[4.x] Cherry pick: fix DoH error when using ip address as hostname

okhttp/src/main/kotlin/okhttp3/internal/connection/RouteSelector.kt

@@ -16,6 +16,7 @@
 package okhttp3.internal.connection
 
 import java.io.IOException
+import java.net.InetAddress
 import java.net.InetSocketAddress
 import java.net.Proxy
 import java.net.SocketException
@@ -26,6 +27,7 @@ import okhttp3.Call
 import okhttp3.EventListener
 import okhttp3.HttpUrl
 import okhttp3.Route
+import okhttp3.internal.canParseAsIpAddress
 import okhttp3.internal.immutableListOf
 import okhttp3.internal.toImmutableList
 
@@ -158,16 +160,21 @@ class RouteSelector(
     if (proxy.type() == Proxy.Type.SOCKS) {
       mutableInetSocketAddresses += InetSocketAddress.createUnresolved(socketHost, socketPort)
     } else {
-      eventListener.dnsStart(call, socketHost)
+      val addresses = if (socketHost.canParseAsIpAddress()) {
+        listOf(InetAddress.getByName(socketHost))
+      } else {
+        eventListener.dnsStart(call, socketHost)
+
+        // Try each address for best behavior in mixed IPv4/IPv6 environments.
+        val result = address.dns.lookup(socketHost)
+        if (result.isEmpty()) {
+          throw UnknownHostException("${address.dns} returned no addresses for $socketHost")
+        }
 
-      // Try each address for best behavior in mixed IPv4/IPv6 environments.
-      val addresses = address.dns.lookup(socketHost)
-      if (addresses.isEmpty()) {
-        throw UnknownHostException("${address.dns} returned no addresses for $socketHost")
+        eventListener.dnsEnd(call, socketHost, result)
+        result
       }
 
-      eventListener.dnsEnd(call, socketHost, addresses)
-
       for (inetAddress in addresses) {
         mutableInetSocketAddresses += InetSocketAddress(inetAddress, socketPort)
       }

okhttp/src/test/java/okhttp3/EventListenerTest.java

@@ -135,6 +135,27 @@ public final class EventListenerTest {
         "ResponseBodyEnd", "ConnectionReleased", "CallEnd");
   }
 
+  @Test public void successfulCallEventSequenceForIpAddress() throws IOException {
+    server.enqueue(new MockResponse()
+      .setBody("abc"));
+
+    String ipAddress = InetAddress.getLoopbackAddress().getHostAddress();
+
+    Call call = client.newCall(new Request.Builder()
+      .url(server.url("/").newBuilder().host(ipAddress).build())
+      .build());
+    Response response = call.execute();
+    assertThat(response.code()).isEqualTo(200);
+    assertThat(response.body().string()).isEqualTo("abc");
+    response.body().close();
+
+    assertThat(listener.recordedEventTypes()).containsExactly("CallStart",
+      "ProxySelectStart", "ProxySelectEnd",
+      "ConnectStart", "ConnectEnd", "ConnectionAcquired", "RequestHeadersStart",
+      "RequestHeadersEnd", "ResponseHeadersStart", "ResponseHeadersEnd", "ResponseBodyStart",
+      "ResponseBodyEnd", "ConnectionReleased", "CallEnd");
+  }
+
   @Test public void successfulCallEventSequenceForEnqueue() throws Exception {
     server.enqueue(new MockResponse()
         .setBody("abc"));