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