version: answer 1.7 to head units offering 4.x and 6.x too, as they accept it

gearslip/src/main/java/app/seb3thehacker/gearslip/ProtocolVersion.kt

@@ -1,6 +1,10 @@
 package app.seb3thehacker.gearslip
 
-/** Advertises our supported 1.x version, as Android Auto does for older head units. */
+/**
+ * Advertises our supported 1.x version, as Android Auto does for older head units. Head units that
+ * offer a newer major version (LIVI asks for 6.1, a RAV4 and the DHU for 4.2) still accept a 1.x
+ * answer, so only a major version of 0 is refused.
+ */
 internal object ProtocolVersion {
     data class Response(val major: Int, val minor: Int, val supported: Boolean) {
         val bytes: ByteArray get() = byteArrayOf(
@@ -9,5 +13,5 @@ internal object ProtocolVersion {
         )
     }
 
-    fun respond(major: Int, minor: Int): Response = Response(1, 7, major == 1 && minor in 0..0xffff)
+    fun respond(major: Int, minor: Int): Response = Response(1, 7, major >= 1 && minor in 0..0xffff)
 }

gearslip/src/test/java/app/seb3thehacker/gearslip/ConnectionLifecycleTest.kt

@@ -104,7 +104,7 @@ class ConnectionLifecycleTest {
     }
 
     @Test fun `unsupported version sends rejection and ends without waiting for peer EOF`() {
-        val input = CountingInput(message(1, byteArrayOf(0, 2, 0, 0)))
+        val input = CountingInput(message(1, byteArrayOf(0, 0, 0, 9)))
         val output = ByteArrayOutputStream()
         val runner = GearslipRunner(input, output, ::identity)
         runner.run()
@@ -112,7 +112,7 @@ class ConnectionLifecycleTest {
         val parser = Frames.Parser()
         parser.append(output.toByteArray(), output.size())
         val response = requireNotNull(parser.next())
-        assertArrayEquals(byteArrayOf(0, 2) + ProtocolVersion.respond(2, 0).bytes, response.payload)
+        assertArrayEquals(byteArrayOf(0, 2) + ProtocolVersion.respond(0, 9).bytes, response.payload)
         assertEquals("Unsupported protocol", SessionStatus.state.value.headline)
     }
 

gearslip/src/test/java/app/seb3thehacker/gearslip/ProtocolVersionTest.kt

@@ -10,8 +10,13 @@ class ProtocolVersionTest {
         assertArrayEquals(byteArrayOf(0, 1, 0, 7, 0, 0), ProtocolVersion.respond(1, 9).bytes)
     }
 
-    @Test fun `unsupported major is never reported as a successful downgrade`() {
-        val response = ProtocolVersion.respond(4, 3)
+    @Test fun `newer head units get the 1x answer they accept`() {
+        assertArrayEquals(byteArrayOf(0, 1, 0, 7, 0, 0), ProtocolVersion.respond(4, 2).bytes)
+        assertArrayEquals(byteArrayOf(0, 1, 0, 7, 0, 0), ProtocolVersion.respond(6, 1).bytes)
+    }
+
+    @Test fun `major version 0 is refused`() {
+        val response = ProtocolVersion.respond(0, 9)
         assertFalse(response.supported)
         assertArrayEquals(byteArrayOf(0, 1, 0, 7, -1, -1), response.bytes)
     }