Merge "Enterprise Policy for Private DNS Setting"

core/java/android/net/NetworkUtils.java

@@ -16,8 +16,13 @@
 
 package android.net;
 
+import static android.system.OsConstants.AF_INET;
+import static android.system.OsConstants.AF_INET6;
+
+import android.annotation.NonNull;
 import android.annotation.UnsupportedAppUsage;
 import android.os.Parcel;
+import android.system.Os;
 import android.util.Log;
 import android.util.Pair;
 
@@ -570,4 +575,30 @@ public class NetworkUtils {
         }
         return routedIPCount;
     }
+
+    private static final int[] ADDRESS_FAMILIES = new int[] {AF_INET, AF_INET6};
+
+    /**
+     * Returns true if the hostname is weakly validated.
+     * @param hostname Name of host to validate.
+     * @return True if it's a valid-ish hostname.
+     *
+     * @hide
+     */
+    public static boolean isWeaklyValidatedHostname(@NonNull String hostname) {
+        // TODO(b/34953048): Use a validation method that permits more accurate,
+        // but still inexpensive, checking of likely valid DNS hostnames.
+        final String weakHostnameRegex = "^[a-zA-Z0-9_.-]+$";
+        if (!hostname.matches(weakHostnameRegex)) {
+            return false;
+        }
+
+        for (int address_family : ADDRESS_FAMILIES) {
+            if (Os.inet_pton(address_family, hostname) != null) {
+                return false;
+            }
+        }
+
+        return true;
+    }
 }