tailscale: update tailfs file and package names (#11590)

This change updates the tailfs file and package names to their new
naming convention.

Updates #tailscale/corp#16827

Signed-off-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>

drive/driveimpl/compositedav/stat_cache.go

@@ -0,0 +1,92 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package compositedav
+
+import (
+	"sync"
+	"time"
+
+	"github.com/jellydator/ttlcache/v3"
+)
+
+// StatCache provides a cache for directory listings and file metadata.
+// Especially when used from the command-line, mapped WebDAV drives can
+// generate repetitive requests for the same file metadata. This cache helps
+// reduce the number of round-trips to the WebDAV server for such requests.
+// This is similar to the DirectoryCacheLifetime setting of Windows' built-in
+// SMB client, see
+// https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-7/ff686200(v=ws.10)
+type StatCache struct {
+	TTL time.Duration
+
+	// mu guards the below values.
+	mu                   sync.Mutex
+	cachesByDepthAndPath map[int]*ttlcache.Cache[string, []byte]
+}
+
+func (c *StatCache) get(name string, depth int) []byte {
+	if c == nil {
+		return nil
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.cachesByDepthAndPath == nil {
+		return nil
+	}
+	cache := c.cachesByDepthAndPath[depth]
+	if cache == nil {
+		return nil
+	}
+	item := cache.Get(name)
+	if item == nil {
+		return nil
+	}
+	return item.Value()
+}
+
+func (c *StatCache) set(name string, depth int, value []byte) {
+	if c == nil {
+		return
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.cachesByDepthAndPath == nil {
+		c.cachesByDepthAndPath = make(map[int]*ttlcache.Cache[string, []byte])
+	}
+	cache := c.cachesByDepthAndPath[depth]
+	if cache == nil {
+		cache = ttlcache.New(
+			ttlcache.WithTTL[string, []byte](c.TTL),
+		)
+		go cache.Start()
+		c.cachesByDepthAndPath[depth] = cache
+	}
+	cache.Set(name, value, ttlcache.DefaultTTL)
+}
+
+func (c *StatCache) invalidate() {
+	if c == nil {
+		return
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	for _, cache := range c.cachesByDepthAndPath {
+		cache.DeleteAll()
+	}
+}
+
+func (c *StatCache) stop() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	for _, cache := range c.cachesByDepthAndPath {
+		cache.Stop()
+	}
+}