paths: generalize IOSSharedDir to cover Android

Also fix an error message while here.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ipn/ipnlocal/local.go

@@ -1821,8 +1821,9 @@ func parseResolver(cfg tailcfg.DNSResolver) (netaddr.IPPort, error) {
 // tailscaleVarRoot returns the root directory of Tailscale's writable
 // storage area. (e.g. "/var/lib/tailscale")
 func tailscaleVarRoot() string {
-	if runtime.GOOS == "ios" {
+	switch runtime.GOOS {
-		dir, _ := paths.IOSSharedDir.Load().(string)
+	case "ios", "android":
+		dir, _ := paths.AppSharedDir.Load().(string)
 		return dir
 	}
 	stateFile := paths.DefaultTailscaledStateFile()
@@ -1926,7 +1927,7 @@ func (b *LocalBackend) initPeerAPIListener() {
 					// ("peerAPIListeners too low").
 					continue
 				}
-				b.logf("[unexpected] peerapi listen(%q) error: %v", a.IP, err)
+				b.logf("[unexpected] peerapi listen(%q) error: %v", a.IP(), err)
 				continue
 			}
 		}

paths/paths.go

@@ -13,9 +13,9 @@ import (
 	"sync/atomic"
 )
 
-// IOSSharedDir is a string set by the iOS app on start
+// AppSharedDir is a string set by the iOS or Android app on start
 // containing a directory we can read/write in.
-var IOSSharedDir atomic.Value
+var AppSharedDir atomic.Value
 
 // DefaultTailscaledSocket returns the path to the tailscaled Unix socket
 // or the empty string if there's no reasonable default.