POSIX: Add code for shuffling file descriptors.

When forking a child process, one often wants to move existing file
descriptors to well known locations (stdout, stderr etc). However,
this is a process bedeviled with corner cases. Consider the case where
you open two file descriptors, get assigned fds 1 and 0 for them and
wish to shuffle them so that they end up in slots 0 and 1. Our current
code fails in this case.

We also have a problem where we're currently trying to mark file
descriptors as close-on-exec rather than closing them in the child
process. This is inherently broken in a multithreaded process where
another thread can open a file descriptor and race the loop which is
trying to mark them.

Thus, on Linux we switch to close-after-fork where we known that no
other threads exist in the process. On Mac, the code is sufficiently
different that this simple fix isn't applicable and one of the Mac
folks will need to take a look.

http://codereview.chromium.org/100127
BUG=11174


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@14978 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 289 insertions, 0 deletions

diff --git a/base/file_descriptor_shuffle_unittest.cc b/base/file_descriptor_shuffle_unittest.cc
new file mode 100644
index 0000000..981eed9
--- /dev/null
+++ b/base/file_descriptor_shuffle_unittest.cc
@@ -0,0 +1,289 @@
+// Copyright (c) 2009 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 "base/file_descriptor_shuffle.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using base::InjectiveMultimap;
+using base::InjectionArc;
+using base::PerformInjectiveMultimap;
+using base::InjectionDelegate;
+
+namespace {
+typedef testing::Test FileDescriptorShuffleTest;
+}
+
+// 'Duplicated' file descriptors start at this number
+static const int kDuplicateBase = 1000;
+
+struct Action {
+  enum Type {
+    CLOSE,
+    MOVE,
+    DUPLICATE,
+  };
+
+  Action(Type in_type, int in_fd1, int in_fd2 = -1)
+      : type(in_type),
+        fd1(in_fd1),
+        fd2(in_fd2) {
+  }
+
+  bool operator==(const Action& other) const {
+    return other.type == type &&
+           other.fd1 == fd1 &&
+           other.fd2 == fd2;
+  }
+
+  Type type;
+  int fd1;
+  int fd2;
+};
+
+class InjectionTracer : public InjectionDelegate {
+ public:
+  InjectionTracer()
+      : next_duplicate_(kDuplicateBase) {
+  }
+
+  bool Duplicate(int* result, int fd) {
+    *result = next_duplicate_++;
+    actions_.push_back(Action(Action::DUPLICATE, *result, fd));
+    return true;
+  }
+
+  bool Move(int src, int dest) {
+    actions_.push_back(Action(Action::MOVE, src, dest));
+    return true;
+  }
+
+  void Close(int fd) {
+    actions_.push_back(Action(Action::CLOSE, fd));
+  }
+
+  const std::vector<Action>& actions() const { return actions_; }
+
+ private:
+  int next_duplicate_;
+  std::vector<Action> actions_;
+};
+
+TEST(FileDescriptorShuffleTest, Empty) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(0u, tracer.actions().size());
+}
+
+TEST(FileDescriptorShuffleTest, Noop) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 0, false));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(0u, tracer.actions().size());
+}
+
+TEST(FileDescriptorShuffleTest, NoopAndClose) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 0, true));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(0u, tracer.actions().size());
+}
+
+TEST(FileDescriptorShuffleTest, Simple1) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, false));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(1u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] == Action(Action::MOVE, 0, 1));
+}
+
+TEST(FileDescriptorShuffleTest, Simple2) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, false));
+  map.push_back(InjectionArc(2, 3, false));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(2u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::MOVE, 2, 3));
+}
+
+TEST(FileDescriptorShuffleTest, Simple3) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, true));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(2u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::CLOSE, 0));
+}
+
+TEST(FileDescriptorShuffleTest, Simple4) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(10, 0, true));
+  map.push_back(InjectionArc(1, 1, true));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(2u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] == Action(Action::MOVE, 10, 0));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::CLOSE, 10));
+}
+
+TEST(FileDescriptorShuffleTest, Cycle) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, false));
+  map.push_back(InjectionArc(1, 0, false));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(4u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] ==
+              Action(Action::DUPLICATE, kDuplicateBase, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[2] == Action(Action::MOVE, kDuplicateBase, 0));
+  EXPECT_TRUE(tracer.actions()[3] == Action(Action::CLOSE, kDuplicateBase));
+}
+
+TEST(FileDescriptorShuffleTest, CycleAndClose1) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, true));
+  map.push_back(InjectionArc(1, 0, false));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(4u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] ==
+              Action(Action::DUPLICATE, kDuplicateBase, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[2] == Action(Action::MOVE, kDuplicateBase, 0));
+  EXPECT_TRUE(tracer.actions()[3] == Action(Action::CLOSE, kDuplicateBase));
+}
+
+TEST(FileDescriptorShuffleTest, CycleAndClose2) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, false));
+  map.push_back(InjectionArc(1, 0, true));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(4u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] ==
+              Action(Action::DUPLICATE, kDuplicateBase, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[2] == Action(Action::MOVE, kDuplicateBase, 0));
+  EXPECT_TRUE(tracer.actions()[3] == Action(Action::CLOSE, kDuplicateBase));
+}
+
+TEST(FileDescriptorShuffleTest, CycleAndClose3) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, true));
+  map.push_back(InjectionArc(1, 0, true));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(4u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] ==
+              Action(Action::DUPLICATE, kDuplicateBase, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[2] == Action(Action::MOVE, kDuplicateBase, 0));
+  EXPECT_TRUE(tracer.actions()[3] == Action(Action::CLOSE, kDuplicateBase));
+}
+
+TEST(FileDescriptorShuffleTest, Fanout) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, false));
+  map.push_back(InjectionArc(0, 2, false));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(2u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::MOVE, 0, 2));
+}
+
+TEST(FileDescriptorShuffleTest, FanoutAndClose1) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, true));
+  map.push_back(InjectionArc(0, 2, false));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(3u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::MOVE, 0, 2));
+  EXPECT_TRUE(tracer.actions()[2] == Action(Action::CLOSE, 0));
+}
+
+TEST(FileDescriptorShuffleTest, FanoutAndClose2) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, false));
+  map.push_back(InjectionArc(0, 2, true));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(3u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::MOVE, 0, 2));
+  EXPECT_TRUE(tracer.actions()[2] == Action(Action::CLOSE, 0));
+}
+
+TEST(FileDescriptorShuffleTest, FanoutAndClose3) {
+  InjectiveMultimap map;
+  InjectionTracer tracer;
+  map.push_back(InjectionArc(0, 1, true));
+  map.push_back(InjectionArc(0, 2, true));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &tracer));
+  EXPECT_EQ(3u, tracer.actions().size());
+  EXPECT_TRUE(tracer.actions()[0] == Action(Action::MOVE, 0, 1));
+  EXPECT_TRUE(tracer.actions()[1] == Action(Action::MOVE, 0, 2));
+  EXPECT_TRUE(tracer.actions()[2] == Action(Action::CLOSE, 0));
+}
+
+class FailingDelegate : public InjectionDelegate {
+ public:
+  bool Duplicate(int* result, int fd) {
+    return false;
+  }
+
+  bool Move(int src, int dest) {
+    return false;
+  }
+
+  void Close(int fd) {
+  }
+};
+
+TEST(FileDescriptorShuffleTest, EmptyWithFailure) {
+  InjectiveMultimap map;
+  FailingDelegate failing;
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &failing));
+}
+
+TEST(FileDescriptorShuffleTest, NoopWithFailure) {
+  InjectiveMultimap map;
+  FailingDelegate failing;
+  map.push_back(InjectionArc(0, 0, false));
+
+  EXPECT_TRUE(PerformInjectiveMultimap(map, &failing));
+}
+
+TEST(FileDescriptorShuffleTest, Simple1WithFailure) {
+  InjectiveMultimap map;
+  FailingDelegate failing;
+  map.push_back(InjectionArc(0, 1, false));
+
+  EXPECT_FALSE(PerformInjectiveMultimap(map, &failing));
+}