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      1 /*
      2  * libjingle
      3  * Copyright 2004--2009, Google Inc.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are met:
      7  *
      8  *  1. Redistributions of source code must retain the above copyright notice,
      9  *     this list of conditions and the following disclaimer.
     10  *  2. Redistributions in binary form must reproduce the above copyright notice,
     11  *     this list of conditions and the following disclaimer in the documentation
     12  *     and/or other materials provided with the distribution.
     13  *  3. The name of the author may not be used to endorse or promote products
     14  *     derived from this software without specific prior written permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 #include "talk/base/posix.h"
     29 
     30 #include <sys/wait.h>
     31 #include <errno.h>
     32 #include <unistd.h>
     33 
     34 #ifdef LINUX
     35 #include "talk/base/linuxfdwalk.h"
     36 #endif
     37 #include "talk/base/logging.h"
     38 
     39 namespace talk_base {
     40 
     41 #ifdef LINUX
     42 static void closefds(void *close_errors, int fd) {
     43   if (fd <= 2) {
     44     // We leave stdin/out/err open to the browser's terminal, if any.
     45     return;
     46   }
     47   if (close(fd) < 0) {
     48     *static_cast<bool *>(close_errors) = true;
     49   }
     50 }
     51 #endif
     52 
     53 enum {
     54   EXIT_FLAG_CHDIR_ERRORS       = 1 << 0,
     55 #ifdef LINUX
     56   EXIT_FLAG_FDWALK_ERRORS      = 1 << 1,
     57   EXIT_FLAG_CLOSE_ERRORS       = 1 << 2,
     58 #endif
     59   EXIT_FLAG_SECOND_FORK_FAILED = 1 << 3,
     60 };
     61 
     62 bool RunAsDaemon(const char *file, const char *const argv[]) {
     63   // Fork intermediate child to daemonize.
     64   pid_t pid = fork();
     65   if (pid < 0) {
     66     LOG_ERR(LS_ERROR) << "fork()";
     67     return false;
     68   } else if (!pid) {
     69     // Child.
     70 
     71     // We try to close all fds and change directory to /, but if that fails we
     72     // keep going because it's not critical.
     73     int exit_code = 0;
     74     if (chdir("/") < 0) {
     75       exit_code |= EXIT_FLAG_CHDIR_ERRORS;
     76     }
     77 #ifdef LINUX
     78     bool close_errors = false;
     79     if (fdwalk(&closefds, &close_errors) < 0) {
     80       exit_code |= EXIT_FLAG_FDWALK_ERRORS;
     81     }
     82     if (close_errors) {
     83       exit_code |= EXIT_FLAG_CLOSE_ERRORS;
     84     }
     85 #endif
     86 
     87     // Fork again to become a daemon.
     88     pid = fork();
     89     // It is important that everything here use _exit() and not exit(), because
     90     // exit() would call the destructors of all global variables in the whole
     91     // process, which is both unnecessary and unsafe.
     92     if (pid < 0) {
     93       exit_code |= EXIT_FLAG_SECOND_FORK_FAILED;
     94       _exit(exit_code);  // if second fork failed
     95     } else if (!pid) {
     96       // Child.
     97       // Successfully daemonized. Run command.
     98       // POSIX requires the args to be typed as non-const for historical
     99       // reasons, but it mandates that the actual implementation be const, so
    100       // the cast is safe.
    101       execvp(file, const_cast<char *const *>(argv));
    102       _exit(255);  // if execvp failed
    103     }
    104 
    105     // Parent.
    106     // Successfully spawned process, but report any problems to the parent where
    107     // we can log them.
    108     _exit(exit_code);
    109   }
    110 
    111   // Parent. Reap intermediate child.
    112   int status;
    113   pid_t child = waitpid(pid, &status, 0);
    114   if (child < 0) {
    115     LOG_ERR(LS_ERROR) << "Error in waitpid()";
    116     return false;
    117   }
    118   if (child != pid) {
    119     // Should never happen (see man page).
    120     LOG(LS_ERROR) << "waitpid() chose wrong child???";
    121     return false;
    122   }
    123   if (!WIFEXITED(status)) {
    124     LOG(LS_ERROR) << "Intermediate child killed uncleanly";  // Probably crashed
    125     return false;
    126   }
    127 
    128   int exit_code = WEXITSTATUS(status);
    129   if (exit_code & EXIT_FLAG_CHDIR_ERRORS) {
    130     LOG(LS_WARNING) << "Child reported probles calling chdir()";
    131   }
    132 #ifdef LINUX
    133   if (exit_code & EXIT_FLAG_FDWALK_ERRORS) {
    134     LOG(LS_WARNING) << "Child reported problems calling fdwalk()";
    135   }
    136   if (exit_code & EXIT_FLAG_CLOSE_ERRORS) {
    137     LOG(LS_WARNING) << "Child reported problems calling close()";
    138   }
    139 #endif
    140   if (exit_code & EXIT_FLAG_SECOND_FORK_FAILED) {
    141     LOG(LS_ERROR) << "Failed to daemonize";
    142     // This means the command was not launched, so failure.
    143     return false;
    144   }
    145   return true;
    146 }
    147 
    148 }  // namespace talk_base
    149