transmission/libtransmission/subprocess-posix.c

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/*
* This file Copyright (C) 2010-2017 Mnemosyne LLC
*
* It may be used under the GNU GPL versions 2 or 3
* or any future license endorsed by Mnemosyne LLC.
*
*/
#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "transmission.h"
#include "error.h"
#include "subprocess.h"
#include "tr-assert.h"
#include "tr-macros.h"
#include "utils.h"
static void handle_sigchld(int i)
{
TR_UNUSED(i);
int rc;
do
{
/* FIXME: Only check for our own PIDs */
rc = waitpid(-1, NULL, WNOHANG);
} while (rc > 0 || (rc == -1 && errno == EINTR));
/* FIXME: Call old handler, if any */
}
static void set_system_error(tr_error** error, int code, char const* what)
{
if (error == NULL)
{
return;
}
if (what == NULL)
{
tr_error_set_literal(error, code, tr_strerror(code));
}
else
{
tr_error_set(error, code, "%s failed: %s", what, tr_strerror(code));
}
}
static bool tr_spawn_async_in_child(char* const* cmd, char* const* env, char const* work_dir, int pipe_fd)
{
if (env != NULL)
{
for (size_t i = 0; env[i] != NULL; ++i)
{
if (putenv(env[i]) != 0)
{
goto FAIL;
}
}
}
if (work_dir != NULL && chdir(work_dir) == -1)
{
goto FAIL;
}
if (execvp(cmd[0], cmd) == -1)
{
goto FAIL;
}
return true;
FAIL:
(void)write(pipe_fd, &errno, sizeof(errno));
return false;
}
static bool tr_spawn_async_in_parent(int pipe_fd, tr_error** error)
{
int child_errno;
ssize_t count;
TR_STATIC_ASSERT(sizeof(child_errno) == sizeof(errno), "");
do
{
count = read(pipe_fd, &child_errno, sizeof(child_errno));
} while (count == -1 && errno == EINTR);
close(pipe_fd);
if (count == -1)
{
/* Read failed (what to do?) */
}
else if (count == 0)
{
/* Child successfully exec-ed */
}
else
{
TR_ASSERT((size_t)count == sizeof(child_errno));
set_system_error(error, child_errno, "Child process setup");
return false;
}
return true;
}
bool tr_spawn_async(char* const* cmd, char* const* env, char const* work_dir, tr_error** error)
{
static bool sigchld_handler_set = false;
if (!sigchld_handler_set)
{
/* FIXME: "The effects of signal() in a multithreaded process are unspecified." (c) man 2 signal */
if (signal(SIGCHLD, &handle_sigchld) == SIG_ERR)
{
set_system_error(error, errno, "Call to signal()");
return false;
}
sigchld_handler_set = true;
}
int pipe_fds[2];
if (pipe(pipe_fds) == -1)
{
set_system_error(error, errno, "Call to pipe()");
return false;
}
2019-07-14 12:40:41 +00:00
if (fcntl(pipe_fds[1], F_SETFD, fcntl(pipe_fds[1], F_GETFD) | FD_CLOEXEC) == -1)
{
set_system_error(error, errno, "Call to fcntl()");
close(pipe_fds[0]);
close(pipe_fds[1]);
return false;
}
int const child_pid = fork();
if (child_pid == -1)
{
set_system_error(error, errno, "Call to fork()");
return false;
}
if (child_pid == 0)
{
close(pipe_fds[0]);
if (!tr_spawn_async_in_child(cmd, env, work_dir, pipe_fds[1]))
{
_exit(0);
}
}
close(pipe_fds[1]);
return tr_spawn_async_in_parent(pipe_fds[0], error);
}