all: detect JetKVM and specialize a handful of things for it

Updates #16524

Change-Id: I183428de8c65d7155d82979d2d33f031c22e3331
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

paths/paths.go

@@ -6,6 +6,7 @@
 package paths
 
 import (
+	"log"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -70,6 +71,37 @@ func DefaultTailscaledStateFile() string {
 	return ""
 }
 
+// DefaultTailscaledStateDir returns the default state directory
+// to use for tailscaled, for use when the user provided neither
+// a state directory or state file path to use.
+//
+// It returns the empty string if there's no reasonable default.
+func DefaultTailscaledStateDir() string {
+	if runtime.GOOS == "plan9" {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			log.Fatalf("failed to get home directory: %v", err)
+		}
+		return filepath.Join(home, "tailscale-state")
+	}
+	return filepath.Dir(DefaultTailscaledStateFile())
+}
+
+// MakeAutomaticStateDir reports whether the platform
+// automatically creates the state directory for tailscaled
+// when it's absent.
+func MakeAutomaticStateDir() bool {
+	switch runtime.GOOS {
+	case "plan9":
+		return true
+	case "linux":
+		if distro.Get() == distro.JetKVM {
+			return true
+		}
+	}
+	return false
+}
+
 // MkStateDir ensures that dirPath, the daemon's configuration directory
 // containing machine keys etc, both exists and has the correct permissions.
 // We want it to only be accessible to the user the daemon is running under.

paths/paths_unix.go

@@ -21,6 +21,9 @@ func init() {
 }
 
 func statePath() string {
+	if runtime.GOOS == "linux" && distro.Get() == distro.JetKVM {
+		return "/userdata/tailscale/var/tailscaled.state"
+	}
 	switch runtime.GOOS {
 	case "linux", "illumos", "solaris":
 		return "/var/lib/tailscale/tailscaled.state"