Use PacketBuffers for outgoing packets.

PiperOrigin-RevId: 280455453

pkg/tcpip/buffer/prependable.go

@@ -77,3 +77,9 @@ func (p *Prependable) Prepend(size int) []byte {
 	p.usedIdx -= size
 	return p.View()[:size:size]
 }
+
+// DeepCopy copies p and the bytes backing it.
+func (p Prependable) DeepCopy() Prependable {
+	p.buf = append(View(nil), p.buf...)
+	return p
+}

pkg/tcpip/link/channel/channel.go

@@ -25,10 +25,9 @@ import (
 
 // PacketInfo holds all the information about an outbound packet.
 type PacketInfo struct {
-	Header  buffer.View
-	Payload buffer.View
-	Proto   tcpip.NetworkProtocolNumber
-	GSO     *stack.GSO
+	Pkt   tcpip.PacketBuffer
+	Proto tcpip.NetworkProtocolNumber
+	GSO   *stack.GSO
 }
 
 // Endpoint is link layer endpoint that stores outbound packets in a channel
@@ -118,12 +117,11 @@ func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
 }
 
 // WritePacket stores outbound packets into the channel.
-func (e *Endpoint) WritePacket(_ *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (e *Endpoint) WritePacket(_ *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
 	p := PacketInfo{
-		Header:  hdr.View(),
-		Proto:   protocol,
-		Payload: payload.ToView(),
-		GSO:     gso,
+		Pkt:   pkt,
+		Proto: protocol,
+		GSO:   gso,
 	}
 
 	select {
@@ -139,15 +137,16 @@ func (e *Endpoint) WritePackets(_ *stack.Route, gso *stack.GSO, hdrs []stack.Pac
 	payloadView := payload.ToView()
 	n := 0
 packetLoop:
-	for i := range hdrs {
-		hdr := &hdrs[i].Hdr
-		off := hdrs[i].Off
-		size := hdrs[i].Size
+	for _, hdr := range hdrs {
+		off := hdr.Off
+		size := hdr.Size
 		p := PacketInfo{
-			Header:  hdr.View(),
-			Proto:   protocol,
-			Payload: buffer.NewViewFromBytes(payloadView[off : off+size]),
-			GSO:     gso,
+			Pkt: tcpip.PacketBuffer{
+				Header: hdr.Hdr,
+				Data:   buffer.NewViewFromBytes(payloadView[off : off+size]).ToVectorisedView(),
+			},
+			Proto: protocol,
+			GSO:   gso,
 		}
 
 		select {
@@ -162,12 +161,11 @@ packetLoop:
 }
 
 // WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *Endpoint) WriteRawPacket(packet buffer.VectorisedView) *tcpip.Error {
+func (e *Endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
 	p := PacketInfo{
-		Header:  packet.ToView(),
-		Proto:   0,
-		Payload: buffer.View{},
-		GSO:     nil,
+		Pkt:   tcpip.PacketBuffer{Data: vv},
+		Proto: 0,
+		GSO:   nil,
 	}
 
 	select {

pkg/tcpip/link/fdbased/endpoint.go

@@ -386,10 +386,11 @@ const (
 
 // WritePacket writes outbound packets to the file descriptor. If it is not
 // currently writable, the packet is dropped.
-func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
 	if e.hdrSize > 0 {
 		// Add ethernet header if needed.
-		eth := header.Ethernet(hdr.Prepend(header.EthernetMinimumSize))
+		eth := header.Ethernet(pkt.Header.Prepend(header.EthernetMinimumSize))
+		pkt.LinkHeader = buffer.View(eth)
 		ethHdr := &header.EthernetFields{
 			DstAddr: r.RemoteLinkAddress,
 			Type:    protocol,
@@ -408,13 +409,13 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 		vnetHdr := virtioNetHdr{}
 		vnetHdrBuf := vnetHdrToByteSlice(&vnetHdr)
 		if gso != nil {
-			vnetHdr.hdrLen = uint16(hdr.UsedLength())
+			vnetHdr.hdrLen = uint16(pkt.Header.UsedLength())
 			if gso.NeedsCsum {
 				vnetHdr.flags = _VIRTIO_NET_HDR_F_NEEDS_CSUM
 				vnetHdr.csumStart = header.EthernetMinimumSize + gso.L3HdrLen
 				vnetHdr.csumOffset = gso.CsumOffset
 			}
-			if gso.Type != stack.GSONone && uint16(payload.Size()) > gso.MSS {
+			if gso.Type != stack.GSONone && uint16(pkt.Data.Size()) > gso.MSS {
 				switch gso.Type {
 				case stack.GSOTCPv4:
 					vnetHdr.gsoType = _VIRTIO_NET_HDR_GSO_TCPV4
@@ -427,14 +428,14 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 			}
 		}
 
-		return rawfile.NonBlockingWrite3(e.fds[0], vnetHdrBuf, hdr.View(), payload.ToView())
+		return rawfile.NonBlockingWrite3(e.fds[0], vnetHdrBuf, pkt.Header.View(), pkt.Data.ToView())
 	}
 
-	if payload.Size() == 0 {
-		return rawfile.NonBlockingWrite(e.fds[0], hdr.View())
+	if pkt.Data.Size() == 0 {
+		return rawfile.NonBlockingWrite(e.fds[0], pkt.Header.View())
 	}
 
-	return rawfile.NonBlockingWrite3(e.fds[0], hdr.View(), payload.ToView(), nil)
+	return rawfile.NonBlockingWrite3(e.fds[0], pkt.Header.View(), pkt.Data.ToView(), nil)
 }
 
 // WritePackets writes outbound packets to the file descriptor. If it is not
@@ -555,8 +556,8 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, hdrs []stack.Pac
 }
 
 // WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *endpoint) WriteRawPacket(packet buffer.VectorisedView) *tcpip.Error {
-	return rawfile.NonBlockingWrite(e.fds[0], packet.ToView())
+func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
+	return rawfile.NonBlockingWrite(e.fds[0], vv.ToView())
 }
 
 // InjectOutobund implements stack.InjectableEndpoint.InjectOutbound.

pkg/tcpip/link/fdbased/endpoint_test.go

@@ -168,7 +168,10 @@ func testWritePacket(t *testing.T, plen int, eth bool, gsoMaxSize uint32) {
 			L3HdrLen:   header.IPv4MaximumHeaderSize,
 		}
 	}
-	if err := c.ep.WritePacket(r, gso, hdr, payload.ToVectorisedView(), proto); err != nil {
+	if err := c.ep.WritePacket(r, gso, proto, tcpip.PacketBuffer{
+		Header: hdr,
+		Data:   payload.ToVectorisedView(),
+	}); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 
@@ -258,7 +261,10 @@ func TestPreserveSrcAddress(t *testing.T) {
 	// WritePacket panics given a prependable with anything less than
 	// the minimum size of the ethernet header.
 	hdr := buffer.NewPrependable(header.EthernetMinimumSize)
-	if err := c.ep.WritePacket(r, nil /* gso */, hdr, buffer.VectorisedView{}, proto); err != nil {
+	if err := c.ep.WritePacket(r, nil /* gso */, proto, tcpip.PacketBuffer{
+		Header: hdr,
+		Data:   buffer.VectorisedView{},
+	}); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 

pkg/tcpip/link/loopback/loopback.go

@@ -76,16 +76,16 @@ func (*endpoint) Wait() {}
 
 // WritePacket implements stack.LinkEndpoint.WritePacket. It delivers outbound
 // packets to the network-layer dispatcher.
-func (e *endpoint) WritePacket(_ *stack.Route, _ *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
-	views := make([]buffer.View, 1, 1+len(payload.Views()))
-	views[0] = hdr.View()
-	views = append(views, payload.Views()...)
+func (e *endpoint) WritePacket(_ *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
+	views := make([]buffer.View, 1, 1+len(pkt.Data.Views()))
+	views[0] = pkt.Header.View()
+	views = append(views, pkt.Data.Views()...)
 
-	// Because we're immediately turning around and writing the packet back to the
-	// rx path, we intentionally don't preserve the remote and local link
-	// addresses from the stack.Route we're passed.
+	// Because we're immediately turning around and writing the packet back
+	// to the rx path, we intentionally don't preserve the remote and local
+	// link addresses from the stack.Route we're passed.
 	e.dispatcher.DeliverNetworkPacket(e, "" /* remote */, "" /* local */, protocol, tcpip.PacketBuffer{
-		Data: buffer.NewVectorisedView(len(views[0])+payload.Size(), views),
+		Data: buffer.NewVectorisedView(len(views[0])+pkt.Data.Size(), views),
 	})
 
 	return nil
@@ -97,17 +97,17 @@ func (e *endpoint) WritePackets(_ *stack.Route, _ *stack.GSO, hdrs []stack.Packe
 }
 
 // WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *endpoint) WriteRawPacket(packet buffer.VectorisedView) *tcpip.Error {
+func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
 	// Reject the packet if it's shorter than an ethernet header.
-	if packet.Size() < header.EthernetMinimumSize {
+	if vv.Size() < header.EthernetMinimumSize {
 		return tcpip.ErrBadAddress
 	}
 
-	// There should be an ethernet header at the beginning of packet.
-	linkHeader := header.Ethernet(packet.First()[:header.EthernetMinimumSize])
-	packet.TrimFront(len(linkHeader))
+	// There should be an ethernet header at the beginning of vv.
+	linkHeader := header.Ethernet(vv.First()[:header.EthernetMinimumSize])
+	vv.TrimFront(len(linkHeader))
 	e.dispatcher.DeliverNetworkPacket(e, "" /* remote */, "" /* local */, linkHeader.Type(), tcpip.PacketBuffer{
-		Data:       packet,
+		Data:       vv,
 		LinkHeader: buffer.View(linkHeader),
 	})
 

pkg/tcpip/link/muxed/injectable.go

@@ -98,15 +98,15 @@ func (m *InjectableEndpoint) WritePackets(r *stack.Route, gso *stack.GSO, hdrs [
 // 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.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (m *InjectableEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
 	if endpoint, ok := m.routes[r.RemoteAddress]; ok {
-		return endpoint.WritePacket(r, gso, hdr, payload, protocol)
+		return endpoint.WritePacket(r, gso, protocol, pkt)
 	}
 	return tcpip.ErrNoRoute
 }
 
 // WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (m *InjectableEndpoint) WriteRawPacket(packet buffer.VectorisedView) *tcpip.Error {
+func (m *InjectableEndpoint) WriteRawPacket(buffer.VectorisedView) *tcpip.Error {
 	// WriteRawPacket doesn't get a route or network address, so there's
 	// nowhere to write this.
 	return tcpip.ErrNoRoute

pkg/tcpip/link/muxed/injectable_test.go

@@ -50,8 +50,10 @@ func TestInjectableEndpointDispatch(t *testing.T) {
 	hdr.Prepend(1)[0] = 0xFA
 	packetRoute := stack.Route{RemoteAddress: dstIP}
 
-	endpoint.WritePacket(&packetRoute, nil /* gso */, hdr,
-		buffer.NewViewFromBytes([]byte{0xFB}).ToVectorisedView(), ipv4.ProtocolNumber)
+	endpoint.WritePacket(&packetRoute, nil /* gso */, ipv4.ProtocolNumber, tcpip.PacketBuffer{
+		Header: hdr,
+		Data:   buffer.NewViewFromBytes([]byte{0xFB}).ToVectorisedView(),
+	})
 
 	buf := make([]byte, 6500)
 	bytesRead, err := sock.Read(buf)
@@ -68,8 +70,10 @@ func TestInjectableEndpointDispatchHdrOnly(t *testing.T) {
 	hdr := buffer.NewPrependable(1)
 	hdr.Prepend(1)[0] = 0xFA
 	packetRoute := stack.Route{RemoteAddress: dstIP}
-	endpoint.WritePacket(&packetRoute, nil /* gso */, hdr,
-		buffer.NewView(0).ToVectorisedView(), ipv4.ProtocolNumber)
+	endpoint.WritePacket(&packetRoute, nil /* gso */, ipv4.ProtocolNumber, tcpip.PacketBuffer{
+		Header: hdr,
+		Data:   buffer.NewView(0).ToVectorisedView(),
+	})
 	buf := make([]byte, 6500)
 	bytesRead, err := sock.Read(buf)
 	if err != nil {

pkg/tcpip/link/sharedmem/sharedmem.go

@@ -185,9 +185,10 @@ func (e *endpoint) LinkAddress() tcpip.LinkAddress {
 
 // WritePacket writes outbound packets to the file descriptor. If it is not
 // currently writable, the packet is dropped.
-func (e *endpoint) WritePacket(r *stack.Route, _ *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (e *endpoint) WritePacket(r *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
 	// Add the ethernet header here.
-	eth := header.Ethernet(hdr.Prepend(header.EthernetMinimumSize))
+	eth := header.Ethernet(pkt.Header.Prepend(header.EthernetMinimumSize))
+	pkt.LinkHeader = buffer.View(eth)
 	ethHdr := &header.EthernetFields{
 		DstAddr: r.RemoteLinkAddress,
 		Type:    protocol,
@@ -199,10 +200,10 @@ func (e *endpoint) WritePacket(r *stack.Route, _ *stack.GSO, hdr buffer.Prependa
 	}
 	eth.Encode(ethHdr)
 
-	v := payload.ToView()
+	v := pkt.Data.ToView()
 	// Transmit the packet.
 	e.mu.Lock()
-	ok := e.tx.transmit(hdr.View(), v)
+	ok := e.tx.transmit(pkt.Header.View(), v)
 	e.mu.Unlock()
 
 	if !ok {
@@ -218,8 +219,8 @@ func (e *endpoint) WritePackets(r *stack.Route, _ *stack.GSO, hdrs []stack.Packe
 }
 
 // WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *endpoint) WriteRawPacket(packet buffer.VectorisedView) *tcpip.Error {
-	v := packet.ToView()
+func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
+	v := vv.ToView()
 	// Transmit the packet.
 	e.mu.Lock()
 	ok := e.tx.transmit(v, buffer.View{})

pkg/tcpip/link/sharedmem/sharedmem_test.go

@@ -273,7 +273,10 @@ func TestSimpleSend(t *testing.T) {
 			randomFill(buf)
 
 			proto := tcpip.NetworkProtocolNumber(rand.Intn(0x10000))
-			if err := c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), proto); err != nil {
+			if err := c.ep.WritePacket(&r, nil /* gso */, proto, tcpip.PacketBuffer{
+				Header: hdr,
+				Data:   buf.ToVectorisedView(),
+			}); err != nil {
 				t.Fatalf("WritePacket failed: %v", err)
 			}
 
@@ -342,7 +345,9 @@ func TestPreserveSrcAddressInSend(t *testing.T) {
 	hdr := buffer.NewPrependable(header.EthernetMinimumSize)
 
 	proto := tcpip.NetworkProtocolNumber(rand.Intn(0x10000))
-	if err := c.ep.WritePacket(&r, nil /* gso */, hdr, buffer.VectorisedView{}, proto); err != nil {
+	if err := c.ep.WritePacket(&r, nil /* gso */, proto, tcpip.PacketBuffer{
+		Header: hdr,
+	}); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 
@@ -396,7 +401,10 @@ func TestFillTxQueue(t *testing.T) {
 	for i := queuePipeSize / 40; i > 0; i-- {
 		hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
 
-		if err := c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), header.IPv4ProtocolNumber); err != nil {
+		if err := c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+			Header: hdr,
+			Data:   buf.ToVectorisedView(),
+		}); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 
@@ -411,7 +419,10 @@ func TestFillTxQueue(t *testing.T) {
 
 	// Next attempt to write must fail.
 	hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
-	if want, err := tcpip.ErrWouldBlock, c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), header.IPv4ProtocolNumber); err != want {
+	if want, err := tcpip.ErrWouldBlock, c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+		Header: hdr,
+		Data:   buf.ToVectorisedView(),
+	}); err != want {
 		t.Fatalf("WritePacket return unexpected result: got %v, want %v", err, want)
 	}
 }
@@ -436,7 +447,10 @@ func TestFillTxQueueAfterBadCompletion(t *testing.T) {
 	// Send two packets so that the id slice has at least two slots.
 	for i := 2; i > 0; i-- {
 		hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
-		if err := c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), header.IPv4ProtocolNumber); err != nil {
+		if err := c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+			Header: hdr,
+			Data:   buf.ToVectorisedView(),
+		}); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 	}
@@ -456,7 +470,10 @@ func TestFillTxQueueAfterBadCompletion(t *testing.T) {
 	ids := make(map[uint64]struct{})
 	for i := queuePipeSize / 40; i > 0; i-- {
 		hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
-		if err := c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), header.IPv4ProtocolNumber); err != nil {
+		if err := c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+			Header: hdr,
+			Data:   buf.ToVectorisedView(),
+		}); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 
@@ -471,7 +488,10 @@ func TestFillTxQueueAfterBadCompletion(t *testing.T) {
 
 	// Next attempt to write must fail.
 	hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
-	if want, err := tcpip.ErrWouldBlock, c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), header.IPv4ProtocolNumber); err != want {
+	if want, err := tcpip.ErrWouldBlock, c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+		Header: hdr,
+		Data:   buf.ToVectorisedView(),
+	}); err != want {
 		t.Fatalf("WritePacket return unexpected result: got %v, want %v", err, want)
 	}
 }
@@ -494,7 +514,10 @@ func TestFillTxMemory(t *testing.T) {
 	ids := make(map[uint64]struct{})
 	for i := queueDataSize / bufferSize; i > 0; i-- {
 		hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
-		if err := c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), header.IPv4ProtocolNumber); err != nil {
+		if err := c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+			Header: hdr,
+			Data:   buf.ToVectorisedView(),
+		}); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 
@@ -510,7 +533,10 @@ func TestFillTxMemory(t *testing.T) {
 
 	// Next attempt to write must fail.
 	hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
-	err := c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), header.IPv4ProtocolNumber)
+	err := c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+		Header: hdr,
+		Data:   buf.ToVectorisedView(),
+	})
 	if want := tcpip.ErrWouldBlock; err != want {
 		t.Fatalf("WritePacket return unexpected result: got %v, want %v", err, want)
 	}
@@ -535,7 +561,10 @@ func TestFillTxMemoryWithMultiBuffer(t *testing.T) {
 	// until there is only one buffer left.
 	for i := queueDataSize/bufferSize - 1; i > 0; i-- {
 		hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
-		if err := c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), header.IPv4ProtocolNumber); err != nil {
+		if err := c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+			Header: hdr,
+			Data:   buf.ToVectorisedView(),
+		}); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 
@@ -548,7 +577,10 @@ func TestFillTxMemoryWithMultiBuffer(t *testing.T) {
 	{
 		hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
 		uu := buffer.NewView(bufferSize).ToVectorisedView()
-		if want, err := tcpip.ErrWouldBlock, c.ep.WritePacket(&r, nil /* gso */, hdr, uu, header.IPv4ProtocolNumber); err != want {
+		if want, err := tcpip.ErrWouldBlock, c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+			Header: hdr,
+			Data:   uu,
+		}); err != want {
 			t.Fatalf("WritePacket return unexpected result: got %v, want %v", err, want)
 		}
 	}
@@ -556,7 +588,10 @@ func TestFillTxMemoryWithMultiBuffer(t *testing.T) {
 	// Attempt to write the one-buffer packet again. It must succeed.
 	{
 		hdr := buffer.NewPrependable(int(c.ep.MaxHeaderLength()))
-		if err := c.ep.WritePacket(&r, nil /* gso */, hdr, buf.ToVectorisedView(), header.IPv4ProtocolNumber); err != nil {
+		if err := c.ep.WritePacket(&r, nil /* gso */, header.IPv4ProtocolNumber, tcpip.PacketBuffer{
+			Header: hdr,
+			Data:   buf.ToVectorisedView(),
+		}); err != nil {
 			t.Fatalf("WritePacket failed unexpectedly: %v", err)
 		}
 	}

pkg/tcpip/link/sniffer/sniffer.go

@@ -193,19 +193,19 @@ func (e *endpoint) GSOMaxSize() uint32 {
 	return 0
 }
 
-func (e *endpoint) dumpPacket(gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) {
+func (e *endpoint) dumpPacket(gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) {
 	if atomic.LoadUint32(&LogPackets) == 1 && e.file == nil {
-		logPacket("send", protocol, hdr.View(), gso)
+		logPacket("send", protocol, pkt.Header.View(), gso)
 	}
 	if e.file != nil && atomic.LoadUint32(&LogPacketsToFile) == 1 {
-		hdrBuf := hdr.View()
-		length := len(hdrBuf) + payload.Size()
+		hdrBuf := pkt.Header.View()
+		length := len(hdrBuf) + pkt.Data.Size()
 		if length > int(e.maxPCAPLen) {
 			length = int(e.maxPCAPLen)
 		}
 
 		buf := bytes.NewBuffer(make([]byte, 0, pcapPacketHeaderLen+length))
-		if err := binary.Write(buf, binary.BigEndian, newPCAPPacketHeader(uint32(length), uint32(len(hdrBuf)+payload.Size()))); err != nil {
+		if err := binary.Write(buf, binary.BigEndian, newPCAPPacketHeader(uint32(length), uint32(len(hdrBuf)+pkt.Data.Size()))); err != nil {
 			panic(err)
 		}
 		if len(hdrBuf) > length {
@@ -215,7 +215,7 @@ func (e *endpoint) dumpPacket(gso *stack.GSO, hdr buffer.Prependable, payload bu
 			panic(err)
 		}
 		length -= len(hdrBuf)
-		logVectorisedView(payload, length, buf)
+		logVectorisedView(pkt.Data, length, buf)
 		if _, err := e.file.Write(buf.Bytes()); err != nil {
 			panic(err)
 		}
@@ -225,9 +225,9 @@ func (e *endpoint) dumpPacket(gso *stack.GSO, hdr buffer.Prependable, payload bu
 // 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.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
-	e.dumpPacket(gso, hdr, payload, protocol)
-	return e.lower.WritePacket(r, gso, hdr, payload, protocol)
+func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
+	e.dumpPacket(gso, protocol, pkt)
+	return e.lower.WritePacket(r, gso, protocol, pkt)
 }
 
 // WritePackets implements the stack.LinkEndpoint interface. It is called by
@@ -236,32 +236,35 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, hdrs []stack.PacketDescriptor, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
 	view := payload.ToView()
 	for _, d := range hdrs {
-		e.dumpPacket(gso, d.Hdr, buffer.NewVectorisedView(d.Size, []buffer.View{view[d.Off:][:d.Size]}), protocol)
+		e.dumpPacket(gso, protocol, tcpip.PacketBuffer{
+			Header: d.Hdr,
+			Data:   view[d.Off:][:d.Size].ToVectorisedView(),
+		})
 	}
 	return e.lower.WritePackets(r, gso, hdrs, payload, protocol)
 }
 
 // WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *endpoint) WriteRawPacket(packet buffer.VectorisedView) *tcpip.Error {
+func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
 	if atomic.LoadUint32(&LogPackets) == 1 && e.file == nil {
 		logPacket("send", 0, buffer.View("[raw packet, no header available]"), nil /* gso */)
 	}
 	if e.file != nil && atomic.LoadUint32(&LogPacketsToFile) == 1 {
-		length := packet.Size()
+		length := vv.Size()
 		if length > int(e.maxPCAPLen) {
 			length = int(e.maxPCAPLen)
 		}
 
 		buf := bytes.NewBuffer(make([]byte, 0, pcapPacketHeaderLen+length))
-		if err := binary.Write(buf, binary.BigEndian, newPCAPPacketHeader(uint32(length), uint32(packet.Size()))); err != nil {
+		if err := binary.Write(buf, binary.BigEndian, newPCAPPacketHeader(uint32(length), uint32(vv.Size()))); err != nil {
 			panic(err)
 		}
-		logVectorisedView(packet, length, buf)
+		logVectorisedView(vv, length, buf)
 		if _, err := e.file.Write(buf.Bytes()); err != nil {
 			panic(err)
 		}
 	}
-	return e.lower.WriteRawPacket(packet)
+	return e.lower.WriteRawPacket(vv)
 }
 
 func logVectorisedView(vv buffer.VectorisedView, length int, buf *bytes.Buffer) {

pkg/tcpip/link/waitable/waitable.go

@@ -99,12 +99,12 @@ 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.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (e *Endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
 	if !e.writeGate.Enter() {
 		return nil
 	}
 
-	err := e.lower.WritePacket(r, gso, hdr, payload, protocol)
+	err := e.lower.WritePacket(r, gso, protocol, pkt)
 	e.writeGate.Leave()
 	return err
 }
@@ -123,12 +123,12 @@ func (e *Endpoint) WritePackets(r *stack.Route, gso *stack.GSO, hdrs []stack.Pac
 }
 
 // WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
-func (e *Endpoint) WriteRawPacket(packet buffer.VectorisedView) *tcpip.Error {
+func (e *Endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
 	if !e.writeGate.Enter() {
 		return nil
 	}
 
-	err := e.lower.WriteRawPacket(packet)
+	err := e.lower.WriteRawPacket(vv)
 	e.writeGate.Leave()
 	return err
 }

pkg/tcpip/link/waitable/waitable_test.go

@@ -65,7 +65,7 @@ func (e *countedEndpoint) LinkAddress() tcpip.LinkAddress {
 	return e.linkAddr
 }
 
-func (e *countedEndpoint) WritePacket(r *stack.Route, _ *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (e *countedEndpoint) WritePacket(r *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
 	e.writeCount++
 	return nil
 }
@@ -76,7 +76,7 @@ func (e *countedEndpoint) WritePackets(r *stack.Route, _ *stack.GSO, hdrs []stac
 	return len(hdrs), nil
 }
 
-func (e *countedEndpoint) WriteRawPacket(packet buffer.VectorisedView) *tcpip.Error {
+func (e *countedEndpoint) WriteRawPacket(buffer.VectorisedView) *tcpip.Error {
 	e.writeCount++
 	return nil
 }
@@ -89,21 +89,21 @@ func TestWaitWrite(t *testing.T) {
 	wep := New(ep)
 
 	// Write and check that it goes through.
-	wep.WritePacket(nil, nil /* gso */, buffer.Prependable{}, buffer.VectorisedView{}, 0)
+	wep.WritePacket(nil, nil /* gso */, 0, tcpip.PacketBuffer{})
 	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(nil, nil /* gso */, buffer.Prependable{}, buffer.VectorisedView{}, 0)
+	wep.WritePacket(nil, nil /* gso */, 0, tcpip.PacketBuffer{})
 	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(nil, nil /* gso */, buffer.Prependable{}, buffer.VectorisedView{}, 0)
+	wep.WritePacket(nil, nil /* gso */, 0, tcpip.PacketBuffer{})
 	if want := 2; ep.writeCount != want {
 		t.Fatalf("Unexpected writeCount: got=%v, want=%v", ep.writeCount, want)
 	}

pkg/tcpip/network/arp/arp.go

@@ -79,7 +79,7 @@ func (e *endpoint) MaxHeaderLength() uint16 {
 
 func (e *endpoint) Close() {}
 
-func (e *endpoint) WritePacket(*stack.Route, *stack.GSO, buffer.Prependable, buffer.VectorisedView, stack.NetworkHeaderParams, stack.PacketLooping) *tcpip.Error {
+func (e *endpoint) WritePacket(*stack.Route, *stack.GSO, stack.NetworkHeaderParams, stack.PacketLooping, tcpip.PacketBuffer) *tcpip.Error {
 	return tcpip.ErrNotSupported
 }
 
@@ -88,7 +88,7 @@ func (e *endpoint) WritePackets(*stack.Route, *stack.GSO, []stack.PacketDescript
 	return 0, tcpip.ErrNotSupported
 }
 
-func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, payload buffer.VectorisedView, loop stack.PacketLooping) *tcpip.Error {
+func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, loop stack.PacketLooping, pkt tcpip.PacketBuffer) *tcpip.Error {
 	return tcpip.ErrNotSupported
 }
 
@@ -106,14 +106,16 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt tcpip.PacketBuffer) {
 			return // we have no useful answer, ignore the request
 		}
 		hdr := buffer.NewPrependable(int(e.linkEP.MaxHeaderLength()) + header.ARPSize)
-		pkt := header.ARP(hdr.Prepend(header.ARPSize))
-		pkt.SetIPv4OverEthernet()
-		pkt.SetOp(header.ARPReply)
-		copy(pkt.HardwareAddressSender(), r.LocalLinkAddress[:])
-		copy(pkt.ProtocolAddressSender(), h.ProtocolAddressTarget())
-		copy(pkt.HardwareAddressTarget(), h.HardwareAddressSender())
-		copy(pkt.ProtocolAddressTarget(), h.ProtocolAddressSender())
-		e.linkEP.WritePacket(r, nil /* gso */, hdr, buffer.VectorisedView{}, ProtocolNumber)
+		packet := header.ARP(hdr.Prepend(header.ARPSize))
+		packet.SetIPv4OverEthernet()
+		packet.SetOp(header.ARPReply)
+		copy(packet.HardwareAddressSender(), r.LocalLinkAddress[:])
+		copy(packet.ProtocolAddressSender(), h.ProtocolAddressTarget())
+		copy(packet.HardwareAddressTarget(), h.HardwareAddressSender())
+		copy(packet.ProtocolAddressTarget(), h.ProtocolAddressSender())
+		e.linkEP.WritePacket(r, nil /* gso */, ProtocolNumber, tcpip.PacketBuffer{
+			Header: hdr,
+		})
 		fallthrough // also fill the cache from requests
 	case header.ARPReply:
 		addr := tcpip.Address(h.ProtocolAddressSender())
@@ -165,7 +167,9 @@ func (*protocol) LinkAddressRequest(addr, localAddr tcpip.Address, linkEP stack.
 	copy(h.ProtocolAddressSender(), localAddr)
 	copy(h.ProtocolAddressTarget(), addr)
 
-	return linkEP.WritePacket(r, nil /* gso */, hdr, buffer.VectorisedView{}, ProtocolNumber)
+	return linkEP.WritePacket(r, nil /* gso */, ProtocolNumber, tcpip.PacketBuffer{
+		Header: hdr,
+	})
 }
 
 // ResolveStaticAddress implements stack.LinkAddressResolver.

pkg/tcpip/network/arp/arp_test.go

@@ -110,13 +110,13 @@ func TestDirectRequest(t *testing.T) {
 	for i, address := range []tcpip.Address{stackAddr1, stackAddr2} {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			inject(address)
-			pkt := <-c.linkEP.C
-			if pkt.Proto != arp.ProtocolNumber {
-				t.Fatalf("expected ARP response, got network protocol number %d", pkt.Proto)
+			pi := <-c.linkEP.C
+			if pi.Proto != arp.ProtocolNumber {
+				t.Fatalf("expected ARP response, got network protocol number %d", pi.Proto)
 			}
-			rep := header.ARP(pkt.Header)
+			rep := header.ARP(pi.Pkt.Header.View())
 			if !rep.IsValid() {
-				t.Fatalf("invalid ARP response len(pkt.Header)=%d", len(pkt.Header))
+				t.Fatalf("invalid ARP response pi.Pkt.Header.UsedLength()=%d", pi.Pkt.Header.UsedLength())
 			}
 			if got, want := tcpip.LinkAddress(rep.HardwareAddressSender()), stackLinkAddr; got != want {
 				t.Errorf("got HardwareAddressSender = %s, want = %s", got, want)

pkg/tcpip/network/ip_test.go

@@ -150,24 +150,24 @@ 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, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (t *testObject) WritePacket(_ *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
 	var prot tcpip.TransportProtocolNumber
 	var srcAddr tcpip.Address
 	var dstAddr tcpip.Address
 
 	if t.v4 {
-		h := header.IPv4(hdr.View())
+		h := header.IPv4(pkt.Header.View())
 		prot = tcpip.TransportProtocolNumber(h.Protocol())
 		srcAddr = h.SourceAddress()
 		dstAddr = h.DestinationAddress()
 
 	} else {
-		h := header.IPv6(hdr.View())
+		h := header.IPv6(pkt.Header.View())
 		prot = tcpip.TransportProtocolNumber(h.NextHeader())
 		srcAddr = h.SourceAddress()
 		dstAddr = h.DestinationAddress()
 	}
-	t.checkValues(prot, payload, srcAddr, dstAddr)
+	t.checkValues(prot, pkt.Data, srcAddr, dstAddr)
 	return nil
 }
 
@@ -239,7 +239,10 @@ func TestIPv4Send(t *testing.T) {
 	if err != nil {
 		t.Fatalf("could not find route: %v", err)
 	}
-	if err := ep.WritePacket(&r, nil /* gso */, hdr, payload.ToVectorisedView(), stack.NetworkHeaderParams{Protocol: 123, TTL: 123, TOS: stack.DefaultTOS}, stack.PacketOut); err != nil {
+	if err := ep.WritePacket(&r, nil /* gso */, stack.NetworkHeaderParams{Protocol: 123, TTL: 123, TOS: stack.DefaultTOS}, stack.PacketOut, tcpip.PacketBuffer{
+		Header: hdr,
+		Data:   payload.ToVectorisedView(),
+	}); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 }
@@ -477,7 +480,10 @@ func TestIPv6Send(t *testing.T) {
 	if err != nil {
 		t.Fatalf("could not find route: %v", err)
 	}
-	if err := ep.WritePacket(&r, nil /* gso */, hdr, payload.ToVectorisedView(), stack.NetworkHeaderParams{Protocol: 123, TTL: 123, TOS: stack.DefaultTOS}, stack.PacketOut); err != nil {
+	if err := ep.WritePacket(&r, nil /* gso */, stack.NetworkHeaderParams{Protocol: 123, TTL: 123, TOS: stack.DefaultTOS}, stack.PacketOut, tcpip.PacketBuffer{
+		Header: hdr,
+		Data:   payload.ToVectorisedView(),
+	}); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 }

pkg/tcpip/network/ipv4/icmp.go

@@ -99,7 +99,11 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt tcpip.PacketBuffer) {
 		pkt.SetChecksum(0)
 		pkt.SetChecksum(^header.Checksum(pkt, header.ChecksumVV(vv, 0)))
 		sent := stats.ICMP.V4PacketsSent
-		if err := r.WritePacket(nil /* gso */, hdr, vv, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}); err != nil {
+		if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, tcpip.PacketBuffer{
+			Header:          hdr,
+			Data:            vv,
+			TransportHeader: buffer.View(pkt),
+		}); err != nil {
 			sent.Dropped.Increment()
 			return
 		}

pkg/tcpip/network/ipv4/ipv4.go

@@ -117,13 +117,14 @@ func (e *endpoint) GSOMaxSize() uint32 {
 }
 
 // writePacketFragments calls e.linkEP.WritePacket with each packet fragment to
-// write. It assumes that the IP header is entirely in hdr but does not assume
-// that only the IP header is in hdr. It assumes that the input packet's stated
-// length matches the length of the hdr+payload. mtu includes the IP header and
-// options. This does not support the DontFragment IP flag.
-func (e *endpoint) writePacketFragments(r *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, mtu int) *tcpip.Error {
+// write. It assumes that the IP header is entirely in pkt.Header but does not
+// assume that only the IP header is in pkt.Header. It assumes that the input
+// packet's stated length matches the length of the header+payload. mtu
+// includes the IP header and options. This does not support the DontFragment
+// IP flag.
+func (e *endpoint) writePacketFragments(r *stack.Route, gso *stack.GSO, mtu int, pkt tcpip.PacketBuffer) *tcpip.Error {
 	// This packet is too big, it needs to be fragmented.
-	ip := header.IPv4(hdr.View())
+	ip := header.IPv4(pkt.Header.View())
 	flags := ip.Flags()
 
 	// Update mtu to take into account the header, which will exist in all
@@ -137,62 +138,77 @@ func (e *endpoint) writePacketFragments(r *stack.Route, gso *stack.GSO, hdr buff
 
 	outerMTU := innerMTU + int(ip.HeaderLength())
 	offset := ip.FragmentOffset()
-	originalAvailableLength := hdr.AvailableLength()
+	originalAvailableLength := pkt.Header.AvailableLength()
 	for i := 0; i < n; i++ {
 		// Where possible, the first fragment that is sent has the same
-		// hdr.UsedLength() as the input packet. The link-layer endpoint may depends
-		// on this for looking at, eg, L4 headers.
+		// pkt.Header.UsedLength() as the input packet. The link-layer
+		// endpoint may depend on this for looking at, eg, L4 headers.
 		h := ip
 		if i > 0 {
-			hdr = buffer.NewPrependable(int(ip.HeaderLength()) + originalAvailableLength)
-			h = header.IPv4(hdr.Prepend(int(ip.HeaderLength())))
+			pkt.Header = buffer.NewPrependable(int(ip.HeaderLength()) + originalAvailableLength)
+			h = header.IPv4(pkt.Header.Prepend(int(ip.HeaderLength())))
 			copy(h, ip[:ip.HeaderLength()])
 		}
 		if i != n-1 {
 			h.SetTotalLength(uint16(outerMTU))
 			h.SetFlagsFragmentOffset(flags|header.IPv4FlagMoreFragments, offset)
 		} else {
-			h.SetTotalLength(uint16(h.HeaderLength()) + uint16(payload.Size()))
+			h.SetTotalLength(uint16(h.HeaderLength()) + uint16(pkt.Data.Size()))
 			h.SetFlagsFragmentOffset(flags, offset)
 		}
 		h.SetChecksum(0)
 		h.SetChecksum(^h.CalculateChecksum())
 		offset += uint16(innerMTU)
 		if i > 0 {
-			newPayload := payload.Clone([]buffer.View{})
+			newPayload := pkt.Data.Clone(nil)
 			newPayload.CapLength(innerMTU)
-			if err := e.linkEP.WritePacket(r, gso, hdr, newPayload, ProtocolNumber); err != nil {
+			if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, tcpip.PacketBuffer{
+				Header:        pkt.Header,
+				Data:          newPayload,
+				NetworkHeader: buffer.View(h),
+			}); err != nil {
 				return err
 			}
 			r.Stats().IP.PacketsSent.Increment()
-			payload.TrimFront(newPayload.Size())
+			pkt.Data.TrimFront(newPayload.Size())
 			continue
 		}
-		// Special handling for the first fragment because it comes from the hdr.
-		if outerMTU >= hdr.UsedLength() {
-			// This fragment can fit all of hdr and possibly some of payload, too.
-			newPayload := payload.Clone([]buffer.View{})
-			newPayloadLength := outerMTU - hdr.UsedLength()
+		// Special handling for the first fragment because it comes
+		// from the header.
+		if outerMTU >= pkt.Header.UsedLength() {
+			// This fragment can fit all of pkt.Header and possibly
+			// some of pkt.Data, too.
+			newPayload := pkt.Data.Clone(nil)
+			newPayloadLength := outerMTU - pkt.Header.UsedLength()
 			newPayload.CapLength(newPayloadLength)
-			if err := e.linkEP.WritePacket(r, gso, hdr, newPayload, ProtocolNumber); err != nil {
+			if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, tcpip.PacketBuffer{
+				Header:        pkt.Header,
+				Data:          newPayload,
+				NetworkHeader: buffer.View(h),
+			}); err != nil {
 				return err
 			}
 			r.Stats().IP.PacketsSent.Increment()
-			payload.TrimFront(newPayloadLength)
+			pkt.Data.TrimFront(newPayloadLength)
 		} else {
-			// The fragment is too small to fit all of hdr.
-			startOfHdr := hdr
-			startOfHdr.TrimBack(hdr.UsedLength() - outerMTU)
+			// The fragment is too small to fit all of pkt.Header.
+			startOfHdr := pkt.Header
+			startOfHdr.TrimBack(pkt.Header.UsedLength() - outerMTU)
 			emptyVV := buffer.NewVectorisedView(0, []buffer.View{})
-			if err := e.linkEP.WritePacket(r, gso, startOfHdr, emptyVV, ProtocolNumber); err != nil {
+			if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, tcpip.PacketBuffer{
+				Header:        startOfHdr,
+				Data:          emptyVV,
+				NetworkHeader: buffer.View(h),
+			}); err != nil {
 				return err
 			}
 			r.Stats().IP.PacketsSent.Increment()
-			// Add the unused bytes of hdr into the payload that remains to be sent.
-			restOfHdr := hdr.View()[outerMTU:]
+			// Add the unused bytes of pkt.Header into the pkt.Data
+			// that remains to be sent.
+			restOfHdr := pkt.Header.View()[outerMTU:]
 			tmp := buffer.NewVectorisedView(len(restOfHdr), []buffer.View{buffer.NewViewFromBytes(restOfHdr)})
-			tmp.Append(payload)
-			payload = tmp
+			tmp.Append(pkt.Data)
+			pkt.Data = tmp
 		}
 	}
 	return nil
@@ -222,17 +238,17 @@ func (e *endpoint) addIPHeader(r *stack.Route, hdr *buffer.Prependable, payloadS
 }
 
 // WritePacket writes a packet to the given destination address and protocol.
-func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, params stack.NetworkHeaderParams, loop stack.PacketLooping) *tcpip.Error {
-	ip := e.addIPHeader(r, &hdr, payload.Size(), params)
+func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, loop stack.PacketLooping, pkt tcpip.PacketBuffer) *tcpip.Error {
+	ip := e.addIPHeader(r, &pkt.Header, pkt.Data.Size(), params)
 
 	if loop&stack.PacketLoop != 0 {
-		views := make([]buffer.View, 1, 1+len(payload.Views()))
-		views[0] = hdr.View()
-		views = append(views, payload.Views()...)
+		views := make([]buffer.View, 1, 1+len(pkt.Data.Views()))
+		views[0] = pkt.Header.View()
+		views = append(views, pkt.Data.Views()...)
 		loopedR := r.MakeLoopedRoute()
 
 		e.HandlePacket(&loopedR, tcpip.PacketBuffer{
-			Data:          buffer.NewVectorisedView(len(views[0])+payload.Size(), views),
+			Data:          buffer.NewVectorisedView(len(views[0])+pkt.Data.Size(), views),
 			NetworkHeader: buffer.View(ip),
 		})
 
@@ -241,10 +257,10 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 	if loop&stack.PacketOut == 0 {
 		return nil
 	}
-	if hdr.UsedLength()+payload.Size() > int(e.linkEP.MTU()) && (gso == nil || gso.Type == stack.GSONone) {
-		return e.writePacketFragments(r, gso, hdr, payload, int(e.linkEP.MTU()))
+	if pkt.Header.UsedLength()+pkt.Data.Size() > int(e.linkEP.MTU()) && (gso == nil || gso.Type == stack.GSONone) {
+		return e.writePacketFragments(r, gso, int(e.linkEP.MTU()), pkt)
 	}
-	if err := e.linkEP.WritePacket(r, gso, hdr, payload, ProtocolNumber); err != nil {
+	if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
 		return err
 	}
 	r.Stats().IP.PacketsSent.Increment()
@@ -270,16 +286,16 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, hdrs []stack.Pac
 
 // WriteHeaderIncludedPacket writes a packet already containing a network
 // header through the given route.
-func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, payload buffer.VectorisedView, loop stack.PacketLooping) *tcpip.Error {
+func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, loop stack.PacketLooping, pkt tcpip.PacketBuffer) *tcpip.Error {
 	// The packet already has an IP header, but there are a few required
 	// checks.
-	ip := header.IPv4(payload.First())
-	if !ip.IsValid(payload.Size()) {
+	ip := header.IPv4(pkt.Data.First())
+	if !ip.IsValid(pkt.Data.Size()) {
 		return tcpip.ErrInvalidOptionValue
 	}
 
 	// Always set the total length.
-	ip.SetTotalLength(uint16(payload.Size()))
+	ip.SetTotalLength(uint16(pkt.Data.Size()))
 
 	// Set the source address when zero.
 	if ip.SourceAddress() == tcpip.Address(([]byte{0, 0, 0, 0})) {
@@ -293,7 +309,7 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, payload buffer.Vect
 	// Set the packet ID when zero.
 	if ip.ID() == 0 {
 		id := uint32(0)
-		if payload.Size() > header.IPv4MaximumHeaderSize+8 {
+		if pkt.Data.Size() > header.IPv4MaximumHeaderSize+8 {
 			// Packets of 68 bytes or less are required by RFC 791 to not be
 			// fragmented, so we only assign ids to larger packets.
 			id = atomic.AddUint32(&e.protocol.ids[hashRoute(r, 0 /* protocol */, e.protocol.hashIV)%buckets], 1)
@@ -306,18 +322,18 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, payload buffer.Vect
 	ip.SetChecksum(^ip.CalculateChecksum())
 
 	if loop&stack.PacketLoop != 0 {
-		e.HandlePacket(r, tcpip.PacketBuffer{
-			Data:          payload,
-			NetworkHeader: buffer.View(ip),
-		})
+		e.HandlePacket(r, pkt.Clone())
 	}
 	if loop&stack.PacketOut == 0 {
 		return nil
 	}
 
-	hdr := buffer.NewPrependableFromView(payload.ToView())
 	r.Stats().IP.PacketsSent.Increment()
-	return e.linkEP.WritePacket(r, nil /* gso */, hdr, buffer.VectorisedView{}, ProtocolNumber)
+
+	ip = ip[:ip.HeaderLength()]
+	pkt.Header = buffer.NewPrependableFromView(buffer.View(ip))
+	pkt.Data.TrimFront(int(ip.HeaderLength()))
+	return e.linkEP.WritePacket(r, nil /* gso */, ProtocolNumber, pkt)
 }
 
 // HandlePacket is called by the link layer when new ipv4 packets arrive for

pkg/tcpip/network/ipv4/ipv4_test.go

@@ -113,12 +113,12 @@ func makeHdrAndPayload(hdrLength int, extraLength int, viewSizes []int) (buffer.
 
 // comparePayloads compared the contents of all the packets against the contents
 // of the source packet.
-func compareFragments(t *testing.T, packets []packetInfo, sourcePacketInfo packetInfo, mtu uint32) {
+func compareFragments(t *testing.T, packets []tcpip.PacketBuffer, sourcePacketInfo tcpip.PacketBuffer, mtu uint32) {
 	t.Helper()
 	// Make a complete array of the sourcePacketInfo packet.
 	source := header.IPv4(packets[0].Header.View()[:header.IPv4MinimumSize])
 	source = append(source, sourcePacketInfo.Header.View()...)
-	source = append(source, sourcePacketInfo.Payload.ToView()...)
+	source = append(source, sourcePacketInfo.Data.ToView()...)
 
 	// Make a copy of the IP header, which will be modified in some fields to make
 	// an expected header.
@@ -132,7 +132,7 @@ func compareFragments(t *testing.T, packets []packetInfo, sourcePacketInfo packe
 	for i, packet := range packets {
 		// Confirm that the packet is valid.
 		allBytes := packet.Header.View().ToVectorisedView()
-		allBytes.Append(packet.Payload)
+		allBytes.Append(packet.Data)
 		ip := header.IPv4(allBytes.ToView())
 		if !ip.IsValid(len(ip)) {
 			t.Errorf("IP packet is invalid:\n%s", hex.Dump(ip))
@@ -173,7 +173,7 @@ func compareFragments(t *testing.T, packets []packetInfo, sourcePacketInfo packe
 
 type errorChannel struct {
 	*channel.Endpoint
-	Ch                    chan packetInfo
+	Ch                    chan tcpip.PacketBuffer
 	packetCollectorErrors []*tcpip.Error
 }
 
@@ -183,17 +183,11 @@ type errorChannel struct {
 func newErrorChannel(size int, mtu uint32, linkAddr tcpip.LinkAddress, packetCollectorErrors []*tcpip.Error) *errorChannel {
 	return &errorChannel{
 		Endpoint:              channel.New(size, mtu, linkAddr),
-		Ch:                    make(chan packetInfo, size),
+		Ch:                    make(chan tcpip.PacketBuffer, size),
 		packetCollectorErrors: packetCollectorErrors,
 	}
 }
 
-// packetInfo holds all the information about an outbound packet.
-type packetInfo struct {
-	Header  buffer.Prependable
-	Payload buffer.VectorisedView
-}
-
 // Drain removes all outbound packets from the channel and counts them.
 func (e *errorChannel) Drain() int {
 	c := 0
@@ -208,14 +202,9 @@ func (e *errorChannel) Drain() int {
 }
 
 // WritePacket stores outbound packets into the channel.
-func (e *errorChannel) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
-	p := packetInfo{
-		Header:  hdr,
-		Payload: payload,
-	}
-
+func (e *errorChannel) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
 	select {
-	case e.Ch <- p:
+	case e.Ch <- pkt:
 	default:
 	}
 
@@ -292,18 +281,21 @@ func TestFragmentation(t *testing.T) {
 	for _, ft := range fragTests {
 		t.Run(ft.description, func(t *testing.T) {
 			hdr, payload := makeHdrAndPayload(ft.hdrLength, ft.extraLength, ft.payloadViewsSizes)
-			source := packetInfo{
+			source := tcpip.PacketBuffer{
 				Header: hdr,
 				// Save the source payload because WritePacket will modify it.
-				Payload: payload.Clone([]buffer.View{}),
+				Data: payload.Clone(nil),
 			}
 			c := buildContext(t, nil, ft.mtu)
-			err := c.Route.WritePacket(ft.gso, hdr, payload, stack.NetworkHeaderParams{Protocol: tcp.ProtocolNumber, TTL: 42, TOS: stack.DefaultTOS})
+			err := c.Route.WritePacket(ft.gso, stack.NetworkHeaderParams{Protocol: tcp.ProtocolNumber, TTL: 42, TOS: stack.DefaultTOS}, tcpip.PacketBuffer{
+				Header: hdr,
+				Data:   payload,
+			})
 			if err != nil {
 				t.Errorf("err got %v, want %v", err, nil)
 			}
 
-			var results []packetInfo
+			var results []tcpip.PacketBuffer
 		L:
 			for {
 				select {
@@ -345,7 +337,10 @@ func TestFragmentationErrors(t *testing.T) {
 		t.Run(ft.description, func(t *testing.T) {
 			hdr, payload := makeHdrAndPayload(ft.hdrLength, header.IPv4MinimumSize, ft.payloadViewsSizes)
 			c := buildContext(t, ft.packetCollectorErrors, ft.mtu)
-			err := c.Route.WritePacket(&stack.GSO{}, hdr, payload, stack.NetworkHeaderParams{Protocol: tcp.ProtocolNumber, TTL: 42, TOS: stack.DefaultTOS})
+			err := c.Route.WritePacket(&stack.GSO{}, stack.NetworkHeaderParams{Protocol: tcp.ProtocolNumber, TTL: 42, TOS: stack.DefaultTOS}, tcpip.PacketBuffer{
+				Header: hdr,
+				Data:   payload,
+			})
 			for i := 0; i < len(ft.packetCollectorErrors)-1; i++ {
 				if got, want := ft.packetCollectorErrors[i], (*tcpip.Error)(nil); got != want {
 					t.Errorf("ft.packetCollectorErrors[%d] got %v, want %v", i, got, want)

pkg/tcpip/network/ipv6/icmp.go

@@ -226,7 +226,9 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt tcpip.P
 		//
 		// 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 */, hdr, buffer.VectorisedView{}, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: header.NDPHopLimit, TOS: stack.DefaultTOS}); err != nil {
+		if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: header.NDPHopLimit, TOS: stack.DefaultTOS}, tcpip.PacketBuffer{
+			Header: hdr,
+		}); err != nil {
 			sent.Dropped.Increment()
 			return
 		}
@@ -291,7 +293,10 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt tcpip.P
 		copy(packet, h)
 		packet.SetType(header.ICMPv6EchoReply)
 		packet.SetChecksum(header.ICMPv6Checksum(packet, r.LocalAddress, r.RemoteAddress, pkt.Data))
-		if err := r.WritePacket(nil /* gso */, hdr, pkt.Data, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}); err != nil {
+		if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, tcpip.PacketBuffer{
+			Header: hdr,
+			Data:   pkt.Data,
+		}); err != nil {
 			sent.Dropped.Increment()
 			return
 		}
@@ -417,7 +422,9 @@ func (*protocol) LinkAddressRequest(addr, localAddr tcpip.Address, linkEP stack.
 	})
 
 	// TODO(stijlist): count this in ICMP stats.
-	return linkEP.WritePacket(r, nil /* gso */, hdr, buffer.VectorisedView{}, ProtocolNumber)
+	return linkEP.WritePacket(r, nil /* gso */, ProtocolNumber, tcpip.PacketBuffer{
+		Header: hdr,
+	})
 }
 
 // ResolveStaticAddress implements stack.LinkAddressResolver.

pkg/tcpip/network/ipv6/icmp_test.go

@@ -55,7 +55,7 @@ func (*stubLinkEndpoint) LinkAddress() tcpip.LinkAddress {
 	return ""
 }
 
-func (*stubLinkEndpoint) WritePacket(*stack.Route, *stack.GSO, buffer.Prependable, buffer.VectorisedView, tcpip.NetworkProtocolNumber) *tcpip.Error {
+func (*stubLinkEndpoint) WritePacket(*stack.Route, *stack.GSO, tcpip.NetworkProtocolNumber, tcpip.PacketBuffer) *tcpip.Error {
 	return nil
 }
 
@@ -276,22 +276,22 @@ type routeArgs struct {
 func routeICMPv6Packet(t *testing.T, args routeArgs, fn func(*testing.T, header.ICMPv6)) {
 	t.Helper()
 
-	pkt := <-args.src.C
+	pi := <-args.src.C
 
 	{
-		views := []buffer.View{pkt.Header, pkt.Payload}
-		size := len(pkt.Header) + len(pkt.Payload)
+		views := []buffer.View{pi.Pkt.Header.View(), pi.Pkt.Data.ToView()}
+		size := pi.Pkt.Header.UsedLength() + pi.Pkt.Data.Size()
 		vv := buffer.NewVectorisedView(size, views)
-		args.dst.InjectLinkAddr(pkt.Proto, args.dst.LinkAddress(), tcpip.PacketBuffer{
+		args.dst.InjectLinkAddr(pi.Proto, args.dst.LinkAddress(), tcpip.PacketBuffer{
 			Data: vv,
 		})
 	}
 
-	if pkt.Proto != ProtocolNumber {
-		t.Errorf("unexpected protocol number %d", pkt.Proto)
+	if pi.Proto != ProtocolNumber {
+		t.Errorf("unexpected protocol number %d", pi.Proto)
 		return
 	}
-	ipv6 := header.IPv6(pkt.Header)
+	ipv6 := header.IPv6(pi.Pkt.Header.View())
 	transProto := tcpip.TransportProtocolNumber(ipv6.NextHeader())
 	if transProto != header.ICMPv6ProtocolNumber {
 		t.Errorf("unexpected transport protocol number %d", transProto)