Add a CTS test for multinetwork features.

For now, just checks that the kernel sysctls are present and
have the right permissions and expected values.

Bug: 15605143
Change-Id: I5feb6cb5f25b97e88cd0d9e8071213d13d4cc6e8

tests/cts/net/src/android/net/cts/MultinetworkTest.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2014 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.cts;
+
+import android.system.ErrnoException;
+import android.system.Os;
+import android.system.OsConstants;
+import android.system.StructStat;
+import android.test.AndroidTestCase;
+
+import java.io.File;
+import java.io.FileDescriptor;
+import java.io.IOException;
+
+/**
+ * Tests for multinetwork functionality.
+ */
+public class MultinetworkTest extends AndroidTestCase {
+
+    // Global sysctls. Must be present and set to 1.
+    private static final String[] GLOBAL_SYSCTLS = {
+        "/proc/sys/net/ipv4/fwmark_reflect",
+        "/proc/sys/net/ipv6/fwmark_reflect",
+        "/proc/sys/net/ipv4/tcp_fwmark_accept",
+    };
+
+    // Per-interface IPv6 autoconf sysctls.
+    private static final String IPV6_SYSCTL_DIR = "/proc/sys/net/ipv6/conf";
+    private static final String AUTOCONF_SYSCTL = "accept_ra_rt_table";
+
+    // Expected mode, UID, and GID of sysctl files.
+    private static final int SYSCTL_MODE = 0100644;
+    private static final int SYSCTL_UID = 0;
+    private static final int SYSCTL_GID = 0;
+
+    private void checkSysctlPermissions(String fileName) throws ErrnoException {
+        StructStat stat = Os.stat(fileName);
+        assertEquals("mode of " + fileName + ":", SYSCTL_MODE, stat.st_mode);
+        assertEquals("UID of " + fileName + ":", SYSCTL_UID, stat.st_uid);
+        assertEquals("GID of " + fileName + ":", SYSCTL_GID, stat.st_gid);
+    }
+
+    private void assertLess(String what, int a, int b) {
+        assertTrue(what + " expected < " + b + " but was: " + a, a < b);
+    }
+
+    private String readFile(String fileName) throws ErrnoException, IOException {
+        byte[] buf = new byte[1024];
+        FileDescriptor fd = Os.open(fileName, 0, OsConstants.O_RDONLY);
+        int bytesRead = Os.read(fd, buf, 0, buf.length);
+        assertLess("length of " + fileName + ":", bytesRead, buf.length);
+        return new String(buf);
+    }
+
+    /**
+     * Checks that the sysctls for multinetwork kernel features are present and
+     * enabled. The necessary kernel commits are:
+     *
+     * Mainline Linux:
+     *   e110861 net: add a sysctl to reflect the fwmark on replies
+     *   1b3c61d net: Use fwmark reflection in PMTU discovery.
+     *   84f39b0 net: support marking accepting TCP sockets
+     *
+     * Common Android tree (e.g., 3.10):
+     *   a03f539 net: ipv6: autoconf routes into per-device tables
+     */
+     public void testProcFiles() throws ErrnoException, IOException, NumberFormatException {
+         for (String sysctl : GLOBAL_SYSCTLS) {
+             checkSysctlPermissions(sysctl);
+             int value = Integer.parseInt(readFile(sysctl).trim());
+             assertEquals("value of " + sysctl + ":", 1, value);
+         }
+
+         File[] interfaceDirs = new File(IPV6_SYSCTL_DIR).listFiles();
+         for (File interfaceDir : interfaceDirs) {
+             if (interfaceDir.getName().equals("all") || interfaceDir.getName().equals("lo")) {
+                 continue;
+             }
+             String sysctl = new File(interfaceDir, AUTOCONF_SYSCTL).getAbsolutePath();
+             checkSysctlPermissions(sysctl);
+             int value = Integer.parseInt(readFile(sysctl).trim());
+             assertLess("value of " + sysctl + ":", value, 0);
+         }
+     }
+}