Update

vendor/github.com/tailscale/wireguard-go/device/packetbuf.go

@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ */
+
+package device
+
+import (
+	"fmt"
+	"sync/atomic"
+
+	"github.com/tailscale/wireguard-go/tun"
+	"golang.org/x/crypto/poly1305"
+)
+
+const (
+	outboundPlaintextHeadroom = MessageEncapsulatingTransportSize + MessageTransportHeaderSize
+
+	outboundPlaintextTailroom = PaddingMultiple - 1 + poly1305.TagSize
+
+	outboundPlaintextSpacing = max(outboundPlaintextHeadroom+outboundPlaintextTailroom, tun.ReadPacketSpacing)
+
+	// singlePacketSlabSize is the size to be used for [packetBuf.slab] when
+	// neither [tun.Device] nor [conn.Bind] support batched reads.
+	singlePacketSlabSize = MaxContentSize + 2*tun.ReadPacketSpacing
+
+	// batchingSlabSize is the size to be used for [packetBuf.slab] when either
+	// [tun.Device] or [conn.Bind] support batched reads. This covers the
+	// [tun.GSOSplit] worst case for minimum-sized MTU/MSS, which is documented
+	// in [tun.TestGSOSplitMinimumGSOSize].
+	batchingSlabSize = 2 * (1<<16 - 1)
+)
+
+// The tun package cannot import device, so we assert [tun.ReadPacketSpacing] is
+// greater than or equal to [outboundPlaintextSpacing] instead.
+const _ = uint(tun.ReadPacketSpacing - outboundPlaintextSpacing)
+
+// packetBuf is a reference counted packet buffer.
+type packetBuf struct {
+	slab     []byte
+	refCount atomic.Int32
+	cleanup  func(*packetBuf)
+}
+
+// newPacketBuf returns a new [*packetBuf] of the provided size with its
+// reference count set to zero. cleanup runs for the returned [*packetBuf] when
+// its ref count moves 1->0.
+func newPacketBuf(size int, cleanup func(*packetBuf)) *packetBuf {
+	return &packetBuf{
+		slab:    make([]byte, size),
+		cleanup: cleanup,
+	}
+}
+
+func (p *packetBuf) incRef() {
+	p.refCount.Add(1)
+}
+
+func (p *packetBuf) decRef() {
+	c := p.refCount.Add(-1)
+	if c == 0 {
+		p.cleanup(p)
+	} else if c < 0 {
+		panic(fmt.Sprintf("packetBuf.decRef below zero (%d)", c))
+	}
+}