1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
3 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
4 // Use of this source code is governed by a BSD-style license that can be
5 // found in the LICENSE file.
6
7 #include "base/file_descriptor_shuffle.h"
8
9 #include <errno.h>
10 #include <unistd.h>
11
12 #include "base/eintr_wrapper.h"
13 #include "base/logging.h"
14
15 namespace base {
16
PerformInjectiveMultimapDestructive(InjectiveMultimap * m,InjectionDelegate * delegate)17 bool PerformInjectiveMultimapDestructive(
18 InjectiveMultimap* m, InjectionDelegate* delegate) {
19 static const size_t kMaxExtraFDs = 16;
20 int extra_fds[kMaxExtraFDs];
21 unsigned next_extra_fd = 0;
22
23 // DANGER: this function may not allocate.
24
25 for (InjectiveMultimap::iterator i = m->begin(); i != m->end(); ++i) {
26 int temp_fd = -1;
27
28 // We DCHECK the injectiveness of the mapping.
29 for (InjectiveMultimap::iterator j = i + 1; j != m->end(); ++j) {
30 DCHECK(i->dest != j->dest) << "Both fd " << i->source
31 << " and " << j->source << " map to " << i->dest;
32 }
33
34 const bool is_identity = i->source == i->dest;
35
36 for (InjectiveMultimap::iterator j = i + 1; j != m->end(); ++j) {
37 if (!is_identity && i->dest == j->source) {
38 if (temp_fd == -1) {
39 if (!delegate->Duplicate(&temp_fd, i->dest))
40 return false;
41 if (next_extra_fd < kMaxExtraFDs) {
42 extra_fds[next_extra_fd++] = temp_fd;
43 } else {
44 DLOG(ERROR) << "PerformInjectiveMultimapDestructive overflowed "
45 << "extra_fds. Leaking file descriptors!";
46 }
47 }
48
49 j->source = temp_fd;
50 j->close = false;
51 }
52
53 if (i->close && i->source == j->dest)
54 i->close = false;
55
56 if (i->close && i->source == j->source) {
57 i->close = false;
58 j->close = true;
59 }
60 }
61
62 if (!is_identity) {
63 if (!delegate->Move(i->source, i->dest))
64 return false;
65 }
66
67 if (!is_identity && i->close)
68 delegate->Close(i->source);
69 }
70
71 for (unsigned i = 0; i < next_extra_fd; i++)
72 delegate->Close(extra_fds[i]);
73
74 return true;
75 }
76
PerformInjectiveMultimap(const InjectiveMultimap & m_in,InjectionDelegate * delegate)77 bool PerformInjectiveMultimap(const InjectiveMultimap& m_in,
78 InjectionDelegate* delegate) {
79 InjectiveMultimap m(m_in);
80 return PerformInjectiveMultimapDestructive(&m, delegate);
81 }
82
Duplicate(int * result,int fd)83 bool FileDescriptorTableInjection::Duplicate(int* result, int fd) {
84 *result = HANDLE_EINTR(dup(fd));
85 return *result >= 0;
86 }
87
Move(int src,int dest)88 bool FileDescriptorTableInjection::Move(int src, int dest) {
89 return HANDLE_EINTR(dup2(src, dest)) != -1;
90 }
91
Close(int fd)92 void FileDescriptorTableInjection::Close(int fd) {
93 HANDLE_EINTR(close(fd));
94 }
95
96 } // namespace base
97