chrome/browser/process_singleton_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 // On Linux, when the user tries to launch a second copy of chrome, we check
   6 // for a socket in the user's profile directory.  If the socket file is open we
   7 // send a message to the first chrome browser process with the current
   8 // directory and second process command line flags.  The second process then
   9 // exits.
  10 //
  11 // Because many networked filesystem implementations do not support unix domain
  12 // sockets, we create the socket in a temporary directory and create a symlink
  13 // in the profile. This temporary directory is no longer bound to the profile,
  14 // and may disappear across a reboot or login to a separate session. To bind
  15 // them, we store a unique cookie in the profile directory, which must also be
  16 // present in the remote directory to connect. The cookie is checked both before
  17 // and after the connection. /tmp is sticky, and different Chrome sessions use
  18 // different cookies. Thus, a matching cookie before and after means the
  19 // connection was to a directory with a valid cookie.
  20 //
  21 // We also have a lock file, which is a symlink to a non-existent destination.
  22 // The destination is a string containing the hostname and process id of
  23 // chrome's browser process, eg. "SingletonLock -> example.com-9156".  When the
  24 // first copy of chrome exits it will delete the lock file on shutdown, so that
  25 // a different instance on a different host may then use the profile directory.
  26 //
  27 // If writing to the socket fails, the hostname in the lock is checked to see if
  28 // another instance is running a different host using a shared filesystem (nfs,
  29 // etc.) If the hostname differs an error is displayed and the second process
  30 // exits.  Otherwise the first process (if any) is killed and the second process
  31 // starts as normal.
  32 //
  33 // When the second process sends the current directory and command line flags to
  34 // the first process, it waits for an ACK message back from the first process
  35 // for a certain time. If there is no ACK message back in time, then the first
  36 // process will be considered as hung for some reason. The second process then
  37 // retrieves the process id from the symbol link and kills it by sending
  38 // SIGKILL. Then the second process starts as normal.
  39
  40 #include "chrome/browser/process_singleton.h"
  41
  42 #include <errno.h>
  43 #include <fcntl.h>
  44 #include <signal.h>
  45 #include <sys/socket.h>
  46 #include <sys/stat.h>
  47 #include <sys/types.h>
  48 #include <sys/un.h>
  49 #include <unistd.h>
  50
  51 #include <cstring>
  52 #include <set>
  53 #include <string>
  54
  55 #include "base/base_paths.h"
  56 #include "base/basictypes.h"
  57 #include "base/bind.h"
  58 #include "base/command_line.h"
  59 #include "base/files/file_path.h"
  60 #include "base/files/file_util.h"
  61 #include "base/logging.h"
  62 #include "base/message_loop/message_loop.h"
  63 #include "base/path_service.h"
  64 #include "base/posix/eintr_wrapper.h"
  65 #include "base/rand_util.h"
  66 #include "base/safe_strerror_posix.h"
  67 #include "base/sequenced_task_runner_helpers.h"
  68 #include "base/stl_util.h"
  69 #include "base/strings/string_number_conversions.h"
  70 #include "base/strings/string_split.h"
  71 #include "base/strings/string_util.h"
  72 #include "base/strings/stringprintf.h"
  73 #include "base/strings/sys_string_conversions.h"
  74 #include "base/strings/utf_string_conversions.h"
  75 #include "base/threading/platform_thread.h"
  76 #include "base/time/time.h"
  77 #include "base/timer/timer.h"
  78 #include "chrome/common/chrome_constants.h"
  79 #include "chrome/grit/chromium_strings.h"
  80 #include "chrome/grit/generated_resources.h"
  81 #include "content/public/browser/browser_thread.h"
  82 #include "net/base/net_util.h"
  83 #include "ui/base/l10n/l10n_util.h"
  84
  85 #if defined(OS_LINUX)
  86 #include "chrome/browser/ui/process_singleton_dialog_linux.h"
  87 #endif
  88
  89 #if defined(TOOLKIT_VIEWS) && defined(OS_LINUX) && !defined(OS_CHROMEOS)
  90 #include "ui/views/linux_ui/linux_ui.h"
  91 #endif
  92
  93 using content::BrowserThread;
  94
  95 namespace {
  96
  97 // Timeout for the current browser process to respond. 20 seconds should be
  98 // enough.
  99 const int kTimeoutInSeconds = 20;
 100 // Number of retries to notify the browser. 20 retries over 20 seconds = 1 try
 101 // per second.
 102 const int kRetryAttempts = 20;
 103 static bool g_disable_prompt;
 104 const char kStartToken[] = "START";
 105 const char kACKToken[] = "ACK";
 106 const char kShutdownToken[] = "SHUTDOWN";
 107 const char kTokenDelimiter = '\0';
 108 const int kMaxMessageLength = 32 * 1024;
 109 const int kMaxACKMessageLength = arraysize(kShutdownToken) - 1;
 110
 111 const char kLockDelimiter = '-';
 112
 113 // Set a file descriptor to be non-blocking.
 114 // Return 0 on success, -1 on failure.
 115 int SetNonBlocking(int fd) {
 116   int flags = fcntl(fd, F_GETFL, 0);
 117   if (-1 == flags)
 118     return flags;
 119   if (flags & O_NONBLOCK)
 120     return 0;
 121   return fcntl(fd, F_SETFL, flags | O_NONBLOCK);
 122 }
 123
 124 // Set the close-on-exec bit on a file descriptor.
 125 // Returns 0 on success, -1 on failure.
 126 int SetCloseOnExec(int fd) {
 127   int flags = fcntl(fd, F_GETFD, 0);
 128   if (-1 == flags)
 129     return flags;
 130   if (flags & FD_CLOEXEC)
 131     return 0;
 132   return fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 133 }
 134
 135 // Close a socket and check return value.
 136 void CloseSocket(int fd) {
 137   int rv = IGNORE_EINTR(close(fd));
 138   DCHECK_EQ(0, rv) << "Error closing socket: " << safe_strerror(errno);
 139 }
 140
 141 // Write a message to a socket fd.
 142 bool WriteToSocket(int fd, const char *message, size_t length) {
 143   DCHECK(message);
 144   DCHECK(length);
 145   size_t bytes_written = 0;
 146   do {
 147     ssize_t rv = HANDLE_EINTR(
 148         write(fd, message + bytes_written, length - bytes_written));
 149     if (rv < 0) {
 150       if (errno == EAGAIN || errno == EWOULDBLOCK) {
 151         // The socket shouldn't block, we're sending so little data.  Just give
 152         // up here, since NotifyOtherProcess() doesn't have an asynchronous api.
 153         LOG(ERROR) << "ProcessSingleton would block on write(), so it gave up.";
 154         return false;
 155       }
 156       PLOG(ERROR) << "write() failed";
 157       return false;
 158     }
 159     bytes_written += rv;
 160   } while (bytes_written < length);
 161
 162   return true;
 163 }
 164
 165 struct timeval TimeDeltaToTimeVal(const base::TimeDelta& delta) {
 166   struct timeval result;
 167   result.tv_sec = delta.InSeconds();
 168   result.tv_usec = delta.InMicroseconds() % base::Time::kMicrosecondsPerSecond;
 169   return result;
 170 }
 171
 172 // Wait a socket for read for a certain timeout.
 173 // Returns -1 if error occurred, 0 if timeout reached, > 0 if the socket is
 174 // ready for read.
 175 int WaitSocketForRead(int fd, const base::TimeDelta& timeout) {
 176   fd_set read_fds;
 177   struct timeval tv = TimeDeltaToTimeVal(timeout);
 178
 179   FD_ZERO(&read_fds);
 180   FD_SET(fd, &read_fds);
 181
 182   return HANDLE_EINTR(select(fd + 1, &read_fds, NULL, NULL, &tv));
 183 }
 184
 185 // Read a message from a socket fd, with an optional timeout.
 186 // If |timeout| <= 0 then read immediately.
 187 // Return number of bytes actually read, or -1 on error.
 188 ssize_t ReadFromSocket(int fd,
 189                        char* buf,
 190                        size_t bufsize,
 191                        const base::TimeDelta& timeout) {
 192   if (timeout > base::TimeDelta()) {
 193     int rv = WaitSocketForRead(fd, timeout);
 194     if (rv <= 0)
 195       return rv;
 196   }
 197
 198   size_t bytes_read = 0;
 199   do {
 200     ssize_t rv = HANDLE_EINTR(read(fd, buf + bytes_read, bufsize - bytes_read));
 201     if (rv < 0) {
 202       if (errno != EAGAIN && errno != EWOULDBLOCK) {
 203         PLOG(ERROR) << "read() failed";
 204         return rv;
 205       } else {
 206         // It would block, so we just return what has been read.
 207         return bytes_read;
 208       }
 209     } else if (!rv) {
 210       // No more data to read.
 211       return bytes_read;
 212     } else {
 213       bytes_read += rv;
 214     }
 215   } while (bytes_read < bufsize);
 216
 217   return bytes_read;
 218 }
 219
 220 // Set up a sockaddr appropriate for messaging.
 221 void SetupSockAddr(const std::string& path, struct sockaddr_un* addr) {
 222   addr->sun_family = AF_UNIX;
 223   CHECK(path.length() < arraysize(addr->sun_path))
 224       << "Socket path too long: " << path;
 225   base::strlcpy(addr->sun_path, path.c_str(), arraysize(addr->sun_path));
 226 }
 227
 228 // Set up a socket appropriate for messaging.
 229 int SetupSocketOnly() {
 230   int sock = socket(PF_UNIX, SOCK_STREAM, 0);
 231   PCHECK(sock >= 0) << "socket() failed";
 232
 233   int rv = SetNonBlocking(sock);
 234   DCHECK_EQ(0, rv) << "Failed to make non-blocking socket.";
 235   rv = SetCloseOnExec(sock);
 236   DCHECK_EQ(0, rv) << "Failed to set CLOEXEC on socket.";
 237
 238   return sock;
 239 }
 240
 241 // Set up a socket and sockaddr appropriate for messaging.
 242 void SetupSocket(const std::string& path, int* sock, struct sockaddr_un* addr) {
 243   *sock = SetupSocketOnly();
 244   SetupSockAddr(path, addr);
 245 }
 246
 247 // Read a symbolic link, return empty string if given path is not a symbol link.
 248 base::FilePath ReadLink(const base::FilePath& path) {
 249   base::FilePath target;
 250   if (!base::ReadSymbolicLink(path, &target)) {
 251     // The only errno that should occur is ENOENT.
 252     if (errno != 0 && errno != ENOENT)
 253       PLOG(ERROR) << "readlink(" << path.value() << ") failed";
 254   }
 255   return target;
 256 }
 257
 258 // Unlink a path. Return true on success.
 259 bool UnlinkPath(const base::FilePath& path) {
 260   int rv = unlink(path.value().c_str());
 261   if (rv < 0 && errno != ENOENT)
 262     PLOG(ERROR) << "Failed to unlink " << path.value();
 263
 264   return rv == 0;
 265 }
 266
 267 // Create a symlink. Returns true on success.
 268 bool SymlinkPath(const base::FilePath& target, const base::FilePath& path) {
 269   if (!base::CreateSymbolicLink(target, path)) {
 270     // Double check the value in case symlink suceeded but we got an incorrect
 271     // failure due to NFS packet loss & retry.
 272     int saved_errno = errno;
 273     if (ReadLink(path) != target) {
 274       // If we failed to create the lock, most likely another instance won the
 275       // startup race.
 276       errno = saved_errno;
 277       PLOG(ERROR) << "Failed to create " << path.value();
 278       return false;
 279     }
 280   }
 281   return true;
 282 }
 283
 284 // Extract the hostname and pid from the lock symlink.
 285 // Returns true if the lock existed.
 286 bool ParseLockPath(const base::FilePath& path,
 287                    std::string* hostname,
 288                    int* pid) {
 289   std::string real_path = ReadLink(path).value();
 290   if (real_path.empty())
 291     return false;
 292
 293   std::string::size_type pos = real_path.rfind(kLockDelimiter);
 294
 295   // If the path is not a symbolic link, or doesn't contain what we expect,
 296   // bail.
 297   if (pos == std::string::npos) {
 298     *hostname = "";
 299     *pid = -1;
 300     return true;
 301   }
 302
 303   *hostname = real_path.substr(0, pos);
 304
 305   const std::string& pid_str = real_path.substr(pos + 1);
 306   if (!base::StringToInt(pid_str, pid))
 307     *pid = -1;
 308
 309   return true;
 310 }
 311
 312 // Returns true if the user opted to unlock the profile.
 313 bool DisplayProfileInUseError(const base::FilePath& lock_path,
 314                               const std::string& hostname,
 315                               int pid) {
 316   base::string16 error = l10n_util::GetStringFUTF16(
 317       IDS_PROFILE_IN_USE_POSIX,
 318       base::IntToString16(pid),
 319       base::ASCIIToUTF16(hostname));
 320   LOG(ERROR) << error;
 321
 322   if (g_disable_prompt)
 323     return false;
 324
 325 #if defined(OS_LINUX)
 326   base::string16 relaunch_button_text = l10n_util::GetStringUTF16(
 327       IDS_PROFILE_IN_USE_LINUX_RELAUNCH);
 328   return ShowProcessSingletonDialog(error, relaunch_button_text);
 329 #elif defined(OS_MACOSX)
 330   // On Mac, always usurp the lock.
 331   return true;
 332 #endif
 333
 334   NOTREACHED();
 335   return false;
 336 }
 337
 338 bool IsChromeProcess(pid_t pid) {
 339   base::FilePath other_chrome_path(base::GetProcessExecutablePath(pid));
 340   return (!other_chrome_path.empty() &&
 341           other_chrome_path.BaseName() ==
 342           base::FilePath(chrome::kBrowserProcessExecutableName));
 343 }
 344
 345 // A helper class to hold onto a socket.
 346 class ScopedSocket {
 347  public:
 348   ScopedSocket() : fd_(-1) { Reset(); }
 349   ~ScopedSocket() { Close(); }
 350   int fd() { return fd_; }
 351   void Reset() {
 352     Close();
 353     fd_ = SetupSocketOnly();
 354   }
 355   void Close() {
 356     if (fd_ >= 0)
 357       CloseSocket(fd_);
 358     fd_ = -1;
 359   }
 360  private:
 361   int fd_;
 362 };
 363
 364 // Returns a random string for uniquifying profile connections.
 365 std::string GenerateCookie() {
 366   return base::Uint64ToString(base::RandUint64());
 367 }
 368
 369 bool CheckCookie(const base::FilePath& path, const base::FilePath& cookie) {
 370   return (cookie == ReadLink(path));
 371 }
 372
 373 bool ConnectSocket(ScopedSocket* socket,
 374                    const base::FilePath& socket_path,
 375                    const base::FilePath& cookie_path) {
 376   base::FilePath socket_target;
 377   if (base::ReadSymbolicLink(socket_path, &socket_target)) {
 378     // It's a symlink. Read the cookie.
 379     base::FilePath cookie = ReadLink(cookie_path);
 380     if (cookie.empty())
 381       return false;
 382     base::FilePath remote_cookie = socket_target.DirName().
 383                              Append(chrome::kSingletonCookieFilename);
 384     // Verify the cookie before connecting.
 385     if (!CheckCookie(remote_cookie, cookie))
 386       return false;
 387     // Now we know the directory was (at that point) created by the profile
 388     // owner. Try to connect.
 389     sockaddr_un addr;
 390     SetupSockAddr(socket_target.value(), &addr);
 391     int ret = HANDLE_EINTR(connect(socket->fd(),
 392                                    reinterpret_cast<sockaddr*>(&addr),
 393                                    sizeof(addr)));
 394     if (ret != 0)
 395       return false;
 396     // Check the cookie again. We only link in /tmp, which is sticky, so, if the
 397     // directory is still correct, it must have been correct in-between when we
 398     // connected. POSIX, sadly, lacks a connectat().
 399     if (!CheckCookie(remote_cookie, cookie)) {
 400       socket->Reset();
 401       return false;
 402     }
 403     // Success!
 404     return true;
 405   } else if (errno == EINVAL) {
 406     // It exists, but is not a symlink (or some other error we detect
 407     // later). Just connect to it directly; this is an older version of Chrome.
 408     sockaddr_un addr;
 409     SetupSockAddr(socket_path.value(), &addr);
 410     int ret = HANDLE_EINTR(connect(socket->fd(),
 411                                    reinterpret_cast<sockaddr*>(&addr),
 412                                    sizeof(addr)));
 413     return (ret == 0);
 414   } else {
 415     // File is missing, or other error.
 416     if (errno != ENOENT)
 417       PLOG(ERROR) << "readlink failed";
 418     return false;
 419   }
 420 }
 421
 422 #if defined(OS_MACOSX)
 423 bool ReplaceOldSingletonLock(const base::FilePath& symlink_content,
 424                              const base::FilePath& lock_path) {
 425   // Try taking an flock(2) on the file. Failure means the lock is taken so we
 426   // should quit.
 427   base::ScopedFD lock_fd(HANDLE_EINTR(
 428       open(lock_path.value().c_str(), O_RDWR | O_CREAT | O_SYMLINK, 0644)));
 429   if (!lock_fd.is_valid()) {
 430     PLOG(ERROR) << "Could not open singleton lock";
 431     return false;
 432   }
 433
 434   int rc = HANDLE_EINTR(flock(lock_fd.get(), LOCK_EX | LOCK_NB));
 435   if (rc == -1) {
 436     if (errno == EWOULDBLOCK) {
 437       LOG(ERROR) << "Singleton lock held by old process.";
 438     } else {
 439       PLOG(ERROR) << "Error locking singleton lock";
 440     }
 441     return false;
 442   }
 443
 444   // Successfully taking the lock means we can replace it with the a new symlink
 445   // lock. We never flock() the lock file from now on. I.e. we assume that an
 446   // old version of Chrome will not run with the same user data dir after this
 447   // version has run.
 448   if (!base::DeleteFile(lock_path, false)) {
 449     PLOG(ERROR) << "Could not delete old singleton lock.";
 450     return false;
 451   }
 452
 453   return SymlinkPath(symlink_content, lock_path);
 454 }
 455 #endif  // defined(OS_MACOSX)
 456
 457 }  // namespace
 458
 459 ///////////////////////////////////////////////////////////////////////////////
 460 // ProcessSingleton::LinuxWatcher
 461 // A helper class for a Linux specific implementation of the process singleton.
 462 // This class sets up a listener on the singleton socket and handles parsing
 463 // messages that come in on the singleton socket.
 464 class ProcessSingleton::LinuxWatcher
 465     : public base::MessageLoopForIO::Watcher,
 466       public base::MessageLoop::DestructionObserver,
 467       public base::RefCountedThreadSafe<ProcessSingleton::LinuxWatcher,
 468                                         BrowserThread::DeleteOnIOThread> {
 469  public:
 470   // A helper class to read message from an established socket.
 471   class SocketReader : public base::MessageLoopForIO::Watcher {
 472    public:
 473     SocketReader(ProcessSingleton::LinuxWatcher* parent,
 474                  base::MessageLoop* ui_message_loop,
 475                  int fd)
 476         : parent_(parent),
 477           ui_message_loop_(ui_message_loop),
 478           fd_(fd),
 479           bytes_read_(0) {
 480       DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 481       // Wait for reads.
 482       base::MessageLoopForIO::current()->WatchFileDescriptor(
 483           fd, true, base::MessageLoopForIO::WATCH_READ, &fd_reader_, this);
 484       // If we haven't completed in a reasonable amount of time, give up.
 485       timer_.Start(FROM_HERE, base::TimeDelta::FromSeconds(kTimeoutInSeconds),
 486                    this, &SocketReader::CleanupAndDeleteSelf);
 487     }
 488
 489     ~SocketReader() override { CloseSocket(fd_); }
 490
 491     // MessageLoopForIO::Watcher impl.
 492     void OnFileCanReadWithoutBlocking(int fd) override;
 493     void OnFileCanWriteWithoutBlocking(int fd) override {
 494       // SocketReader only watches for accept (read) events.
 495       NOTREACHED();
 496     }
 497
 498     // Finish handling the incoming message by optionally sending back an ACK
 499     // message and removing this SocketReader.
 500     void FinishWithACK(const char *message, size_t length);
 501
 502    private:
 503     void CleanupAndDeleteSelf() {
 504       DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 505
 506       parent_->RemoveSocketReader(this);
 507       // We're deleted beyond this point.
 508     }
 509
 510     base::MessageLoopForIO::FileDescriptorWatcher fd_reader_;
 511
 512     // The ProcessSingleton::LinuxWatcher that owns us.
 513     ProcessSingleton::LinuxWatcher* const parent_;
 514
 515     // A reference to the UI message loop.
 516     base::MessageLoop* const ui_message_loop_;
 517
 518     // The file descriptor we're reading.
 519     const int fd_;
 520
 521     // Store the message in this buffer.
 522     char buf_[kMaxMessageLength];
 523
 524     // Tracks the number of bytes we've read in case we're getting partial
 525     // reads.
 526     size_t bytes_read_;
 527
 528     base::OneShotTimer<SocketReader> timer_;
 529
 530     DISALLOW_COPY_AND_ASSIGN(SocketReader);
 531   };
 532
 533   // We expect to only be constructed on the UI thread.
 534   explicit LinuxWatcher(ProcessSingleton* parent)
 535       : ui_message_loop_(base::MessageLoop::current()),
 536         parent_(parent) {
 537   }
 538
 539   // Start listening for connections on the socket.  This method should be
 540   // called from the IO thread.
 541   void StartListening(int socket);
 542
 543   // This method determines if we should use the same process and if we should,
 544   // opens a new browser tab.  This runs on the UI thread.
 545   // |reader| is for sending back ACK message.
 546   void HandleMessage(const std::string& current_dir,
 547                      const std::vector<std::string>& argv,
 548                      SocketReader* reader);
 549
 550   // MessageLoopForIO::Watcher impl.  These run on the IO thread.
 551   void OnFileCanReadWithoutBlocking(int fd) override;
 552   void OnFileCanWriteWithoutBlocking(int fd) override {
 553     // ProcessSingleton only watches for accept (read) events.
 554     NOTREACHED();
 555   }
 556
 557   // MessageLoop::DestructionObserver
 558   void WillDestroyCurrentMessageLoop() override {
 559     fd_watcher_.StopWatchingFileDescriptor();
 560   }
 561
 562  private:
 563   friend struct BrowserThread::DeleteOnThread<BrowserThread::IO>;
 564   friend class base::DeleteHelper<ProcessSingleton::LinuxWatcher>;
 565
 566   ~LinuxWatcher() override {
 567     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 568     STLDeleteElements(&readers_);
 569
 570     base::MessageLoopForIO* ml = base::MessageLoopForIO::current();
 571     ml->RemoveDestructionObserver(this);
 572   }
 573
 574   // Removes and deletes the SocketReader.
 575   void RemoveSocketReader(SocketReader* reader);
 576
 577   base::MessageLoopForIO::FileDescriptorWatcher fd_watcher_;
 578
 579   // A reference to the UI message loop (i.e., the message loop we were
 580   // constructed on).
 581   base::MessageLoop* ui_message_loop_;
 582
 583   // The ProcessSingleton that owns us.
 584   ProcessSingleton* const parent_;
 585
 586   std::set<SocketReader*> readers_;
 587
 588   DISALLOW_COPY_AND_ASSIGN(LinuxWatcher);
 589 };
 590
 591 void ProcessSingleton::LinuxWatcher::OnFileCanReadWithoutBlocking(int fd) {
 592   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 593   // Accepting incoming client.
 594   sockaddr_un from;
 595   socklen_t from_len = sizeof(from);
 596   int connection_socket = HANDLE_EINTR(accept(
 597       fd, reinterpret_cast<sockaddr*>(&from), &from_len));
 598   if (-1 == connection_socket) {
 599     PLOG(ERROR) << "accept() failed";
 600     return;
 601   }
 602   int rv = SetNonBlocking(connection_socket);
 603   DCHECK_EQ(0, rv) << "Failed to make non-blocking socket.";
 604   SocketReader* reader = new SocketReader(this,
 605                                           ui_message_loop_,
 606                                           connection_socket);
 607   readers_.insert(reader);
 608 }
 609
 610 void ProcessSingleton::LinuxWatcher::StartListening(int socket) {
 611   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 612   // Watch for client connections on this socket.
 613   base::MessageLoopForIO* ml = base::MessageLoopForIO::current();
 614   ml->AddDestructionObserver(this);
 615   ml->WatchFileDescriptor(socket, true, base::MessageLoopForIO::WATCH_READ,
 616                           &fd_watcher_, this);
 617 }
 618
 619 void ProcessSingleton::LinuxWatcher::HandleMessage(
 620     const std::string& current_dir, const std::vector<std::string>& argv,
 621     SocketReader* reader) {
 622   DCHECK(ui_message_loop_ == base::MessageLoop::current());
 623   DCHECK(reader);
 624
 625   if (parent_->notification_callback_.Run(base::CommandLine(argv),
 626                                           base::FilePath(current_dir))) {
 627     // Send back "ACK" message to prevent the client process from starting up.
 628     reader->FinishWithACK(kACKToken, arraysize(kACKToken) - 1);
 629   } else {
 630     LOG(WARNING) << "Not handling interprocess notification as browser"
 631                     " is shutting down";
 632     // Send back "SHUTDOWN" message, so that the client process can start up
 633     // without killing this process.
 634     reader->FinishWithACK(kShutdownToken, arraysize(kShutdownToken) - 1);
 635     return;
 636   }
 637 }
 638
 639 void ProcessSingleton::LinuxWatcher::RemoveSocketReader(SocketReader* reader) {
 640   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 641   DCHECK(reader);
 642   readers_.erase(reader);
 643   delete reader;
 644 }
 645
 646 ///////////////////////////////////////////////////////////////////////////////
 647 // ProcessSingleton::LinuxWatcher::SocketReader
 648 //
 649
 650 void ProcessSingleton::LinuxWatcher::SocketReader::OnFileCanReadWithoutBlocking(
 651     int fd) {
 652   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 653   DCHECK_EQ(fd, fd_);
 654   while (bytes_read_ < sizeof(buf_)) {
 655     ssize_t rv = HANDLE_EINTR(
 656         read(fd, buf_ + bytes_read_, sizeof(buf_) - bytes_read_));
 657     if (rv < 0) {
 658       if (errno != EAGAIN && errno != EWOULDBLOCK) {
 659         PLOG(ERROR) << "read() failed";
 660         CloseSocket(fd);
 661         return;
 662       } else {
 663         // It would block, so we just return and continue to watch for the next
 664         // opportunity to read.
 665         return;
 666       }
 667     } else if (!rv) {
 668       // No more data to read.  It's time to process the message.
 669       break;
 670     } else {
 671       bytes_read_ += rv;
 672     }
 673   }
 674
 675   // Validate the message.  The shortest message is kStartToken\0x\0x
 676   const size_t kMinMessageLength = arraysize(kStartToken) + 4;
 677   if (bytes_read_ < kMinMessageLength) {
 678     buf_[bytes_read_] = 0;
 679     LOG(ERROR) << "Invalid socket message (wrong length):" << buf_;
 680     CleanupAndDeleteSelf();
 681     return;
 682   }
 683
 684   std::string str(buf_, bytes_read_);
 685   std::vector<std::string> tokens;
 686   base::SplitString(str, kTokenDelimiter, &tokens);
 687
 688   if (tokens.size() < 3 || tokens[0] != kStartToken) {
 689     LOG(ERROR) << "Wrong message format: " << str;
 690     CleanupAndDeleteSelf();
 691     return;
 692   }
 693
 694   // Stop the expiration timer to prevent this SocketReader object from being
 695   // terminated unexpectly.
 696   timer_.Stop();
 697
 698   std::string current_dir = tokens[1];
 699   // Remove the first two tokens.  The remaining tokens should be the command
 700   // line argv array.
 701   tokens.erase(tokens.begin());
 702   tokens.erase(tokens.begin());
 703
 704   // Return to the UI thread to handle opening a new browser tab.
 705   ui_message_loop_->PostTask(FROM_HERE, base::Bind(
 706       &ProcessSingleton::LinuxWatcher::HandleMessage,
 707       parent_,
 708       current_dir,
 709       tokens,
 710       this));
 711   fd_reader_.StopWatchingFileDescriptor();
 712
 713   // LinuxWatcher::HandleMessage() is in charge of destroying this SocketReader
 714   // object by invoking SocketReader::FinishWithACK().
 715 }
 716
 717 void ProcessSingleton::LinuxWatcher::SocketReader::FinishWithACK(
 718     const char *message, size_t length) {
 719   if (message && length) {
 720     // Not necessary to care about the return value.
 721     WriteToSocket(fd_, message, length);
 722   }
 723
 724   if (shutdown(fd_, SHUT_WR) < 0)
 725     PLOG(ERROR) << "shutdown() failed";
 726
 727   BrowserThread::PostTask(
 728       BrowserThread::IO,
 729       FROM_HERE,
 730       base::Bind(&ProcessSingleton::LinuxWatcher::RemoveSocketReader,
 731                  parent_,
 732                  this));
 733   // We will be deleted once the posted RemoveSocketReader task runs.
 734 }
 735
 736 ///////////////////////////////////////////////////////////////////////////////
 737 // ProcessSingleton
 738 //
 739 ProcessSingleton::ProcessSingleton(
 740     const base::FilePath& user_data_dir,
 741     const NotificationCallback& notification_callback)
 742     : notification_callback_(notification_callback),
 743       current_pid_(base::GetCurrentProcId()),
 744       watcher_(new LinuxWatcher(this)) {
 745   socket_path_ = user_data_dir.Append(chrome::kSingletonSocketFilename);
 746   lock_path_ = user_data_dir.Append(chrome::kSingletonLockFilename);
 747   cookie_path_ = user_data_dir.Append(chrome::kSingletonCookieFilename);
 748
 749   kill_callback_ = base::Bind(&ProcessSingleton::KillProcess,
 750                               base::Unretained(this));
 751 }
 752
 753 ProcessSingleton::~ProcessSingleton() {
 754 }
 755
 756 ProcessSingleton::NotifyResult ProcessSingleton::NotifyOtherProcess() {
 757   return NotifyOtherProcessWithTimeout(
 758       *base::CommandLine::ForCurrentProcess(), kRetryAttempts,
 759       base::TimeDelta::FromSeconds(kTimeoutInSeconds), true);
 760 }
 761
 762 ProcessSingleton::NotifyResult ProcessSingleton::NotifyOtherProcessWithTimeout(
 763     const base::CommandLine& cmd_line,
 764     int retry_attempts,
 765     const base::TimeDelta& timeout,
 766     bool kill_unresponsive) {
 767   DCHECK_GE(retry_attempts, 0);
 768   DCHECK_GE(timeout.InMicroseconds(), 0);
 769
 770   base::TimeDelta sleep_interval = timeout / retry_attempts;
 771
 772   ScopedSocket socket;
 773   for (int retries = 0; retries <= retry_attempts; ++retries) {
 774     // Try to connect to the socket.
 775     if (ConnectSocket(&socket, socket_path_, cookie_path_))
 776       break;
 777
 778     // If we're in a race with another process, they may be in Create() and have
 779     // created the lock but not attached to the socket.  So we check if the
 780     // process with the pid from the lockfile is currently running and is a
 781     // chrome browser.  If so, we loop and try again for |timeout|.
 782
 783     std::string hostname;
 784     int pid;
 785     if (!ParseLockPath(lock_path_, &hostname, &pid)) {
 786       // No lockfile exists.
 787       return PROCESS_NONE;
 788     }
 789
 790     if (hostname.empty()) {
 791       // Invalid lockfile.
 792       UnlinkPath(lock_path_);
 793       return PROCESS_NONE;
 794     }
 795
 796     if (hostname != net::GetHostName() && !IsChromeProcess(pid)) {
 797       // Locked by process on another host. If the user selected to unlock
 798       // the profile, try to continue; otherwise quit.
 799       if (DisplayProfileInUseError(lock_path_, hostname, pid)) {
 800         UnlinkPath(lock_path_);
 801         return PROCESS_NONE;
 802       }
 803       return PROFILE_IN_USE;
 804     }
 805
 806     if (!IsChromeProcess(pid)) {
 807       // Orphaned lockfile (no process with pid, or non-chrome process.)
 808       UnlinkPath(lock_path_);
 809       return PROCESS_NONE;
 810     }
 811
 812     if (IsSameChromeInstance(pid)) {
 813       // Orphaned lockfile (pid is part of same chrome instance we are, even
 814       // though we haven't tried to create a lockfile yet).
 815       UnlinkPath(lock_path_);
 816       return PROCESS_NONE;
 817     }
 818
 819     if (retries == retry_attempts) {
 820       // Retries failed.  Kill the unresponsive chrome process and continue.
 821       if (!kill_unresponsive || !KillProcessByLockPath())
 822         return PROFILE_IN_USE;
 823       return PROCESS_NONE;
 824     }
 825
 826     base::PlatformThread::Sleep(sleep_interval);
 827   }
 828
 829   timeval socket_timeout = TimeDeltaToTimeVal(timeout);
 830   setsockopt(socket.fd(),
 831              SOL_SOCKET,
 832              SO_SNDTIMEO,
 833              &socket_timeout,
 834              sizeof(socket_timeout));
 835
 836   // Found another process, prepare our command line
 837   // format is "START\0<current dir>\0<argv[0]>\0...\0<argv[n]>".
 838   std::string to_send(kStartToken);
 839   to_send.push_back(kTokenDelimiter);
 840
 841   base::FilePath current_dir;
 842   if (!PathService::Get(base::DIR_CURRENT, &current_dir))
 843     return PROCESS_NONE;
 844   to_send.append(current_dir.value());
 845
 846   const std::vector<std::string>& argv = cmd_line.argv();
 847   for (std::vector<std::string>::const_iterator it = argv.begin();
 848       it != argv.end(); ++it) {
 849     to_send.push_back(kTokenDelimiter);
 850     to_send.append(*it);
 851   }
 852
 853   // Send the message
 854   if (!WriteToSocket(socket.fd(), to_send.data(), to_send.length())) {
 855     // Try to kill the other process, because it might have been dead.
 856     if (!kill_unresponsive || !KillProcessByLockPath())
 857       return PROFILE_IN_USE;
 858     return PROCESS_NONE;
 859   }
 860
 861   if (shutdown(socket.fd(), SHUT_WR) < 0)
 862     PLOG(ERROR) << "shutdown() failed";
 863
 864   // Read ACK message from the other process. It might be blocked for a certain
 865   // timeout, to make sure the other process has enough time to return ACK.
 866   char buf[kMaxACKMessageLength + 1];
 867   ssize_t len = ReadFromSocket(socket.fd(), buf, kMaxACKMessageLength, timeout);
 868
 869   // Failed to read ACK, the other process might have been frozen.
 870   if (len <= 0) {
 871     if (!kill_unresponsive || !KillProcessByLockPath())
 872       return PROFILE_IN_USE;
 873     return PROCESS_NONE;
 874   }
 875
 876   buf[len] = '\0';
 877   if (strncmp(buf, kShutdownToken, arraysize(kShutdownToken) - 1) == 0) {
 878     // The other process is shutting down, it's safe to start a new process.
 879     return PROCESS_NONE;
 880   } else if (strncmp(buf, kACKToken, arraysize(kACKToken) - 1) == 0) {
 881 #if defined(TOOLKIT_VIEWS) && defined(OS_LINUX) && !defined(OS_CHROMEOS)
 882     // Likely NULL in unit tests.
 883     views::LinuxUI* linux_ui = views::LinuxUI::instance();
 884     if (linux_ui)
 885       linux_ui->NotifyWindowManagerStartupComplete();
 886 #endif
 887
 888     // Assume the other process is handling the request.
 889     return PROCESS_NOTIFIED;
 890   }
 891
 892   NOTREACHED() << "The other process returned unknown message: " << buf;
 893   return PROCESS_NOTIFIED;
 894 }
 895
 896 ProcessSingleton::NotifyResult ProcessSingleton::NotifyOtherProcessOrCreate() {
 897   return NotifyOtherProcessWithTimeoutOrCreate(
 898       *base::CommandLine::ForCurrentProcess(), kRetryAttempts,
 899       base::TimeDelta::FromSeconds(kTimeoutInSeconds));
 900 }
 901
 902 ProcessSingleton::NotifyResult
 903 ProcessSingleton::NotifyOtherProcessWithTimeoutOrCreate(
 904     const base::CommandLine& command_line,
 905     int retry_attempts,
 906     const base::TimeDelta& timeout) {
 907   NotifyResult result = NotifyOtherProcessWithTimeout(
 908       command_line, retry_attempts, timeout, true);
 909   if (result != PROCESS_NONE)
 910     return result;
 911   if (Create())
 912     return PROCESS_NONE;
 913   // If the Create() failed, try again to notify. (It could be that another
 914   // instance was starting at the same time and managed to grab the lock before
 915   // we did.)
 916   // This time, we don't want to kill anything if we aren't successful, since we
 917   // aren't going to try to take over the lock ourselves.
 918   result = NotifyOtherProcessWithTimeout(
 919       command_line, retry_attempts, timeout, false);
 920   if (result != PROCESS_NONE)
 921     return result;
 922
 923   return LOCK_ERROR;
 924 }
 925
 926 void ProcessSingleton::OverrideCurrentPidForTesting(base::ProcessId pid) {
 927   current_pid_ = pid;
 928 }
 929
 930 void ProcessSingleton::OverrideKillCallbackForTesting(
 931     const base::Callback<void(int)>& callback) {
 932   kill_callback_ = callback;
 933 }
 934
 935 void ProcessSingleton::DisablePromptForTesting() {
 936   g_disable_prompt = true;
 937 }
 938
 939 bool ProcessSingleton::Create() {
 940   int sock;
 941   sockaddr_un addr;
 942
 943   // The symlink lock is pointed to the hostname and process id, so other
 944   // processes can find it out.
 945   base::FilePath symlink_content(base::StringPrintf(
 946       "%s%c%u",
 947       net::GetHostName().c_str(),
 948       kLockDelimiter,
 949       current_pid_));
 950
 951   // Create symbol link before binding the socket, to ensure only one instance
 952   // can have the socket open.
 953   if (!SymlinkPath(symlink_content, lock_path_)) {
 954     // TODO(jackhou): Remove this case once this code is stable on Mac.
 955     // http://crbug.com/367612
 956 #if defined(OS_MACOSX)
 957     // On Mac, an existing non-symlink lock file means the lock could be held by
 958     // the old process singleton code. If we can successfully replace the lock,
 959     // continue as normal.
 960     if (base::IsLink(lock_path_) ||
 961         !ReplaceOldSingletonLock(symlink_content, lock_path_)) {
 962       return false;
 963     }
 964 #else
 965     // If we failed to create the lock, most likely another instance won the
 966     // startup race.
 967     return false;
 968 #endif
 969   }
 970
 971   // Create the socket file somewhere in /tmp which is usually mounted as a
 972   // normal filesystem. Some network filesystems (notably AFS) are screwy and
 973   // do not support Unix domain sockets.
 974   if (!socket_dir_.CreateUniqueTempDir()) {
 975     LOG(ERROR) << "Failed to create socket directory.";
 976     return false;
 977   }
 978
 979   // Check that the directory was created with the correct permissions.
 980   int dir_mode = 0;
 981   CHECK(base::GetPosixFilePermissions(socket_dir_.path(), &dir_mode) &&
 982         dir_mode == base::FILE_PERMISSION_USER_MASK)
 983       << "Temp directory mode is not 700: " << std::oct << dir_mode;
 984
 985   // Setup the socket symlink and the two cookies.
 986   base::FilePath socket_target_path =
 987       socket_dir_.path().Append(chrome::kSingletonSocketFilename);
 988   base::FilePath cookie(GenerateCookie());
 989   base::FilePath remote_cookie_path =
 990       socket_dir_.path().Append(chrome::kSingletonCookieFilename);
 991   UnlinkPath(socket_path_);
 992   UnlinkPath(cookie_path_);
 993   if (!SymlinkPath(socket_target_path, socket_path_) ||
 994       !SymlinkPath(cookie, cookie_path_) ||
 995       !SymlinkPath(cookie, remote_cookie_path)) {
 996     // We've already locked things, so we can't have lost the startup race,
 997     // but something doesn't like us.
 998     LOG(ERROR) << "Failed to create symlinks.";
 999     if (!socket_dir_.Delete())
1000       LOG(ERROR) << "Encountered a problem when deleting socket directory.";
1001     return false;
1002   }
1003
1004   SetupSocket(socket_target_path.value(), &sock, &addr);
1005
1006   if (bind(sock, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) < 0) {
1007     PLOG(ERROR) << "Failed to bind() " << socket_target_path.value();
1008     CloseSocket(sock);
1009     return false;
1010   }
1011
1012   if (listen(sock, 5) < 0)
1013     NOTREACHED() << "listen failed: " << safe_strerror(errno);
1014
1015   DCHECK(BrowserThread::IsMessageLoopValid(BrowserThread::IO));
1016   BrowserThread::PostTask(
1017       BrowserThread::IO,
1018       FROM_HERE,
1019       base::Bind(&ProcessSingleton::LinuxWatcher::StartListening,
1020                  watcher_.get(),
1021                  sock));
1022
1023   return true;
1024 }
1025
1026 void ProcessSingleton::Cleanup() {
1027   UnlinkPath(socket_path_);
1028   UnlinkPath(cookie_path_);
1029   UnlinkPath(lock_path_);
1030 }
1031
1032 bool ProcessSingleton::IsSameChromeInstance(pid_t pid) {
1033   pid_t cur_pid = current_pid_;
1034   while (pid != cur_pid) {
1035     pid = base::GetParentProcessId(pid);
1036     if (pid < 0)
1037       return false;
1038     if (!IsChromeProcess(pid))
1039       return false;
1040   }
1041   return true;
1042 }
1043
1044 bool ProcessSingleton::KillProcessByLockPath() {
1045   std::string hostname;
1046   int pid;
1047   ParseLockPath(lock_path_, &hostname, &pid);
1048
1049   if (!hostname.empty() && hostname != net::GetHostName()) {
1050     return DisplayProfileInUseError(lock_path_, hostname, pid);
1051   }
1052   UnlinkPath(lock_path_);
1053
1054   if (IsSameChromeInstance(pid))
1055     return true;
1056
1057   if (pid > 0) {
1058     kill_callback_.Run(pid);
1059     return true;
1060   }
1061
1062   LOG(ERROR) << "Failed to extract pid from path: " << lock_path_.value();
1063   return true;
1064 }
1065
1066 void ProcessSingleton::KillProcess(int pid) {
1067   // TODO(james.su@gmail.com): Is SIGKILL ok?
1068   int rv = kill(static_cast<base::ProcessHandle>(pid), SIGKILL);
1069   // ESRCH = No Such Process (can happen if the other process is already in
1070   // progress of shutting down and finishes before we try to kill it).
1071   DCHECK(rv == 0 || errno == ESRCH) << "Error killing process: "
1072                                     << safe_strerror(errno);
1073 }