Move a couple of utility functions to a new namespace_utils class.

sandbox/linux/services/namespace_utils_unittest.cc

Index: sandbox/linux/services/namespace_utils_unittest.cc
diff --git a/sandbox/linux/services/namespace_utils_unittest.cc b/sandbox/linux/services/namespace_utils_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..33ead9423c3bbc0233b34317a47072e301b1b222
--- /dev/null
+++ b/sandbox/linux/services/namespace_utils_unittest.cc
@@ -0,0 +1,65 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sandbox/linux/services/namespace_utils.h"
+
+#include <errno.h>
+#include <sched.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
+#include "base/process/launch.h"
+#include "sandbox/linux/services/credentials.h"
+#include "sandbox/linux/tests/unit_tests.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace sandbox {
+
+namespace {
+
+SANDBOX_TEST(NamespaceUtils, KernelSupportsUnprivilegedNamespace) {
+  const bool can_create_user_ns = Credentials::CanCreateProcessInNewUserNS();
+  const bool supports_user_ns =
+      NamespaceUtils::KernelSupportsUnprivilegedNamespace(CLONE_NEWUSER);
+  // can_create_user_ns implies supports_user_ns, but the converse is not
+  // necessarily true, as creating a user namespace can fail for various
+  // reasons.
+  if (can_create_user_ns) {
+    SANDBOX_ASSERT(supports_user_ns);
+  }
+}
+
+SANDBOX_TEST(NamespaceUtils, WriteToIdMapFile) {
+  if (!Credentials::CanCreateProcessInNewUserNS()) {
+    return;
+  }
+
+  const uid_t uid = getuid();
+  const gid_t gid = getgid();
+
+  const pid_t pid =
+      base::ForkWithFlags(CLONE_NEWUSER | SIGCHLD, nullptr, nullptr);
+  ASSERT_NE(-1, pid);
+  if (pid == 0) {
+    RAW_CHECK(getuid() != uid);
+    NamespaceUtils::WriteToIdMapFile("/proc/self/uid_map", uid);
+    RAW_CHECK(getuid() == uid);
+
+    RAW_CHECK(getgid() != gid);
+    NamespaceUtils::WriteToIdMapFile("/proc/self/gid_map", gid);
+    RAW_CHECK(getgid() == gid);
+
+    _exit(0);
+  }
+
+  int status = 42;
+  SANDBOX_ASSERT_EQ(pid, HANDLE_EINTR(waitpid(pid, &status, 0)));
+  SANDBOX_ASSERT_EQ(0, status);
+}
+
+}  // namespace.
+
+}  // namespace sandbox.