Migrate to PacketHeader API for PacketBuffer.

Formerly, when a packet is constructed or parsed, all headers are set by the
client code. This almost always involved prepending to pk.Header buffer or
trimming pk.Data portion. This is known to prone to bugs, due to the complexity
and number of the invariants assumed across netstack to maintain.

In the new PacketHeader API, client will call Push()/Consume() method to
construct/parse an outgoing/incoming packet. All invariants, such as slicing
and trimming, are maintained by the API itself.

NewPacketBuffer() is introduced to create new PacketBuffer. Zero value is no
longer valid.

PacketBuffer now assumes the packet is a concatenation of following portions:
* LinkHeader
* NetworkHeader
* TransportHeader
* Data
Any of them could be empty, or zero-length.

PiperOrigin-RevId: 326507688

3 files changed, 65 insertions, 76 deletions

diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 4a2b6c03a..73608783c 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -986,13 +986,16 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 // sendUDP sends a UDP segment via the provided network endpoint and under the
 // provided identity.
 func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort uint16, ttl uint8, useDefaultTTL bool, tos uint8, owner tcpip.PacketOwner, noChecksum bool) *tcpip.Error {
-	// Allocate a buffer for the UDP header.
-	hdr := buffer.NewPrependable(header.UDPMinimumSize + int(r.MaxHeaderLength()))
+	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
+		ReserveHeaderBytes: header.UDPMinimumSize + int(r.MaxHeaderLength()),
+		Data:               data,
+	})
+	pkt.Owner = owner
 
-	// Initialize the header.
-	udp := header.UDP(hdr.Prepend(header.UDPMinimumSize))
+	// Initialize the UDP header.
+	udp := header.UDP(pkt.TransportHeader().Push(header.UDPMinimumSize))
 
-	length := uint16(hdr.UsedLength() + data.Size())
+	length := uint16(pkt.Size())
 	udp.Encode(&header.UDPFields{
 		SrcPort: localPort,
 		DstPort: remotePort,
@@ -1019,12 +1022,7 @@ func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort u
 		Protocol: ProtocolNumber,
 		TTL:      ttl,
 		TOS:      tos,
-	}, &stack.PacketBuffer{
-		Header:          hdr,
-		Data:            data,
-		TransportHeader: buffer.View(udp),
-		Owner:           owner,
-	}); err != nil {
+	}, pkt); err != nil {
 		r.Stats().UDP.PacketSendErrors.Increment()
 		return err
 	}
@@ -1372,7 +1370,7 @@ 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.TransportHeader)
+	hdr := header.UDP(pkt.TransportHeader().View())
 	if int(hdr.Length()) > pkt.Data.Size()+header.UDPMinimumSize {
 		// Malformed packet.
 		e.stack.Stats().UDP.MalformedPacketsReceived.Increment()
@@ -1443,9 +1441,9 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pk
 	// Save any useful information from the network header to the packet.
 	switch r.NetProto {
 	case header.IPv4ProtocolNumber:
-		packet.tos, _ = header.IPv4(pkt.NetworkHeader).TOS()
+		packet.tos, _ = header.IPv4(pkt.NetworkHeader().View()).TOS()
 	case header.IPv6ProtocolNumber:
-		packet.tos, _ = header.IPv6(pkt.NetworkHeader).TOS()
+		packet.tos, _ = header.IPv6(pkt.NetworkHeader().View()).TOS()
 	}
 
 	// TODO(gvisor.dev/issue/3556): r.LocalAddress may be a multicast or broadcast
diff --git a/pkg/tcpip/transport/udp/protocol.go b/pkg/tcpip/transport/udp/protocol.go
index 0e7464e3a..63d4bed7c 100644
--- a/pkg/tcpip/transport/udp/protocol.go
+++ b/pkg/tcpip/transport/udp/protocol.go
@@ -82,7 +82,7 @@ func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
 // HandleUnknownDestinationPacket handles packets targeted at this protocol but
 // that don't match any existing endpoint.
 func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) bool {
-	hdr := header.UDP(pkt.TransportHeader)
+	hdr := header.UDP(pkt.TransportHeader().View())
 	if int(hdr.Length()) > pkt.Data.Size()+header.UDPMinimumSize {
 		// Malformed packet.
 		r.Stack().Stats().UDP.MalformedPacketsReceived.Increment()
@@ -130,7 +130,7 @@ func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.Trans
 		}
 		headerLen := int(r.MaxHeaderLength()) + header.ICMPv4MinimumSize
 		available := int(mtu) - headerLen
-		payloadLen := len(pkt.NetworkHeader) + len(pkt.TransportHeader) + pkt.Data.Size()
+		payloadLen := pkt.NetworkHeader().View().Size() + pkt.TransportHeader().View().Size() + pkt.Data.Size()
 		if payloadLen > available {
 			payloadLen = available
 		}
@@ -139,22 +139,21 @@ func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.Trans
 		// For example, a raw or packet socket may use what UDP
 		// considers an unreachable destination. Thus we deep copy pkt
 		// to prevent multiple ownership and SR errors.
-		newHeader := append(buffer.View(nil), pkt.NetworkHeader...)
-		newHeader = append(newHeader, pkt.TransportHeader...)
+		newHeader := append(buffer.View(nil), pkt.NetworkHeader().View()...)
+		newHeader = append(newHeader, pkt.TransportHeader().View()...)
 		payload := newHeader.ToVectorisedView()
 		payload.AppendView(pkt.Data.ToView())
 		payload.CapLength(payloadLen)
 
-		hdr := buffer.NewPrependable(headerLen)
-		pkt := header.ICMPv4(hdr.Prepend(header.ICMPv4MinimumSize))
-		pkt.SetType(header.ICMPv4DstUnreachable)
-		pkt.SetCode(header.ICMPv4PortUnreachable)
-		pkt.SetChecksum(header.ICMPv4Checksum(pkt, payload))
-		r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, &stack.PacketBuffer{
-			Header:          hdr,
-			TransportHeader: buffer.View(pkt),
-			Data:            payload,
+		icmpPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
+			ReserveHeaderBytes: headerLen,
+			Data:               payload,
 		})
+		icmpHdr := header.ICMPv4(icmpPkt.TransportHeader().Push(header.ICMPv4MinimumSize))
+		icmpHdr.SetType(header.ICMPv4DstUnreachable)
+		icmpHdr.SetCode(header.ICMPv4PortUnreachable)
+		icmpHdr.SetChecksum(header.ICMPv4Checksum(icmpHdr, icmpPkt.Data))
+		r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, icmpPkt)
 
 	case header.IPv6AddressSize:
 		if !r.Stack().AllowICMPMessage() {
@@ -175,24 +174,24 @@ func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.Trans
 		}
 		headerLen := int(r.MaxHeaderLength()) + header.ICMPv6DstUnreachableMinimumSize
 		available := int(mtu) - headerLen
-		payloadLen := len(pkt.NetworkHeader) + len(pkt.TransportHeader) + pkt.Data.Size()
+		network, transport := pkt.NetworkHeader().View(), pkt.TransportHeader().View()
+		payloadLen := len(network) + len(transport) + pkt.Data.Size()
 		if payloadLen > available {
 			payloadLen = available
 		}
-		payload := buffer.NewVectorisedView(len(pkt.NetworkHeader)+len(pkt.TransportHeader), []buffer.View{pkt.NetworkHeader, pkt.TransportHeader})
+		payload := buffer.NewVectorisedView(len(network)+len(transport), []buffer.View{network, transport})
 		payload.Append(pkt.Data)
 		payload.CapLength(payloadLen)
 
-		hdr := buffer.NewPrependable(headerLen)
-		pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6DstUnreachableMinimumSize))
-		pkt.SetType(header.ICMPv6DstUnreachable)
-		pkt.SetCode(header.ICMPv6PortUnreachable)
-		pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, payload))
-		r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, &stack.PacketBuffer{
-			Header:          hdr,
-			TransportHeader: buffer.View(pkt),
-			Data:            payload,
+		icmpPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
+			ReserveHeaderBytes: headerLen,
+			Data:               payload,
 		})
+		icmpHdr := header.ICMPv6(icmpPkt.TransportHeader().Push(header.ICMPv6DstUnreachableMinimumSize))
+		icmpHdr.SetType(header.ICMPv6DstUnreachable)
+		icmpHdr.SetCode(header.ICMPv6PortUnreachable)
+		icmpHdr.SetChecksum(header.ICMPv6Checksum(icmpHdr, r.LocalAddress, r.RemoteAddress, icmpPkt.Data))
+		r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, icmpPkt)
 	}
 	return true
 }
@@ -215,14 +214,8 @@ func (*protocol) Wait() {}
 
 // Parse implements stack.TransportProtocol.Parse.
 func (*protocol) Parse(pkt *stack.PacketBuffer) bool {
-	h, ok := pkt.Data.PullUp(header.UDPMinimumSize)
-	if !ok {
-		// Packet is too small
-		return false
-	}
-	pkt.TransportHeader = h
-	pkt.Data.TrimFront(header.UDPMinimumSize)
-	return true
+	_, ok := pkt.TransportHeader().Consume(header.UDPMinimumSize)
+	return ok
 }
 
 // NewProtocol returns a UDP transport protocol.
diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go
index 1a32622ca..71776d6db 100644
--- a/pkg/tcpip/transport/udp/udp_test.go
+++ b/pkg/tcpip/transport/udp/udp_test.go
@@ -388,8 +388,8 @@ func (c *testContext) getPacketAndVerify(flow testFlow, checkers ...checker.Netw
 		c.t.Fatalf("Bad network protocol: got %v, wanted %v", p.Proto, flow.netProto())
 	}
 
-	hdr := p.Pkt.Header.View()
-	b := append(hdr[:len(hdr):len(hdr)], p.Pkt.Data.ToView()...)
+	vv := buffer.NewVectorisedView(p.Pkt.Size(), p.Pkt.Views())
+	b := vv.ToView()
 
 	h := flow.header4Tuple(outgoing)
 	checkers = append(
@@ -410,14 +410,14 @@ func (c *testContext) injectPacket(flow testFlow, payload []byte) {
 	h := flow.header4Tuple(incoming)
 	if flow.isV4() {
 		buf := c.buildV4Packet(payload, &h)
-		c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
+		c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 			Data: buf.ToVectorisedView(),
-		})
+		}))
 	} else {
 		buf := c.buildV6Packet(payload, &h)
-		c.linkEP.InjectInbound(ipv6.ProtocolNumber, &stack.PacketBuffer{
+		c.linkEP.InjectInbound(ipv6.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 			Data: buf.ToVectorisedView(),
-		})
+		}))
 	}
 }
 
@@ -804,9 +804,9 @@ func TestV4ReadSelfSource(t *testing.T) {
 			h.srcAddr = h.dstAddr
 
 			buf := c.buildV4Packet(payload, &h)
-			c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
+			c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 				Data: buf.ToVectorisedView(),
-			})
+			}))
 
 			if got := c.s.Stats().IP.InvalidSourceAddressesReceived.Value(); got != tt.wantInvalidSource {
 				t.Errorf("c.s.Stats().IP.InvalidSourceAddressesReceived got %d, want %d", got, tt.wantInvalidSource)
@@ -1766,9 +1766,8 @@ func TestV4UnknownDestination(t *testing.T) {
 				return
 			}
 
-			var pkt []byte
-			pkt = append(pkt, p.Pkt.Header.View()...)
-			pkt = append(pkt, p.Pkt.Data.ToView()...)
+			vv := buffer.NewVectorisedView(p.Pkt.Size(), p.Pkt.Views())
+			pkt := vv.ToView()
 			if got, want := len(pkt), header.IPv4MinimumProcessableDatagramSize; got > want {
 				t.Fatalf("got an ICMP packet of size: %d, want: sz <= %d", got, want)
 			}
@@ -1844,9 +1843,8 @@ func TestV6UnknownDestination(t *testing.T) {
 				return
 			}
 
-			var pkt []byte
-			pkt = append(pkt, p.Pkt.Header.View()...)
-			pkt = append(pkt, p.Pkt.Data.ToView()...)
+			vv := buffer.NewVectorisedView(p.Pkt.Size(), p.Pkt.Views())
+			pkt := vv.ToView()
 			if got, want := len(pkt), header.IPv6MinimumMTU; got > want {
 				t.Fatalf("got an ICMP packet of size: %d, want: sz <= %d", got, want)
 			}
@@ -1897,9 +1895,9 @@ func TestIncrementMalformedPacketsReceived(t *testing.T) {
 	u := header.UDP(buf[header.IPv6MinimumSize:])
 	u.SetLength(u.Length() + 1)
 
-	c.linkEP.InjectInbound(ipv6.ProtocolNumber, &stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv6.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: buf.ToVectorisedView(),
-	})
+	}))
 
 	const want = 1
 	if got := c.s.Stats().UDP.MalformedPacketsReceived.Value(); got != want {
@@ -1952,9 +1950,9 @@ func TestShortHeader(t *testing.T) {
 	copy(buf[header.IPv6MinimumSize:], udpHdr)
 
 	// Inject packet.
-	c.linkEP.InjectInbound(ipv6.ProtocolNumber, &stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv6.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: buf.ToVectorisedView(),
-	})
+	}))
 
 	if got, want := c.s.Stats().MalformedRcvdPackets.Value(), uint64(1); got != want {
 		t.Errorf("got c.s.Stats().MalformedRcvdPackets.Value() = %d, want = %d", got, want)
@@ -1986,9 +1984,9 @@ func TestIncrementChecksumErrorsV4(t *testing.T) {
 		}
 	}
 
-	c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: buf.ToVectorisedView(),
-	})
+	}))
 
 	const want = 1
 	if got := c.s.Stats().UDP.ChecksumErrors.Value(); got != want {
@@ -2019,9 +2017,9 @@ func TestIncrementChecksumErrorsV6(t *testing.T) {
 	u := header.UDP(buf[header.IPv6MinimumSize:])
 	u.SetChecksum(u.Checksum() + 1)
 
-	c.linkEP.InjectInbound(ipv6.ProtocolNumber, &stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv6.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: buf.ToVectorisedView(),
-	})
+	}))
 
 	const want = 1
 	if got := c.s.Stats().UDP.ChecksumErrors.Value(); got != want {
@@ -2049,9 +2047,9 @@ func TestPayloadModifiedV4(t *testing.T) {
 	buf := c.buildV4Packet(payload, &h)
 	// Modify the payload so that the checksum value in the UDP header will be incorrect.
 	buf[len(buf)-1]++
-	c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: buf.ToVectorisedView(),
-	})
+	}))
 
 	const want = 1
 	if got := c.s.Stats().UDP.ChecksumErrors.Value(); got != want {
@@ -2079,9 +2077,9 @@ func TestPayloadModifiedV6(t *testing.T) {
 	buf := c.buildV6Packet(payload, &h)
 	// Modify the payload so that the checksum value in the UDP header will be incorrect.
 	buf[len(buf)-1]++
-	c.linkEP.InjectInbound(ipv6.ProtocolNumber, &stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv6.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: buf.ToVectorisedView(),
-	})
+	}))
 
 	const want = 1
 	if got := c.s.Stats().UDP.ChecksumErrors.Value(); got != want {
@@ -2110,9 +2108,9 @@ func TestChecksumZeroV4(t *testing.T) {
 	// Set the checksum field in the UDP header to zero.
 	u := header.UDP(buf[header.IPv4MinimumSize:])
 	u.SetChecksum(0)
-	c.linkEP.InjectInbound(ipv4.ProtocolNumber, &stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv4.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: buf.ToVectorisedView(),
-	})
+	}))
 
 	const want = 0
 	if got := c.s.Stats().UDP.ChecksumErrors.Value(); got != want {
@@ -2141,9 +2139,9 @@ func TestChecksumZeroV6(t *testing.T) {
 	// Set the checksum field in the UDP header to zero.
 	u := header.UDP(buf[header.IPv6MinimumSize:])
 	u.SetChecksum(0)
-	c.linkEP.InjectInbound(ipv6.ProtocolNumber, &stack.PacketBuffer{
+	c.linkEP.InjectInbound(ipv6.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: buf.ToVectorisedView(),
-	})
+	}))
 
 	const want = 1
 	if got := c.s.Stats().UDP.ChecksumErrors.Value(); got != want {