mojo/embedder/platform_channel_pair_posix.cc

   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
  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
  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
  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
  77 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