chrome/common/multi_process_lock_linux.cc

   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 "chrome/common/multi_process_lock.h"
   6
   7 #include <stdio.h>
   8 #include <sys/socket.h>
   9 #include <sys/un.h>
  10 #include <unistd.h>
  11
  12 #include "base/compiler_specific.h"
  13 #include "base/logging.h"
  14 #include "base/posix/eintr_wrapper.h"
  15
  16 class MultiProcessLockLinux : public MultiProcessLock {
  17  public:
  18   explicit MultiProcessLockLinux(const std::string& name)
  19       : name_(name), fd_(-1) { }
  20
  21   ~MultiProcessLockLinux() override {
  22     if (fd_ != -1) {
  23       Unlock();
  24     }
  25   }
  26
  27   bool TryLock() override {
  28     struct sockaddr_un address;
  29
  30     // +1 for terminator, +1 for 0 in position 0 that makes it an
  31     // abstract named socket.
  32     const size_t max_len = sizeof(address.sun_path) - 2;
  33
  34     if (fd_ != -1) {
  35       DLOG(ERROR) << "MultiProcessLock is already locked - " << name_;
  36       return true;
  37     }
  38
  39     if (name_.length() > max_len) {
  40       LOG(ERROR) << "Socket name too long (" << name_.length()
  41                  << " > " << max_len << ") - " << name_;
  42       return false;
  43     }
  44
  45     memset(&address, 0, sizeof(address));
  46     int print_length = snprintf(&address.sun_path[1],
  47                                 max_len + 1,
  48                                 "%s", name_.c_str());
  49
  50     if (print_length < 0 ||
  51         print_length > static_cast<int>(max_len)) {
  52       PLOG(ERROR) << "Couldn't create sun_path - " << name_;
  53       return false;
  54     }
  55
  56     // Must set the first character of the path to something non-zero
  57     // before we call SUN_LEN which depends on strcpy working.
  58     address.sun_path[0] = '@';
  59     size_t length = SUN_LEN(&address);
  60
  61     // Reset the first character of the path back to zero so that
  62     // bind returns an abstract name socket.
  63     address.sun_path[0] = 0;
  64     address.sun_family = AF_LOCAL;
  65
  66     int socket_fd = socket(AF_LOCAL, SOCK_STREAM, 0);
  67     if (socket_fd < 0) {
  68       PLOG(ERROR) << "Couldn't create socket - " << name_;
  69       return false;
  70     }
  71
  72     if (bind(socket_fd,
  73              reinterpret_cast<sockaddr *>(&address),
  74              length) == 0) {
  75       fd_ = socket_fd;
  76       return true;
  77     } else {
  78       DVLOG(1) << "Couldn't bind socket - "
  79                << &(address.sun_path[1])
  80                << " Length: " << length;
  81       if (IGNORE_EINTR(close(socket_fd)) < 0) {
  82         PLOG(ERROR) << "close";
  83       }
  84       return false;
  85     }
  86   }
  87
  88   void Unlock() override {
  89     if (fd_ == -1) {
  90       DLOG(ERROR) << "Over-unlocked MultiProcessLock - " << name_;
  91       return;
  92     }
  93     if (IGNORE_EINTR(close(fd_)) < 0) {
  94       DPLOG(ERROR) << "close";
  95     }
  96     fd_ = -1;
  97   }
  98
  99  private:
 100   std::string name_;
 101   int fd_;
 102   DISALLOW_COPY_AND_ASSIGN(MultiProcessLockLinux);
 103 };
 104
 105 MultiProcessLock* MultiProcessLock::Create(const std::string &name) {
 106   return new MultiProcessLockLinux(name);
 107 }