client,cmd/tailscale,ipn/{ipnlocal,localapi}: add debug CLI command to clear netmap caches (#19213)

This is a follow-up to #19117, adding a debug CLI command allowing the operator
to explicitly discard cached netmap data, as a safety and recovery measure.

Updates #12639

Change-Id: I5c3c47c0204754b9c8e526a4ff8f69d6974db6d0
Signed-off-by: M. J. Fromberger <fromberger@tailscale.com>

cmd/tailscale/cli/debug-cachenetmap.go

@@ -0,0 +1,31 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !ios && !ts_omit_cachenetmap
+
+package cli
+
+import (
+	"context"
+	"errors"
+
+	"github.com/peterbourgon/ff/v3/ffcli"
+)
+
+func init() {
+	debugClearNetmapCacheCmd = func() *ffcli.Command {
+		return &ffcli.Command{
+			Name:       "clear-netmap-cache",
+			ShortUsage: "tailscale debug clear-netmap-cache",
+			ShortHelp:  "Remove and discard cached network maps (if any)",
+			Exec:       runDebugClearNetmapCache,
+		}
+	}
+}
+
+func runDebugClearNetmapCache(ctx context.Context, args []string) error {
+	if len(args) != 0 {
+		return errors.New("unexpected arguments")
+	}
+	return localClient.DebugAction(ctx, "clear-netmap-cache")
+}

cmd/tailscale/cli/debug.go

@@ -51,9 +51,10 @@ import (
 )
 
 var (
-	debugCaptureCmd   func() *ffcli.Command // or nil
-	debugPortmapCmd   func() *ffcli.Command // or nil
-	debugPeerRelayCmd func() *ffcli.Command // or nil
+	debugCaptureCmd          func() *ffcli.Command // or nil
+	debugPortmapCmd          func() *ffcli.Command // or nil
+	debugPeerRelayCmd        func() *ffcli.Command // or nil
+	debugClearNetmapCacheCmd func() *ffcli.Command // or nil
 )
 
 func debugCmd() *ffcli.Command {
@@ -394,6 +395,7 @@ func debugCmd() *ffcli.Command {
 				Exec:       runPrintStateDir,
 			},
 			ccall(debugPeerRelayCmd),
+			ccall(debugClearNetmapCacheCmd),
 		}...),
 	}
 }