struct {
 	routeInfo RouteInfo
-	gso       *GSO
 	proto     tcpip.NetworkProtocolNumber
 	pkt       pendingPacketBuffer
 }
@@ -119,7 +118,7 @@ func (f *packetsPendingLinkResolution) dequeue(ch <-chan struct{}, linkAddr tcpi
 // If the maximum number of pending resolutions is reached, the packets
 // associated with the oldest link resolution will be dequeued as if they failed
 // link resolution.
-func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
+func (f *packetsPendingLinkResolution) enqueue(r *Route, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
 	f.mu.Lock()
 	// Make sure we attempt resolution while holding f's lock so that we avoid
 	// a race where link resolution completes before we enqueue the packets.
@@ -137,7 +136,7 @@ func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.N
 		// The route resolved immediately, so we don't need to wait for link
 		// resolution to send the packet.
 		f.mu.Unlock()
-		return f.nic.writePacketBuffer(routeInfo, gso, proto, pkt)
+		return f.nic.writePacketBuffer(routeInfo, proto, pkt)
 	case *tcpip.ErrWouldBlock:
 		// We need to wait for link resolution to complete.
 	default:
@@ -150,7 +149,6 @@ func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.N
 	packets, ok := f.mu.packets[ch]
 	packets = append(packets, pendingPacket{
 		routeInfo: routeInfo,
-		gso:       gso,
 		proto:     proto,
 		pkt:       pkt,
 	})
@@ -211,7 +209,7 @@ func (f *packetsPendingLinkResolution) dequeuePackets(packets []pendingPacket, l
 	for _, p := range packets {
 		if err == nil {
 			p.routeInfo.RemoteLinkAddress = linkAddr
-			_, _ = f.nic.writePacketBuffer(p.routeInfo, p.gso, p.proto, p.pkt)
+			_, _ = f.nic.writePacketBuffer(p.routeInfo, p.proto, p.pkt)
 		} else {
 			f.incrementOutgoingPacketErrors(p.proto, p.pkt)
 
diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go
index ff3a385e1..7ad206f6d 100644
--- a/pkg/tcpip/stack/registration.go
+++ b/pkg/tcpip/stack/registration.go
@@ -537,14 +537,14 @@ type NetworkInterface interface {
 	CheckLocalAddress(tcpip.NetworkProtocolNumber, tcpip.Address) bool
 
 	// WritePacketToRemote writes the packet to the given remote link address.
-	WritePacketToRemote(tcpip.LinkAddress, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
+	WritePacketToRemote(tcpip.LinkAddress, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
 
 	// WritePacket writes a packet with the given protocol through the given
 	// route.
 	//
 	// WritePacket takes ownership of the packet buffer. The packet buffer's
 	// network and transport header must be set.
-	WritePacket(*Route, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
+	WritePacket(*Route, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
 
 	// WritePackets writes packets with the given protocol through the given
 	// route. Must not be called with an empty list of packet buffers.
@@ -554,7 +554,7 @@ type NetworkInterface interface {
 	// Right now, WritePackets is used only when the software segmentation
 	// offload is enabled. If it will be used for something else, syscall filters
 	// may need to be updated.
-	WritePackets(*Route, *GSO, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
+	WritePackets(*Route, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
 
 	// HandleNeighborProbe processes an incoming neighbor probe (e.g. ARP
 	// request or NDP Neighbor Solicitation).
@@ -610,12 +610,12 @@ type NetworkEndpoint interface {
 	// WritePacket writes a packet to the given destination address and
 	// protocol. It takes ownership of pkt. pkt.TransportHeader must have
 	// already been set.
-	WritePacket(r *Route, gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error
+	WritePacket(r *Route, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error
 
 	// WritePackets writes packets to the given destination address and
 	// protocol. pkts must not be zero length. It takes ownership of pkts and
 	// underlying packets.
-	WritePackets(r *Route, gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error)
+	WritePackets(r *Route, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error)
 
 	// WriteHeaderIncludedPacket writes a packet that includes a network
 	// header to the given destination address. It takes ownership of pkt.
@@ -832,7 +832,7 @@ type LinkEndpoint interface {
 	// To participate in transparent bridging, a LinkEndpoint implementation
 	// should call eth.Encode with header.EthernetFields.SrcAddr set to
 	// r.LocalLinkAddress if it is provided.
-	WritePacket(RouteInfo, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
+	WritePacket(RouteInfo, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
 
 	// WritePackets writes packets with the given protocol and route. Must not be
 	// called with an empty list of packet buffers.
@@ -842,7 +842,7 @@ type LinkEndpoint interface {
 	// Right now, WritePackets is used only when the software segmentation
 	// offload is enabled. If it will be used for something else, syscall filters
 	// may need to be updated.
-	WritePackets(RouteInfo, *GSO, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
+	WritePackets(RouteInfo, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
 }
 
 // InjectableLinkEndpoint is a LinkEndpoint where inbound packets are
diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index 4ae6bed5a..4ecde5995 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -448,22 +448,22 @@ func (r *Route) isValidForOutgoingRLocked() bool {
 }
 
 // WritePacket writes the packet through the given route.
-func (r *Route) WritePacket(gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
+func (r *Route) WritePacket(params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
 	if !r.isValidForOutgoing() {
 		return &tcpip.ErrInvalidEndpointState{}
 	}
 
-	return r.outgoingNIC.getNetworkEndpoint(r.NetProto()).WritePacket(r, gso, params, pkt)
+	return r.outgoingNIC.getNetworkEndpoint(r.NetProto()).WritePacket(r, params, pkt)
 }
 
 // WritePackets writes a list of n packets through the given route and returns
 // the number of packets written.
-func (r *Route) WritePackets(gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
+func (r *Route) WritePackets(pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
 	if !r.isValidForOutgoing() {
 		return 0, &tcpip.ErrInvalidEndpointState{}
 	}
 
-	return r.outgoingNIC.getNetworkEndpoint(r.NetProto()).WritePackets(r, gso, pkts, params)
+	return r.outgoingNIC.getNetworkEndpoint(r.NetProto()).WritePackets(r, pkts, params)
 }
 
 // WriteHeaderIncludedPacket writes a packet already containing a network
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index 21cfbad71..843118b13 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -1573,7 +1573,7 @@ func (s *Stack) WritePacketToRemote(nicID tcpip.NICID, remote tcpip.LinkAddress,
 		ReserveHeaderBytes: int(nic.MaxHeaderLength()),
 		Data:               payload,
 	})
-	return nic.WritePacketToRemote(remote, nil, netProto, pkt)
+	return nic.WritePacketToRemote(remote, netProto, pkt)
 }
 
 // NetworkProtocolInstance returns the protocol instance in the stack for the
diff --git a/pkg/tcpip/stack/stack_test.go b/pkg/tcpip/stack/stack_test.go
index a0bd69d9a..8ead3b8df 100644
--- a/pkg/tcpip/stack/stack_test.go
+++ b/pkg/tcpip/stack/stack_test.go
@@ -171,7 +171,7 @@ func (f *fakeNetworkEndpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumbe
 	return f.proto.Number()
 }
 
-func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
+func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
 	// Increment the sent packet count in the protocol descriptor.
 	f.proto.sendPacketCount[int(r.RemoteAddress()[0])%len(f.proto.sendPacketCount)]++
 
@@ -190,11 +190,11 @@ func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, params
 		return nil
 	}
 
-	return f.nic.WritePacket(r, gso, fakeNetNumber, pkt)
+	return f.nic.WritePacket(r, fakeNetNumber, pkt)
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (*fakeNetworkEndpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
+func (*fakeNetworkEndpoint) WritePackets(r *stack.Route, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
@@ -437,7 +437,7 @@ func sendTo(s *stack.Stack, addr tcpip.Address, payload buffer.View) tcpip.Error
 }
 
 func send(r *stack.Route, payload buffer.View) tcpip.Error {
-	return r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: fakeTransNumber, TTL: 123, TOS: stack.DefaultTOS}, stack.NewPacketBuffer(stack.PacketBufferOptions{
+	return r.WritePacket(stack.NetworkHeaderParams{Protocol: fakeTransNumber, TTL: 123, TOS: stack.DefaultTOS}, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		ReserveHeaderBytes: int(r.MaxHeaderLength()),
 		Data:               payload.ToVectorisedView(),
 	}))
@@ -1462,7 +1462,7 @@ func TestExternalSendWithHandleLocal(t *testing.T) {
 					if n := ep.Drain(); n != 0 {
 						t.Fatalf("got ep.Drain() = %d, want = 0", n)
 					}
-					if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
+					if err := r.WritePacket(stack.NetworkHeaderParams{
 						Protocol: fakeTransNumber,
 						TTL:      123,
 						TOS:      stack.DefaultTOS,
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index 0adedd7c0..839178809 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -106,7 +106,7 @@ func (f *fakeTransportEndpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions
 		Data:               buffer.View(v).ToVectorisedView(),
 	})
 	_ = pkt.TransportHeader().Push(fakeTransHeaderLen)
-	if err := f.route.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: fakeTransNumber, TTL: 123, TOS: stack.DefaultTOS}, pkt); err != nil {
+	if err := f.route.WritePacket(stack.NetworkHeaderParams{Protocol: fakeTransNumber, TTL: 123, TOS: stack.DefaultTOS}, pkt); err != nil {
 		return 0, err
 	}
 
diff --git a/pkg/tcpip/tests/integration/iptables_test.go b/pkg/tcpip/tests/integration/iptables_test.go
index 1cfd854a0..c61d4e788 100644
--- a/pkg/tcpip/tests/integration/iptables_test.go
+++ b/pkg/tcpip/tests/integration/iptables_test.go
@@ -347,7 +347,7 @@ type channelEndpointWithoutWritePacket struct {
 	t *testing.T
 }
 
-func (c *channelEndpointWithoutWritePacket) WritePacket(stack.RouteInfo, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
+func (c *channelEndpointWithoutWritePacket) WritePacket(stack.RouteInfo, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
 	c.t.Error("unexpectedly called WritePacket; all writes should go through WritePackets")
 	return &tcpip.ErrNotSupported{}
 }
@@ -627,7 +627,7 @@ func TestIPTableWritePackets(t *testing.T) {
 
 			pkts := test.genPacket(r)
 			pktsLen := pkts.Len()
-			if n, err := r.WritePackets(nil /* gso */, pkts, stack.NetworkHeaderParams{
+			if n, err := r.WritePackets(pkts, stack.NetworkHeaderParams{
 				Protocol: header.UDPProtocolNumber,
 				TTL:      64,
 			}); err != nil {
diff --git a/pkg/tcpip/tests/integration/link_resolution_test.go b/pkg/tcpip/tests/integration/link_resolution_test.go
index d39809e1c..c657714ba 100644
--- a/pkg/tcpip/tests/integration/link_resolution_test.go
+++ b/pkg/tcpip/tests/integration/link_resolution_test.go
@@ -687,10 +687,10 @@ func TestWritePacketsLinkResolution(t *testing.T) {
 				TOS:      stack.DefaultTOS,
 			}
 
-			if n, err := r.WritePackets(nil /* gso */, pkts, params); err != nil {
-				t.Fatalf("r.WritePackets(nil, %#v, _): %s", params, err)
+			if n, err := r.WritePackets(pkts, params); err != nil {
+				t.Fatalf("r.WritePackets(_, %#v): %s", params, err)
 			} else if want := pkts.Len(); want != n {
-				t.Fatalf("got r.WritePackets(nil, %#v, _) = %d, want = %d", n, params, want)
+				t.Fatalf("got r.WritePackets(_, %#v) = %d, want = %d", params, n, want)
 			}
 
 			var writer bytes.Buffer
diff --git a/pkg/tcpip/tests/integration/loopback_test.go b/pkg/tcpip/tests/integration/loopback_test.go
index b04169751..3df1bbd68 100644
--- a/pkg/tcpip/tests/integration/loopback_test.go
+++ b/pkg/tcpip/tests/integration/loopback_test.go
@@ -315,11 +315,11 @@ func TestLoopbackSubnetLifetimeBoundToAddr(t *testing.T) {
 		TOS:      stack.DefaultTOS,
 	}
 	data := buffer.View([]byte{1, 2, 3, 4})
-	if err := r.WritePacket(nil /* gso */, params, stack.NewPacketBuffer(stack.PacketBufferOptions{
+	if err := r.WritePacket(params, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		ReserveHeaderBytes: int(r.MaxHeaderLength()),
 		Data:               data.ToVectorisedView(),
 	})); err != nil {
-		t.Fatalf("r.WritePacket(nil, %#v, _): %s", params, err)
+		t.Fatalf("r.WritePacket(%#v, _): %s", params, err)
 	}
 
 	// Removing the address should make the endpoint invalid.
@@ -327,12 +327,12 @@ func TestLoopbackSubnetLifetimeBoundToAddr(t *testing.T) {
 		t.Fatalf("s.RemoveAddress(%d, %s): %s", nicID, protoAddr.AddressWithPrefix.Address, err)
 	}
 	{
-		err := r.WritePacket(nil /* gso */, params, stack.NewPacketBuffer(stack.PacketBufferOptions{
+		err := r.WritePacket(params, stack.NewPacketBuffer(stack.PacketBufferOptions{
 			ReserveHeaderBytes: int(r.MaxHeaderLength()),
 			Data:               data.ToVectorisedView(),
 		}))
 		if _, ok := err.(*tcpip.ErrInvalidEndpointState); !ok {
-			t.Fatalf("got r.WritePacket(nil, %#v, _) = %s, want = %s", params, err, &tcpip.ErrInvalidEndpointState{})
+			t.Fatalf("got r.WritePacket(%#v, _) = %s, want = %s", params, err, &tcpip.ErrInvalidEndpointState{})
 		}
 	}
 }
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index 33ed78f54..9948f305b 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -431,7 +431,7 @@ func send4(r *stack.Route, ident uint16, data buffer.View, ttl uint8, owner tcpi
 		ttl = r.DefaultTTL()
 	}
 
-	if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS}, pkt); err != nil {
+	if err := r.WritePacket(stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS}, pkt); err != nil {
 		r.Stats().ICMP.V4.PacketsSent.Dropped.Increment()
 		return err
 	}
@@ -478,7 +478,7 @@ func send6(r *stack.Route, ident uint16, data buffer.View, ttl uint8) tcpip.Erro
 		ttl = r.DefaultTTL()
 	}
 
-	if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS}, pkt); err != nil {
+	if err := r.WritePacket(stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS}, pkt); err != nil {
 		r.Stats().ICMP.V6.PacketsSent.Dropped.Increment()
 	}
 
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index 10453a42a..bcec3d2e7 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -354,7 +354,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 			Data:               buffer.View(payloadBytes).ToVectorisedView(),
 		})
 		pkt.Owner = owner
-		if err := route.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
+		if err := route.WritePacket(stack.NetworkHeaderParams{
 			Protocol: e.TransProto,
 			TTL:      route.DefaultTTL(),
 			TOS:      stack.DefaultTOS,
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 7bc6b08f0..524d5cabf 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -721,14 +721,14 @@ type tcpFields struct {
 func (e *endpoint) sendSynTCP(r *stack.Route, tf tcpFields, opts header.TCPSynOptions) tcpip.Error {
 	tf.opts = makeSynOptions(opts)
 	// We ignore SYN send errors and let the callers re-attempt send.
-	if err := e.sendTCP(r, tf, buffer.VectorisedView{}, nil); err != nil {
+	if err := e.sendTCP(r, tf, buffer.VectorisedView{}, stack.GSO{}); err != nil {
 		e.stats.SendErrors.SynSendToNetworkFailed.Increment()
 	}
 	putOptions(tf.opts)
 	return nil
 }
 
-func (e *endpoint) sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stack.GSO) tcpip.Error {
+func (e *endpoint) sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso stack.GSO) tcpip.Error {
 	tf.txHash = e.txHash
 	if err := sendTCP(r, tf, data, gso, e.owner); err != nil {
 		e.stats.SendErrors.SegmentSendToNetworkFailed.Increment()
@@ -738,7 +738,7 @@ func (e *endpoint) sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedV
 	return nil
 }
 
-func buildTCPHdr(r *stack.Route, tf tcpFields, pkt *stack.PacketBuffer, gso *stack.GSO) {
+func buildTCPHdr(r *stack.Route, tf tcpFields, pkt *stack.PacketBuffer, gso stack.GSO) {
 	optLen := len(tf.opts)
 	tcp := header.TCP(pkt.TransportHeader().Push(header.TCPMinimumSize + optLen))
 	pkt.TransportProtocolNumber = header.TCPProtocolNumber
@@ -755,7 +755,7 @@ func buildTCPHdr(r *stack.Route, tf tcpFields, pkt *stack.PacketBuffer, gso *sta
 
 	xsum := r.PseudoHeaderChecksum(ProtocolNumber, uint16(pkt.Size()))
 	// Only calculate the checksum if offloading isn't supported.
-	if gso != nil && gso.NeedsCsum {
+	if gso.Type != stack.GSONone && gso.NeedsCsum {
 		// This is called CHECKSUM_PARTIAL in the Linux kernel. We
 		// calculate a checksum of the pseudo-header and save it in the
 		// TCP header, then the kernel calculate a checksum of the
@@ -767,7 +767,7 @@ func buildTCPHdr(r *stack.Route, tf tcpFields, pkt *stack.PacketBuffer, gso *sta
 	}
 }
 
-func sendTCPBatch(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stack.GSO, owner tcpip.PacketOwner) tcpip.Error {
+func sendTCPBatch(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso stack.GSO, owner tcpip.PacketOwner) tcpip.Error {
 	// We need to shallow clone the VectorisedView here as ReadToView will
 	// split the VectorisedView and Trim underlying views as it splits. Not
 	// doing the clone here will cause the underlying views of data itself
@@ -799,13 +799,14 @@ func sendTCPBatch(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso
 		pkt.Data().ReadFromVV(&data, packetSize)
 		buildTCPHdr(r, tf, pkt, gso)
 		tf.seq = tf.seq.Add(seqnum.Size(packetSize))
+		pkt.GSOOptions = gso
 		pkts.PushBack(pkt)
 	}
 
 	if tf.ttl == 0 {
 		tf.ttl = r.DefaultTTL()
 	}
-	sent, err := r.WritePackets(gso, pkts, stack.NetworkHeaderParams{Protocol: ProtocolNumber, TTL: tf.ttl, TOS: tf.tos})
+	sent, err := r.WritePackets(pkts, stack.NetworkHeaderParams{Protocol: ProtocolNumber, TTL: tf.ttl, TOS: tf.tos})
 	if err != nil {
 		r.Stats().TCP.SegmentSendErrors.IncrementBy(uint64(n - sent))
 	}
@@ -815,13 +816,13 @@ func sendTCPBatch(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso
 
 // sendTCP sends a TCP segment with the provided options via the provided
 // network endpoint and under the provided identity.
-func sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stack.GSO, owner tcpip.PacketOwner) tcpip.Error {
+func sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso stack.GSO, owner tcpip.PacketOwner) tcpip.Error {
 	optLen := len(tf.opts)
 	if tf.rcvWnd > math.MaxUint16 {
 		tf.rcvWnd = math.MaxUint16
 	}
 
-	if r.Loop()&stack.PacketLoop == 0 && gso != nil && gso.Type == stack.GSOSW && int(gso.MSS) < data.Size() {
+	if r.Loop()&stack.PacketLoop == 0 && gso.Type == stack.GSOSW && int(gso.MSS) < data.Size() {
 		return sendTCPBatch(r, tf, data, gso, owner)
 	}
 
@@ -829,6 +830,7 @@ func sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stac
 		ReserveHeaderBytes: header.TCPMinimumSize + int(r.MaxHeaderLength()) + optLen,
 		Data:               data,
 	})
+	pkt.GSOOptions = gso
 	pkt.Hash = tf.txHash
 	pkt.Owner = owner
 	buildTCPHdr(r, tf, pkt, gso)
@@ -836,7 +838,7 @@ func sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stac
 	if tf.ttl == 0 {
 		tf.ttl = r.DefaultTTL()
 	}
-	if err := r.WritePacket(gso, stack.NetworkHeaderParams{Protocol: ProtocolNumber, TTL: tf.ttl, TOS: tf.tos}, pkt); err != nil {
+	if err := r.WritePacket(stack.NetworkHeaderParams{Protocol: ProtocolNumber, TTL: tf.ttl, TOS: tf.tos}, pkt); err != nil {
 		r.Stats().TCP.SegmentSendErrors.Increment()
 		return err
 	}
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index f25dc781a..50f72bf38 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -599,7 +599,7 @@ type endpoint struct {
 	// applied while sending packets. Defaults to 0 as on Linux.
 	sendTOS uint8
 
-	gso *stack.GSO
+	gso stack.GSO
 
 	// TODO(b/142022063): Add ability to save and restore per endpoint stats.
 	stats Stats `state:"nosave"`
@@ -2943,28 +2943,26 @@ func (e *endpoint) completeStateLocked() stack.TCPEndpointState {
 }
 
 func (e *endpoint) initHardwareGSO() {
-	gso := &stack.GSO{}
 	switch e.route.NetProto() {
 	case header.IPv4ProtocolNumber:
-		gso.Type = stack.GSOTCPv4
-		gso.L3HdrLen = header.IPv4MinimumSize
+		e.gso.Type = stack.GSOTCPv4
+		e.gso.L3HdrLen = header.IPv4MinimumSize
 	case header.IPv6ProtocolNumber:
-		gso.Type = stack.GSOTCPv6
-		gso.L3HdrLen = header.IPv6MinimumSize
+		e.gso.Type = stack.GSOTCPv6
+		e.gso.L3HdrLen = header.IPv6MinimumSize
 	default:
 		panic(fmt.Sprintf("Unknown netProto: %v", e.NetProto))
 	}
-	gso.NeedsCsum = true
-	gso.CsumOffset = header.TCPChecksumOffset
-	gso.MaxSize = e.route.GSOMaxSize()
-	e.gso = gso
+	e.gso.NeedsCsum = true
+	e.gso.CsumOffset = header.TCPChecksumOffset
+	e.gso.MaxSize = e.route.GSOMaxSize()
 }
 
 func (e *endpoint) initGSO() {
 	if e.route.HasHardwareGSOCapability() {
 		e.initHardwareGSO()
 	} else if e.route.HasSoftwareGSOCapability() {
-		e.gso = &stack.GSO{
+		e.gso = stack.GSO{
 			MaxSize:   e.route.GSOMaxSize(),
 			Type:      stack.GSOSW,
 			NeedsCsum: false,
diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
index fe0d7f10f..a3d1aa1a3 100644
--- a/pkg/tcpip/transport/tcp/protocol.go
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -159,8 +159,8 @@ func (p *protocol) HandleUnknownDestinationPacket(id stack.TransportEndpointID,
 // replyWithReset replies to the given segment with a reset segment.
 //
 // If the passed TTL is 0, then the route's default TTL will be used.
-func replyWithReset(stack *stack.Stack, s *segment, tos, ttl uint8) tcpip.Error {
-	route, err := stack.FindRoute(s.nicID, s.dstAddr, s.srcAddr, s.netProto, false /* multicastLoop */)
+func replyWithReset(st *stack.Stack, s *segment, tos, ttl uint8) tcpip.Error {
+	route, err := st.FindRoute(s.nicID, s.dstAddr, s.srcAddr, s.netProto, false /* multicastLoop */)
 	if err != nil {
 		return err
 	}
@@ -200,7 +200,7 @@ func replyWithReset(stack *stack.Stack, s *segment, tos, ttl uint8) tcpip.Error
 		seq:    seq,
 		ack:    ack,
 		rcvWnd: 0,
-	}, buffer.VectorisedView{}, nil /* gso */, nil /* PacketOwner */)
+	}, buffer.VectorisedView{}, stack.GSO{}, nil /* PacketOwner */)
 }
 
 // SetOption implements stack.TransportProtocol.SetOption.
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index cf2e8dcd8..2b32cb7b2 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -180,7 +180,7 @@ func newSender(ep *endpoint, iss, irs seqnum.Value, sndWnd seqnum.Size, mss uint
 			},
 			RTO: 1 * time.Second,
 		},
-		gso: ep.gso != nil,
+		gso: ep.gso.Type != stack.GSONone,
 	}
 
 	if s.gso {
@@ -830,7 +830,7 @@ 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 {
+		if s.ep.gso.Type == stack.GSONone && available > s.MaxPayloadSize {
 			available = s.MaxPayloadSize
 		}
 
diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go
index 7578d64ec..16f8c5212 100644
--- a/pkg/tcpip/transport/tcp/testing/context/context.go
+++ b/pkg/tcpip/transport/tcp/testing/context/context.go
@@ -331,8 +331,8 @@ func (c *Context) GetPacketWithTimeout(timeout time.Duration) []byte {
 	vv := buffer.NewVectorisedView(p.Pkt.Size(), p.Pkt.Views())
 	b := vv.ToView()
 
-	if p.GSO != nil && p.GSO.L3HdrLen != header.IPv4MinimumSize {
-		c.t.Errorf("L3HdrLen %v (expected %v)", p.GSO.L3HdrLen, header.IPv4MinimumSize)
+	if p.Pkt.GSOOptions.Type != stack.GSONone && p.Pkt.GSOOptions.L3HdrLen != header.IPv4MinimumSize {
+		c.t.Errorf("got L3HdrLen = %d, want = %d", p.Pkt.GSOOptions.L3HdrLen, header.IPv4MinimumSize)
 	}
 
 	checker.IPv4(c.t, b, checker.SrcAddr(StackAddr), checker.DstAddr(TestAddr))
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index c9f2f3efc..f7dd50d35 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -848,7 +848,7 @@ func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort u
 	if useDefaultTTL {
 		ttl = r.DefaultTTL()
 	}
-	if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
+	if err := r.WritePacket(stack.NetworkHeaderParams{
 		Protocol: ProtocolNumber,
 		TTL:      ttl,
 		TOS:      tos,