/* * 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 #include #include #include #include #include #include #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 UNUSED) { 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: 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; } if (fcntl(pipe_fds[1], F_SETFD, fcntl(pipe_fds[1], F_GETFD) | FD_CLOEXEC)) { 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); }