Automated rollback of changelist 308163542

PiperOrigin-RevId: 308674219

pkg/sentry/socket/netfilter/tcp_matcher.go

@@ -121,13 +121,12 @@ func (tm *TCPMatcher) Match(hook stack.Hook, pkt stack.PacketBuffer, interfaceNa
 		tcpHeader = header.TCP(pkt.TransportHeader)
 	} else {
 		// The TCP header hasn't been parsed yet. We have to do it here.
-		hdr, ok := pkt.Data.PullUp(header.TCPMinimumSize)
-		if !ok {
+		if len(pkt.Data.First()) < header.TCPMinimumSize {
 			// There's no valid TCP header here, so we hotdrop the
 			// packet.
 			return false, true
 		}
-		tcpHeader = header.TCP(hdr)
+		tcpHeader = header.TCP(pkt.Data.First())
 	}
 
 	// Check whether the source and destination ports are within the

pkg/sentry/socket/netfilter/udp_matcher.go

@@ -120,13 +120,12 @@ func (um *UDPMatcher) Match(hook stack.Hook, pkt stack.PacketBuffer, interfaceNa
 		udpHeader = header.UDP(pkt.TransportHeader)
 	} else {
 		// The UDP header hasn't been parsed yet. We have to do it here.
-		hdr, ok := pkt.Data.PullUp(header.UDPMinimumSize)
-		if !ok {
+		if len(pkt.Data.First()) < header.UDPMinimumSize {
 			// There's no valid UDP header here, so we hotdrop the
 			// packet.
 			return false, true
 		}
-		udpHeader = header.UDP(hdr)
+		udpHeader = header.UDP(pkt.Data.First())
 	}
 
 	// Check whether the source and destination ports are within the

pkg/tcpip/buffer/view.go

@@ -77,8 +77,7 @@ func NewVectorisedView(size int, views []View) VectorisedView {
 	return VectorisedView{views: views, size: size}
 }
 
-// TrimFront removes the first "count" bytes of the vectorised view. It panics
-// if count > vv.Size().
+// TrimFront removes the first "count" bytes of the vectorised view.
 func (vv *VectorisedView) TrimFront(count int) {
 	for count > 0 && len(vv.views) > 0 {
 		if count < len(vv.views[0]) {
@@ -87,7 +86,7 @@ func (vv *VectorisedView) TrimFront(count int) {
 			return
 		}
 		count -= len(vv.views[0])
-		vv.removeFirst()
+		vv.RemoveFirst()
 	}
 }
 
@@ -105,7 +104,7 @@ func (vv *VectorisedView) Read(v View) (copied int, err error) {
 		count -= len(vv.views[0])
 		copy(v[copied:], vv.views[0])
 		copied += len(vv.views[0])
-		vv.removeFirst()
+		vv.RemoveFirst()
 	}
 	if copied == 0 {
 		return 0, io.EOF
@@ -127,7 +126,7 @@ func (vv *VectorisedView) ReadToVV(dstVV *VectorisedView, count int) (copied int
 		count -= len(vv.views[0])
 		dstVV.AppendView(vv.views[0])
 		copied += len(vv.views[0])
-		vv.removeFirst()
+		vv.RemoveFirst()
 	}
 	return copied
 }
@@ -163,37 +162,22 @@ func (vv *VectorisedView) Clone(buffer []View) VectorisedView {
 	return VectorisedView{views: append(buffer[:0], vv.views...), size: vv.size}
 }
 
-// PullUp returns the first "count" bytes of the vectorised view. If those
-// bytes aren't already contiguous inside the vectorised view, PullUp will
-// reallocate as needed to make them contiguous. PullUp fails and returns false
-// when count > vv.Size().
-func (vv *VectorisedView) PullUp(count int) (View, bool) {
+// First returns the first view of the vectorised view.
+func (vv *VectorisedView) First() View {
 	if len(vv.views) == 0 {
-		return nil, count == 0
-	}
-	if count <= len(vv.views[0]) {
-		return vv.views[0][:count], true
-	}
-	if count > vv.size {
-		return nil, false
+		return nil
 	}
+	return vv.views[0]
+}
 
-	newFirst := NewView(count)
-	i := 0
-	for offset := 0; offset < count; i++ {
-		copy(newFirst[offset:], vv.views[i])
-		if count-offset < len(vv.views[i]) {
-			vv.views[i].TrimFront(count - offset)
-			break
-		}
-		offset += len(vv.views[i])
-		vv.views[i] = nil
+// RemoveFirst removes the first view of the vectorised view.
+func (vv *VectorisedView) RemoveFirst() {
+	if len(vv.views) == 0 {
+		return
 	}
-	// We're guaranteed that i > 0, since count is too large for the first
-	// view.
-	vv.views[i-1] = newFirst
-	vv.views = vv.views[i-1:]
-	return newFirst, true
+	vv.size -= len(vv.views[0])
+	vv.views[0] = nil
+	vv.views = vv.views[1:]
 }
 
 // Size returns the size in bytes of the entire content stored in the vectorised view.
@@ -241,10 +225,3 @@ func (vv *VectorisedView) Readers() []bytes.Reader {
 	}
 	return readers
 }
-
-// removeFirst panics when len(vv.views) < 1.
-func (vv *VectorisedView) removeFirst() {
-	vv.size -= len(vv.views[0])
-	vv.views[0] = nil
-	vv.views = vv.views[1:]
-}

pkg/tcpip/buffer/view_test.go

@@ -16,7 +16,6 @@
 package buffer
 
 import (
-	"bytes"
 	"reflect"
 	"testing"
 )
@@ -371,115 +370,3 @@ func TestVVRead(t *testing.T) {
 		})
 	}
 }
-
-var pullUpTestCases = []struct {
-	comment string
-	in      VectorisedView
-	count   int
-	want    []byte
-	result  VectorisedView
-	ok      bool
-}{
-	{
-		comment: "simple case",
-		in:      vv(2, "12"),
-		count:   1,
-		want:    []byte("1"),
-		result:  vv(2, "12"),
-		ok:      true,
-	},
-	{
-		comment: "entire View",
-		in:      vv(2, "1", "2"),
-		count:   1,
-		want:    []byte("1"),
-		result:  vv(2, "1", "2"),
-		ok:      true,
-	},
-	{
-		comment: "spanning across two Views",
-		in:      vv(3, "1", "23"),
-		count:   2,
-		want:    []byte("12"),
-		result:  vv(3, "12", "3"),
-		ok:      true,
-	},
-	{
-		comment: "spanning across all Views",
-		in:      vv(5, "1", "23", "45"),
-		count:   5,
-		want:    []byte("12345"),
-		result:  vv(5, "12345"),
-		ok:      true,
-	},
-	{
-		comment: "count = 0",
-		in:      vv(1, "1"),
-		count:   0,
-		want:    []byte{},
-		result:  vv(1, "1"),
-		ok:      true,
-	},
-	{
-		comment: "count = size",
-		in:      vv(1, "1"),
-		count:   1,
-		want:    []byte("1"),
-		result:  vv(1, "1"),
-		ok:      true,
-	},
-	{
-		comment: "count too large",
-		in:      vv(3, "1", "23"),
-		count:   4,
-		want:    nil,
-		result:  vv(3, "1", "23"),
-		ok:      false,
-	},
-	{
-		comment: "empty vv",
-		in:      vv(0, ""),
-		count:   1,
-		want:    nil,
-		result:  vv(0, ""),
-		ok:      false,
-	},
-	{
-		comment: "empty vv, count = 0",
-		in:      vv(0, ""),
-		count:   0,
-		want:    nil,
-		result:  vv(0, ""),
-		ok:      true,
-	},
-	{
-		comment: "empty views",
-		in:      vv(3, "", "1", "", "23"),
-		count:   2,
-		want:    []byte("12"),
-		result:  vv(3, "12", "3"),
-		ok:      true,
-	},
-}
-
-func TestPullUp(t *testing.T) {
-	for _, c := range pullUpTestCases {
-		got, ok := c.in.PullUp(c.count)
-
-		// Is the return value right?
-		if ok != c.ok {
-			t.Errorf("Test %q failed when calling PullUp(%d) on %v. Got an ok of %t. Want %t",
-				c.comment, c.count, c.in, ok, c.ok)
-		}
-		if bytes.Compare(got, View(c.want)) != 0 {
-			t.Errorf("Test %q failed when calling PullUp(%d) on %v. Got %v. Want %v",
-				c.comment, c.count, c.in, got, c.want)
-		}
-
-		// Is the underlying structure right?
-		if !reflect.DeepEqual(c.in, c.result) {
-			t.Errorf("Test %q failed when calling PullUp(%d). Got vv with structure %v. Wanted %v",
-				c.comment, c.count, c.in, c.result)
-		}
-	}
-}

pkg/tcpip/link/loopback/loopback.go

@@ -98,13 +98,13 @@ func (e *endpoint) WritePackets(*stack.Route, *stack.GSO, stack.PacketBufferList
 
 // WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
 func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
-	// There should be an ethernet header at the beginning of vv.
-	hdr, ok := vv.PullUp(header.EthernetMinimumSize)
-	if !ok {
-		// Reject the packet if it's shorter than an ethernet header.
+	// Reject the packet if it's shorter than an ethernet header.
+	if vv.Size() < header.EthernetMinimumSize {
 		return tcpip.ErrBadAddress
 	}
-	linkHeader := header.Ethernet(hdr)
+
+	// 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(), stack.PacketBuffer{
 		Data:       vv,

pkg/tcpip/link/rawfile/BUILD

@@ -1,4 +1,4 @@
-load("//tools:defs.bzl", "go_library", "go_test")
+load("//tools:defs.bzl", "go_library")
 
 package(licenses = ["notice"])
 
@@ -18,10 +18,3 @@ go_library(
         "@org_golang_x_sys//unix:go_default_library",
     ],
 )
-
-go_test(
-    name = "rawfile_test",
-    size = "small",
-    srcs = ["rawfile_test.go"],
-    library = ":rawfile",
-)

pkg/tcpip/link/rawfile/rawfile_test.go

@@ -1,46 +0,0 @@
-// Copyright 2020 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// +build linux
-
-package rawfile
-
-import (
-	"syscall"
-	"testing"
-)
-
-func TestNonBlockingWrite3ZeroLength(t *testing.T) {
-	fd, err := syscall.Open("/dev/null", syscall.O_WRONLY, 0)
-	if err != nil {
-		t.Fatalf("failed to open /dev/null: %v", err)
-	}
-	defer syscall.Close(fd)
-
-	if err := NonBlockingWrite3(fd, []byte{}, []byte{0}, nil); err != nil {
-		t.Fatalf("failed to write: %v", err)
-	}
-}
-
-func TestNonBlockingWrite3Nil(t *testing.T) {
-	fd, err := syscall.Open("/dev/null", syscall.O_WRONLY, 0)
-	if err != nil {
-		t.Fatalf("failed to open /dev/null: %v", err)
-	}
-	defer syscall.Close(fd)
-
-	if err := NonBlockingWrite3(fd, nil, []byte{0}, nil); err != nil {
-		t.Fatalf("failed to write: %v", err)
-	}
-}

pkg/tcpip/link/rawfile/rawfile_unsafe.go

@@ -76,13 +76,9 @@ func NonBlockingWrite3(fd int, b1, b2, b3 []byte) *tcpip.Error {
 
 	// We have two buffers. Build the iovec that represents them and issue
 	// a writev syscall.
-	var base *byte
-	if len(b1) > 0 {
-		base = &b1[0]
-	}
 	iovec := [3]syscall.Iovec{
 		{
-			Base: base,
+			Base: &b1[0],
 			Len:  uint64(len(b1)),
 		},
 		{

pkg/tcpip/link/sharedmem/sharedmem_test.go

@@ -674,7 +674,7 @@ func TestSimpleReceive(t *testing.T) {
 		// Wait for packet to be received, then check it.
 		c.waitForPackets(1, time.After(5*time.Second), "Timeout waiting for packet")
 		c.mu.Lock()
-		rcvd := []byte(c.packets[0].vv.ToView())
+		rcvd := []byte(c.packets[0].vv.First())
 		c.packets = c.packets[:0]
 		c.mu.Unlock()
 

pkg/tcpip/link/sniffer/sniffer.go

@@ -171,7 +171,11 @@ func (e *endpoint) GSOMaxSize() uint32 {
 func (e *endpoint) dumpPacket(prefix string, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
 	writer := e.writer
 	if writer == nil && atomic.LoadUint32(&LogPackets) == 1 {
-		logPacket(prefix, protocol, pkt, gso)
+		first := pkt.Header.View()
+		if len(first) == 0 {
+			first = pkt.Data.First()
+		}
+		logPacket(prefix, protocol, first, gso)
 	}
 	if writer != nil && atomic.LoadUint32(&LogPacketsToPCAP) == 1 {
 		totalLength := pkt.Header.UsedLength() + pkt.Data.Size()
@@ -234,7 +238,7 @@ func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
 // Wait implements stack.LinkEndpoint.Wait.
 func (e *endpoint) Wait() { e.lower.Wait() }
 
-func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer, gso *stack.GSO) {
+func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.View, gso *stack.GSO) {
 	// Figure out the network layer info.
 	var transProto uint8
 	src := tcpip.Address("unknown")
@@ -243,49 +247,28 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, pkt *stack.P
 	size := uint16(0)
 	var fragmentOffset uint16
 	var moreFragments bool
-
-	// Create a clone of pkt, including any headers if present. Avoid allocating
-	// backing memory for the clone.
-	views := [8]buffer.View{}
-	vv := buffer.NewVectorisedView(0, views[:0])
-	vv.AppendView(pkt.Header.View())
-	vv.Append(pkt.Data)
-
 	switch protocol {
 	case header.IPv4ProtocolNumber:
-		hdr, ok := vv.PullUp(header.IPv4MinimumSize)
-		if !ok {
-			return
-		}
-		ipv4 := header.IPv4(hdr)
+		ipv4 := header.IPv4(b)
 		fragmentOffset = ipv4.FragmentOffset()
 		moreFragments = ipv4.Flags()&header.IPv4FlagMoreFragments == header.IPv4FlagMoreFragments
 		src = ipv4.SourceAddress()
 		dst = ipv4.DestinationAddress()
 		transProto = ipv4.Protocol()
 		size = ipv4.TotalLength() - uint16(ipv4.HeaderLength())
-		vv.TrimFront(int(ipv4.HeaderLength()))
+		b = b[ipv4.HeaderLength():]
 		id = int(ipv4.ID())
 
 	case header.IPv6ProtocolNumber:
-		hdr, ok := vv.PullUp(header.IPv6MinimumSize)
-		if !ok {
-			return
-		}
-		ipv6 := header.IPv6(hdr)
+		ipv6 := header.IPv6(b)
 		src = ipv6.SourceAddress()
 		dst = ipv6.DestinationAddress()
 		transProto = ipv6.NextHeader()
 		size = ipv6.PayloadLength()
-		vv.TrimFront(header.IPv6MinimumSize)
+		b = b[header.IPv6MinimumSize:]
 
 	case header.ARPProtocolNumber:
-		hdr, ok := vv.PullUp(header.ARPSize)
-		if !ok {
-			return
-		}
-		vv.TrimFront(header.ARPSize)
-		arp := header.ARP(hdr)
+		arp := header.ARP(b)
 		log.Infof(
 			"%s arp %v (%v) -> %v (%v) valid:%v",
 			prefix,
@@ -301,7 +284,7 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, pkt *stack.P
 
 	// We aren't guaranteed to have a transport header - it's possible for
 	// writes via raw endpoints to contain only network headers.
-	if minSize, ok := transportProtocolMinSizes[tcpip.TransportProtocolNumber(transProto)]; ok && vv.Size() < minSize {
+	if minSize, ok := transportProtocolMinSizes[tcpip.TransportProtocolNumber(transProto)]; ok && len(b) < minSize {
 		log.Infof("%s %v -> %v transport protocol: %d, but no transport header found (possible raw packet)", prefix, src, dst, transProto)
 		return
 	}
@@ -314,11 +297,7 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, pkt *stack.P
 	switch tcpip.TransportProtocolNumber(transProto) {
 	case header.ICMPv4ProtocolNumber:
 		transName = "icmp"
-		hdr, ok := vv.PullUp(header.ICMPv4MinimumSize)
-		if !ok {
-			break
-		}
-		icmp := header.ICMPv4(hdr)
+		icmp := header.ICMPv4(b)
 		icmpType := "unknown"
 		if fragmentOffset == 0 {
 			switch icmp.Type() {
@@ -351,11 +330,7 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, pkt *stack.P
 
 	case header.ICMPv6ProtocolNumber:
 		transName = "icmp"
-		hdr, ok := vv.PullUp(header.ICMPv6MinimumSize)
-		if !ok {
-			break
-		}
-		icmp := header.ICMPv6(hdr)
+		icmp := header.ICMPv6(b)
 		icmpType := "unknown"
 		switch icmp.Type() {
 		case header.ICMPv6DstUnreachable:
@@ -386,11 +361,7 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, pkt *stack.P
 
 	case header.UDPProtocolNumber:
 		transName = "udp"
-		hdr, ok := vv.PullUp(header.UDPMinimumSize)
-		if !ok {
-			break
-		}
-		udp := header.UDP(hdr)
+		udp := header.UDP(b)
 		if fragmentOffset == 0 && len(udp) >= header.UDPMinimumSize {
 			srcPort = udp.SourcePort()
 			dstPort = udp.DestinationPort()
@@ -400,11 +371,7 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, pkt *stack.P
 
 	case header.TCPProtocolNumber:
 		transName = "tcp"
-		hdr, ok := vv.PullUp(header.TCPMinimumSize)
-		if !ok {
-			break
-		}
-		tcp := header.TCP(hdr)
+		tcp := header.TCP(b)
 		if fragmentOffset == 0 && len(tcp) >= header.TCPMinimumSize {
 			offset := int(tcp.DataOffset())
 			if offset < header.TCPMinimumSize {

pkg/tcpip/network/arp/arp.go

@@ -93,10 +93,7 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt stack.PacketBuf
 }
 
 func (e *endpoint) HandlePacket(r *stack.Route, pkt stack.PacketBuffer) {
-	v, ok := pkt.Data.PullUp(header.ARPSize)
-	if !ok {
-		return
-	}
+	v := pkt.Data.First()
 	h := header.ARP(v)
 	if !h.IsValid() {
 		return

pkg/tcpip/network/ipv4/icmp.go

@@ -25,11 +25,7 @@ import (
 // used to find out which transport endpoint must be notified about the ICMP
 // packet.
 func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt stack.PacketBuffer) {
-	h, ok := pkt.Data.PullUp(header.IPv4MinimumSize)
-	if !ok {
-		return
-	}
-	hdr := header.IPv4(h)
+	h := header.IPv4(pkt.Data.First())
 
 	// We don't use IsValid() here because ICMP only requires that the IP
 	// header plus 8 bytes of the transport header be included. So it's
@@ -38,12 +34,12 @@ func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt stack.
 	//
 	// Drop packet if it doesn't have the basic IPv4 header or if the
 	// original source address doesn't match the endpoint's address.
-	if hdr.SourceAddress() != e.id.LocalAddress {
+	if len(h) < header.IPv4MinimumSize || h.SourceAddress() != e.id.LocalAddress {
 		return
 	}
 
-	hlen := int(hdr.HeaderLength())
-	if pkt.Data.Size() < hlen || hdr.FragmentOffset() != 0 {
+	hlen := int(h.HeaderLength())
+	if pkt.Data.Size() < hlen || h.FragmentOffset() != 0 {
 		// We won't be able to handle this if it doesn't contain the
 		// full IPv4 header, or if it's a fragment not at offset 0
 		// (because it won't have the transport header).
@@ -52,15 +48,15 @@ func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt stack.
 
 	// Skip the ip header, then deliver control message.
 	pkt.Data.TrimFront(hlen)
-	p := hdr.TransportProtocol()
-	e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, hdr.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt)
+	p := h.TransportProtocol()
+	e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, h.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt)
 }
 
 func (e *endpoint) handleICMP(r *stack.Route, pkt stack.PacketBuffer) {
 	stats := r.Stats()
 	received := stats.ICMP.V4PacketsReceived
-	v, ok := pkt.Data.PullUp(header.ICMPv4MinimumSize)
-	if !ok {
+	v := pkt.Data.First()
+	if len(v) < header.ICMPv4MinimumSize {
 		received.Invalid.Increment()
 		return
 	}

pkg/tcpip/network/ipv4/ipv4.go

@@ -328,11 +328,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt stack.PacketBuffer) *tcpip.Error {
 	// The packet already has an IP header, but there are a few required
 	// checks.
-	h, ok := pkt.Data.PullUp(header.IPv4MinimumSize)
-	if !ok {
-		return tcpip.ErrInvalidOptionValue
-	}
-	ip := header.IPv4(h)
+	ip := header.IPv4(pkt.Data.First())
 	if !ip.IsValid(pkt.Data.Size()) {
 		return tcpip.ErrInvalidOptionValue
 	}
@@ -382,11 +378,7 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt stack.PacketBuf
 // HandlePacket is called by the link layer when new ipv4 packets arrive for
 // this endpoint.
 func (e *endpoint) HandlePacket(r *stack.Route, pkt stack.PacketBuffer) {
-	headerView, ok := pkt.Data.PullUp(header.IPv4MinimumSize)
-	if !ok {
-		r.Stats().IP.MalformedPacketsReceived.Increment()
-		return
-	}
+	headerView := pkt.Data.First()
 	h := header.IPv4(headerView)
 	if !h.IsValid(pkt.Data.Size()) {
 		r.Stats().IP.MalformedPacketsReceived.Increment()

pkg/tcpip/network/ipv6/icmp.go

@@ -28,11 +28,7 @@ import (
 // used to find out which transport endpoint must be notified about the ICMP
 // packet.
 func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt stack.PacketBuffer) {
-	h, ok := pkt.Data.PullUp(header.IPv6MinimumSize)
-	if !ok {
-		return
-	}
-	hdr := header.IPv6(h)
+	h := header.IPv6(pkt.Data.First())
 
 	// We don't use IsValid() here because ICMP only requires that up to
 	// 1280 bytes of the original packet be included. So it's likely that it
@@ -40,21 +36,17 @@ func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt stack.
 	//
 	// Drop packet if it doesn't have the basic IPv6 header or if the
 	// original source address doesn't match the endpoint's address.
-	if hdr.SourceAddress() != e.id.LocalAddress {
+	if len(h) < header.IPv6MinimumSize || h.SourceAddress() != e.id.LocalAddress {
 		return
 	}
 
 	// Skip the IP header, then handle the fragmentation header if there
 	// is one.
 	pkt.Data.TrimFront(header.IPv6MinimumSize)
-	p := hdr.TransportProtocol()
+	p := h.TransportProtocol()
 	if p == header.IPv6FragmentHeader {
-		f, ok := pkt.Data.PullUp(header.IPv6FragmentHeaderSize)
-		if !ok {
-			return
-		}
-		fragHdr := header.IPv6Fragment(f)
-		if !fragHdr.IsValid() || fragHdr.FragmentOffset() != 0 {
+		f := header.IPv6Fragment(pkt.Data.First())
+		if !f.IsValid() || f.FragmentOffset() != 0 {
 			// We can't handle fragments that aren't at offset 0
 			// because they don't have the transport headers.
 			return
@@ -63,19 +55,19 @@ func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt stack.
 		// Skip fragmentation header and find out the actual protocol
 		// number.
 		pkt.Data.TrimFront(header.IPv6FragmentHeaderSize)
-		p = fragHdr.TransportProtocol()
+		p = f.TransportProtocol()
 	}
 
 	// Deliver the control packet to the transport endpoint.
-	e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, hdr.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt)
+	e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, h.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt)
 }
 
 func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.PacketBuffer, hasFragmentHeader bool) {
 	stats := r.Stats().ICMP
 	sent := stats.V6PacketsSent
 	received := stats.V6PacketsReceived
-	v, ok := pkt.Data.PullUp(header.ICMPv6HeaderSize)
-	if !ok {
+	v := pkt.Data.First()
+	if len(v) < header.ICMPv6MinimumSize {
 		received.Invalid.Increment()
 		return
 	}
@@ -84,9 +76,11 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 
 	// Validate ICMPv6 checksum before processing the packet.
 	//
+	// Only the first view in vv is accounted for by h. To account for the
+	// rest of vv, a shallow copy is made and the first view is removed.
 	// This copy is used as extra payload during the checksum calculation.
 	payload := pkt.Data.Clone(nil)
-	payload.TrimFront(len(h))
+	payload.RemoveFirst()
 	if got, want := h.Checksum(), header.ICMPv6Checksum(h, iph.SourceAddress(), iph.DestinationAddress(), payload); got != want {
 		received.Invalid.Increment()
 		return
@@ -107,40 +101,34 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 	switch h.Type() {
 	case header.ICMPv6PacketTooBig:
 		received.PacketTooBig.Increment()
-		hdr, ok := pkt.Data.PullUp(header.ICMPv6PacketTooBigMinimumSize)
-		if !ok {
+		if len(v) < header.ICMPv6PacketTooBigMinimumSize {
 			received.Invalid.Increment()
 			return
 		}
 		pkt.Data.TrimFront(header.ICMPv6PacketTooBigMinimumSize)
-		mtu := header.ICMPv6(hdr).MTU()
+		mtu := h.MTU()
 		e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), pkt)
 
 	case header.ICMPv6DstUnreachable:
 		received.DstUnreachable.Increment()
-		hdr, ok := pkt.Data.PullUp(header.ICMPv6DstUnreachableMinimumSize)
-		if !ok {
+		if len(v) < header.ICMPv6DstUnreachableMinimumSize {
 			received.Invalid.Increment()
 			return
 		}
 		pkt.Data.TrimFront(header.ICMPv6DstUnreachableMinimumSize)
-		switch header.ICMPv6(hdr).Code() {
+		switch h.Code() {
 		case header.ICMPv6PortUnreachable:
 			e.handleControl(stack.ControlPortUnreachable, 0, pkt)
 		}
 
 	case header.ICMPv6NeighborSolicit:
 		received.NeighborSolicit.Increment()
-		if pkt.Data.Size() < header.ICMPv6NeighborSolicitMinimumSize || !isNDPValid() {
+		if len(v) < header.ICMPv6NeighborSolicitMinimumSize || !isNDPValid() {
 			received.Invalid.Increment()
 			return
 		}
 
-		// The remainder of payload must be only the neighbor solicitation, so
-		// payload.ToView() always returns the solicitation. Per RFC 6980 section 5,
-		// NDP messages cannot be fragmented. Also note that in the common case NDP
-		// datagrams are very small and ToView() will not incur allocations.
-		ns := header.NDPNeighborSolicit(payload.ToView())
+		ns := header.NDPNeighborSolicit(h.NDPPayload())
 		it, err := ns.Options().Iter(true)
 		if err != nil {
 			// If we have a malformed NDP NS option, drop the packet.
@@ -298,16 +286,12 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 
 	case header.ICMPv6NeighborAdvert:
 		received.NeighborAdvert.Increment()
-		if pkt.Data.Size() < header.ICMPv6NeighborAdvertSize || !isNDPValid() {
+		if len(v) < header.ICMPv6NeighborAdvertSize || !isNDPValid() {
 			received.Invalid.Increment()
 			return
 		}
 
-		// The remainder of payload must be only the neighbor advertisement, so
-		// payload.ToView() always returns the advertisement. Per RFC 6980 section
-		// 5, NDP messages cannot be fragmented. Also note that in the common case
-		// NDP datagrams are very small and ToView() will not incur allocations.
-		na := header.NDPNeighborAdvert(payload.ToView())
+		na := header.NDPNeighborAdvert(h.NDPPayload())
 		it, err := na.Options().Iter(true)
 		if err != nil {
 			// If we have a malformed NDP NA option, drop the packet.
@@ -379,15 +363,14 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 
 	case header.ICMPv6EchoRequest:
 		received.EchoRequest.Increment()
-		icmpHdr, ok := pkt.Data.PullUp(header.ICMPv6EchoMinimumSize)
-		if !ok {
+		if len(v) < header.ICMPv6EchoMinimumSize {
 			received.Invalid.Increment()
 			return
 		}
 		pkt.Data.TrimFront(header.ICMPv6EchoMinimumSize)
 		hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.ICMPv6EchoMinimumSize)
 		packet := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize))
-		copy(packet, icmpHdr)
+		copy(packet, h)
 		packet.SetType(header.ICMPv6EchoReply)
 		packet.SetChecksum(header.ICMPv6Checksum(packet, r.LocalAddress, r.RemoteAddress, pkt.Data))
 		if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, stack.PacketBuffer{
@@ -401,7 +384,7 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 
 	case header.ICMPv6EchoReply:
 		received.EchoReply.Increment()
-		if pkt.Data.Size() < header.ICMPv6EchoMinimumSize {
+		if len(v) < header.ICMPv6EchoMinimumSize {
 			received.Invalid.Increment()
 			return
 		}
@@ -423,9 +406,8 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 	case header.ICMPv6RouterAdvert:
 		received.RouterAdvert.Increment()
 
-		// Is the NDP payload of sufficient size to hold a Router
-		// Advertisement?
-		if pkt.Data.Size()-header.ICMPv6HeaderSize < header.NDPRAMinimumSize || !isNDPValid() {
+		p := h.NDPPayload()
+		if len(p) < header.NDPRAMinimumSize || !isNDPValid() {
 			received.Invalid.Increment()
 			return
 		}
@@ -443,11 +425,7 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 			return
 		}
 
-		// The remainder of payload must be only the router advertisement, so
-		// payload.ToView() always returns the advertisement. Per RFC 6980 section
-		// 5, NDP messages cannot be fragmented. Also note that in the common case
-		// NDP datagrams are very small and ToView() will not incur allocations.
-		ra := header.NDPRouterAdvert(payload.ToView())
+		ra := header.NDPRouterAdvert(p)
 		opts := ra.Options()
 
 		// Are options valid as per the wire format?

pkg/tcpip/network/ipv6/icmp_test.go

@@ -166,8 +166,7 @@ func TestICMPCounts(t *testing.T) {
 		},
 		{
 			typ:  header.ICMPv6NeighborSolicit,
-			size: header.ICMPv6NeighborSolicitMinimumSize,
-		},
+			size: header.ICMPv6NeighborSolicitMinimumSize},
 		{
 			typ:       header.ICMPv6NeighborAdvert,
 			size:      header.ICMPv6NeighborAdvertMinimumSize,

pkg/tcpip/network/ipv6/ipv6.go

@@ -171,11 +171,7 @@ func (*endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt stack.PacketBuffe
 // HandlePacket is called by the link layer when new ipv6 packets arrive for
 // this endpoint.
 func (e *endpoint) HandlePacket(r *stack.Route, pkt stack.PacketBuffer) {
-	headerView, ok := pkt.Data.PullUp(header.IPv6MinimumSize)
-	if !ok {
-		r.Stats().IP.MalformedPacketsReceived.Increment()
-		return
-	}
+	headerView := pkt.Data.First()
 	h := header.IPv6(headerView)
 	if !h.IsValid(pkt.Data.Size()) {
 		r.Stats().IP.MalformedPacketsReceived.Increment()

pkg/tcpip/stack/forwarder_test.go

@@ -70,10 +70,7 @@ func (f *fwdTestNetworkEndpoint) ID() *NetworkEndpointID {
 
 func (f *fwdTestNetworkEndpoint) HandlePacket(r *Route, pkt PacketBuffer) {
 	// Consume the network header.
-	b, ok := pkt.Data.PullUp(fwdTestNetHeaderLen)
-	if !ok {
-		return
-	}
+	b := pkt.Data.First()
 	pkt.Data.TrimFront(fwdTestNetHeaderLen)
 
 	// Dispatch the packet to the transport protocol.
@@ -476,7 +473,7 @@ func TestForwardingWithFakeResolverPartialTimeout(t *testing.T) {
 		t.Fatal("packet not forwarded")
 	}
 
-	b := p.Pkt.Data.ToView()
+	b := p.Pkt.Header.View()
 	if b[0] != 3 {
 		t.Fatalf("got b[0] = %d, want = 3", b[0])
 	}
@@ -520,7 +517,7 @@ func TestForwardingWithFakeResolverTwoPackets(t *testing.T) {
 			t.Fatal("packet not forwarded")
 		}
 
-		b := p.Pkt.Data.ToView()
+		b := p.Pkt.Header.View()
 		if b[0] != 3 {
 			t.Fatalf("got b[0] = %d, want = 3", b[0])
 		}
@@ -567,7 +564,7 @@ func TestForwardingWithFakeResolverManyPackets(t *testing.T) {
 			t.Fatal("packet not forwarded")
 		}
 
-		b := p.Pkt.Data.ToView()
+		b := p.Pkt.Header.View()
 		if b[0] != 3 {
 			t.Fatalf("got b[0] = %d, want = 3", b[0])
 		}
@@ -622,7 +619,7 @@ func TestForwardingWithFakeResolverManyResolutions(t *testing.T) {
 
 		// The first 5 packets (address 3 to 7) should not be forwarded
 		// because their address resolutions are interrupted.
-		b := p.Pkt.Data.ToView()
+		b := p.Pkt.Header.View()
 		if b[0] < 8 {
 			t.Fatalf("got b[0] = %d, want b[0] >= 8", b[0])
 		}

pkg/tcpip/stack/iptables.go

@@ -212,11 +212,6 @@ func (it *IPTables) Check(hook Hook, pkt PacketBuffer) bool {
 // CheckPackets runs pkts through the rules for hook and returns a map of packets that
 // should not go forward.
 //
-// Precondition: pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
-//
-// TODO(gvisor.dev/issue/170): pk.NetworkHeader will always be set as a
-// precondition.
-//
 // NOTE: unlike the Check API the returned map contains packets that should be
 // dropped.
 func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList) (drop map[*PacketBuffer]struct{}) {
@@ -231,9 +226,7 @@ func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList) (drop map[*Pa
 	return drop
 }
 
-// Precondition: pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
-// TODO(gvisor.dev/issue/170): pk.NetworkHeader will always be set as a
-// precondition.
+// Precondition: pkt.NetworkHeader is set.
 func (it *IPTables) checkChain(hook Hook, pkt PacketBuffer, table Table, ruleIdx int) chainVerdict {
 	// Start from ruleIdx and walk the list of rules until a rule gives us
 	// a verdict.
@@ -278,21 +271,14 @@ func (it *IPTables) checkChain(hook Hook, pkt PacketBuffer, table Table, ruleIdx
 	return chainDrop
 }
 
-// Precondition: pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
-// TODO(gvisor.dev/issue/170): pk.NetworkHeader will always be set as a
-// precondition.
+// Precondition: pk.NetworkHeader is set.
 func (it *IPTables) checkRule(hook Hook, pkt PacketBuffer, table Table, ruleIdx int) (RuleVerdict, int) {
 	rule := table.Rules[ruleIdx]
 
 	// If pkt.NetworkHeader hasn't been set yet, it will be contained in
-	// pkt.Data.
+	// pkt.Data.First().
 	if pkt.NetworkHeader == nil {
-		var ok bool
-		pkt.NetworkHeader, ok = pkt.Data.PullUp(header.IPv4MinimumSize)
-		if !ok {
-			// Precondition has been violated.
-			panic(fmt.Sprintf("iptables checks require IPv4 headers of at least %d bytes", header.IPv4MinimumSize))
-		}
+		pkt.NetworkHeader = pkt.Data.First()
 	}
 
 	// Check whether the packet matches the IP header filter.

pkg/tcpip/stack/iptables_targets.go

@@ -96,12 +96,9 @@ func (rt RedirectTarget) Action(pkt PacketBuffer) (RuleVerdict, int) {
 	newPkt := pkt.Clone()
 
 	// Set network header.
-	headerView, ok := newPkt.Data.PullUp(header.IPv4MinimumSize)
-	if !ok {
-		return RuleDrop, 0
-	}
+	headerView := newPkt.Data.First()
 	netHeader := header.IPv4(headerView)
-	newPkt.NetworkHeader = headerView
+	newPkt.NetworkHeader = headerView[:header.IPv4MinimumSize]
 
 	hlen := int(netHeader.HeaderLength())
 	tlen := int(netHeader.TotalLength())
@@ -120,14 +117,10 @@ func (rt RedirectTarget) Action(pkt PacketBuffer) (RuleVerdict, int) {
 		if newPkt.TransportHeader != nil {
 			udpHeader = header.UDP(newPkt.TransportHeader)
 		} else {
-			if pkt.Data.Size() < header.UDPMinimumSize {
+			if len(pkt.Data.First()) < header.UDPMinimumSize {
 				return RuleDrop, 0
 			}
-			hdr, ok := newPkt.Data.PullUp(header.UDPMinimumSize)
-			if !ok {
-				return RuleDrop, 0
-			}
-			udpHeader = header.UDP(hdr)
+			udpHeader = header.UDP(newPkt.Data.First())
 		}
 		udpHeader.SetDestinationPort(rt.MinPort)
 	case header.TCPProtocolNumber:
@@ -135,14 +128,10 @@ func (rt RedirectTarget) Action(pkt PacketBuffer) (RuleVerdict, int) {
 		if newPkt.TransportHeader != nil {
 			tcpHeader = header.TCP(newPkt.TransportHeader)
 		} else {
-			if pkt.Data.Size() < header.TCPMinimumSize {
+			if len(pkt.Data.First()) < header.TCPMinimumSize {
 				return RuleDrop, 0
 			}
-			hdr, ok := newPkt.Data.PullUp(header.TCPMinimumSize)
-			if !ok {
-				return RuleDrop, 0
-			}
-			tcpHeader = header.TCP(hdr)
+			tcpHeader = header.TCP(newPkt.TransportHeader)
 		}
 		// TODO(gvisor.dev/issue/170): Need to recompute checksum
 		// and implement nat connection tracking to support TCP.

pkg/tcpip/stack/nic.go

@@ -1203,12 +1203,12 @@ func (n *NIC) DeliverNetworkPacket(linkEP LinkEndpoint, remote, local tcpip.Link
 		n.stack.stats.IP.PacketsReceived.Increment()
 	}
 
-	netHeader, ok := pkt.Data.PullUp(netProto.MinimumPacketSize())
-	if !ok {
+	if len(pkt.Data.First()) < netProto.MinimumPacketSize() {
 		n.stack.stats.MalformedRcvdPackets.Increment()
 		return
 	}
-	src, dst := netProto.ParseAddresses(netHeader)
+
+	src, dst := netProto.ParseAddresses(pkt.Data.First())
 
 	if n.stack.handleLocal && !n.isLoopback() && n.getRef(protocol, src) != nil {
 		// The source address is one of our own, so we never should have gotten a
@@ -1289,8 +1289,22 @@ func (n *NIC) DeliverNetworkPacket(linkEP LinkEndpoint, remote, local tcpip.Link
 
 func (n *NIC) forwardPacket(r *Route, protocol tcpip.NetworkProtocolNumber, pkt PacketBuffer) {
 	// TODO(b/143425874) Decrease the TTL field in forwarded packets.
-	if linkHeaderLen := int(n.linkEP.MaxHeaderLength()); linkHeaderLen != 0 {
-		pkt.Header = buffer.NewPrependable(linkHeaderLen)
+
+	firstData := pkt.Data.First()
+	pkt.Data.RemoveFirst()
+
+	if linkHeaderLen := int(n.linkEP.MaxHeaderLength()); linkHeaderLen == 0 {
+		pkt.Header = buffer.NewPrependableFromView(firstData)
+	} else {
+		firstDataLen := len(firstData)
+
+		// pkt.Header should have enough capacity to hold n.linkEP's headers.
+		pkt.Header = buffer.NewPrependable(firstDataLen + linkHeaderLen)
+
+		// TODO(b/151227689): avoid copying the packet when forwarding
+		if n := copy(pkt.Header.Prepend(firstDataLen), firstData); n != firstDataLen {
+			panic(fmt.Sprintf("copied %d bytes, expected %d", n, firstDataLen))
+		}
 	}
 
 	if err := n.linkEP.WritePacket(r, nil /* gso */, protocol, pkt); err != nil {
@@ -1318,13 +1332,12 @@ func (n *NIC) DeliverTransportPacket(r *Route, protocol tcpip.TransportProtocolN
 	// validly formed.
 	n.stack.demux.deliverRawPacket(r, protocol, pkt)
 
-	transHeader, ok := pkt.Data.PullUp(transProto.MinimumPacketSize())
-	if !ok {
+	if len(pkt.Data.First()) < transProto.MinimumPacketSize() {
 		n.stack.stats.MalformedRcvdPackets.Increment()
 		return
 	}
 
-	srcPort, dstPort, err := transProto.ParsePorts(transHeader)
+	srcPort, dstPort, err := transProto.ParsePorts(pkt.Data.First())
 	if err != nil {
 		n.stack.stats.MalformedRcvdPackets.Increment()
 		return
@@ -1362,12 +1375,11 @@ func (n *NIC) DeliverTransportControlPacket(local, remote tcpip.Address, net tcp
 	// ICMPv4 only guarantees that 8 bytes of the transport protocol will
 	// be present in the payload. We know that the ports are within the
 	// first 8 bytes for all known transport protocols.
-	transHeader, ok := pkt.Data.PullUp(8)
-	if !ok {
+	if len(pkt.Data.First()) < 8 {
 		return
 	}
 
-	srcPort, dstPort, err := transProto.ParsePorts(transHeader)
+	srcPort, dstPort, err := transProto.ParsePorts(pkt.Data.First())
 	if err != nil {
 		return
 	}