Merge release-20200422.0-11-g5e1e61f (automated)

19 files changed, 267 insertions, 132 deletions

diff --git a/pkg/sentry/socket/netfilter/tcp_matcher.go b/pkg/sentry/socket/netfilter/tcp_matcher.go
index ff1cfd8f6..55c0f04f3 100755
--- a/pkg/sentry/socket/netfilter/tcp_matcher.go
+++ b/pkg/sentry/socket/netfilter/tcp_matcher.go
@@ -121,12 +121,13 @@ 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.
-		if len(pkt.Data.First()) < header.TCPMinimumSize {
+		hdr, ok := pkt.Data.PullUp(header.TCPMinimumSize)
+		if !ok {
 			// There's no valid TCP header here, so we hotdrop the
 			// packet.
 			return false, true
 		}
-		tcpHeader = header.TCP(pkt.Data.First())
+		tcpHeader = header.TCP(hdr)
 	}
 
 	// Check whether the source and destination ports are within the
diff --git a/pkg/sentry/socket/netfilter/udp_matcher.go b/pkg/sentry/socket/netfilter/udp_matcher.go
index 3359418c1..04d03d494 100755
--- a/pkg/sentry/socket/netfilter/udp_matcher.go
+++ b/pkg/sentry/socket/netfilter/udp_matcher.go
@@ -120,12 +120,13 @@ 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.
-		if len(pkt.Data.First()) < header.UDPMinimumSize {
+		hdr, ok := pkt.Data.PullUp(header.UDPMinimumSize)
+		if !ok {
 			// There's no valid UDP header here, so we hotdrop the
 			// packet.
 			return false, true
 		}
-		udpHeader = header.UDP(pkt.Data.First())
+		udpHeader = header.UDP(hdr)
 	}
 
 	// Check whether the source and destination ports are within the
diff --git a/pkg/tcpip/buffer/view.go b/pkg/tcpip/buffer/view.go
index 8ec5d5d5c..f01217c91 100644
--- a/pkg/tcpip/buffer/view.go
+++ b/pkg/tcpip/buffer/view.go
@@ -77,7 +77,8 @@ func NewVectorisedView(size int, views []View) VectorisedView {
 	return VectorisedView{views: views, size: size}
 }
 
-// TrimFront removes the first "count" bytes of the vectorised view.
+// TrimFront removes the first "count" bytes of the vectorised view. It panics
+// if count > vv.Size().
 func (vv *VectorisedView) TrimFront(count int) {
 	for count > 0 && len(vv.views) > 0 {
 		if count < len(vv.views[0]) {
@@ -86,7 +87,7 @@ func (vv *VectorisedView) TrimFront(count int) {
 			return
 		}
 		count -= len(vv.views[0])
-		vv.RemoveFirst()
+		vv.removeFirst()
 	}
 }
 
@@ -104,7 +105,7 @@ 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
@@ -126,7 +127,7 @@ 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
 }
@@ -162,22 +163,37 @@ func (vv *VectorisedView) Clone(buffer []View) VectorisedView {
 	return VectorisedView{views: append(buffer[:0], vv.views...), size: vv.size}
 }
 
-// First returns the first view of the vectorised view.
-func (vv *VectorisedView) First() View {
+// 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) {
 	if len(vv.views) == 0 {
-		return nil
+		return nil, count == 0
+	}
+	if count <= len(vv.views[0]) {
+		return vv.views[0][:count], true
+	}
+	if count > vv.size {
+		return nil, false
 	}
-	return vv.views[0]
-}
 
-// RemoveFirst removes the first view of the vectorised view.
-func (vv *VectorisedView) RemoveFirst() {
-	if len(vv.views) == 0 {
-		return
+	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
 	}
-	vv.size -= len(vv.views[0])
-	vv.views[0] = nil
-	vv.views = vv.views[1:]
+	// 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
 }
 
 // Size returns the size in bytes of the entire content stored in the vectorised view.
@@ -225,3 +241,10 @@ 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:]
+}
diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index 53a9712c6..affa1bbdf 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -436,6 +436,9 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.Ne
 	if pkt.Data.Size() == 0 {
 		return rawfile.NonBlockingWrite(fd, pkt.Header.View())
 	}
+	if pkt.Header.UsedLength() == 0 {
+		return rawfile.NonBlockingWrite(fd, pkt.Data.ToView())
+	}
 
 	return rawfile.NonBlockingWrite3(fd, pkt.Header.View(), pkt.Data.ToView(), nil)
 }
diff --git a/pkg/tcpip/link/loopback/loopback.go b/pkg/tcpip/link/loopback/loopback.go
index 1e2255bfa..073c84ef9 100644
--- a/pkg/tcpip/link/loopback/loopback.go
+++ b/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 {
-	// Reject the packet if it's shorter than an ethernet header.
-	if vv.Size() < header.EthernetMinimumSize {
+	// 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.
 		return tcpip.ErrBadAddress
 	}
-
-	// There should be an ethernet header at the beginning of vv.
-	linkHeader := header.Ethernet(vv.First()[:header.EthernetMinimumSize])
+	linkHeader := header.Ethernet(hdr)
 	vv.TrimFront(len(linkHeader))
 	e.dispatcher.DeliverNetworkPacket(e, "" /* remote */, "" /* local */, linkHeader.Type(), stack.PacketBuffer{
 		Data:       vv,
diff --git a/pkg/tcpip/link/sniffer/sniffer.go b/pkg/tcpip/link/sniffer/sniffer.go
index be2537a82..0799c8f4d 100644
--- a/pkg/tcpip/link/sniffer/sniffer.go
+++ b/pkg/tcpip/link/sniffer/sniffer.go
@@ -171,11 +171,7 @@ 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 {
-		first := pkt.Header.View()
-		if len(first) == 0 {
-			first = pkt.Data.First()
-		}
-		logPacket(prefix, protocol, first, gso)
+		logPacket(prefix, protocol, pkt, gso)
 	}
 	if writer != nil && atomic.LoadUint32(&LogPacketsToPCAP) == 1 {
 		totalLength := pkt.Header.UsedLength() + pkt.Data.Size()
@@ -238,7 +234,7 @@ 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, b buffer.View, gso *stack.GSO) {
+func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer, gso *stack.GSO) {
 	// Figure out the network layer info.
 	var transProto uint8
 	src := tcpip.Address("unknown")
@@ -247,28 +243,49 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.Vie
 	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:
-		ipv4 := header.IPv4(b)
+		hdr, ok := vv.PullUp(header.IPv4MinimumSize)
+		if !ok {
+			return
+		}
+		ipv4 := header.IPv4(hdr)
 		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())
-		b = b[ipv4.HeaderLength():]
+		vv.TrimFront(int(ipv4.HeaderLength()))
 		id = int(ipv4.ID())
 
 	case header.IPv6ProtocolNumber:
-		ipv6 := header.IPv6(b)
+		hdr, ok := vv.PullUp(header.IPv6MinimumSize)
+		if !ok {
+			return
+		}
+		ipv6 := header.IPv6(hdr)
 		src = ipv6.SourceAddress()
 		dst = ipv6.DestinationAddress()
 		transProto = ipv6.NextHeader()
 		size = ipv6.PayloadLength()
-		b = b[header.IPv6MinimumSize:]
+		vv.TrimFront(header.IPv6MinimumSize)
 
 	case header.ARPProtocolNumber:
-		arp := header.ARP(b)
+		hdr, ok := vv.PullUp(header.ARPSize)
+		if !ok {
+			return
+		}
+		vv.TrimFront(header.ARPSize)
+		arp := header.ARP(hdr)
 		log.Infof(
 			"%s arp %v (%v) -> %v (%v) valid:%v",
 			prefix,
@@ -284,7 +301,7 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.Vie
 
 	// 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 && len(b) < minSize {
+	if minSize, ok := transportProtocolMinSizes[tcpip.TransportProtocolNumber(transProto)]; ok && vv.Size() < minSize {
 		log.Infof("%s %v -> %v transport protocol: %d, but no transport header found (possible raw packet)", prefix, src, dst, transProto)
 		return
 	}
@@ -297,7 +314,11 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.Vie
 	switch tcpip.TransportProtocolNumber(transProto) {
 	case header.ICMPv4ProtocolNumber:
 		transName = "icmp"
-		icmp := header.ICMPv4(b)
+		hdr, ok := vv.PullUp(header.ICMPv4MinimumSize)
+		if !ok {
+			break
+		}
+		icmp := header.ICMPv4(hdr)
 		icmpType := "unknown"
 		if fragmentOffset == 0 {
 			switch icmp.Type() {
@@ -330,7 +351,11 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.Vie
 
 	case header.ICMPv6ProtocolNumber:
 		transName = "icmp"
-		icmp := header.ICMPv6(b)
+		hdr, ok := vv.PullUp(header.ICMPv6MinimumSize)
+		if !ok {
+			break
+		}
+		icmp := header.ICMPv6(hdr)
 		icmpType := "unknown"
 		switch icmp.Type() {
 		case header.ICMPv6DstUnreachable:
@@ -361,7 +386,11 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.Vie
 
 	case header.UDPProtocolNumber:
 		transName = "udp"
-		udp := header.UDP(b)
+		hdr, ok := vv.PullUp(header.UDPMinimumSize)
+		if !ok {
+			break
+		}
+		udp := header.UDP(hdr)
 		if fragmentOffset == 0 && len(udp) >= header.UDPMinimumSize {
 			srcPort = udp.SourcePort()
 			dstPort = udp.DestinationPort()
@@ -371,7 +400,11 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.Vie
 
 	case header.TCPProtocolNumber:
 		transName = "tcp"
-		tcp := header.TCP(b)
+		hdr, ok := vv.PullUp(header.TCPMinimumSize)
+		if !ok {
+			break
+		}
+		tcp := header.TCP(hdr)
 		if fragmentOffset == 0 && len(tcp) >= header.TCPMinimumSize {
 			offset := int(tcp.DataOffset())
 			if offset < header.TCPMinimumSize {
diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go
index 9f47b4ff2..9d0797af7 100644
--- a/pkg/tcpip/network/arp/arp.go
+++ b/pkg/tcpip/network/arp/arp.go
@@ -99,7 +99,10 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt stack.PacketBuf
 }
 
 func (e *endpoint) HandlePacket(r *stack.Route, pkt stack.PacketBuffer) {
-	v := pkt.Data.First()
+	v, ok := pkt.Data.PullUp(header.ARPSize)
+	if !ok {
+		return
+	}
 	h := header.ARP(v)
 	if !h.IsValid() {
 		return
diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go
index c4bf1ba5c..4cbefe5ab 100644
--- a/pkg/tcpip/network/ipv4/icmp.go
+++ b/pkg/tcpip/network/ipv4/icmp.go
@@ -25,7 +25,11 @@ 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 := header.IPv4(pkt.Data.First())
+	h, ok := pkt.Data.PullUp(header.IPv4MinimumSize)
+	if !ok {
+		return
+	}
+	hdr := header.IPv4(h)
 
 	// 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
@@ -34,12 +38,12 @@ 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 len(h) < header.IPv4MinimumSize || h.SourceAddress() != e.id.LocalAddress {
+	if hdr.SourceAddress() != e.id.LocalAddress {
 		return
 	}
 
-	hlen := int(h.HeaderLength())
-	if pkt.Data.Size() < hlen || h.FragmentOffset() != 0 {
+	hlen := int(hdr.HeaderLength())
+	if pkt.Data.Size() < hlen || hdr.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).
@@ -48,15 +52,15 @@ func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt stack.
 
 	// Skip the ip header, then deliver control message.
 	pkt.Data.TrimFront(hlen)
-	p := h.TransportProtocol()
-	e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, h.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt)
+	p := hdr.TransportProtocol()
+	e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, hdr.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt)
 }
 
 func (e *endpoint) handleICMP(r *stack.Route, pkt stack.PacketBuffer) {
 	stats := r.Stats()
 	received := stats.ICMP.V4PacketsReceived
-	v := pkt.Data.First()
-	if len(v) < header.ICMPv4MinimumSize {
+	v, ok := pkt.Data.PullUp(header.ICMPv4MinimumSize)
+	if !ok {
 		received.Invalid.Increment()
 		return
 	}
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index a9dec0c0e..1d61fddad 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -333,7 +333,11 @@ 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.
-	ip := header.IPv4(pkt.Data.First())
+	h, ok := pkt.Data.PullUp(header.IPv4MinimumSize)
+	if !ok {
+		return tcpip.ErrInvalidOptionValue
+	}
+	ip := header.IPv4(h)
 	if !ip.IsValid(pkt.Data.Size()) {
 		return tcpip.ErrInvalidOptionValue
 	}
@@ -383,7 +387,11 @@ 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 := pkt.Data.First()
+	headerView, ok := pkt.Data.PullUp(header.IPv4MinimumSize)
+	if !ok {
+		r.Stats().IP.MalformedPacketsReceived.Increment()
+		return
+	}
 	h := header.IPv4(headerView)
 	if !h.IsValid(pkt.Data.Size()) {
 		r.Stats().IP.MalformedPacketsReceived.Increment()
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index b68983d10..bdf3a0d25 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -28,7 +28,11 @@ 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 := header.IPv6(pkt.Data.First())
+	h, ok := pkt.Data.PullUp(header.IPv6MinimumSize)
+	if !ok {
+		return
+	}
+	hdr := header.IPv6(h)
 
 	// 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
@@ -36,17 +40,21 @@ 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 len(h) < header.IPv6MinimumSize || h.SourceAddress() != e.id.LocalAddress {
+	if hdr.SourceAddress() != e.id.LocalAddress {
 		return
 	}
 
 	// Skip the IP header, then handle the fragmentation header if there
 	// is one.
 	pkt.Data.TrimFront(header.IPv6MinimumSize)
-	p := h.TransportProtocol()
+	p := hdr.TransportProtocol()
 	if p == header.IPv6FragmentHeader {
-		f := header.IPv6Fragment(pkt.Data.First())
-		if !f.IsValid() || f.FragmentOffset() != 0 {
+		f, ok := pkt.Data.PullUp(header.IPv6FragmentHeaderSize)
+		if !ok {
+			return
+		}
+		fragHdr := header.IPv6Fragment(f)
+		if !fragHdr.IsValid() || fragHdr.FragmentOffset() != 0 {
 			// We can't handle fragments that aren't at offset 0
 			// because they don't have the transport headers.
 			return
@@ -55,19 +63,19 @@ 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 = f.TransportProtocol()
+		p = fragHdr.TransportProtocol()
 	}
 
 	// Deliver the control packet to the transport endpoint.
-	e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, h.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt)
+	e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, hdr.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 := pkt.Data.First()
-	if len(v) < header.ICMPv6MinimumSize {
+	v, ok := pkt.Data.PullUp(header.ICMPv6HeaderSize)
+	if !ok {
 		received.Invalid.Increment()
 		return
 	}
@@ -76,11 +84,9 @@ 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.RemoveFirst()
+	payload.TrimFront(len(h))
 	if got, want := h.Checksum(), header.ICMPv6Checksum(h, iph.SourceAddress(), iph.DestinationAddress(), payload); got != want {
 		received.Invalid.Increment()
 		return
@@ -101,34 +107,40 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 	switch h.Type() {
 	case header.ICMPv6PacketTooBig:
 		received.PacketTooBig.Increment()
-		if len(v) < header.ICMPv6PacketTooBigMinimumSize {
+		hdr, ok := pkt.Data.PullUp(header.ICMPv6PacketTooBigMinimumSize)
+		if !ok {
 			received.Invalid.Increment()
 			return
 		}
 		pkt.Data.TrimFront(header.ICMPv6PacketTooBigMinimumSize)
-		mtu := h.MTU()
+		mtu := header.ICMPv6(hdr).MTU()
 		e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), pkt)
 
 	case header.ICMPv6DstUnreachable:
 		received.DstUnreachable.Increment()
-		if len(v) < header.ICMPv6DstUnreachableMinimumSize {
+		hdr, ok := pkt.Data.PullUp(header.ICMPv6DstUnreachableMinimumSize)
+		if !ok {
 			received.Invalid.Increment()
 			return
 		}
 		pkt.Data.TrimFront(header.ICMPv6DstUnreachableMinimumSize)
-		switch h.Code() {
+		switch header.ICMPv6(hdr).Code() {
 		case header.ICMPv6PortUnreachable:
 			e.handleControl(stack.ControlPortUnreachable, 0, pkt)
 		}
 
 	case header.ICMPv6NeighborSolicit:
 		received.NeighborSolicit.Increment()
-		if len(v) < header.ICMPv6NeighborSolicitMinimumSize || !isNDPValid() {
+		if pkt.Data.Size() < header.ICMPv6NeighborSolicitMinimumSize || !isNDPValid() {
 			received.Invalid.Increment()
 			return
 		}
 
-		ns := header.NDPNeighborSolicit(h.NDPPayload())
+		// 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())
 		it, err := ns.Options().Iter(true)
 		if err != nil {
 			// If we have a malformed NDP NS option, drop the packet.
@@ -286,12 +298,16 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 
 	case header.ICMPv6NeighborAdvert:
 		received.NeighborAdvert.Increment()
-		if len(v) < header.ICMPv6NeighborAdvertSize || !isNDPValid() {
+		if pkt.Data.Size() < header.ICMPv6NeighborAdvertSize || !isNDPValid() {
 			received.Invalid.Increment()
 			return
 		}
 
-		na := header.NDPNeighborAdvert(h.NDPPayload())
+		// 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())
 		it, err := na.Options().Iter(true)
 		if err != nil {
 			// If we have a malformed NDP NA option, drop the packet.
@@ -363,14 +379,15 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 
 	case header.ICMPv6EchoRequest:
 		received.EchoRequest.Increment()
-		if len(v) < header.ICMPv6EchoMinimumSize {
+		icmpHdr, ok := pkt.Data.PullUp(header.ICMPv6EchoMinimumSize)
+		if !ok {
 			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, h)
+		copy(packet, icmpHdr)
 		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{
@@ -384,7 +401,7 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 
 	case header.ICMPv6EchoReply:
 		received.EchoReply.Increment()
-		if len(v) < header.ICMPv6EchoMinimumSize {
+		if pkt.Data.Size() < header.ICMPv6EchoMinimumSize {
 			received.Invalid.Increment()
 			return
 		}
@@ -406,8 +423,9 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 	case header.ICMPv6RouterAdvert:
 		received.RouterAdvert.Increment()
 
-		p := h.NDPPayload()
-		if len(p) < header.NDPRAMinimumSize || !isNDPValid() {
+		// Is the NDP payload of sufficient size to hold a Router
+		// Advertisement?
+		if pkt.Data.Size()-header.ICMPv6HeaderSize < header.NDPRAMinimumSize || !isNDPValid() {
 			received.Invalid.Increment()
 			return
 		}
@@ -425,7 +443,11 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt stack.P
 			return
 		}
 
-		ra := header.NDPRouterAdvert(p)
+		// 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())
 		opts := ra.Options()
 
 		// Are options valid as per the wire format?
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 82928fb66..daf1fcbc6 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -171,7 +171,11 @@ 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 := pkt.Data.First()
+	headerView, ok := pkt.Data.PullUp(header.IPv6MinimumSize)
+	if !ok {
+		r.Stats().IP.MalformedPacketsReceived.Increment()
+		return
+	}
 	h := header.IPv6(headerView)
 	if !h.IsValid(pkt.Data.Size()) {
 		r.Stats().IP.MalformedPacketsReceived.Increment()
diff --git a/pkg/tcpip/stack/iptables.go b/pkg/tcpip/stack/iptables.go
index 6c0a4b24d..6b91159d4 100755
--- a/pkg/tcpip/stack/iptables.go
+++ b/pkg/tcpip/stack/iptables.go
@@ -212,6 +212,11 @@ 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{}) {
@@ -226,7 +231,9 @@ func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList) (drop map[*Pa
 	return drop
 }
 
-// Precondition: pkt.NetworkHeader is set.
+// 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.
 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.
@@ -271,14 +278,21 @@ func (it *IPTables) checkChain(hook Hook, pkt PacketBuffer, table Table, ruleIdx
 	return chainDrop
 }
 
-// Precondition: pk.NetworkHeader is set.
+// 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.
 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.First().
+	// pkt.Data.
 	if pkt.NetworkHeader == nil {
-		pkt.NetworkHeader = pkt.Data.First()
+		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))
+		}
 	}
 
 	// Check whether the packet matches the IP header filter.
diff --git a/pkg/tcpip/stack/iptables_targets.go b/pkg/tcpip/stack/iptables_targets.go
index 7b4543caf..8be61f4b1 100755
--- a/pkg/tcpip/stack/iptables_targets.go
+++ b/pkg/tcpip/stack/iptables_targets.go
@@ -96,9 +96,12 @@ func (rt RedirectTarget) Action(pkt PacketBuffer) (RuleVerdict, int) {
 	newPkt := pkt.Clone()
 
 	// Set network header.
-	headerView := newPkt.Data.First()
+	headerView, ok := newPkt.Data.PullUp(header.IPv4MinimumSize)
+	if !ok {
+		return RuleDrop, 0
+	}
 	netHeader := header.IPv4(headerView)
-	newPkt.NetworkHeader = headerView[:header.IPv4MinimumSize]
+	newPkt.NetworkHeader = headerView
 
 	hlen := int(netHeader.HeaderLength())
 	tlen := int(netHeader.TotalLength())
@@ -117,10 +120,14 @@ func (rt RedirectTarget) Action(pkt PacketBuffer) (RuleVerdict, int) {
 		if newPkt.TransportHeader != nil {
 			udpHeader = header.UDP(newPkt.TransportHeader)
 		} else {
-			if len(pkt.Data.First()) < header.UDPMinimumSize {
+			if pkt.Data.Size() < header.UDPMinimumSize {
+				return RuleDrop, 0
+			}
+			hdr, ok := newPkt.Data.PullUp(header.UDPMinimumSize)
+			if !ok {
 				return RuleDrop, 0
 			}
-			udpHeader = header.UDP(newPkt.Data.First())
+			udpHeader = header.UDP(hdr)
 		}
 		udpHeader.SetDestinationPort(rt.MinPort)
 	case header.TCPProtocolNumber:
@@ -128,10 +135,14 @@ func (rt RedirectTarget) Action(pkt PacketBuffer) (RuleVerdict, int) {
 		if newPkt.TransportHeader != nil {
 			tcpHeader = header.TCP(newPkt.TransportHeader)
 		} else {
-			if len(pkt.Data.First()) < header.TCPMinimumSize {
+			if pkt.Data.Size() < header.TCPMinimumSize {
 				return RuleDrop, 0
 			}
-			tcpHeader = header.TCP(newPkt.TransportHeader)
+			hdr, ok := newPkt.Data.PullUp(header.TCPMinimumSize)
+			if !ok {
+				return RuleDrop, 0
+			}
+			tcpHeader = header.TCP(hdr)
 		}
 		// TODO(gvisor.dev/issue/170): Need to recompute checksum
 		// and implement nat connection tracking to support TCP.
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index 440970a21..7b54919bb 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -1212,12 +1212,12 @@ func (n *NIC) DeliverNetworkPacket(linkEP LinkEndpoint, remote, local tcpip.Link
 		n.stack.stats.IP.PacketsReceived.Increment()
 	}
 
-	if len(pkt.Data.First()) < netProto.MinimumPacketSize() {
+	netHeader, ok := pkt.Data.PullUp(netProto.MinimumPacketSize())
+	if !ok {
 		n.stack.stats.MalformedRcvdPackets.Increment()
 		return
 	}
-
-	src, dst := netProto.ParseAddresses(pkt.Data.First())
+	src, dst := netProto.ParseAddresses(netHeader)
 
 	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
@@ -1298,22 +1298,8 @@ 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.
-
-	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 linkHeaderLen := int(n.linkEP.MaxHeaderLength()); linkHeaderLen != 0 {
+		pkt.Header = buffer.NewPrependable(linkHeaderLen)
 	}
 
 	if err := n.linkEP.WritePacket(r, nil /* gso */, protocol, pkt); err != nil {
@@ -1341,12 +1327,13 @@ func (n *NIC) DeliverTransportPacket(r *Route, protocol tcpip.TransportProtocolN
 	// validly formed.
 	n.stack.demux.deliverRawPacket(r, protocol, pkt)
 
-	if len(pkt.Data.First()) < transProto.MinimumPacketSize() {
+	transHeader, ok := pkt.Data.PullUp(transProto.MinimumPacketSize())
+	if !ok {
 		n.stack.stats.MalformedRcvdPackets.Increment()
 		return
 	}
 
-	srcPort, dstPort, err := transProto.ParsePorts(pkt.Data.First())
+	srcPort, dstPort, err := transProto.ParsePorts(transHeader)
 	if err != nil {
 		n.stack.stats.MalformedRcvdPackets.Increment()
 		return
@@ -1384,11 +1371,12 @@ 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.
-	if len(pkt.Data.First()) < 8 {
+	transHeader, ok := pkt.Data.PullUp(8)
+	if !ok {
 		return
 	}
 
-	srcPort, dstPort, err := transProto.ParsePorts(pkt.Data.First())
+	srcPort, dstPort, err := transProto.ParsePorts(transHeader)
 	if err != nil {
 		return
 	}
diff --git a/pkg/tcpip/stack/packet_buffer.go b/pkg/tcpip/stack/packet_buffer.go
index 06d312207..9ff80ab24 100755
--- a/pkg/tcpip/stack/packet_buffer.go
+++ b/pkg/tcpip/stack/packet_buffer.go
@@ -37,7 +37,13 @@ type PacketBuffer struct {
 	Data buffer.VectorisedView
 
 	// Header holds the headers of outbound packets. As a packet is passed
-	// down the stack, each layer adds to Header.
+	// down the stack, each layer adds to Header. Note that forwarded
+	// packets don't populate Headers on their way out -- their headers and
+	// payload are never parsed out and remain in Data.
+	//
+	// TODO(gvisor.dev/issue/170): Forwarded packets don't currently
+	// populate Header, but should. This will be doable once early parsing
+	// (https://github.com/google/gvisor/pull/1995) is supported.
 	Header buffer.Prependable
 
 	// These fields are used by both inbound and outbound packets. They
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index feef8dca0..b1d820372 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -747,15 +747,15 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pk
 	// Only accept echo replies.
 	switch e.NetProto {
 	case header.IPv4ProtocolNumber:
-		h := header.ICMPv4(pkt.Data.First())
-		if h.Type() != header.ICMPv4EchoReply {
+		h, ok := pkt.Data.PullUp(header.ICMPv4MinimumSize)
+		if !ok || header.ICMPv4(h).Type() != header.ICMPv4EchoReply {
 			e.stack.Stats().DroppedPackets.Increment()
 			e.stats.ReceiveErrors.MalformedPacketsReceived.Increment()
 			return
 		}
 	case header.IPv6ProtocolNumber:
-		h := header.ICMPv6(pkt.Data.First())
-		if h.Type() != header.ICMPv6EchoReply {
+		h, ok := pkt.Data.PullUp(header.ICMPv6MinimumSize)
+		if !ok || header.ICMPv6(h).Type() != header.ICMPv6EchoReply {
 			e.stack.Stats().DroppedPackets.Increment()
 			e.stats.ReceiveErrors.MalformedPacketsReceived.Increment()
 			return
diff --git a/pkg/tcpip/transport/tcp/segment.go b/pkg/tcpip/transport/tcp/segment.go
index 40461fd31..7712ce652 100644
--- a/pkg/tcpip/transport/tcp/segment.go
+++ b/pkg/tcpip/transport/tcp/segment.go
@@ -144,7 +144,11 @@ func (s *segment) logicalLen() seqnum.Size {
 // TCP checksum and stores the checksum and result of checksum verification in
 // the csum and csumValid fields of the segment.
 func (s *segment) parse() bool {
-	h := header.TCP(s.data.First())
+	h, ok := s.data.PullUp(header.TCPMinimumSize)
+	if !ok {
+		return false
+	}
+	hdr := header.TCP(h)
 
 	// h is the header followed by the payload. We check that the offset to
 	// the data respects the following constraints:
@@ -156,12 +160,16 @@ func (s *segment) parse() bool {
 	// N.B. The segment has already been validated as having at least the
 	//      minimum TCP size before reaching here, so it's safe to read the
 	//      fields.
-	offset := int(h.DataOffset())
-	if offset < header.TCPMinimumSize || offset > len(h) {
+	offset := int(hdr.DataOffset())
+	if offset < header.TCPMinimumSize {
+		return false
+	}
+	hdrWithOpts, ok := s.data.PullUp(offset)
+	if !ok {
 		return false
 	}
 
-	s.options = []byte(h[header.TCPMinimumSize:offset])
+	s.options = []byte(hdrWithOpts[header.TCPMinimumSize:])
 	s.parsedOptions = header.ParseTCPOptions(s.options)
 
 	// Query the link capabilities to decide if checksum validation is
@@ -173,18 +181,19 @@ func (s *segment) parse() bool {
 		s.data.TrimFront(offset)
 	}
 	if verifyChecksum {
-		s.csum = h.Checksum()
+		hdr = header.TCP(hdrWithOpts)
+		s.csum = hdr.Checksum()
 		xsum := s.route.PseudoHeaderChecksum(ProtocolNumber, uint16(s.data.Size()))
-		xsum = h.CalculateChecksum(xsum)
+		xsum = hdr.CalculateChecksum(xsum)
 		s.data.TrimFront(offset)
 		xsum = header.ChecksumVV(s.data, xsum)
 		s.csumValid = xsum == 0xffff
 	}
 
-	s.sequenceNumber = seqnum.Value(h.SequenceNumber())
-	s.ackNumber = seqnum.Value(h.AckNumber())
-	s.flags = h.Flags()
-	s.window = seqnum.Size(h.WindowSize())
+	s.sequenceNumber = seqnum.Value(hdr.SequenceNumber())
+	s.ackNumber = seqnum.Value(hdr.AckNumber())
+	s.flags = hdr.Flags()
+	s.window = seqnum.Size(hdr.WindowSize())
 	return true
 }
 
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index edb54f0be..756ab913a 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -1250,8 +1250,8 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 // endpoint.
 func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) {
 	// Get the header then trim it from the view.
-	hdr := header.UDP(pkt.Data.First())
-	if int(hdr.Length()) > pkt.Data.Size() {
+	hdr, ok := pkt.Data.PullUp(header.UDPMinimumSize)
+	if !ok || int(header.UDP(hdr).Length()) > pkt.Data.Size() {
 		// Malformed packet.
 		e.stack.Stats().UDP.MalformedPacketsReceived.Increment()
 		e.stats.ReceiveErrors.MalformedPacketsReceived.Increment()
@@ -1286,7 +1286,7 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pk
 		senderAddress: tcpip.FullAddress{
 			NIC:  r.NICID(),
 			Addr: id.RemoteAddress,
-			Port: hdr.SourcePort(),
+			Port: header.UDP(hdr).SourcePort(),
 		},
 	}
 	packet.data = pkt.Data
diff --git a/pkg/tcpip/transport/udp/protocol.go b/pkg/tcpip/transport/udp/protocol.go
index 6e31a9bac..52af6de22 100644
--- a/pkg/tcpip/transport/udp/protocol.go
+++ b/pkg/tcpip/transport/udp/protocol.go
@@ -68,8 +68,13 @@ func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
 // that don't match any existing endpoint.
 func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, pkt stack.PacketBuffer) bool {
 	// Get the header then trim it from the view.
-	hdr := header.UDP(pkt.Data.First())
-	if int(hdr.Length()) > pkt.Data.Size() {
+	h, ok := pkt.Data.PullUp(header.UDPMinimumSize)
+	if !ok {
+		// Malformed packet.
+		r.Stack().Stats().UDP.MalformedPacketsReceived.Increment()
+		return true
+	}
+	if int(header.UDP(h).Length()) > pkt.Data.Size() {
 		// Malformed packet.
 		r.Stack().Stats().UDP.MalformedPacketsReceived.Increment()
 		return true