1 // Copyright 2014 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 "mojo/embedder/platform_channel_pair.h"
6
7 #include <fcntl.h>
8 #include <sys/socket.h>
9 #include <sys/types.h>
10 #include <unistd.h>
11
12 #include "base/command_line.h"
13 #include "base/logging.h"
14 #include "base/posix/global_descriptors.h"
15 #include "base/strings/string_number_conversions.h"
16 #include "build/build_config.h"
17 #include "mojo/embedder/platform_handle.h"
18
19 namespace mojo {
20 namespace embedder {
21
22 namespace {
23
IsTargetDescriptorUsed(const base::FileHandleMappingVector & file_handle_mapping,int target_fd)24 bool IsTargetDescriptorUsed(
25 const base::FileHandleMappingVector& file_handle_mapping,
26 int target_fd) {
27 for (size_t i = 0; i < file_handle_mapping.size(); i++) {
28 if (file_handle_mapping[i].second == target_fd)
29 return true;
30 }
31 return false;
32 }
33
34 } // namespace
35
PlatformChannelPair()36 PlatformChannelPair::PlatformChannelPair() {
37 // Create the Unix domain socket and set the ends to nonblocking.
38 int fds[2];
39 // TODO(vtl): Maybe fail gracefully if |socketpair()| fails.
40 PCHECK(socketpair(AF_UNIX, SOCK_STREAM, 0, fds) == 0);
41 PCHECK(fcntl(fds[0], F_SETFL, O_NONBLOCK) == 0);
42 PCHECK(fcntl(fds[1], F_SETFL, O_NONBLOCK) == 0);
43
44 #if defined(OS_MACOSX)
45 // This turns off |SIGPIPE| when writing to a closed socket (causing it to
46 // fail with |EPIPE| instead). On Linux, we have to use |send...()| with
47 // |MSG_NOSIGNAL| -- which is not supported on Mac -- instead.
48 int no_sigpipe = 1;
49 PCHECK(setsockopt(fds[0], SOL_SOCKET, SO_NOSIGPIPE, &no_sigpipe,
50 sizeof(no_sigpipe)) == 0);
51 PCHECK(setsockopt(fds[1], SOL_SOCKET, SO_NOSIGPIPE, &no_sigpipe,
52 sizeof(no_sigpipe)) == 0);
53 #endif // defined(OS_MACOSX)
54
55 server_handle_.reset(PlatformHandle(fds[0]));
56 DCHECK(server_handle_.is_valid());
57 client_handle_.reset(PlatformHandle(fds[1]));
58 DCHECK(client_handle_.is_valid());
59 }
60
61 // static
PassClientHandleFromParentProcess(const base::CommandLine & command_line)62 ScopedPlatformHandle PlatformChannelPair::PassClientHandleFromParentProcess(
63 const base::CommandLine& command_line) {
64 std::string client_fd_string =
65 command_line.GetSwitchValueASCII(kMojoPlatformChannelHandleSwitch);
66 int client_fd = -1;
67 if (client_fd_string.empty() ||
68 !base::StringToInt(client_fd_string, &client_fd) ||
69 client_fd < base::GlobalDescriptors::kBaseDescriptor) {
70 LOG(ERROR) << "Missing or invalid --" << kMojoPlatformChannelHandleSwitch;
71 return ScopedPlatformHandle();
72 }
73
74 return ScopedPlatformHandle(PlatformHandle(client_fd));
75 }
76
PrepareToPassClientHandleToChildProcess(base::CommandLine * command_line,base::FileHandleMappingVector * handle_passing_info) const77 void PlatformChannelPair::PrepareToPassClientHandleToChildProcess(
78 base::CommandLine* command_line,
79 base::FileHandleMappingVector* handle_passing_info) const {
80 DCHECK(command_line);
81 DCHECK(handle_passing_info);
82 // This is an arbitrary sanity check. (Note that this guarantees that the loop
83 // below will terminate sanely.)
84 CHECK_LT(handle_passing_info->size(), 1000u);
85
86 DCHECK(client_handle_.is_valid());
87
88 // Find a suitable FD to map our client handle to in the child process.
89 // This has quadratic time complexity in the size of |*handle_passing_info|,
90 // but |*handle_passing_info| should be very small (usually/often empty).
91 int target_fd = base::GlobalDescriptors::kBaseDescriptor;
92 while (IsTargetDescriptorUsed(*handle_passing_info, target_fd))
93 target_fd++;
94
95 handle_passing_info->push_back(std::pair<int, int>(client_handle_.get().fd,
96 target_fd));
97 // Log a warning if the command line already has the switch, but "clobber" it
98 // anyway, since it's reasonably likely that all the switches were just copied
99 // from the parent.
100 LOG_IF(WARNING, command_line->HasSwitch(kMojoPlatformChannelHandleSwitch))
101 << "Child command line already has switch --"
102 << kMojoPlatformChannelHandleSwitch << "="
103 << command_line->GetSwitchValueASCII(kMojoPlatformChannelHandleSwitch);
104 // (Any existing switch won't actually be removed from the command line, but
105 // the last one appended takes precedence.)
106 command_line->AppendSwitchASCII(kMojoPlatformChannelHandleSwitch,
107 base::IntToString(target_fd));
108 }
109
110 } // namespace embedder
111 } // namespace mojo
112