Update PacketBuffer to hold a Buffer struct instead of a Buffer pointer.

The extra pointer indirection is not necessary and allows for a nil buffer.
This change bumps the PacketBuffer struct size from 296 to 792 bytes.

PiperOrigin-RevId: 422669812

pkg/buffer/view.go

@@ -380,8 +380,8 @@ func (v *View) Copy() (other View) {
 
 // Clone makes a more shallow copy compared to Copy. The underlying payload
 // slice (buffer.data) is shared but the buffers themselves are copied.
-func (v *View) Clone() *View {
-	other := &View{
+func (v *View) Clone() View {
+	other := View{
 		size: v.size,
 	}
 	for buf := v.data.Front(); buf != nil; buf = buf.Next() {

pkg/tcpip/network/internal/fragmentation/fragmentation_test.go

@@ -107,7 +107,7 @@ func TestFragmentationProcess(t *testing.T) {
 	}
 	for _, c := range processTestCases {
 		t.Run(c.comment, func(t *testing.T) {
-			f := NewFragmentation(minBlockSize, 1024, 512, reassembleTimeout, &faketime.NullClock{}, nil)
+			f := NewFragmentation(minBlockSize, 2048, 512, reassembleTimeout, &faketime.NullClock{}, nil)
 			firstFragmentProto := c.in[0].proto
 			for i, in := range c.in {
 				defer in.pkt.DecRef()

pkg/tcpip/stack/packet_buffer.go

@@ -106,7 +106,7 @@ type PacketBuffer struct {
 
 	// buf is the underlying buffer for the packet. See struct level docs for
 	// details.
-	buf      *buffer.Buffer
+	buf      buffer.Buffer
 	reserved int
 	pushed   int
 	consumed int
@@ -169,7 +169,6 @@ type PacketBuffer struct {
 func NewPacketBuffer(opts PacketBufferOptions) *PacketBuffer {
 	pk := pkPool.Get().(*PacketBuffer)
 	pk.reset()
-	pk.buf = &buffer.Buffer{}
 	if opts.ReserveHeaderBytes != 0 {
 		pk.buf.AppendOwned(make([]byte, opts.ReserveHeaderBytes))
 		pk.reserved = opts.ReserveHeaderBytes
@@ -558,7 +557,7 @@ func (d PacketData) AppendView(v tcpipbuffer.View) {
 // frag and frag should not be used again.
 func MergeFragment(dst, frag *PacketBuffer) {
 	frag.buf.TrimFront(int64(frag.dataOffset()))
-	dst.buf.Merge(frag.buf)
+	dst.buf.Merge(&frag.buf)
 }
 
 // ReadFromVV moves at most count bytes from the beginning of srcVV to the end