tailfs: replace webdavfs with reverse proxies

Instead of modeling remote WebDAV servers as actual
webdav.FS instances, we now just proxy traffic to them.
This not only simplifies the code, but it also allows
WebDAV locking to work correctly by making sure locks are
handled by the servers that need to (i.e. the ones actually
serving the files).

Updates tailscale/corp#16827

Signed-off-by: Percy Wegmann <percy@tailscale.com>

client/tailscale/localclient_test.go

@@ -36,7 +36,7 @@ func TestDeps(t *testing.T) {
 			// Make sure we don't again accidentally bring in a dependency on
 			// TailFS or its transitive dependencies
 			"tailscale.com/tailfs/tailfsimpl": "https://github.com/tailscale/tailscale/pull/10631",
-			"github.com/tailscale/gowebdav":   "https://github.com/tailscale/tailscale/pull/10631",
+			"github.com/studio-b12/gowebdav":  "https://github.com/tailscale/tailscale/pull/10631",
 		},
 	}.Check(t)
 }

cmd/tailscaled/depaware.txt

@@ -109,7 +109,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
    L    github.com/insomniacslk/dhcp/iana                            from github.com/insomniacslk/dhcp/dhcpv4
    L    github.com/insomniacslk/dhcp/interfaces                      from github.com/insomniacslk/dhcp/dhcpv4
    L    github.com/insomniacslk/dhcp/rfc1035label                    from github.com/insomniacslk/dhcp/dhcpv4
-        github.com/jellydator/ttlcache/v3                            from tailscale.com/tailfs/tailfsimpl/webdavfs
+        github.com/jellydator/ttlcache/v3                            from tailscale.com/tailfs/tailfsimpl/compositedav
    L    github.com/jmespath/go-jmespath                              from github.com/aws/aws-sdk-go-v2/service/ssm
    L    github.com/josharian/native                                  from github.com/mdlayher/netlink+
    L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces+
@@ -155,7 +155,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         github.com/tailscale/goupnp/scpd                             from github.com/tailscale/goupnp
         github.com/tailscale/goupnp/soap                             from github.com/tailscale/goupnp+
         github.com/tailscale/goupnp/ssdp                             from github.com/tailscale/goupnp
-        github.com/tailscale/gowebdav                                from tailscale.com/tailfs/tailfsimpl/webdavfs
         github.com/tailscale/hujson                                  from tailscale.com/ipn/conffile
    L 💣 github.com/tailscale/netlink                                 from tailscale.com/net/routetable+
         github.com/tailscale/peercred                                from tailscale.com/ipn/ipnauth
@@ -323,9 +322,9 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/taildrop                                       from tailscale.com/ipn/ipnlocal+
         tailscale.com/tailfs                                         from tailscale.com/client/tailscale+
         tailscale.com/tailfs/tailfsimpl                              from tailscale.com/cmd/tailscaled
-        tailscale.com/tailfs/tailfsimpl/compositefs                  from tailscale.com/tailfs/tailfsimpl
+        tailscale.com/tailfs/tailfsimpl/compositedav                 from tailscale.com/tailfs/tailfsimpl
+        tailscale.com/tailfs/tailfsimpl/dirfs                        from tailscale.com/tailfs/tailfsimpl+
         tailscale.com/tailfs/tailfsimpl/shared                       from tailscale.com/tailfs/tailfsimpl+
-        tailscale.com/tailfs/tailfsimpl/webdavfs                     from tailscale.com/tailfs/tailfsimpl
      💣 tailscale.com/tempfork/device                                from tailscale.com/net/tstun/table
   LD    tailscale.com/tempfork/gliderlabs/ssh                        from tailscale.com/ssh/tailssh
         tailscale.com/tempfork/heap                                  from tailscale.com/wgengine/magicsock

go.mod

@@ -63,12 +63,12 @@ require (
 	github.com/prometheus/common v0.46.0
 	github.com/safchain/ethtool v0.3.0
 	github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e
+	github.com/studio-b12/gowebdav v0.9.0
 	github.com/tailscale/certstore v0.1.1-0.20231202035212-d3fa0460f47e
 	github.com/tailscale/depaware v0.0.0-20210622194025-720c4b409502
 	github.com/tailscale/goexpect v0.0.0-20210902213824-6e8c725cea41
 	github.com/tailscale/golang-x-crypto v0.0.0-20240108194725-7ce1f622c780
 	github.com/tailscale/goupnp v1.0.1-0.20210804011211-c64d0f06ea05
-	github.com/tailscale/gowebdav v0.0.0-20240130173557-d49b872b5126
 	github.com/tailscale/hujson v0.0.0-20221223112325-20486734a56a
 	github.com/tailscale/mkctr v0.0.0-20240102155253-bf50773ba734
 	github.com/tailscale/netlink v1.1.1-0.20211101221916-cabfb018fe85

go.sum

@@ -853,6 +853,8 @@ github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o
 github.com/stretchr/testify v1.8.3/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/studio-b12/gowebdav v0.9.0 h1:1j1sc9gQnNxbXXM4M/CebPOX4aXYtr7MojAVcN4dHjU=
+github.com/studio-b12/gowebdav v0.9.0/go.mod h1:bHA7t77X/QFExdeAnDzK6vKM34kEZAcE1OX4MfiwjkE=
 github.com/subosito/gotenv v1.4.2 h1:X1TuBLAMDFbaTAChgCBLu3DU3UPyELpnF2jjJ2cz/S8=
 github.com/subosito/gotenv v1.4.2/go.mod h1:ayKnFf/c6rvx/2iiLrJUk1e6plDbT3edrFNGqEflhK0=
 github.com/t-yuki/gocover-cobertura v0.0.0-20180217150009-aaee18c8195c h1:+aPplBwWcHBo6q9xrfWdMrT9o4kltkmmvpemgIjep/8=
@@ -869,8 +871,6 @@ github.com/tailscale/golang-x-crypto v0.0.0-20240108194725-7ce1f622c780 h1:U0J2C
 github.com/tailscale/golang-x-crypto v0.0.0-20240108194725-7ce1f622c780/go.mod h1:ikbF+YT089eInTp9f2vmvy4+ZVnW5hzX1q2WknxSprQ=
 github.com/tailscale/goupnp v1.0.1-0.20210804011211-c64d0f06ea05 h1:4chzWmimtJPxRs2O36yuGRW3f9SYV+bMTTvMBI0EKio=
 github.com/tailscale/goupnp v1.0.1-0.20210804011211-c64d0f06ea05/go.mod h1:PdCqy9JzfWMJf1H5UJW2ip33/d4YkoKN0r67yKH1mG8=
-github.com/tailscale/gowebdav v0.0.0-20240130173557-d49b872b5126 h1:EBLH+PeC3efXmUi82yEMxjlcKhDwAUZTi0tIT4Q8oTg=
-github.com/tailscale/gowebdav v0.0.0-20240130173557-d49b872b5126/go.mod h1:UCbnLJ2ebWLs28V9ubpXbq4Qx3e0q1TVoM1AC3Z2b40=
 github.com/tailscale/hujson v0.0.0-20221223112325-20486734a56a h1:SJy1Pu0eH1C29XwJucQo73FrleVK6t4kYz4NVhp34Yw=
 github.com/tailscale/hujson v0.0.0-20221223112325-20486734a56a/go.mod h1:DFSS3NAGHthKo1gTlmEcSBiZrRJXi28rLNd/1udP1c8=
 github.com/tailscale/mkctr v0.0.0-20240102155253-bf50773ba734 h1:93cvKHbvsPK3MKfFTvR00d0b0R0bzRKBW9yrj813fhI=

tailcfg/tailcfg_test.go

@@ -850,7 +850,7 @@ func TestDeps(t *testing.T) {
 			// Make sure we don't again accidentally bring in a dependency on
 			// TailFS or its transitive dependencies
 			"tailscale.com/tailfs/tailfsimpl": "https://github.com/tailscale/tailscale/pull/10631",
-			"github.com/tailscale/gowebdav":   "https://github.com/tailscale/tailscale/pull/10631",
+			"github.com/studio-b12/gowebdav":  "https://github.com/tailscale/tailscale/pull/10631",
 		},
 	}.Check(t)
 }

tailfs/tailfsimpl/compositedav/compositedav.go

@@ -0,0 +1,233 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package compositedav provides an http.Handler that composes multiple WebDAV
+// services into a single WebDAV service that presents each of them as its own
+// folder.
+package compositedav
+
+import (
+	"log"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"path"
+	"slices"
+	"strings"
+	"sync"
+
+	"github.com/tailscale/xnet/webdav"
+	"tailscale.com/tailfs/tailfsimpl/dirfs"
+	"tailscale.com/tailfs/tailfsimpl/shared"
+	"tailscale.com/tstime"
+	"tailscale.com/types/logger"
+)
+
+// Child is a child folder of this compositedav.
+type Child struct {
+	*dirfs.Child
+
+	// BaseURL is the base URL of the WebDAV service to which we'll proxy
+	// requests for this Child. We will append the filename from the original
+	// URL to this.
+	BaseURL string
+
+	// Transport (if specified) is the http transport to use when communicating
+	// with this Child's WebDAV service.
+	Transport http.RoundTripper
+
+	rp       *httputil.ReverseProxy
+	initOnce sync.Once
+}
+
+// CloseIdleConnections forcibly closes any idle connections on this Child's
+// reverse proxy.
+func (c *Child) CloseIdleConnections() {
+	tr, ok := c.Transport.(*http.Transport)
+	if ok {
+		tr.CloseIdleConnections()
+	}
+}
+
+func (c *Child) init() {
+	c.initOnce.Do(func() {
+		c.rp = &httputil.ReverseProxy{
+			Transport: c.Transport,
+			Rewrite:   func(r *httputil.ProxyRequest) {},
+		}
+	})
+}
+
+// Handler implements http.Handler by using a dirfs.FS for showing a virtual
+// read-only folder that represents the Child WebDAV services as sub-folders
+// and proxying all requests for resources on the children to those children
+// via httputil.ReverseProxy instances.
+type Handler struct {
+	// Logf specifies a logging function to use.
+	Logf logger.Logf
+
+	// Clock, if specified, determines the current time. If not specified, we
+	// default to time.Now().
+	Clock tstime.Clock
+
+	// StatCache is an optional cache for PROPFIND results.
+	StatCache *StatCache
+
+	// childrenMu guards the fields below. Note that we do read the contents of
+	// children after releasing the read lock, which we can do because we never
+	// modify children but only ever replace it in SetChildren.
+	childrenMu sync.RWMutex
+	children   []*Child
+	staticRoot string
+}
+
+// ServeHTTP implements http.Handler.
+func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method == "PROPFIND" {
+		h.handlePROPFIND(w, r)
+		return
+	}
+
+	if r.Method != "GET" {
+		// If the user is performing a modification (e.g. PUT, MKDIR, etc),
+		// we need to invalidate the StatCache to make sure we're not knowingly
+		// showing stale stats.
+		// TODO(oxtoacart): maybe be more selective about invalidating cache
+		h.StatCache.invalidate()
+	}
+
+	mpl := h.maxPathLength(r)
+	pathComponents := shared.CleanAndSplit(r.URL.Path)
+
+	if len(pathComponents) >= mpl {
+		h.delegate(pathComponents[mpl-1:], w, r)
+		return
+	}
+	h.handle(w, r)
+}
+
+// handle handles the request locally using our dirfs.FS.
+func (h *Handler) handle(w http.ResponseWriter, r *http.Request) {
+	h.childrenMu.RLock()
+	clk, kids, root := h.Clock, h.children, h.staticRoot
+	h.childrenMu.RUnlock()
+
+	children := make([]*dirfs.Child, 0, len(kids))
+	for _, child := range kids {
+		children = append(children, child.Child)
+	}
+	wh := &webdav.Handler{
+		LockSystem: webdav.NewMemLS(),
+		FileSystem: &dirfs.FS{
+			Clock:      clk,
+			Children:   children,
+			StaticRoot: root,
+		},
+	}
+
+	wh.ServeHTTP(w, r)
+}
+
+// delegate sends the request to the Child WebDAV server.
+func (h *Handler) delegate(pathComponents []string, w http.ResponseWriter, r *http.Request) string {
+	childName := pathComponents[0]
+	child := h.GetChild(childName)
+	if child == nil {
+		w.WriteHeader(http.StatusNotFound)
+		return childName
+	}
+	u, err := url.Parse(child.BaseURL)
+	if err != nil {
+		h.logf("warning: parse base URL %s failed: %s", child.BaseURL, err)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return childName
+	}
+	u.Path = path.Join(u.Path, shared.Join(pathComponents[1:]...))
+	r.URL = u
+	r.Host = u.Host
+	child.rp.ServeHTTP(w, r)
+	return childName
+}
+
+// SetChildren replaces the entire existing set of children with the given
+// ones. If staticRoot is given, the children will appear with a subfolder
+// bearing named <staticRoot>.
+func (h *Handler) SetChildren(staticRoot string, children ...*Child) {
+	for _, child := range children {
+		child.init()
+	}
+
+	slices.SortFunc(children, func(a, b *Child) int {
+		return strings.Compare(a.Name, b.Name)
+	})
+
+	h.childrenMu.Lock()
+	oldChildren := children
+	h.children = children
+	h.staticRoot = staticRoot
+	h.childrenMu.Unlock()
+
+	for _, child := range oldChildren {
+		child.CloseIdleConnections()
+	}
+}
+
+// GetChild gets the Child identified by name, or nil if no matching child
+// found.
+func (h *Handler) GetChild(name string) *Child {
+	h.childrenMu.RLock()
+	defer h.childrenMu.RUnlock()
+
+	_, child := h.findChildLocked(name)
+	return child
+}
+
+// Close closes this Handler,including closing all idle connections on children
+// and stopping the StatCache (if caching is enabled).
+func (h *Handler) Close() {
+	h.childrenMu.RLock()
+	oldChildren := h.children
+	h.children = nil
+	h.childrenMu.RUnlock()
+
+	for _, child := range oldChildren {
+		child.CloseIdleConnections()
+	}
+
+	if h.StatCache != nil {
+		h.StatCache.stop()
+	}
+}
+
+func (h *Handler) findChildLocked(name string) (int, *Child) {
+	var child *Child
+	i, found := slices.BinarySearchFunc(h.children, name, func(child *Child, name string) int {
+		return strings.Compare(child.Name, name)
+	})
+	if found {
+		return i, h.children[i]
+	}
+	return i, child
+}
+
+func (h *Handler) logf(format string, args ...any) {
+	if h.Logf != nil {
+		h.Logf(format, args...)
+		return
+	}
+
+	log.Printf(format, args...)
+}
+
+// maxPathLength calculates the maximum length of a path that can be handled by
+// this handler without delegating to a Child. It's always at least 1, and if
+// staticRoot is configured, it's 2.
+func (h *Handler) maxPathLength(r *http.Request) int {
+	h.childrenMu.RLock()
+	defer h.childrenMu.RUnlock()
+
+	if h.staticRoot != "" {
+		return 2
+	}
+	return 1
+}

tailfs/tailfsimpl/compositedav/propfind.go

@@ -0,0 +1,84 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package compositedav
+
+import (
+	"bytes"
+	"fmt"
+	"math"
+	"net/http"
+	"regexp"
+
+	"tailscale.com/tailfs/tailfsimpl/shared"
+)
+
+var (
+	hrefRegex = regexp.MustCompile(`(?s)<D:href>/?([^<]*)/?</D:href>`)
+)
+
+func (h *Handler) handlePROPFIND(w http.ResponseWriter, r *http.Request) {
+	pathComponents := shared.CleanAndSplit(r.URL.Path)
+	mpl := h.maxPathLength(r)
+	if !shared.IsRoot(r.URL.Path) && len(pathComponents)+getDepth(r) > mpl {
+		// Delegate to a Child.
+		depth := getDepth(r)
+
+		cached := h.StatCache.get(r.URL.Path, depth)
+		if cached != nil {
+			w.Header().Del("Content-Length")
+			w.WriteHeader(http.StatusMultiStatus)
+			w.Write(cached)
+			return
+		}
+
+		// Use a buffering ResponseWriter so that we can manipulate the result.
+		// The only thing we use from the original ResponseWriter is Header().
+		bw := &bufferingResponseWriter{ResponseWriter: w}
+
+		mpl := h.maxPathLength(r)
+		h.delegate(pathComponents[mpl-1:], bw, r)
+
+		// Fixup paths to add the requested path as a prefix.
+		pathPrefix := shared.Join(pathComponents[0:mpl]...)
+		b := hrefRegex.ReplaceAll(bw.buf.Bytes(), []byte(fmt.Sprintf("<D:href>%s/$1</D:href>", pathPrefix)))
+
+		if h.StatCache != nil && bw.status == http.StatusMultiStatus && b != nil {
+			h.StatCache.set(r.URL.Path, depth, b)
+		}
+
+		w.Header().Del("Content-Length")
+		w.WriteHeader(bw.status)
+		w.Write(b)
+
+		return
+	}
+
+	h.handle(w, r)
+}
+
+func getDepth(r *http.Request) int {
+	switch r.Header.Get("Depth") {
+	case "0":
+		return 0
+	case "1":
+		return 1
+	case "infinity":
+		return math.MaxInt
+	}
+	return 0
+}
+
+type bufferingResponseWriter struct {
+	http.ResponseWriter
+	status int
+	buf    bytes.Buffer
+}
+
+func (bw *bufferingResponseWriter) WriteHeader(statusCode int) {
+	bw.status = statusCode
+}
+
+func (bw *bufferingResponseWriter) Write(p []byte) (int, error) {
+	return bw.buf.Write(p)
+}

tailfs/tailfsimpl/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()
+	}
+}

tailfs/tailfsimpl/compositedav/stat_cache_test.go

@@ -0,0 +1,75 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package compositedav
+
+import (
+	"bytes"
+	"testing"
+	"time"
+
+	"tailscale.com/tstest"
+)
+
+var (
+	val  = []byte("1")
+	file = "file"
+)
+
+func TestStatCacheNoTimeout(t *testing.T) {
+	// Make sure we don't leak goroutines
+	tstest.ResourceCheck(t)
+
+	c := &StatCache{TTL: 5 * time.Second}
+	defer c.stop()
+
+	// check get before set
+	fetched := c.get(file, 1)
+	if fetched != nil {
+		t.Errorf("got %q, want nil", fetched)
+	}
+
+	// set new stat
+	c.set(file, 1, val)
+	fetched = c.get(file, 1)
+	if !bytes.Equal(fetched, val) {
+		t.Errorf("got %q, want %q", fetched, val)
+	}
+
+	// fetch stat again, should still be cached
+	fetched = c.get(file, 1)
+	if !bytes.Equal(fetched, val) {
+		t.Errorf("got %q, want %q", fetched, val)
+	}
+}
+
+func TestStatCacheTimeout(t *testing.T) {
+	// Make sure we don't leak goroutines
+	tstest.ResourceCheck(t)
+
+	c := &StatCache{TTL: 250 * time.Millisecond}
+	defer c.stop()
+
+	// set new stat
+	c.set(file, 1, val)
+	fetched := c.get(file, 1)
+	if !bytes.Equal(fetched, val) {
+		t.Errorf("got %q, want %q", fetched, val)
+	}
+
+	// wait for cache to expire and refetch stat, should be empty now
+	time.Sleep(c.TTL * 2)
+
+	fetched = c.get(file, 1)
+	if fetched != nil {
+		t.Errorf("invalidate should have cleared cached value")
+	}
+
+	c.set(file, 1, val)
+	// invalidate the cache and make sure nothing is returned
+	c.invalidate()
+	fetched = c.get(file, 1)
+	if fetched != nil {
+		t.Errorf("invalidate should have cleared cached value")
+	}
+}

tailfs/tailfsimpl/compositefs/compositefs.go

@@ -1,227 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-// Package compositefs provides a webdav.FileSystem that is composi
-package compositefs
-
-import (
-	"io"
-	"log"
-	"os"
-	"path"
-	"slices"
-	"strings"
-	"sync"
-	"time"
-
-	"github.com/tailscale/xnet/webdav"
-	"tailscale.com/tailfs/tailfsimpl/shared"
-	"tailscale.com/tstime"
-	"tailscale.com/types/logger"
-)
-
-// Child is a child filesystem of a CompositeFileSystem
-type Child struct {
-	// Name is the name of the child
-	Name string
-	// FS is the child's FileSystem
-	FS webdav.FileSystem
-	// Available is a function indicating whether or not the child is currently
-	// available.
-	Available func() bool
-}
-
-func (c *Child) isAvailable() bool {
-	if c.Available == nil {
-		return true
-	}
-	return c.Available()
-}
-
-// Options specifies options for configuring a CompositeFileSystem.
-type Options struct {
-	// Logf specifies a logging function to use
-	Logf logger.Logf
-	// StatChildren, if true, causes the CompositeFileSystem to stat its child
-	// folders when generating a root directory listing. This gives more
-	// accurate information but increases latency.
-	StatChildren bool
-	// Clock, if specified, determines the current time. If not specified, we
-	// default to time.Now().
-	Clock tstime.Clock
-}
-
-// New constructs a CompositeFileSystem that logs using the given logf.
-func New(opts Options) *CompositeFileSystem {
-	logf := opts.Logf
-	if logf == nil {
-		logf = log.Printf
-	}
-	fs := &CompositeFileSystem{
-		logf:         logf,
-		statChildren: opts.StatChildren,
-	}
-	if opts.Clock != nil {
-		fs.now = opts.Clock.Now
-	} else {
-		fs.now = time.Now
-	}
-	return fs
-}
-
-// CompositeFileSystem is a webdav.FileSystem that is composed of multiple
-// child webdav.FileSystems. Each child is identified by a name and appears
-// as a folder within the root of the CompositeFileSystem, with the children
-// sorted lexicographically by name.
-//
-// Children in a CompositeFileSystem can only be added or removed via calls to
-// the AddChild and RemoveChild methods, they cannot be added via operations
-// on the webdav.FileSystem interface like filesystem.Mkdir or filesystem.OpenFile.
-// In other words, the root of the CompositeFileSystem acts as read-only, not
-// permitting the addition, removal or renaming of folders.
-//
-// Rename is only supported within a single child. Renaming across children
-// is not supported, as it wouldn't be possible to perform it atomically.
-type CompositeFileSystem struct {
-	logf         logger.Logf
-	statChildren bool
-	now          func() time.Time
-
-	// childrenMu guards children
-	childrenMu sync.Mutex
-	children   []*Child
-}
-
-// AddChild ads a single child with the given name, replacing any existing
-// child with the same name.
-func (cfs *CompositeFileSystem) AddChild(child *Child) {
-	cfs.childrenMu.Lock()
-	oldIdx, oldChild := cfs.findChildLocked(child.Name)
-	if oldChild != nil {
-		// replace old child
-		cfs.children[oldIdx] = child
-	} else {
-		// insert new child
-		cfs.children = slices.Insert(cfs.children, oldIdx, child)
-	}
-	cfs.childrenMu.Unlock()
-
-	if oldChild != nil {
-		if c, ok := oldChild.FS.(io.Closer); ok {
-			if err := c.Close(); err != nil {
-				cfs.logf("closing child filesystem %v: %v", child.Name, err)
-			}
-		}
-	}
-}
-
-// RemoveChild removes the child with the given name, if it exists.
-func (cfs *CompositeFileSystem) RemoveChild(name string) {
-	cfs.childrenMu.Lock()
-	oldPos, oldChild := cfs.findChildLocked(name)
-	if oldChild != nil {
-		// remove old child
-		copy(cfs.children[oldPos:], cfs.children[oldPos+1:])
-		cfs.children = cfs.children[:len(cfs.children)-1]
-	}
-	cfs.childrenMu.Unlock()
-
-	if oldChild != nil {
-		closer, ok := oldChild.FS.(io.Closer)
-		if ok {
-			err := closer.Close()
-			if err != nil {
-				cfs.logf("failed to close child filesystem %v: %v", name, err)
-			}
-		}
-	}
-}
-
-// SetChildren replaces the entire existing set of children with the given
-// ones.
-func (cfs *CompositeFileSystem) SetChildren(children ...*Child) {
-	slices.SortFunc(children, func(a, b *Child) int {
-		return strings.Compare(a.Name, b.Name)
-	})
-
-	cfs.childrenMu.Lock()
-	oldChildren := cfs.children
-	cfs.children = children
-	cfs.childrenMu.Unlock()
-
-	for _, child := range oldChildren {
-		closer, ok := child.FS.(io.Closer)
-		if ok {
-			_ = closer.Close()
-		}
-	}
-}
-
-// GetChild returns the child with the given name and a boolean indicating
-// whether or not it was found.
-func (cfs *CompositeFileSystem) GetChild(name string) (webdav.FileSystem, bool) {
-	_, child := cfs.findChildLocked(name)
-	if child == nil {
-		return nil, false
-	}
-	return child.FS, true
-}
-
-func (cfs *CompositeFileSystem) findChildLocked(name string) (int, *Child) {
-	var child *Child
-	i, found := slices.BinarySearchFunc(cfs.children, name, func(child *Child, name string) int {
-		return strings.Compare(child.Name, name)
-	})
-	if found {
-		child = cfs.children[i]
-	}
-	return i, child
-}
-
-// pathInfoFor returns a pathInfo for the given filename. If the filename
-// refers to a Child that does not exist within this CompositeFileSystem,
-// it will return the error os.ErrNotExist. Even when returning an error,
-// it will still return a complete pathInfo.
-func (cfs *CompositeFileSystem) pathInfoFor(name string) (pathInfo, error) {
-	cfs.childrenMu.Lock()
-	defer cfs.childrenMu.Unlock()
-
-	var info pathInfo
-	pathComponents := shared.CleanAndSplit(name)
-	_, info.child = cfs.findChildLocked(pathComponents[0])
-	info.refersToChild = len(pathComponents) == 1
-	if !info.refersToChild {
-		info.pathOnChild = path.Join(pathComponents[1:]...)
-	}
-	if info.child == nil {
-		return info, os.ErrNotExist
-	}
-	return info, nil
-}
-
-// pathInfo provides information about a path
-type pathInfo struct {
-	// child is the Child corresponding to the first component of the path.
-	child *Child
-	// refersToChild indicates that that path refers directly to the child
-	// (i.e. the path has only 1 component).
-	refersToChild bool
-	// pathOnChild is the path within the child (i.e. path minus leading component)
-	// if and only if refersToChild is false.
-	pathOnChild string
-}
-
-func (cfs *CompositeFileSystem) Close() error {
-	cfs.childrenMu.Lock()
-	children := cfs.children
-	cfs.childrenMu.Unlock()
-
-	for _, child := range children {
-		closer, ok := child.FS.(io.Closer)
-		if ok {
-			_ = closer.Close()
-		}
-	}
-
-	return nil
-}

tailfs/tailfsimpl/compositefs/compositefs_test.go

@@ -1,497 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package compositefs
-
-import (
-	"context"
-	"errors"
-	"io/fs"
-	"net"
-	"net/http"
-	"os"
-	"path/filepath"
-	"testing"
-	"time"
-
-	"github.com/tailscale/xnet/webdav"
-	"tailscale.com/tailfs/tailfsimpl/shared"
-	"tailscale.com/tstest"
-)
-
-func TestStat(t *testing.T) {
-	cfs, dir1, _, clock, close := createFileSystem(t, nil)
-	defer close()
-
-	tests := []struct {
-		label    string
-		name     string
-		expected fs.FileInfo
-		err      error
-	}{
-		{
-			label: "root folder",
-			name:  "/",
-			expected: &shared.StaticFileInfo{
-				Named:      "/",
-				Sized:      0,
-				ModdedTime: clock.Now(),
-				Dir:        true,
-			},
-		},
-		{
-			label: "remote1",
-			name:  "/remote1",
-			expected: &shared.StaticFileInfo{
-				Named:      "/remote1",
-				Sized:      0,
-				ModdedTime: clock.Now(),
-				Dir:        true,
-			},
-		},
-		{
-			label: "remote2",
-			name:  "/remote2",
-			expected: &shared.StaticFileInfo{
-				Named:      "/remote2",
-				Sized:      0,
-				ModdedTime: clock.Now(),
-				Dir:        true,
-			},
-		},
-		{
-			label: "non-existent remote",
-			name:  "/remote3",
-			err:   os.ErrNotExist,
-		},
-		{
-			label: "file on remote1",
-			name:  "/remote1/file1.txt",
-			expected: &shared.StaticFileInfo{
-				Named:      "/remote1/file1.txt",
-				Sized:      stat(t, filepath.Join(dir1, "file1.txt")).Size(),
-				ModdedTime: stat(t, filepath.Join(dir1, "file1.txt")).ModTime(),
-				Dir:        false,
-			},
-		},
-	}
-
-	ctx := context.Background()
-	for _, test := range tests {
-		t.Run(test.label, func(t *testing.T) {
-			fi, err := cfs.Stat(ctx, test.name)
-			if test.err != nil {
-				if err == nil || !errors.Is(err, test.err) {
-					t.Errorf("expected error: %v   got: %v", test.err, err)
-				}
-			} else {
-				if err != nil {
-					t.Errorf("unable to stat file: %v", err)
-				} else {
-					infosEqual(t, test.expected, fi)
-				}
-			}
-		})
-	}
-}
-
-func TestStatWithStatChildren(t *testing.T) {
-	cfs, dir1, dir2, _, close := createFileSystem(t, &Options{StatChildren: true})
-	defer close()
-
-	tests := []struct {
-		label    string
-		name     string
-		expected fs.FileInfo
-	}{
-		{
-			label: "root folder",
-			name:  "/",
-			expected: &shared.StaticFileInfo{
-				Named:      "/",
-				Sized:      0,
-				ModdedTime: stat(t, dir2).ModTime(), // ModTime should be greatest modtime of children
-				Dir:        true,
-			},
-		},
-		{
-			label: "remote1",
-			name:  "/remote1",
-			expected: &shared.StaticFileInfo{
-				Named:      "/remote1",
-				Sized:      stat(t, dir1).Size(),
-				ModdedTime: stat(t, dir1).ModTime(),
-				Dir:        true,
-			},
-		},
-		{
-			label: "remote2",
-			name:  "/remote2",
-			expected: &shared.StaticFileInfo{
-				Named:      "/remote2",
-				Sized:      stat(t, dir2).Size(),
-				ModdedTime: stat(t, dir2).ModTime(),
-				Dir:        true,
-			},
-		},
-	}
-
-	ctx := context.Background()
-	for _, test := range tests {
-		t.Run(test.label, func(t *testing.T) {
-			fi, err := cfs.Stat(ctx, test.name)
-			if err != nil {
-				t.Errorf("unable to stat file: %v", err)
-			} else {
-				infosEqual(t, test.expected, fi)
-			}
-		})
-	}
-}
-
-func TestMkdir(t *testing.T) {
-	fs, _, _, _, close := createFileSystem(t, nil)
-	defer close()
-
-	tests := []struct {
-		label string
-		name  string
-		perm  os.FileMode
-		err   error
-	}{
-		{
-			label: "attempt to create root folder",
-			name:  "/",
-		},
-		{
-			label: "attempt to create remote",
-			name:  "/remote1",
-		},
-		{
-			label: "attempt to create non-existent remote",
-			name:  "/remote3",
-			err:   os.ErrPermission,
-		},
-		{
-			label: "attempt to create file on non-existent remote",
-			name:  "/remote3/somefile.txt",
-			err:   os.ErrNotExist,
-		},
-		{
-			label: "success",
-			name:  "/remote1/newfile.txt",
-			perm:  0772,
-		},
-	}
-
-	ctx := context.Background()
-	for _, test := range tests {
-		t.Run(test.label, func(t *testing.T) {
-			err := fs.Mkdir(ctx, test.name, test.perm)
-			if test.err != nil {
-				if err == nil || !errors.Is(err, test.err) {
-					t.Errorf("expected error: %v   got: %v", test.err, err)
-				}
-			} else {
-				if err != nil {
-					t.Errorf("unexpected error: %v", err)
-				} else {
-					fi, err := fs.Stat(ctx, test.name)
-					if err != nil {
-						t.Errorf("unable to stat file: %v", err)
-					} else {
-						if fi.Name() != test.name {
-							t.Errorf("expected name: %v   got: %v", test.name, fi.Name())
-						}
-						if !fi.IsDir() {
-							t.Error("expected directory")
-						}
-					}
-				}
-			}
-		})
-	}
-}
-
-func TestRemoveAll(t *testing.T) {
-	fs, _, _, _, close := createFileSystem(t, nil)
-	defer close()
-
-	tests := []struct {
-		label string
-		name  string
-		err   error
-	}{
-		{
-			label: "attempt to remove root folder",
-			name:  "/",
-			err:   os.ErrPermission,
-		},
-		{
-			label: "attempt to remove remote",
-			name:  "/remote1",
-			err:   os.ErrPermission,
-		},
-		{
-			label: "attempt to remove non-existent remote",
-			name:  "/remote3",
-			err:   os.ErrPermission,
-		},
-		{
-			label: "attempt to remove file on non-existent remote",
-			name:  "/remote3/somefile.txt",
-			err:   os.ErrNotExist,
-		},
-		{
-			label: "remove non-existent file",
-			name:  "/remote1/nonexistent.txt",
-		},
-		{
-			label: "remove existing file",
-			name:  "/remote1/dir1",
-		},
-	}
-
-	ctx := context.Background()
-	for _, test := range tests {
-		t.Run(test.label, func(t *testing.T) {
-			err := fs.RemoveAll(ctx, test.name)
-			if test.err != nil {
-				if err == nil || !errors.Is(err, test.err) {
-					t.Errorf("expected error: %v   got: %v", test.err, err)
-				}
-			} else {
-				if err != nil {
-					t.Errorf("unexpected error: %v", err)
-				} else {
-					_, err := fs.Stat(ctx, test.name)
-					if !os.IsNotExist(err) {
-						t.Errorf("expected dir to be gone: %v", err)
-					}
-				}
-			}
-		})
-	}
-}
-
-func TestRename(t *testing.T) {
-	fs, _, _, _, close := createFileSystem(t, nil)
-	defer close()
-
-	tests := []struct {
-		label           string
-		oldName         string
-		newName         string
-		err             error
-		expectedNewInfo *shared.StaticFileInfo
-	}{
-		{
-			label:   "attempt to move root folder",
-			oldName: "/",
-			newName: "/remote2/copy.txt",
-			err:     os.ErrPermission,
-		},
-		{
-			label:   "attempt to move to root folder",
-			oldName: "/remote1/file1.txt",
-			newName: "/",
-			err:     os.ErrPermission,
-		},
-		{
-			label:   "attempt to move to remote",
-			oldName: "/remote1/file1.txt",
-			newName: "/remote2",
-			err:     os.ErrPermission,
-		},
-		{
-			label:   "attempt to move to non-existent remote",
-			oldName: "/remote1/file1.txt",
-			newName: "/remote3",
-			err:     os.ErrPermission,
-		},
-		{
-			label:   "attempt to move file from non-existent remote",
-			oldName: "/remote3/file1.txt",
-			newName: "/remote1/file1.txt",
-			err:     os.ErrNotExist,
-		},
-		{
-			label:   "attempt to move file to a non-existent remote",
-			oldName: "/remote2/file2.txt",
-			newName: "/remote3/file2.txt",
-			err:     os.ErrNotExist,
-		},
-		{
-			label:   "attempt to move file across remotes",
-			oldName: "/remote1/file1.txt",
-			newName: "/remote2/file1.txt",
-			err:     os.ErrPermission,
-		},
-		{
-			label:   "attempt to move remote itself",
-			oldName: "/remote1",
-			newName: "/remote2",
-			err:     os.ErrPermission,
-		},
-		{
-			label:   "attempt to move to a remote",
-			oldName: "/remote1/file2.txt",
-			newName: "/remote2",
-			err:     os.ErrPermission,
-		},
-		{
-			label:   "move file within remote",
-			oldName: "/remote2/file2.txt",
-			newName: "/remote2/file3.txt",
-			expectedNewInfo: &shared.StaticFileInfo{
-				Named: "/remote2/file3.txt",
-				Sized: 5,
-				Dir:   false,
-			},
-		},
-	}
-
-	ctx := context.Background()
-	for _, test := range tests {
-		t.Run(test.label, func(t *testing.T) {
-			err := fs.Rename(ctx, test.oldName, test.newName)
-			if test.err != nil {
-				if err == nil || test.err.Error() != err.Error() {
-					t.Errorf("expected error: %v   got: %v", test.err, err)
-				}
-			} else {
-				if err != nil {
-					t.Errorf("unexpected error: %v", err)
-				} else {
-					fi, err := fs.Stat(ctx, test.newName)
-					if err != nil {
-						t.Errorf("unexpected error: %v", err)
-					} else {
-						// Override modTime to avoid having to compare it
-						test.expectedNewInfo.ModdedTime = fi.ModTime()
-						infosEqual(t, test.expectedNewInfo, fi)
-					}
-				}
-			}
-		})
-	}
-}
-
-func createFileSystem(t *testing.T, opts *Options) (webdav.FileSystem, string, string, *tstest.Clock, func()) {
-	l1, dir1 := startRemote(t)
-	l2, dir2 := startRemote(t)
-
-	// Make some files, use perms 0666 as lowest common denominator that works
-	// on both UNIX and Windows.
-	err := os.WriteFile(filepath.Join(dir1, "file1.txt"), []byte("12345"), 0666)
-	if err != nil {
-		t.Fatal(err)
-	}
-	err = os.WriteFile(filepath.Join(dir2, "file2.txt"), []byte("54321"), 0666)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// make some directories
-	err = os.Mkdir(filepath.Join(dir1, "dir1"), 0666)
-	if err != nil {
-		t.Fatal(err)
-	}
-	err = os.Mkdir(filepath.Join(dir2, "dir2"), 0666)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if opts == nil {
-		opts = &Options{}
-	}
-	if opts.Logf == nil {
-		opts.Logf = t.Logf
-	}
-	clock := tstest.NewClock(tstest.ClockOpts{Start: time.Now()})
-	opts.Clock = clock
-
-	fs := New(*opts)
-	fs.AddChild(&Child{Name: "remote4", FS: &closeableFS{webdav.Dir(dir2)}})
-	fs.SetChildren(&Child{Name: "remote2", FS: webdav.Dir(dir2)},
-		&Child{Name: "remote3", FS: &closeableFS{webdav.Dir(dir2)}},
-	)
-	fs.AddChild(&Child{Name: "remote1", FS: webdav.Dir(dir1)})
-	fs.RemoveChild("remote3")
-
-	child, ok := fs.GetChild("remote1")
-	if !ok || child == nil {
-		t.Fatal("unable to GetChild(remote1)")
-	}
-	child, ok = fs.GetChild("remote2")
-	if !ok || child == nil {
-		t.Fatal("unable to GetChild(remote2)")
-	}
-	child, ok = fs.GetChild("remote3")
-	if ok || child != nil {
-		t.Fatal("should have been able to GetChild(remote3)")
-	}
-	child, ok = fs.GetChild("remote4")
-	if ok || child != nil {
-		t.Fatal("should have been able to GetChild(remote4)")
-	}
-
-	return fs, dir1, dir2, clock, func() {
-		defer l1.Close()
-		defer os.RemoveAll(dir1)
-		defer l2.Close()
-		defer os.RemoveAll(dir2)
-	}
-}
-
-func stat(t *testing.T, path string) fs.FileInfo {
-	fi, err := os.Stat(path)
-	if err != nil {
-		t.Fatal(err)
-	}
-	return fi
-}
-
-func startRemote(t *testing.T) (net.Listener, string) {
-	dir := t.TempDir()
-
-	l, err := net.Listen("tcp", "127.0.0.1:")
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	h := &webdav.Handler{
-		FileSystem: webdav.Dir(dir),
-		LockSystem: webdav.NewMemLS(),
-	}
-
-	s := &http.Server{Handler: h}
-	go s.Serve(l)
-
-	return l, dir
-}
-
-func infosEqual(t *testing.T, expected, actual fs.FileInfo) {
-	t.Helper()
-	if expected.Name() != actual.Name() {
-		t.Errorf("expected name: %v   got: %v", expected.Name(), actual.Name())
-	}
-	if expected.Size() != actual.Size() {
-		t.Errorf("expected Size: %v   got: %v", expected.Size(), actual.Size())
-	}
-	if !expected.ModTime().Truncate(time.Second).UTC().Equal(actual.ModTime().Truncate(time.Second).UTC()) {
-		t.Errorf("expected ModTime: %v   got: %v", expected.ModTime(), actual.ModTime())
-	}
-	if expected.IsDir() != actual.IsDir() {
-		t.Errorf("expected IsDir: %v   got: %v", expected.IsDir(), actual.IsDir())
-	}
-}
-
-// closeableFS is a webdav.FileSystem that implements io.Closer()
-type closeableFS struct {
-	webdav.FileSystem
-}
-
-func (cfs *closeableFS) Close() error {
-	return nil
-}

tailfs/tailfsimpl/compositefs/mkdir.go

@@ -1,39 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package compositefs
-
-import (
-	"context"
-	"os"
-
-	"tailscale.com/tailfs/tailfsimpl/shared"
-)
-
-// Mkdir implements webdav.Filesystem. The root of this file system is
-// read-only, so any attempts to make directories within the root will fail
-// with os.ErrPermission. Attempts to make directories within one of the child
-// filesystems will be handled by the respective child.
-func (cfs *CompositeFileSystem) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
-	if shared.IsRoot(name) {
-		// root directory already exists, consider this okay
-		return nil
-	}
-
-	pathInfo, err := cfs.pathInfoFor(name)
-	if pathInfo.refersToChild {
-		// children can't be made
-		if pathInfo.child != nil {
-			// since child already exists, consider this okay
-			return nil
-		}
-		// since child doesn't exist, return permission error
-		return os.ErrPermission
-	}
-
-	if err != nil {
-		return err
-	}
-
-	return pathInfo.child.FS.Mkdir(ctx, pathInfo.pathOnChild, perm)
-}

tailfs/tailfsimpl/compositefs/openfile.go

@@ -1,65 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package compositefs
-
-import (
-	"context"
-	"io/fs"
-	"os"
-
-	"github.com/tailscale/xnet/webdav"
-	"tailscale.com/tailfs/tailfsimpl/shared"
-)
-
-// OpenFile implements interface webdav.Filesystem.
-func (cfs *CompositeFileSystem) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
-	if !shared.IsRoot(name) {
-		pathInfo, err := cfs.pathInfoFor(name)
-		if err != nil {
-			return nil, err
-		}
-
-		if pathInfo.refersToChild {
-			// this is the child itself, ask it to open its root
-			return pathInfo.child.FS.OpenFile(ctx, "/", flag, perm)
-		}
-
-		return pathInfo.child.FS.OpenFile(ctx, pathInfo.pathOnChild, flag, perm)
-	}
-
-	// the root directory contains one directory for each child
-	di, err := cfs.Stat(ctx, name)
-	if err != nil {
-		return nil, err
-	}
-
-	return &shared.DirFile{
-		Info: di,
-		LoadChildren: func() ([]fs.FileInfo, error) {
-			cfs.childrenMu.Lock()
-			children := cfs.children
-			cfs.childrenMu.Unlock()
-
-			childInfos := make([]fs.FileInfo, 0, len(cfs.children))
-			for _, c := range children {
-				if c.isAvailable() {
-					var childInfo fs.FileInfo
-					if cfs.statChildren {
-						fi, err := c.FS.Stat(ctx, "/")
-						if err != nil {
-							return nil, err
-						}
-						// we use the full name
-						childInfo = shared.RenamedFileInfo(ctx, c.Name, fi)
-					} else {
-						// always use now() as the modified time to bust caches
-						childInfo = shared.ReadOnlyDirInfo(c.Name, cfs.now())
-					}
-					childInfos = append(childInfos, childInfo)
-				}
-			}
-			return childInfos, nil
-		},
-	}, nil
-}

tailfs/tailfsimpl/compositefs/removeall.go

@@ -1,33 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package compositefs
-
-import (
-	"context"
-	"os"
-
-	"tailscale.com/tailfs/tailfsimpl/shared"
-)
-
-// RemoveAll implements webdav.File. The root of this file system is read-only,
-// so attempting to call RemoveAll on the root will fail with os.ErrPermission.
-// RemoveAll within a child will be handled by the respective child.
-func (cfs *CompositeFileSystem) RemoveAll(ctx context.Context, name string) error {
-	if shared.IsRoot(name) {
-		// root directory is read-only
-		return os.ErrPermission
-	}
-
-	pathInfo, err := cfs.pathInfoFor(name)
-	if pathInfo.refersToChild {
-		// children can't be removed
-		return os.ErrPermission
-	}
-
-	if err != nil {
-		return err
-	}
-
-	return pathInfo.child.FS.RemoveAll(ctx, pathInfo.pathOnChild)
-}

tailfs/tailfsimpl/compositefs/rename.go

@@ -1,49 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package compositefs
-
-import (
-	"context"
-	"os"
-
-	"tailscale.com/tailfs/tailfsimpl/shared"
-)
-
-// Rename implements interface webdav.FileSystem. The root of this file system
-// is read-only, so any attempt to rename a child within the root of this
-// filesystem will fail with os.ErrPermission. Renaming across children is not
-// supported and will fail with os.ErrPermission. Renaming within a child will
-// be handled by the respective child.
-func (cfs *CompositeFileSystem) Rename(ctx context.Context, oldName, newName string) error {
-	if shared.IsRoot(oldName) || shared.IsRoot(newName) {
-		// root directory is read-only
-		return os.ErrPermission
-	}
-
-	oldPathInfo, err := cfs.pathInfoFor(oldName)
-	if oldPathInfo.refersToChild {
-		// children themselves are read-only
-		return os.ErrPermission
-	}
-	if err != nil {
-		return err
-	}
-
-	newPathInfo, err := cfs.pathInfoFor(newName)
-	if newPathInfo.refersToChild {
-		// children themselves are read-only
-		return os.ErrPermission
-	}
-	if err != nil {
-		return err
-	}
-
-	if oldPathInfo.child != newPathInfo.child {
-		// moving a file across children is not permitted
-		return os.ErrPermission
-	}
-
-	// file is moving within the same child, let the child handle it
-	return oldPathInfo.child.FS.Rename(ctx, oldPathInfo.pathOnChild, newPathInfo.pathOnChild)
-}

tailfs/tailfsimpl/compositefs/stat.go

@@ -1,55 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package compositefs
-
-import (
-	"context"
-	"io/fs"
-
-	"tailscale.com/tailfs/tailfsimpl/shared"
-)
-
-// Stat implements webdav.FileSystem.
-func (cfs *CompositeFileSystem) Stat(ctx context.Context, name string) (fs.FileInfo, error) {
-	if shared.IsRoot(name) {
-		// Root is a directory
-		// always use now() as the modified time to bust caches
-		fi := shared.ReadOnlyDirInfo(name, cfs.now())
-		if cfs.statChildren {
-			// update last modified time based on children
-			cfs.childrenMu.Lock()
-			children := cfs.children
-			cfs.childrenMu.Unlock()
-			for i, child := range children {
-				childInfo, err := child.FS.Stat(ctx, "/")
-				if err != nil {
-					return nil, err
-				}
-				if i == 0 || childInfo.ModTime().After(fi.ModTime()) {
-					fi.ModdedTime = childInfo.ModTime()
-				}
-			}
-		}
-		return fi, nil
-	}
-
-	pathInfo, err := cfs.pathInfoFor(name)
-	if err != nil {
-		return nil, err
-	}
-
-	if pathInfo.refersToChild && !cfs.statChildren {
-		// Return a read-only FileInfo for this child.
-		// Always use now() as the modified time to bust caches.
-		return shared.ReadOnlyDirInfo(name, cfs.now()), nil
-	}
-
-	fi, err := pathInfo.child.FS.Stat(ctx, pathInfo.pathOnChild)
-	if err != nil {
-		return nil, err
-	}
-
-	// we use the full name, which is different than what the child sees
-	return shared.RenamedFileInfo(ctx, name, fi), nil
-}

tailfs/tailfsimpl/dirfs/dirfs.go

@@ -0,0 +1,101 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package dirfs provides a webdav.FileSystem that looks like a read-only
+// directory containing only subdirectories.
+package dirfs
+
+import (
+	"slices"
+	"strings"
+	"time"
+
+	"tailscale.com/tailfs/tailfsimpl/shared"
+	"tailscale.com/tstime"
+)
+
+// Child is subdirectory of an FS.
+type Child struct {
+	// Name is the name of the child
+	Name string
+
+	// Available is a function indicating whether or not the child is currently
+	// available. Unavailable children are excluded from the FS's directory
+	// listing. Available must be safe for concurrent use.
+	Available func() bool
+}
+
+func (c *Child) isAvailable() bool {
+	if c.Available == nil {
+		return true
+	}
+	return c.Available()
+}
+
+// FS is a read-only webdav.FileSystem that is composed of multiple child
+// folders.
+//
+// When listing the contents of this FileSystem's root directory, children will
+// be ordered in the order they're given to the FS.
+//
+// Children in an FS cannot be added, removed or renamed via operations on the
+// webdav.FileSystem interface like filesystem.Mkdir or filesystem.OpenFile.
+//
+// Any attempts to perform operations on paths inside of children will result
+// in a panic, as these are not expected to be performed on this FS.
+//
+// An FS an optionally have a StaticRoot, which will insert a folder with that
+// StaticRoot into the tree, like this:
+//
+// -- <StaticRoot>
+// ----- <Child>
+// ----- <Child>
+type FS struct {
+	// Children configures the full set of children of this FS.
+	Children []*Child
+
+	// Clock, if given, will cause this FS to use Clock.now() as the current
+	// time.
+	Clock tstime.Clock
+
+	// StaticRoot, if given, will insert the given name as a static root into
+	// every path.
+	StaticRoot string
+}
+
+func (dfs *FS) findChild(name string) (int, *Child) {
+	var child *Child
+	i, found := slices.BinarySearchFunc(dfs.Children, name, func(child *Child, name string) int {
+		return strings.Compare(child.Name, name)
+	})
+	if found {
+		child = dfs.Children[i]
+	}
+	return i, child
+}
+
+// childFor returns the child for the given filename. If the filename refers to
+// a path inside of a child, this will panic.
+func (dfs *FS) childFor(name string) *Child {
+	pathComponents := shared.CleanAndSplit(name)
+	if len(pathComponents) != 1 {
+		panic("dirfs does not permit reaching into child directories")
+	}
+	_, child := dfs.findChild(pathComponents[0])
+	return child
+}
+
+func (dfs *FS) now() time.Time {
+	if dfs.Clock != nil {
+		return dfs.Clock.Now()
+	}
+	return time.Now()
+}
+
+func (dfs *FS) trimStaticRoot(name string) (string, bool) {
+	before, after, found := strings.Cut(name, "/"+dfs.StaticRoot)
+	if !found {
+		return before, false
+	}
+	return after, shared.IsRoot(after)
+}

tailfs/tailfsimpl/dirfs/dirfs_test.go

@@ -0,0 +1,348 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package dirfs
+
+import (
+	"context"
+	"errors"
+	"io/fs"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/tailscale/xnet/webdav"
+	"tailscale.com/tailfs/tailfsimpl/shared"
+	"tailscale.com/tstest"
+)
+
+func TestStat(t *testing.T) {
+	cfs, _, _, clock := createFileSystem(t)
+
+	tests := []struct {
+		label    string
+		name     string
+		expected fs.FileInfo
+		err      error
+	}{
+		{
+			label: "root folder",
+			name:  "",
+			expected: &shared.StaticFileInfo{
+				Named:      "",
+				Sized:      0,
+				Moded:      0555,
+				ModdedTime: clock.Now(),
+				Dir:        true,
+			},
+		},
+		{
+			label: "static root folder",
+			name:  "/domain",
+			expected: &shared.StaticFileInfo{
+				Named:      "domain",
+				Sized:      0,
+				Moded:      0555,
+				ModdedTime: clock.Now(),
+				Dir:        true,
+			},
+		},
+		{
+			label: "remote1",
+			name:  "/domain/remote1",
+			expected: &shared.StaticFileInfo{
+				Named:      "remote1",
+				Sized:      0,
+				Moded:      0555,
+				ModdedTime: clock.Now(),
+				Dir:        true,
+			},
+		},
+		{
+			label: "remote2",
+			name:  "/domain/remote2",
+			expected: &shared.StaticFileInfo{
+				Named:      "remote2",
+				Sized:      0,
+				Moded:      0555,
+				ModdedTime: clock.Now(),
+				Dir:        true,
+			},
+		},
+		{
+			label: "non-existent remote",
+			name:  "remote3",
+			err:   os.ErrNotExist,
+		},
+	}
+
+	ctx := context.Background()
+	for _, test := range tests {
+		t.Run(test.label, func(t *testing.T) {
+			fi, err := cfs.Stat(ctx, test.name)
+			if test.err != nil {
+				if !errors.Is(err, test.err) {
+					t.Errorf("got %v, want %v", err, test.err)
+				}
+			} else {
+				if err != nil {
+					t.Errorf("unable to stat file: %v", err)
+				} else {
+					infosEqual(t, test.expected, fi)
+				}
+			}
+		})
+	}
+}
+
+func TestListDir(t *testing.T) {
+	cfs, _, _, clock := createFileSystem(t)
+
+	tests := []struct {
+		label    string
+		name     string
+		expected []fs.FileInfo
+		err      error
+	}{
+		{
+			label: "root folder",
+			name:  "",
+			expected: []fs.FileInfo{
+				&shared.StaticFileInfo{
+					Named:      "domain",
+					Sized:      0,
+					Moded:      0555,
+					ModdedTime: clock.Now(),
+					Dir:        true,
+				},
+			},
+		},
+		{
+			label: "static root folder",
+			name:  "/domain",
+			expected: []fs.FileInfo{
+				&shared.StaticFileInfo{
+					Named:      "remote1",
+					Sized:      0,
+					Moded:      0555,
+					ModdedTime: clock.Now(),
+					Dir:        true,
+				},
+				&shared.StaticFileInfo{
+					Named:      "remote2",
+					Sized:      0,
+					Moded:      0555,
+					ModdedTime: clock.Now(),
+					Dir:        true,
+				},
+				&shared.StaticFileInfo{
+					Named:      "remote4",
+					Sized:      0,
+					Moded:      0555,
+					ModdedTime: clock.Now(),
+					Dir:        true,
+				},
+			},
+		},
+	}
+
+	ctx := context.Background()
+	for _, test := range tests {
+		t.Run(test.label, func(t *testing.T) {
+			var infos []fs.FileInfo
+			file, err := cfs.OpenFile(ctx, test.name, os.O_RDONLY, 0)
+			if err == nil {
+				defer file.Close()
+				infos, err = file.Readdir(0)
+			}
+			if test.err != nil {
+				if !errors.Is(err, test.err) {
+					t.Errorf("got %v, want %v", err, test.err)
+				}
+			} else {
+				if err != nil {
+					t.Errorf("unable to stat file: %v", err)
+				} else {
+					if len(infos) != len(test.expected) {
+						t.Errorf("wrong number of file infos, want %d, got %d", len(test.expected), len(infos))
+					} else {
+						for i, expected := range test.expected {
+							infosEqual(t, expected, infos[i])
+						}
+					}
+				}
+			}
+		})
+	}
+}
+
+func TestMkdir(t *testing.T) {
+	fs, _, _, _ := createFileSystem(t)
+
+	tests := []struct {
+		label string
+		name  string
+		perm  os.FileMode
+		err   error
+	}{
+		{
+			label: "attempt to create root folder",
+			name:  "/",
+		},
+		{
+			label: "attempt to create static root folder",
+			name:  "/domain",
+		},
+		{
+			label: "attempt to create remote",
+			name:  "/domain/remote1",
+		},
+		{
+			label: "attempt to create non-existent remote",
+			name:  "/domain/remote3",
+			err:   os.ErrPermission,
+		},
+	}
+
+	ctx := context.Background()
+	for _, test := range tests {
+		t.Run(test.label, func(t *testing.T) {
+			err := fs.Mkdir(ctx, test.name, test.perm)
+			if test.err != nil {
+				if !errors.Is(err, test.err) {
+					t.Errorf("got %v, want %v", err, test.err)
+				}
+			} else if err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+		})
+	}
+}
+
+func TestRemoveAll(t *testing.T) {
+	fs, _, _, _ := createFileSystem(t)
+
+	tests := []struct {
+		label string
+		name  string
+		err   error
+	}{
+		{
+			label: "attempt to remove root folder",
+			name:  "/",
+			err:   os.ErrPermission,
+		},
+	}
+
+	ctx := context.Background()
+	for _, test := range tests {
+		t.Run(test.label, func(t *testing.T) {
+			err := fs.RemoveAll(ctx, test.name)
+			if !errors.Is(err, test.err) {
+				t.Errorf("got %v, want %v", err, test.err)
+			}
+		})
+	}
+}
+
+func TestRename(t *testing.T) {
+	fs, _, _, _ := createFileSystem(t)
+
+	tests := []struct {
+		label   string
+		oldName string
+		newName string
+		err     error
+	}{
+		{
+			label:   "attempt to move root folder",
+			oldName: "/",
+			newName: "/domain/remote2/copy.txt",
+			err:     os.ErrPermission,
+		},
+	}
+
+	ctx := context.Background()
+	for _, test := range tests {
+		t.Run(test.label, func(t *testing.T) {
+			err := fs.Rename(ctx, test.oldName, test.newName)
+			if !errors.Is(err, test.err) {
+				t.Errorf("got %v, want: %v", err, test.err)
+			}
+		})
+	}
+}
+
+func createFileSystem(t *testing.T) (webdav.FileSystem, string, string, *tstest.Clock) {
+	s1, dir1 := startRemote(t)
+	s2, dir2 := startRemote(t)
+
+	// Make some files, use perms 0666 as lowest common denominator that works
+	// on both UNIX and Windows.
+	err := os.WriteFile(filepath.Join(dir1, "file1.txt"), []byte("12345"), 0666)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.WriteFile(filepath.Join(dir2, "file2.txt"), []byte("54321"), 0666)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// make some directories
+	err = os.Mkdir(filepath.Join(dir1, "dir1"), 0666)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.Mkdir(filepath.Join(dir2, "dir2"), 0666)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	clock := tstest.NewClock(tstest.ClockOpts{Start: time.Now()})
+	fs := &FS{
+		Clock:      clock,
+		StaticRoot: "domain",
+		Children: []*Child{
+			{Name: "remote1"},
+			{Name: "remote2"},
+			{Name: "remote4"},
+		},
+	}
+
+	t.Cleanup(func() {
+		defer s1.Close()
+		defer os.RemoveAll(dir1)
+		defer s2.Close()
+		defer os.RemoveAll(dir2)
+	})
+
+	return fs, dir1, dir2, clock
+}
+
+func startRemote(t *testing.T) (*httptest.Server, string) {
+	dir := t.TempDir()
+
+	h := &webdav.Handler{
+		FileSystem: webdav.Dir(dir),
+		LockSystem: webdav.NewMemLS(),
+	}
+
+	s := httptest.NewServer(h)
+	t.Cleanup(s.Close)
+	return s, dir
+}
+
+func infosEqual(t *testing.T, expected, actual fs.FileInfo) {
+	t.Helper()
+	sfi, ok := actual.(*shared.StaticFileInfo)
+	if ok {
+		// zero out BirthedTime because we don't want to compare that
+		sfi.BirthedTime = time.Time{}
+	}
+	if diff := cmp.Diff(actual, expected); diff != "" {
+		t.Errorf("Wrong file info (-got, +want):\n%s", diff)
+	}
+}

tailfs/tailfsimpl/dirfs/mkdir.go

@@ -0,0 +1,30 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package dirfs
+
+import (
+	"context"
+	"os"
+
+	"tailscale.com/tailfs/tailfsimpl/shared"
+)
+
+// Mkdir implements webdav.FileSystem. All attempts to Mkdir a directory that
+// already exists will succeed. All other attempts will fail with
+// os.ErrPermission.
+func (dfs *FS) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
+	nameWithoutStaticRoot, isStaticRoot := dfs.trimStaticRoot(name)
+	if isStaticRoot || shared.IsRoot(name) {
+		// root directory already exists, consider this okay
+		return nil
+	}
+
+	child := dfs.childFor(nameWithoutStaticRoot)
+	if child != nil {
+		// child already exists, consider this okay
+		return nil
+	}
+
+	return &os.PathError{Op: "mkdir", Path: name, Err: os.ErrPermission}
+}

tailfs/tailfsimpl/dirfs/openfile.go

@@ -0,0 +1,63 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package dirfs
+
+import (
+	"context"
+	"io/fs"
+	"os"
+
+	"github.com/tailscale/xnet/webdav"
+	"tailscale.com/tailfs/tailfsimpl/shared"
+)
+
+// OpenFile implements interface webdav.Filesystem.
+func (dfs *FS) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
+	_, isStaticRoot := dfs.trimStaticRoot(name)
+	if !isStaticRoot && !shared.IsRoot(name) {
+		// Show a folder with no children to represent the requested child. In
+		// practice, the children of this folder are never read, we just need
+		// to give webdav a file here which it uses to call file.Stat(). So,
+		// even though the Child may in fact have its own children, it doesn't
+		// matter here.
+		return &shared.DirFile{
+			Info: shared.ReadOnlyDirInfo(name, dfs.now()),
+			LoadChildren: func() ([]fs.FileInfo, error) {
+				return nil, nil
+			},
+		}, nil
+	}
+
+	di, err := dfs.Stat(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+
+	if dfs.StaticRoot != "" && !isStaticRoot {
+		// Show a folder with a single subfolder that is the static root.
+		return &shared.DirFile{
+			Info: di,
+			LoadChildren: func() ([]fs.FileInfo, error) {
+				return []fs.FileInfo{
+					shared.ReadOnlyDirInfo(dfs.StaticRoot, dfs.now()),
+				}, nil
+			},
+		}, nil
+	}
+
+	// Show a folder with one subfolder for each Child of this FS.
+	return &shared.DirFile{
+		Info: di,
+		LoadChildren: func() ([]fs.FileInfo, error) {
+			childInfos := make([]fs.FileInfo, 0, len(dfs.Children))
+			for _, c := range dfs.Children {
+				if c.isAvailable() {
+					childInfo := shared.ReadOnlyDirInfo(c.Name, dfs.now())
+					childInfos = append(childInfos, childInfo)
+				}
+			}
+			return childInfos, nil
+		},
+	}, nil
+}

tailfs/tailfsimpl/dirfs/removeall.go

@@ -0,0 +1,15 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package dirfs
+
+import (
+	"context"
+	"os"
+)
+
+// RemoveAll implements webdav.File. No removal is supported and this always
+// returns os.ErrPermission.
+func (dfs *FS) RemoveAll(ctx context.Context, name string) error {
+	return &os.PathError{Op: "rm", Path: name, Err: os.ErrPermission}
+}

tailfs/tailfsimpl/dirfs/rename.go

@@ -0,0 +1,15 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package dirfs
+
+import (
+	"context"
+	"os"
+)
+
+// Rename implements interface webdav.FileSystem. No renaming is supported and
+// this always returns os.ErrPermission.
+func (dfs *FS) Rename(ctx context.Context, oldName, newName string) error {
+	return &os.PathError{Op: "mv", Path: oldName, Err: os.ErrPermission}
+}

tailfs/tailfsimpl/dirfs/stat.go

@@ -0,0 +1,30 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package dirfs
+
+import (
+	"context"
+	"io/fs"
+	"os"
+
+	"tailscale.com/tailfs/tailfsimpl/shared"
+)
+
+// Stat implements webdav.FileSystem.
+func (dfs *FS) Stat(ctx context.Context, name string) (fs.FileInfo, error) {
+	nameWithoutStaticRoot, isStaticRoot := dfs.trimStaticRoot(name)
+	if isStaticRoot || shared.IsRoot(name) {
+		// Static root is a directory, always use now() as the modified time to
+		// bust caches.
+		fi := shared.ReadOnlyDirInfo(name, dfs.now())
+		return fi, nil
+	}
+
+	child := dfs.childFor(nameWithoutStaticRoot)
+	if child == nil {
+		return nil, &os.PathError{Op: "stat", Path: name, Err: os.ErrNotExist}
+	}
+
+	return shared.ReadOnlyDirInfo(name, dfs.now()), nil
+}

tailfs/tailfsimpl/local_impl.go

@@ -10,10 +10,9 @@ import (
 	"net/http"
 	"time"
 
-	"github.com/tailscale/xnet/webdav"
 	"tailscale.com/tailfs"
-	"tailscale.com/tailfs/tailfsimpl/compositefs"
+	"tailscale.com/tailfs/tailfsimpl/compositedav"
-	"tailscale.com/tailfs/tailfsimpl/webdavfs"
+	"tailscale.com/tailfs/tailfsimpl/dirfs"
 	"tailscale.com/types/logger"
 )
 
@@ -33,7 +32,10 @@ func NewFileSystemForLocal(logf logger.Logf) *FileSystemForLocal {
 	}
 	fs := &FileSystemForLocal{
 		logf: logf,
-		cfs:      compositefs.New(compositefs.Options{Logf: logf}),
+		h: &compositedav.Handler{
+			Logf:      logf,
+			StatCache: &compositedav.StatCache{TTL: statCacheTTL},
+		},
 		listener: newConnListener(),
 	}
 	fs.startServing()
@@ -44,17 +46,12 @@ func NewFileSystemForLocal(logf logger.Logf) *FileSystemForLocal {
 // provides a unified WebDAV interface to remote TailFS shares on other nodes.
 type FileSystemForLocal struct {
 	logf     logger.Logf
-	cfs      *compositefs.CompositeFileSystem
+	h        *compositedav.Handler
 	listener *connListener
 }
 
 func (s *FileSystemForLocal) startServing() {
-	hs := &http.Server{
+	hs := &http.Server{Handler: s.h}
-		Handler: &webdav.Handler{
-			FileSystem: s.cfs,
-			LockSystem: webdav.NewMemLS(),
-		},
-	}
 	go func() {
 		err := hs.Serve(s.listener)
 		if err != nil {
@@ -73,31 +70,24 @@ func (s *FileSystemForLocal) HandleConn(conn net.Conn, remoteAddr net.Addr) erro
 // using a map of name -> url. If transport is specified, that transport
 // will be used to connect to these remotes.
 func (s *FileSystemForLocal) SetRemotes(domain string, remotes []*tailfs.Remote, transport http.RoundTripper) {
-	children := make([]*compositefs.Child, 0, len(remotes))
+	children := make([]*compositedav.Child, 0, len(remotes))
 	for _, remote := range remotes {
-		opts := webdavfs.Options{
+		children = append(children, &compositedav.Child{
-			URL:          remote.URL,
+			Child: &dirfs.Child{
-			Transport:    transport,
-			StatCacheTTL: statCacheTTL,
-			Logf:         s.logf,
-		}
-		children = append(children, &compositefs.Child{
 				Name:      remote.Name,
-			FS:        webdavfs.New(opts),
 				Available: remote.Available,
+			},
+			BaseURL:   remote.URL,
+			Transport: transport,
 		})
 	}
 
-	domainChild, found := s.cfs.GetChild(domain)
+	s.h.SetChildren(domain, children...)
-	if !found {
-		domainChild = compositefs.New(compositefs.Options{Logf: s.logf})
-		s.cfs.SetChildren(&compositefs.Child{Name: domain, FS: domainChild})
-	}
-	domainChild.(*compositefs.CompositeFileSystem).SetChildren(children...)
 }
 
 // Close() stops serving the WebDAV content
 func (s *FileSystemForLocal) Close() error {
-	s.cfs.Close()
+	err := s.listener.Close()
-	return s.listener.Close()
+	s.h.Close()
+	return err
 }

tailfs/tailfsimpl/remote_impl.go

@@ -12,6 +12,7 @@ import (
 	"net"
 	"net/http"
 	"net/netip"
+	"net/url"
 	"os"
 	"os/exec"
 	"strings"
@@ -21,9 +22,9 @@ import (
 	"github.com/tailscale/xnet/webdav"
 	"tailscale.com/safesocket"
 	"tailscale.com/tailfs"
-	"tailscale.com/tailfs/tailfsimpl/compositefs"
+	"tailscale.com/tailfs/tailfsimpl/compositedav"
+	"tailscale.com/tailfs/tailfsimpl/dirfs"
 	"tailscale.com/tailfs/tailfsimpl/shared"
-	"tailscale.com/tailfs/tailfsimpl/webdavfs"
 	"tailscale.com/types/logger"
 )
 
@@ -34,7 +35,7 @@ func NewFileSystemForRemote(logf logger.Logf) *FileSystemForRemote {
 	fs := &FileSystemForRemote{
 		logf:        logf,
 		lockSystem:  webdav.NewMemLS(),
-		fileSystems: make(map[string]webdav.FileSystem),
+		children:    make(map[string]*compositedav.Child),
 		userServers: make(map[string]*userServer),
 	}
 	return fs
@@ -50,7 +51,7 @@ type FileSystemForRemote struct {
 	mu             sync.RWMutex
 	fileServerAddr string
 	shares         map[string]*tailfs.Share
-	fileSystems    map[string]webdav.FileSystem
+	children       map[string]*compositedav.Child
 	userServers    map[string]*userServer
 }
 
@@ -81,27 +82,29 @@ func (s *FileSystemForRemote) SetShares(shares map[string]*tailfs.Share) {
 		}
 	}
 
-	fileSystems := make(map[string]webdav.FileSystem, len(shares))
+	children := make(map[string]*compositedav.Child, len(shares))
 	for _, share := range shares {
-		fileSystems[share.Name] = s.buildWebDAVFS(share)
+		children[share.Name] = s.buildChild(share)
 	}
 
 	s.mu.Lock()
 	s.shares = shares
-	oldFileSystems := s.fileSystems
 	oldUserServers := s.userServers
-	s.fileSystems = fileSystems
+	oldChildren := s.children
+	s.children = children
 	s.userServers = userServers
 	s.mu.Unlock()
 
 	s.stopUserServers(oldUserServers)
-	s.closeFileSystems(oldFileSystems)
+	s.closeChildren(oldChildren)
 }
 
-func (s *FileSystemForRemote) buildWebDAVFS(share *tailfs.Share) webdav.FileSystem {
+func (s *FileSystemForRemote) buildChild(share *tailfs.Share) *compositedav.Child {
-	return webdavfs.New(webdavfs.Options{
+	return &compositedav.Child{
-		Logf: s.logf,
+		Child: &dirfs.Child{
-		URL:  fmt.Sprintf("http://%v/%v", hex.EncodeToString([]byte(share.Name)), share.Name),
+			Name: share.Name,
+		},
+		BaseURL: fmt.Sprintf("http://%v/%v", hex.EncodeToString([]byte(share.Name)), url.PathEscape(share.Name)),
 		Transport: &http.Transport{
 			Dial: func(_, shareAddr string) (net.Conn, error) {
 				shareNameHex, _, err := net.SplitHostPort(shareAddr)
@@ -151,8 +154,7 @@ func (s *FileSystemForRemote) buildWebDAVFS(share *tailfs.Share) webdav.FileSyst
 				return safesocket.Connect(addr)
 			},
 		},
-		StatRoot: true,
+	}
-	})
 }
 
 // ServeHTTPWithPerms implements tailfs.FileSystemForRemote.
@@ -173,29 +175,23 @@ func (s *FileSystemForRemote) ServeHTTPWithPerms(permissions tailfs.Permissions,
 	}
 
 	s.mu.RLock()
-	fileSystems := s.fileSystems
+	childrenMap := s.children
 	s.mu.RUnlock()
 
-	children := make([]*compositefs.Child, 0, len(fileSystems))
+	children := make([]*compositedav.Child, 0, len(childrenMap))
 	// filter out shares to which the connecting principal has no access
-	for name, fs := range fileSystems {
+	for name, child := range childrenMap {
 		if permissions.For(name) == tailfs.PermissionNone {
 			continue
 		}
 
-		children = append(children, &compositefs.Child{Name: name, FS: fs})
+		children = append(children, child)
 	}
 
-	cfs := compositefs.New(
+	h := compositedav.Handler{
-		compositefs.Options{
 		Logf: s.logf,
-			StatChildren: true,
-		})
-	cfs.SetChildren(children...)
-	h := webdav.Handler{
-		FileSystem: cfs,
-		LockSystem: s.lockSystem,
 	}
+	h.SetChildren("", children...)
 	h.ServeHTTP(w, r)
 }
 
@@ -207,14 +203,9 @@ func (s *FileSystemForRemote) stopUserServers(userServers map[string]*userServer
 	}
 }
 
-func (s *FileSystemForRemote) closeFileSystems(fileSystems map[string]webdav.FileSystem) {
+func (s *FileSystemForRemote) closeChildren(children map[string]*compositedav.Child) {
-	for _, fs := range fileSystems {
+	for _, child := range children {
-		closer, ok := fs.(interface{ Close() error })
+		child.CloseIdleConnections()
-		if ok {
-			if err := closer.Close(); err != nil {
-				s.logf("error closing tailfs filesystem: %v", err)
-			}
-		}
 	}
 }
 
@@ -222,11 +213,13 @@ func (s *FileSystemForRemote) closeFileSystems(fileSystems map[string]webdav.Fil
 func (s *FileSystemForRemote) Close() error {
 	s.mu.Lock()
 	userServers := s.userServers
-	fileSystems := s.fileSystems
+	children := s.children
+	s.userServers = make(map[string]*userServer)
+	s.children = make(map[string]*compositedav.Child)
 	s.mu.Unlock()
 
 	s.stopUserServers(userServers)
-	s.closeFileSystems(fileSystems)
+	s.closeChildren(children)
 	return nil
 }
 

tailfs/tailfsimpl/shared/pathutil.go

@@ -40,3 +40,11 @@ func Join(parts ...string) string {
 func IsRoot(p string) bool {
 	return p == "" || p == sepString
 }
+
+// Base is like path.Base except that it returns "" for the root folder
+func Base(p string) string {
+	if IsRoot(p) {
+		return ""
+	}
+	return path.Base(p)
+}

tailfs/tailfsimpl/shared/stat.go

@@ -50,7 +50,7 @@ func RenamedFileInfo(ctx context.Context, name string, fi fs.FileInfo) *StaticFi
 	}
 
 	return &StaticFileInfo{
-		Named:          name,
+		Named:          Base(name),
 		Sized:          fi.Size(),
 		Moded:          fi.Mode(),
 		BirthedTime:    birthTime,
@@ -63,7 +63,7 @@ func RenamedFileInfo(ctx context.Context, name string, fi fs.FileInfo) *StaticFi
 // ReadOnlyDirInfo returns a static fs.FileInfo for a read-only directory
 func ReadOnlyDirInfo(name string, ts time.Time) *StaticFileInfo {
 	return &StaticFileInfo{
-		Named:       name,
+		Named:       Base(name),
 		Sized:       0,
 		Moded:       0555,
 		BirthedTime: ts,

tailfs/tailfsimpl/tailfs_test.go

@@ -4,9 +4,7 @@
 package tailfsimpl
 
 import (
-	"context"
 	"fmt"
-	"io"
 	"io/fs"
 	"log"
 	"net"
@@ -19,10 +17,9 @@ import (
 	"time"
 
 	"github.com/google/go-cmp/cmp"
-	"github.com/tailscale/xnet/webdav"
+	"github.com/studio-b12/gowebdav"
 	"tailscale.com/tailfs"
 	"tailscale.com/tailfs/tailfsimpl/shared"
-	"tailscale.com/tailfs/tailfsimpl/webdavfs"
 	"tailscale.com/tstest"
 )
 
@@ -46,24 +43,28 @@ func init() {
 // going over the Tailscale network stack.
 func TestDirectoryListing(t *testing.T) {
 	s := newSystem(t)
-	defer s.stop()
 
 	s.addRemote(remote1)
 	s.checkDirList("root directory should contain the one and only domain once a remote has been set", "/", domain)
 	s.checkDirList("domain should contain its only remote", shared.Join(domain), remote1)
 	s.checkDirList("remote with no shares should be empty", shared.Join(domain, remote1))
+
 	s.addShare(remote1, share11, tailfs.PermissionReadWrite)
 	s.checkDirList("remote with one share should contain that share", shared.Join(domain, remote1), share11)
 	s.addShare(remote1, share12, tailfs.PermissionReadOnly)
 	s.checkDirList("remote with two shares should contain both in lexicographical order", shared.Join(domain, remote1), share12, share11)
-	s.checkDirListIncremental("remote with two shares should contain both in lexicographical order even when reading directory incrementally", shared.Join(domain, remote1), share12, share11)
+	s.writeFile("writing file to read/write remote should succeed", remote1, share11, file111, "hello world", true)
+	s.checkDirList("remote share should contain file", shared.Join(domain, remote1, share11), file111)
 
 	s.addRemote(remote2)
 	s.checkDirList("domain with two remotes should contain both in lexicographical order", shared.Join(domain), remote2, remote1)
 
 	s.freezeRemote(remote1)
 	s.checkDirList("domain with two remotes should contain both in lexicographical order even if one is unreachable", shared.Join(domain), remote2, remote1)
-	s.checkDirList("directory listing for offline remote should return empty list", shared.Join(domain, remote1))
+	_, err := s.client.ReadDir(shared.Join(domain, remote1))
+	if err == nil {
+		t.Error("directory listing for offline remote should fail")
+	}
 	s.unfreezeRemote(remote1)
 
 	s.checkDirList("attempt at lateral traversal should simply list shares", shared.Join(domain, remote1, share11, ".."), share12, share11)
@@ -71,7 +72,6 @@ func TestDirectoryListing(t *testing.T) {
 
 func TestFileManipulation(t *testing.T) {
 	s := newSystem(t)
-	defer s.stop()
 
 	s.addRemote(remote1)
 	s.addShare(remote1, share11, tailfs.PermissionReadWrite)
@@ -86,178 +86,6 @@ func TestFileManipulation(t *testing.T) {
 	s.writeFile("writing file to non-existent share should fail", remote1, "non-existent", file111, "hello world", false)
 }
 
-func TestFileOps(t *testing.T) {
-	ctx := context.Background()
-
-	s := newSystem(t)
-	defer s.stop()
-
-	s.addRemote(remote1)
-	s.addShare(remote1, share11, tailfs.PermissionReadWrite)
-	s.writeFile("writing file to read/write remote should succeed", remote1, share11, file111, "hello world", true)
-	fi, err := s.fs.Stat(context.Background(), pathTo(remote1, share11, file111))
-	if err != nil {
-		t.Fatalf("failed to Stat: %s", err)
-	}
-	bt, ok := fi.(webdav.BirthTimer)
-	if !ok {
-		t.Fatal("FileInfo should be a BirthTimer")
-	}
-	birthTime, err := bt.BirthTime(ctx)
-	if err != nil {
-		t.Fatalf("failed to BirthTime: %s", err)
-	}
-	if birthTime.IsZero() {
-		t.Fatal("BirthTime() should return a non-zero time")
-	}
-
-	_, err = s.fs.OpenFile(ctx, pathTo(remote1, share11, "nonexistent.txt"), os.O_RDONLY, 0)
-	if err == nil {
-		t.Fatal("opening non-existent file for read should fail")
-	}
-
-	dir, err := s.fs.OpenFile(ctx, shared.Join(domain, remote1), os.O_RDONLY, 0)
-	if err != nil {
-		t.Fatalf("failed to open directory for read: %s", err)
-	}
-	defer dir.Close()
-
-	_, err = dir.Seek(0, io.SeekStart)
-	if err == nil {
-		t.Fatal("seeking in directory should fail")
-	}
-
-	_, err = dir.Read(make([]byte, 8))
-	if err == nil {
-		t.Fatal("reading bytes from directory should fail")
-	}
-	_, err = dir.Write(make([]byte, 8))
-	if err == nil {
-		t.Fatal("writing bytes to directory should fail")
-	}
-
-	readOnlyFile, err := s.fs.OpenFile(ctx, pathTo(remote1, share11, file111), os.O_RDONLY, 0)
-	if err != nil {
-		t.Fatalf("failed to open file for read: %s", err)
-	}
-	defer readOnlyFile.Close()
-
-	n, err := readOnlyFile.Seek(0, io.SeekStart)
-	if err != nil {
-		t.Fatalf("failed to seek 0 from start of read-only file: %s", err)
-	}
-	if n != 0 {
-		t.Fatal("seeking 0 from start of read-only file should return 0")
-	}
-
-	n, err = readOnlyFile.Seek(1, io.SeekStart)
-	if err != nil {
-		t.Fatalf("failed to seek 1 from start of read-only file: %s", err)
-	}
-	if n != 1 {
-		t.Fatal("seeking 1 from start of read-only file should return 1")
-	}
-
-	n, err = readOnlyFile.Seek(0, io.SeekEnd)
-	if err != nil {
-		t.Fatalf("failed to seek 0 from end of read-only file: %s", err)
-	}
-	if n != fi.Size() {
-		t.Fatal("seeking 0 from end of read-only file should return file size")
-	}
-
-	_, err = readOnlyFile.Seek(1, io.SeekEnd)
-	if err == nil {
-		t.Fatal("seeking 1 from end of read-only file should fail")
-	}
-
-	_, err = readOnlyFile.Seek(0, io.SeekCurrent)
-	if err == nil {
-		t.Fatal("seeking from current of read-only file should fail")
-	}
-
-	_, err = readOnlyFile.Write(make([]byte, 8))
-	if err == nil {
-		t.Fatal("writing bytes to read-only file should fail")
-	}
-
-	writeOnlyFile, err := s.fs.OpenFile(ctx, pathTo(remote1, share11, file111), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0)
-	if err != nil {
-		t.Fatalf("failed to OpenFile for write: %s", err)
-	}
-	defer writeOnlyFile.Close()
-
-	_, err = writeOnlyFile.Seek(0, io.SeekStart)
-	if err == nil {
-		t.Fatal("seeking in write only file should fail")
-	}
-
-	_, err = writeOnlyFile.Read(make([]byte, 8))
-	if err == nil {
-		t.Fatal("reading bytes from a write only file should fail")
-	}
-}
-
-func TestFileRewind(t *testing.T) {
-	ctx := context.Background()
-
-	s := newSystem(t)
-	defer s.stop()
-
-	s.addRemote(remote1)
-	s.addShare(remote1, share11, tailfs.PermissionReadWrite)
-
-	// Create a file slightly longer than our max rewind buffer of 512
-	fileLength := webdavfs.MaxRewindBuffer + 1
-	data := make([]byte, fileLength)
-	for i := 0; i < fileLength; i++ {
-		data[i] = byte(i % 256)
-	}
-	s.writeFile("writing file to read/write remote should succeed", remote1, share11, file111, string(data), true)
-
-	// Try reading and rewinding in every size up to the maximum buffer length
-	for i := 0; i < webdavfs.MaxRewindBuffer; i++ {
-		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
-			f, err := s.fs.OpenFile(ctx, pathTo(remote1, share11, file111), os.O_RDONLY, 0)
-			if err != nil {
-				t.Fatalf("failed top OpenFile for read: %s", err)
-			}
-			defer f.Close()
-
-			b := make([]byte, fileLength)
-
-			n, err := io.ReadFull(f, b[:i])
-			if err != nil {
-				t.Fatalf("failed to read first %d bytes from file: %s", i, err)
-			}
-			if n != i {
-				log.Fatalf("Reading first %d bytes should report correct count, but reported %d", i, n)
-			}
-
-			_, err = f.Seek(0, io.SeekStart)
-			if err != nil {
-				t.Fatalf("failed to seek back %d bytes: %s", i, err)
-			}
-
-			n, err = io.ReadFull(f, b)
-			if err != nil {
-				t.Fatalf("failed to read full file: %s", err)
-			}
-			if n != fileLength {
-				t.Fatalf("reading full file reported incorrect count, got %d, want %d", n, fileLength)
-			}
-			if string(b) != string(data) {
-				t.Fatalf("read wrong data, got %q, want %q", b, data)
-			}
-
-			_, err = f.Seek(0, io.SeekStart)
-			if err == nil {
-				t.Fatal("Attempting to seek to beginning of file after having read past rewind buffer should fail")
-			}
-		})
-	}
-}
-
 type local struct {
 	l  net.Listener
 	fs *FileSystemForLocal
@@ -289,7 +117,7 @@ func (r *remote) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 type system struct {
 	t       *testing.T
 	local   *local
-	fs      webdav.FileSystem
+	client  *gowebdav.Client
 	remotes map[string]*remote
 }
 
@@ -314,15 +142,16 @@ func newSystem(t *testing.T) *system {
 		}
 	}()
 
-	return &system{
+	client := gowebdav.NewClient(fmt.Sprintf("http://%s", l.Addr()), "", "")
+	client.SetTransport(&http.Transport{DisableKeepAlives: true})
+	s := &system{
 		t:       t,
 		local:   &local{l: l, fs: fs},
-		fs: webdavfs.New(webdavfs.Options{
+		client:  client,
-			URL:       fmt.Sprintf("http://%s", l.Addr()),
-			Transport: &http.Transport{DisableKeepAlives: true},
-		}),
 		remotes: make(map[string]*remote),
 	}
+	t.Cleanup(s.stop)
+	return s
 }
 
 func (s *system) addRemote(name string) {
@@ -357,7 +186,13 @@ func (s *system) addRemote(name string) {
 			URL:  fmt.Sprintf("http://%s", r.l.Addr()),
 		})
 	}
-	s.local.fs.SetRemotes(domain, remotes, &http.Transport{})
+	s.local.fs.SetRemotes(
+		domain,
+		remotes,
+		&http.Transport{
+			DisableKeepAlives:     true,
+			ResponseHeaderTimeout: 5 * time.Second,
+		})
 }
 
 func (s *system) addShare(remoteName, shareName string, permission tailfs.Permission) {
@@ -399,27 +234,12 @@ func (s *system) unfreezeRemote(remoteName string) {
 
 func (s *system) writeFile(label, remoteName, shareName, name, contents string, expectSuccess bool) {
 	path := pathTo(remoteName, shareName, name)
-	file, err := s.fs.OpenFile(context.Background(), path, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
+	err := s.client.Write(path, []byte(contents), 0644)
 	if expectSuccess && err != nil {
 		s.t.Fatalf("%v: expected success writing file %q, but got error %v", label, path, err)
-	}
+	} else if !expectSuccess && err == nil {
-	defer func() {
-		if !expectSuccess && err == nil {
 		s.t.Fatalf("%v: expected error writing file %q", label, path)
 	}
-	}()
-
-	defer func() {
-		err = file.Close()
-		if expectSuccess && err != nil {
-			s.t.Fatalf("error closing %v: %v", path, err)
-		}
-	}()
-
-	_, err = file.Write([]byte(contents))
-	if expectSuccess && err != nil {
-		s.t.Fatalf("%v: writing file %q: %v", label, path, err)
-	}
 }
 
 func (s *system) checkFileStatus(remoteName, shareName, name string) {
@@ -437,12 +257,7 @@ func (s *system) checkFileContents(remoteName, shareName, name string) {
 }
 
 func (s *system) checkDirList(label string, path string, want ...string) {
-	file, err := s.fs.OpenFile(context.Background(), path, os.O_RDONLY, 0)
+	got, err := s.client.ReadDir(path)
-	if err != nil {
-		s.t.Fatalf("failed to OpenFile: %s", err)
-	}
-
-	got, err := file.Readdir(0)
 	if err != nil {
 		s.t.Fatalf("failed to Readdir: %s", err)
 	}
@@ -460,35 +275,6 @@ func (s *system) checkDirList(label string, path string, want ...string) {
 	}
 }
 
-func (s *system) checkDirListIncremental(label string, path string, want ...string) {
-	file, err := s.fs.OpenFile(context.Background(), path, os.O_RDONLY, 0)
-	if err != nil {
-		s.t.Fatal(err)
-	}
-
-	var gotNames []string
-	for {
-		got, err := file.Readdir(1)
-		for _, fi := range got {
-			gotNames = append(gotNames, fi.Name())
-		}
-		if err == io.EOF {
-			break
-		}
-		if err != nil {
-			s.t.Fatalf("failed to Readdir: %s", err)
-		}
-	}
-
-	if len(want) == 0 && len(gotNames) == 0 {
-		return
-	}
-
-	if diff := cmp.Diff(want, gotNames); diff != "" {
-		s.t.Errorf("%v: (-got, +want):\n%s", label, diff)
-	}
-}
-
 func (s *system) stat(remoteName, shareName, name string) os.FileInfo {
 	filename := filepath.Join(s.remotes[remoteName].shares[shareName], name)
 	fi, err := os.Stat(filename)
@@ -501,7 +287,7 @@ func (s *system) stat(remoteName, shareName, name string) os.FileInfo {
 
 func (s *system) statViaWebDAV(remoteName, shareName, name string) os.FileInfo {
 	path := pathTo(remoteName, shareName, name)
-	fi, err := s.fs.Stat(context.Background(), path)
+	fi, err := s.client.Stat(path)
 	if err != nil {
 		s.t.Fatalf("failed to Stat: %s", err)
 	}
@@ -521,17 +307,10 @@ func (s *system) read(remoteName, shareName, name string) string {
 
 func (s *system) readViaWebDAV(remoteName, shareName, name string) string {
 	path := pathTo(remoteName, shareName, name)
-	file, err := s.fs.OpenFile(context.Background(), path, os.O_RDONLY, 0)
+	b, err := s.client.Read(path)
 	if err != nil {
 		s.t.Fatalf("failed to OpenFile: %s", err)
 	}
-	defer file.Close()
-
-	b, err := io.ReadAll(file)
-	if err != nil {
-		s.t.Fatalf("failed to ReadAll: %s", err)
-	}
-
 	return string(b)
 }
 

tailfs/tailfsimpl/webdavfs/readonly_file.go

@@ -1,192 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package webdavfs
-
-import (
-	"context"
-	"errors"
-	"io"
-	"io/fs"
-	"os"
-	"sync"
-
-	"github.com/tailscale/gowebdav"
-)
-
-const (
-	// MaxRewindBuffer specifies the size of the rewind buffer for reading
-	// from files. For some files, net/http performs content type detection
-	// by reading up to the first 512 bytes of a file, then seeking back to the
-	// beginning before actually transmitting the file. To support this, we
-	// maintain a rewind buffer of 512 bytes.
-	MaxRewindBuffer = 512
-)
-
-type readOnlyFile struct {
-	name         string
-	client       *gowebdav.Client
-	rewindBuffer []byte
-	position     int
-
-	// mu guards the below values. Acquire a write lock before updating any of
-	// them, acquire a read lock before reading any of them.
-	mu sync.RWMutex
-	io.ReadCloser
-	initialFI fs.FileInfo
-	fi        fs.FileInfo
-}
-
-// Readdir implements webdav.File. Since this is a file, it always failes with
-// an os.PathError.
-func (f *readOnlyFile) Readdir(count int) ([]fs.FileInfo, error) {
-	return nil, &os.PathError{
-		Op:   "readdir",
-		Path: f.fi.Name(),
-		Err:  errors.New("is a file"), // TODO(oxtoacart): make sure this and below errors match what a regular os.File does
-	}
-}
-
-// Seek implements webdav.File. Only the specific types of seek used by the
-// webdav package are implemented, namely:
-//
-//   - Seek to 0 from end of file
-//   - Seek to 0 from beginning of file, provided that fewer than 512 bytes
-//     have already been read.
-//   - Seek to n from beginning of file, provided that no bytes have already
-//     been read.
-//
-// Any other type of seek will fail with an os.PathError.
-func (f *readOnlyFile) Seek(offset int64, whence int) (int64, error) {
-	err := f.statIfNecessary()
-	if err != nil {
-		return 0, err
-	}
-
-	switch whence {
-	case io.SeekEnd:
-		if offset == 0 {
-			// seek to end is usually done to check size, let's play along
-			size := f.fi.Size()
-			return size, nil
-		}
-	case io.SeekStart:
-		if offset == 0 {
-			// this is usually done to start reading after getting size
-			if f.position > MaxRewindBuffer {
-				return 0, errors.New("attempted seek after having read past rewind buffer")
-			}
-			f.position = 0
-			return 0, nil
-		} else if f.position == 0 {
-			// this is usually done to perform a range request to skip the head of the file
-			f.position = int(offset)
-			return offset, nil
-		}
-	}
-
-	// unknown seek scenario, error out
-	return 0, &os.PathError{
-		Op:   "seek",
-		Path: f.fi.Name(),
-		Err:  errors.New("seek not supported"),
-	}
-}
-
-// Stat implements webdav.File, returning either the FileInfo with which this
-// file was initialized, or the more recently fetched FileInfo if available.
-func (f *readOnlyFile) Stat() (fs.FileInfo, error) {
-	f.mu.RLock()
-	defer f.mu.RUnlock()
-	if f.fi != nil {
-		return f.fi, nil
-	}
-	return f.initialFI, nil
-}
-
-// Read implements webdav.File.
-func (f *readOnlyFile) Read(p []byte) (int, error) {
-	err := f.initReaderIfNecessary()
-	if err != nil {
-		return 0, err
-	}
-
-	amountToReadFromBuffer := len(f.rewindBuffer) - f.position
-	if amountToReadFromBuffer > 0 {
-		n := copy(p, f.rewindBuffer)
-		f.position += n
-		return n, nil
-	}
-
-	n, err := f.ReadCloser.Read(p)
-	if n > 0 && f.position < MaxRewindBuffer {
-		amountToReadIntoBuffer := MaxRewindBuffer - f.position
-		if amountToReadIntoBuffer > n {
-			amountToReadIntoBuffer = n
-		}
-		f.rewindBuffer = append(f.rewindBuffer, p[:amountToReadIntoBuffer]...)
-	}
-
-	f.position += n
-	return n, err
-}
-
-// Write implements webdav.File. As this file is read-only, it always fails
-// with an os.PathError.
-func (f *readOnlyFile) Write(p []byte) (int, error) {
-	return 0, &os.PathError{
-		Op:   "write",
-		Path: f.fi.Name(),
-		Err:  errors.New("read-only"),
-	}
-}
-
-// Close implements webdav.File.
-func (f *readOnlyFile) Close() error {
-	f.mu.Lock()
-	defer f.mu.Unlock()
-
-	if f.ReadCloser == nil {
-		return nil
-	}
-	return f.ReadCloser.Close()
-}
-
-// statIfNecessary lazily initializes the FileInfo, bypassing the stat cache to
-// make sure we have fresh info before trying to read the file.
-func (f *readOnlyFile) statIfNecessary() error {
-	f.mu.Lock()
-	defer f.mu.Unlock()
-
-	if f.fi == nil {
-		ctxWithTimeout, cancel := context.WithTimeout(context.Background(), opTimeout)
-		defer cancel()
-
-		var err error
-		f.fi, err = f.client.Stat(ctxWithTimeout, f.name)
-		if err != nil {
-			return translateWebDAVError(err)
-		}
-	}
-
-	return nil
-}
-
-// initReaderIfNecessary initializes the Reader if it hasn't been opened yet. We
-// do this lazily because github.com/tailscale/xnet/webdav often opens files in
-// read-only mode without ever actually reading from them, so we can improve
-// performance by avoiding the round-trip to the server.
-func (f *readOnlyFile) initReaderIfNecessary() error {
-	f.mu.Lock()
-	defer f.mu.Unlock()
-
-	if f.ReadCloser == nil {
-		var err error
-		f.ReadCloser, err = f.client.ReadStreamOffset(context.Background(), f.name, f.position)
-		if err != nil {
-			return translateWebDAVError(err)
-		}
-	}
-
-	return nil
-}

tailfs/tailfsimpl/webdavfs/stat_cache.go

@@ -1,71 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package webdavfs
-
-import (
-	"io/fs"
-	"path/filepath"
-	"sync"
-	"time"
-
-	"github.com/jellydator/ttlcache/v3"
-)
-
-// statCache provides a cache for file directory 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.
-type statCache struct {
-	// mu guards the below values.
-	mu    sync.Mutex
-	cache *ttlcache.Cache[string, fs.FileInfo]
-}
-
-func newStatCache(ttl time.Duration) *statCache {
-	cache := ttlcache.New(
-		ttlcache.WithTTL[string, fs.FileInfo](ttl),
-	)
-	go cache.Start()
-	return &statCache{cache: cache}
-}
-
-func (c *statCache) getOrFetch(name string, fetch func(string) (fs.FileInfo, error)) (fs.FileInfo, error) {
-	c.mu.Lock()
-	item := c.cache.Get(name)
-	c.mu.Unlock()
-
-	if item != nil {
-		return item.Value(), nil
-	}
-
-	fi, err := fetch(name)
-	if err == nil {
-		c.mu.Lock()
-		c.cache.Set(name, fi, ttlcache.DefaultTTL)
-		c.mu.Unlock()
-	}
-
-	return fi, err
-}
-
-func (c *statCache) set(parentPath string, infos []fs.FileInfo) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	for _, info := range infos {
-		path := filepath.Join(parentPath, filepath.Base(info.Name()))
-		c.cache.Set(path, info, ttlcache.DefaultTTL)
-	}
-}
-
-func (c *statCache) invalidate() {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	c.cache.DeleteAll()
-}
-
-func (c *statCache) stop() {
-	c.cache.Stop()
-}

tailfs/tailfsimpl/webdavfs/stat_cache_test.go

@@ -1,104 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package webdavfs
-
-import (
-	"io/fs"
-	"os"
-	"path/filepath"
-	"testing"
-	"time"
-
-	"tailscale.com/tailfs/tailfsimpl/shared"
-	"tailscale.com/tstest"
-)
-
-func TestStatCache(t *testing.T) {
-	// Make sure we don't leak goroutines
-	tstest.ResourceCheck(t)
-
-	dir, err := os.MkdirTemp("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// create file of size 1
-	filename := filepath.Join(dir, "thefile")
-	err = os.WriteFile(filename, []byte("1"), 0644)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	stat := func(name string) (os.FileInfo, error) {
-		return os.Stat(name)
-	}
-	ttl := 1 * time.Second
-	c := newStatCache(ttl)
-
-	// fetch new stat
-	fi, err := c.getOrFetch(filename, stat)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if fi.Size() != 1 {
-		t.Errorf("got size %d, want 1", fi.Size())
-	}
-	// save original FileInfo as a StaticFileInfo so we can reuse it later
-	// without worrying about the underlying FileInfo changing.
-	originalFI := &shared.StaticFileInfo{
-		Named:      fi.Name(),
-		Sized:      fi.Size(),
-		Moded:      fi.Mode(),
-		ModdedTime: fi.ModTime(),
-		Dir:        fi.IsDir(),
-	}
-
-	// update file to size 2
-	err = os.WriteFile(filename, []byte("12"), 0644)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// fetch stat again, should still be cached
-	fi, err = c.getOrFetch(filename, stat)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if fi.Size() != 1 {
-		t.Errorf("got size %d, want 1", fi.Size())
-	}
-
-	// wait for cache to expire and refetch stat, size should reflect new size
-	time.Sleep(ttl * 2)
-
-	fi, err = c.getOrFetch(filename, stat)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if fi.Size() != 2 {
-		t.Errorf("got size %d, want 2", fi.Size())
-	}
-
-	// explicitly set the original FileInfo and make sure it's returned
-	c.set(dir, []fs.FileInfo{originalFI})
-	fi, err = c.getOrFetch(filename, stat)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if fi.Size() != 1 {
-		t.Errorf("got size %d, want 1", fi.Size())
-	}
-
-	// invalidate the cache and make sure the new size is returned
-	c.invalidate()
-	fi, err = c.getOrFetch(filename, stat)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if fi.Size() != 2 {
-		t.Errorf("got size %d, want 2", fi.Size())
-	}
-
-	c.stop()
-}

tailfs/tailfsimpl/webdavfs/webdavfs.go

@@ -1,256 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-// Package webdavfs provides an implementation of webdav.FileSystem backed by
-// a gowebdav.Client.
-package webdavfs
-
-import (
-	"context"
-	"errors"
-	"fmt"
-	"io"
-	"io/fs"
-	"log"
-	"net/http"
-	"os"
-	"time"
-
-	"github.com/tailscale/gowebdav"
-	"github.com/tailscale/xnet/webdav"
-
-	"tailscale.com/tailfs/tailfsimpl/shared"
-	"tailscale.com/tstime"
-	"tailscale.com/types/logger"
-)
-
-const (
-	// keep requests from taking too long if the server is down or slow to respond
-	opTimeout = 2 * time.Second // TODO(oxtoacart): tune this
-)
-
-type Options struct {
-	// Logf us a logging function to use for debug and error logging.
-	Logf logger.Logf
-	// URL is the base URL of the remote WebDAV server.
-	URL string
-	// Transport is the http.Transport to use for connecting to the WebDAV
-	// server.
-	Transport http.RoundTripper
-	// StatRoot, if true, will cause this filesystem to actually stat its own
-	// root via the remote server. If false, it will use a static directory
-	// info for the root to avoid a round-trip.
-	StatRoot bool
-	// StatCacheTTL, when greater than 0, enables caching of file metadata
-	StatCacheTTL time.Duration
-	// Clock, if specified, determines the current time. If not specified, we
-	// default to time.Now().
-	Clock tstime.Clock
-}
-
-// webdavFS adapts gowebdav.Client to webdav.FileSystem
-type webdavFS struct {
-	logf      logger.Logf
-	transport http.RoundTripper
-	*gowebdav.Client
-	now       func() time.Time
-	statRoot  bool
-	statCache *statCache
-}
-
-// New creates a new webdav.FileSystem backed by the given gowebdav.Client.
-// If cacheTTL is greater than zero, the filesystem will cache results from
-// Stat calls for the given duration.
-func New(opts Options) webdav.FileSystem {
-	if opts.Logf == nil {
-		opts.Logf = log.Printf
-	}
-	wfs := &webdavFS{
-		logf:      opts.Logf,
-		transport: opts.Transport,
-		Client:    gowebdav.New(&gowebdav.Opts{URI: opts.URL, Transport: opts.Transport}),
-		statRoot:  opts.StatRoot,
-	}
-	if opts.StatCacheTTL > 0 {
-		wfs.statCache = newStatCache(opts.StatCacheTTL)
-	}
-	if opts.Clock != nil {
-		wfs.now = opts.Clock.Now
-	} else {
-		wfs.now = time.Now
-	}
-	return wfs
-}
-
-// Mkdir implements webdav.FileSystem.
-func (wfs *webdavFS) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
-	ctxWithTimeout, cancel := context.WithTimeout(ctx, opTimeout)
-	defer cancel()
-
-	if wfs.statCache != nil {
-		wfs.statCache.invalidate()
-	}
-	return translateWebDAVError(wfs.Client.Mkdir(ctxWithTimeout, name, perm))
-}
-
-// OpenFile implements webdav.FileSystem.
-func (wfs *webdavFS) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
-	if hasFlag(flag, os.O_APPEND) {
-		return nil, &os.PathError{
-			Op:   "open",
-			Path: name,
-			Err:  errors.New("mode APPEND not supported"),
-		}
-	}
-
-	ctxWithTimeout, cancel := context.WithTimeout(ctx, opTimeout)
-	defer cancel()
-
-	if hasFlag(flag, os.O_WRONLY) || hasFlag(flag, os.O_RDWR) {
-		if wfs.statCache != nil {
-			wfs.statCache.invalidate()
-		}
-
-		fi, err := wfs.Stat(ctxWithTimeout, name)
-		if err != nil && !errors.Is(err, os.ErrNotExist) {
-			return nil, err
-		}
-		if err == nil && fi.IsDir() {
-			return nil, &os.PathError{
-				Op:   "open",
-				Path: name,
-				Err:  errors.New("is a directory"),
-			}
-		}
-
-		pipeReader, pipeWriter := io.Pipe()
-		f := &writeOnlyFile{
-			WriteCloser: pipeWriter,
-			name:        name,
-			perm:        perm,
-			fs:          wfs,
-			finalError:  make(chan error, 1),
-		}
-		go func() {
-			defer pipeReader.Close()
-			err := wfs.Client.WriteStream(context.Background(), name, pipeReader, perm)
-			f.finalError <- err
-			close(f.finalError)
-		}()
-
-		return f, nil
-	}
-
-	// Assume reading
-	fi, err := wfs.Stat(ctxWithTimeout, name)
-	if err != nil {
-		return nil, translateWebDAVError(err)
-	}
-	if fi.IsDir() {
-		return wfs.dirWithChildren(name, fi), nil
-	}
-
-	return &readOnlyFile{
-		client:       wfs.Client,
-		name:         name,
-		initialFI:    fi,
-		rewindBuffer: make([]byte, 0, MaxRewindBuffer),
-	}, nil
-}
-
-func (wfs *webdavFS) dirWithChildren(name string, fi fs.FileInfo) webdav.File {
-	return &shared.DirFile{
-		Info: fi,
-		LoadChildren: func() ([]fs.FileInfo, error) {
-			ctxWithTimeout, cancel := context.WithTimeout(context.Background(), opTimeout)
-			defer cancel()
-
-			dirInfos, err := wfs.Client.ReadDir(ctxWithTimeout, name)
-			if err != nil {
-				wfs.logf("encountered error reading children of '%v', returning empty list: %v", name, err)
-				// We do not return the actual error here because some WebDAV clients
-				// will take that as an invitation to retry, hanging in the process.
-				return dirInfos, nil
-			}
-			if wfs.statCache != nil {
-				wfs.statCache.set(name, dirInfos)
-			}
-			return dirInfos, nil
-		},
-	}
-}
-
-// RemoveAll implements webdav.FileSystem.
-func (wfs *webdavFS) RemoveAll(ctx context.Context, name string) error {
-	ctxWithTimeout, cancel := context.WithTimeout(ctx, opTimeout)
-	defer cancel()
-
-	if wfs.statCache != nil {
-		wfs.statCache.invalidate()
-	}
-	return wfs.Client.RemoveAll(ctxWithTimeout, name)
-}
-
-// Rename implements webdav.FileSystem.
-func (wfs *webdavFS) Rename(ctx context.Context, oldName, newName string) error {
-	ctxWithTimeout, cancel := context.WithTimeout(ctx, opTimeout)
-	defer cancel()
-
-	if wfs.statCache != nil {
-		wfs.statCache.invalidate()
-	}
-	return wfs.Client.Rename(ctxWithTimeout, oldName, newName, false)
-}
-
-// Stat implements webdav.FileSystem.
-func (wfs *webdavFS) Stat(ctx context.Context, name string) (fs.FileInfo, error) {
-	if wfs.statCache != nil {
-		return wfs.statCache.getOrFetch(name, wfs.doStat)
-	}
-	return wfs.doStat(name)
-}
-
-// Close implements webdav.FileSystem.
-func (wfs *webdavFS) Close() error {
-	if wfs.statCache != nil {
-		wfs.statCache.stop()
-	}
-	tr, ok := wfs.transport.(*http.Transport)
-	if ok {
-		tr.CloseIdleConnections()
-	}
-	return nil
-}
-
-func (wfs *webdavFS) doStat(name string) (fs.FileInfo, error) {
-	ctxWithTimeout, cancel := context.WithTimeout(context.Background(), opTimeout)
-	defer cancel()
-
-	if !wfs.statRoot && shared.IsRoot(name) {
-		// use a static directory info for the root
-		// always use now() as the modified time to bust caches
-		return shared.ReadOnlyDirInfo(name, wfs.now()), nil
-	}
-	fi, err := wfs.Client.Stat(ctxWithTimeout, name)
-	return fi, translateWebDAVError(err)
-}
-
-func translateWebDAVError(err error) error {
-	if err == nil {
-		return nil
-	}
-	var se gowebdav.StatusError
-	if errors.As(err, &se) {
-		if se.Status == http.StatusNotFound {
-			return os.ErrNotExist
-		}
-	}
-	// Note, we intentionally don't wrap the error because we don't want
-	// github.com/tailscale/xnet/webdav to try to interpret the underlying
-	// error.
-	return fmt.Errorf("unexpected WebDAV error: %v", err)
-}
-
-func hasFlag(flags int, flag int) bool {
-	return (flags & flag) == flag
-}

tailfs/tailfsimpl/webdavfs/writeonly_file.go

@@ -1,89 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package webdavfs
-
-import (
-	"context"
-	"errors"
-	"io"
-	"io/fs"
-	"os"
-
-	"tailscale.com/tailfs/tailfsimpl/shared"
-)
-
-type writeOnlyFile struct {
-	io.WriteCloser
-	name       string
-	perm       os.FileMode
-	fs         *webdavFS
-	finalError chan error
-}
-
-// Readdir implements webdav.File. As this is a file, this always fails with an
-// os.PathError.
-func (f *writeOnlyFile) Readdir(count int) ([]fs.FileInfo, error) {
-	return nil, &os.PathError{
-		Op:   "readdir",
-		Path: f.name,
-		Err:  errors.New("is a file"), // TODO(oxtoacart): make sure this and below errors match what a regular os.File does
-	}
-}
-
-// Seek implements webdav.File. This always fails with an os.PathError.
-func (f *writeOnlyFile) Seek(offset int64, whence int) (int64, error) {
-	return 0, &os.PathError{
-		Op:   "seek",
-		Path: f.name,
-		Err:  errors.New("seek not supported"),
-	}
-}
-
-// Stat implements webdav.File.
-func (f *writeOnlyFile) Stat() (fs.FileInfo, error) {
-	fi, err := f.fs.Stat(context.Background(), f.name)
-	if err != nil {
-		// use static info for newly created file
-		now := f.fs.now()
-		fi = &shared.StaticFileInfo{
-			Named:       f.name,
-			Sized:       0,
-			Moded:       f.perm,
-			BirthedTime: now,
-			ModdedTime:  now,
-			Dir:         false,
-		}
-	}
-	return fi, nil
-}
-
-// Read implements webdav.File. As this is a write-only file, it always fails
-// with an os.PathError.
-func (f *writeOnlyFile) Read(p []byte) (int, error) {
-	return 0, &os.PathError{
-		Op:   "write",
-		Path: f.name,
-		Err:  errors.New("write-only"),
-	}
-}
-
-// Write implements webdav.File.
-func (f *writeOnlyFile) Write(p []byte) (int, error) {
-	select {
-	case err := <-f.finalError:
-		return 0, err
-	default:
-		return f.WriteCloser.Write(p)
-	}
-}
-
-// Close implements webdav.File.
-func (f *writeOnlyFile) Close() error {
-	err := f.WriteCloser.Close()
-	writeErr := <-f.finalError
-	if writeErr != nil {
-		return writeErr
-	}
-	return err
-}