Update

vendor/tailscale.com/drive/local.go

@@ -1,4 +1,4 @@
-// Copyright (c) Tailscale Inc & AUTHORS
+// Copyright (c) Tailscale Inc & contributors
 // SPDX-License-Identifier: BSD-3-Clause
 
 // Package drive provides a filesystem that allows sharing folders between
@@ -10,6 +10,7 @@
 package drive
 
 import (
+	"iter"
 	"net"
 	"net/http"
 )
@@ -21,16 +22,46 @@ type Remote struct {
 	Available func() bool
 }
 
+// RemoteSource provides the current set of remote Taildrive nodes
+// on demand. The drive filesystem consults Generation on each request
+// and only rebuilds its internal child list when the value differs
+// from the previously cached one. This lets callers avoid the
+// per-netmap O(n) rebuild that an eager SetRemotes call would
+// require.
+//
+// All methods may be called concurrently.
+type RemoteSource interface {
+	// Domain returns the current tailnet domain under which remotes
+	// appear as sub-folders.
+	Domain() string
+
+	// Transport returns the http.RoundTripper used to reach remotes.
+	Transport() http.RoundTripper
+
+	// Remotes yields the current set of remote nodes.
+	// It is called by the drive filesystem only when Generation has
+	// changed since the last call.
+	Remotes() iter.Seq[*Remote]
+
+	// Generation returns a monotonically-increasing counter that
+	// changes whenever the values returned by Domain, Transport, or
+	// Remotes might have changed. The drive filesystem reads it on
+	// every request and skips the rebuild path entirely when it
+	// matches the previously-cached value.
+	Generation() uint64
+}
+
 // FileSystemForLocal is the Taildrive filesystem exposed to local clients. It
 // provides a unified WebDAV interface to remote Taildrive shares on other nodes.
 type FileSystemForLocal interface {
 	// HandleConn handles connections from local WebDAV clients
 	HandleConn(conn net.Conn, remoteAddr net.Addr) error
 
-	// SetRemotes sets the complete set of remotes on the given tailnet domain
-	// using a map of name -> url. If transport is specified, that transport
-	// will be used to connect to these remotes.
-	SetRemotes(domain string, remotes []*Remote, transport http.RoundTripper)
+	// SetRemoteSource sets the source from which the filesystem
+	// reads the current set of remotes. The source is consulted
+	// lazily on incoming WebDAV requests, so a stale cap or empty
+	// tailnet costs nothing per netmap update.
+	SetRemoteSource(source RemoteSource)
 
 	// Close() stops serving the WebDAV content
 	Close() error