1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "base/posix/file_descriptor_shuffle.h"
6
7#include <unistd.h>
8#include <stddef.h>
9#include <ostream>
10
11#include "base/posix/eintr_wrapper.h"
12#include "base/logging.h"
13
14namespace base {
15
16bool PerformInjectiveMultimapDestructive(
17    InjectiveMultimap* m, InjectionDelegate* delegate) {
18  static const size_t kMaxExtraFDs = 16;
19  int extra_fds[kMaxExtraFDs];
20  unsigned next_extra_fd = 0;
21
22  // DANGER: this function must not allocate or lock.
23  // Cannot use STL iterators here, since debug iterators use locks.
24
25  for (size_t i_index = 0; i_index < m->size(); ++i_index) {
26    InjectiveMultimap::value_type* i = &(*m)[i_index];
27    int temp_fd = -1;
28
29    // We DCHECK the injectiveness of the mapping.
30    for (size_t j_index = i_index + 1; j_index < m->size(); ++j_index) {
31      InjectiveMultimap::value_type* j = &(*m)[j_index];
32      DCHECK(i->dest != j->dest) << "Both fd " << i->source
33          << " and " << j->source << " map to " << i->dest;
34    }
35
36    const bool is_identity = i->source == i->dest;
37
38    for (size_t j_index = i_index + 1; j_index < m->size(); ++j_index) {
39      InjectiveMultimap::value_type* j = &(*m)[j_index];
40      if (!is_identity && i->dest == j->source) {
41        if (temp_fd == -1) {
42          if (!delegate->Duplicate(&temp_fd, i->dest))
43            return false;
44          if (next_extra_fd < kMaxExtraFDs) {
45            extra_fds[next_extra_fd++] = temp_fd;
46          } else {
47            RAW_LOG(ERROR, "PerformInjectiveMultimapDestructive overflowed "
48                           "extra_fds. Leaking file descriptors!");
49          }
50        }
51
52        j->source = temp_fd;
53        j->close = false;
54      }
55
56      if (i->close && i->source == j->dest)
57        i->close = false;
58
59      if (i->close && i->source == j->source) {
60        i->close = false;
61        j->close = true;
62      }
63    }
64
65    if (!is_identity) {
66      if (!delegate->Move(i->source, i->dest))
67        return false;
68    }
69
70    if (!is_identity && i->close)
71      delegate->Close(i->source);
72  }
73
74  for (unsigned i = 0; i < next_extra_fd; i++)
75    delegate->Close(extra_fds[i]);
76
77  return true;
78}
79
80bool PerformInjectiveMultimap(const InjectiveMultimap& m_in,
81                              InjectionDelegate* delegate) {
82  InjectiveMultimap m(m_in);
83  return PerformInjectiveMultimapDestructive(&m, delegate);
84}
85
86bool FileDescriptorTableInjection::Duplicate(int* result, int fd) {
87  *result = HANDLE_EINTR(dup(fd));
88  return *result >= 0;
89}
90
91bool FileDescriptorTableInjection::Move(int src, int dest) {
92  return HANDLE_EINTR(dup2(src, dest)) != -1;
93}
94
95void FileDescriptorTableInjection::Close(int fd) {
96  int ret = IGNORE_EINTR(close(fd));
97  DPCHECK(ret == 0);
98}
99
100}  // namespace base
101