Avoid a reverse DNS-lookup for a numeric proxy address

When the proxy is specified as an IP address the RouteSelector
would force a reverse-lookup. This can introduce extra latency
when the DNS is slow or missing. It also then turns the name
back into a set of IPs, which may result in the original IP
address not being given priority.

This is upstream commit:
https://github.com/square/okhttp/commit/9acd5e7b54fb55f62a5dd16865c30787dfba4c8b

Bug: 18327075
Change-Id: Idafd72f4d5b901e267081f924377db4ada9afe1b

2 files changed, 37 insertions, 1 deletions

diff --git a/okhttp-tests/src/test/java/com/squareup/okhttp/internal/http/RouteSelectorTest.java b/okhttp-tests/src/test/java/com/squareup/okhttp/internal/http/RouteSelectorTest.java
index dd806c6..e4f5a5a 100644
--- a/okhttp-tests/src/test/java/com/squareup/okhttp/internal/http/RouteSelectorTest.java
+++ b/okhttp-tests/src/test/java/com/squareup/okhttp/internal/http/RouteSelectorTest.java
@@ -336,6 +336,24 @@ public final class RouteSelectorTest {
     assertEquals(regularRoutes.size(), routesWithFailedRoute.size());
   }
 
+  @Test public void getHostString() throws Exception {
+    // Name proxy specification.
+    InetSocketAddress socketAddress = InetSocketAddress.createUnresolved("host", 1234);
+    assertEquals("host", RouteSelector.getHostString(socketAddress));
+    socketAddress = InetSocketAddress.createUnresolved("127.0.0.1", 1234);
+    assertEquals("127.0.0.1", RouteSelector.getHostString(socketAddress));
+
+    // InetAddress proxy specification.
+    socketAddress = new InetSocketAddress(InetAddress.getByName("localhost"), 1234);
+    assertEquals("127.0.0.1", RouteSelector.getHostString(socketAddress));
+    socketAddress = new InetSocketAddress(
+        InetAddress.getByAddress(new byte[] { 127, 0, 0, 1 }), 1234);
+    assertEquals("127.0.0.1", RouteSelector.getHostString(socketAddress));
+    socketAddress = new InetSocketAddress(
+        InetAddress.getByAddress("foobar", new byte[] { 127, 0, 0, 1 }), 1234);
+    assertEquals("127.0.0.1", RouteSelector.getHostString(socketAddress));
+  }
+
   private void assertConnection(Connection connection, Address address, Proxy proxy,
       InetAddress socketAddress, int socketPort) {
     assertEquals(address, connection.getRoute().getAddress());
diff --git a/okhttp/src/main/java/com/squareup/okhttp/internal/http/RouteSelector.java b/okhttp/src/main/java/com/squareup/okhttp/internal/http/RouteSelector.java
index a5ffa77..876bac4 100644
--- a/okhttp/src/main/java/com/squareup/okhttp/internal/http/RouteSelector.java
+++ b/okhttp/src/main/java/com/squareup/okhttp/internal/http/RouteSelector.java
@@ -197,7 +197,7 @@ public final class RouteSelector {
             "Proxy.address() is not an " + "InetSocketAddress: " + proxyAddress.getClass());
       }
       InetSocketAddress proxySocketAddress = (InetSocketAddress) proxyAddress;
-      socketHost = proxySocketAddress.getHostName();
+      socketHost = getHostString(proxySocketAddress);
       socketPort = proxySocketAddress.getPort();
     }
 
@@ -206,6 +206,24 @@ public final class RouteSelector {
     nextSocketAddressIndex = 0;
   }
 
+  /**
+   * Obtain a "host" from an {@link InetSocketAddress}. This returns a string containing either an
+   * actual host name or a numeric IP address.
+   */
+  // Visible for testing
+  static String getHostString(InetSocketAddress socketAddress) {
+    InetAddress address = socketAddress.getAddress();
+    if (address == null) {
+      // The InetSocketAddress was specified with a string (either a numeric IP or a host name). If
+      // it is a name, all IPs for that name should be tried. If it is an IP address, only that IP
+      // address should be tried.
+      return socketAddress.getHostName();
+    }
+    // The InetSocketAddress has a specific address: we should only try that address. Therefore we
+    // return the address and ignore any host name that may be available.
+    return address.getHostAddress();
+  }
+
   /** Returns true if there's another socket address to try. */
   private boolean hasNextInetSocketAddress() {
     return socketAddresses != null;