p2p: sanity check for network name

Bug: 120259460
Test: Unit test - atest android.net.wifi.p2p.WifiP2pConfigTest
Change-Id: I4ba5643a9fdded7b9f9837a21b24a89fac98a5ce

wifi/java/android/net/wifi/p2p/WifiP2pConfig.java

@@ -26,6 +26,7 @@ import android.text.TextUtils;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.regex.PatternSyntaxException;
 
 /**
  * A class representing a Wi-Fi P2p configuration for setting up a connection
@@ -252,7 +253,12 @@ public class WifiP2pConfig implements Parcelable {
          * Specify the network name, a.k.a. group name,
          * for creating or joining a group.
          * <p>
-         *     Must be called - an empty network name is not valid.
+         * A network name shall begin with "DIRECT-xy". x and y are selected
+         * from the following character set: upper case letters, lower case
+         * letters and numbers.
+         * <p>
+         *     Must be called - an empty network name or an network name
+         *     not conforming to the P2P Group ID naming rule is not valid.
          *
          * @param networkName network name of a group.
          * @return The builder to facilitate chaining
@@ -263,6 +269,14 @@ public class WifiP2pConfig implements Parcelable {
                 throw new IllegalArgumentException(
                         "network name must be non-empty.");
             }
+            try {
+                if (!networkName.matches("^DIRECT-[a-zA-Z0-9]{2}.*")) {
+                    throw new IllegalArgumentException(
+                            "network name must starts with the prefix DIRECT-xy.");
+                }
+            } catch (PatternSyntaxException e) {
+                // can never happen (fixed pattern)
+            }
             mNetworkName = networkName;
             return this;
         }

wifi/tests/src/android/net/wifi/p2p/WifiP2pConfigTest.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.net.wifi.p2p;
+
+import static org.junit.Assert.fail;
+
+import androidx.test.filters.SmallTest;
+
+import org.junit.Test;
+
+/**
+ * Unit test harness for {@link android.net.wifi.p2p.WifiP2pConfig}
+ */
+@SmallTest
+public class WifiP2pConfigTest {
+    /**
+     * Check network name setter
+     */
+    @Test
+    public void testBuilderInvalidNetworkName() throws Exception {
+        WifiP2pConfig.Builder b = new WifiP2pConfig.Builder();
+
+        // sunny case
+        try {
+            b.setNetworkName("DIRECT-ab-Hello");
+        } catch (IllegalArgumentException e) {
+            fail("Unexpected IllegalArgumentException");
+        }
+
+        // sunny case, no trailing string
+        try {
+            b.setNetworkName("DIRECT-WR");
+        } catch (IllegalArgumentException e) {
+            fail("Unexpected IllegalArgumentException");
+        }
+
+        // less than 9 characters.
+        try {
+            b.setNetworkName("DIRECT-z");
+            fail("expected IllegalArgumentException");
+        } catch (IllegalArgumentException e) { }
+
+        // not starts with DIRECT-xy.
+        try {
+            b.setNetworkName("ABCDEFGHIJK");
+            fail("expected IllegalArgumentException");
+        } catch (IllegalArgumentException e) { }
+
+        // not starts with uppercase DIRECT-xy
+        try {
+            b.setNetworkName("direct-ab");
+            fail("expected IllegalArgumentException");
+        } catch (IllegalArgumentException e) { }
+
+        // x and y are not selected from upper case letters, lower case letters or
+        // numbers.
+        try {
+            b.setNetworkName("direct-a?");
+            fail("expected IllegalArgumentException");
+        } catch (IllegalArgumentException e) { }
+    }
+}