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Diffstat (limited to 'nslcd/daemonize.c')
| -rw-r--r-- | nslcd/daemonize.c | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/nslcd/daemonize.c b/nslcd/daemonize.c new file mode 100644 index 0000000..c9fb5e4 --- /dev/null +++ b/nslcd/daemonize.c @@ -0,0 +1,191 @@ +/* + daemoninze.c - functions for properly daemonising an application + + Copyright (C) 2014 Arthur de Jong + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + This library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with this library; if not, write to the Free Software + Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + 02110-1301 USA +*/ + +#include "config.h" + +#include <unistd.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <string.h> +#include <errno.h> +#include <stdio.h> +#include <stdlib.h> + +#include "daemonize.h" + +/* the write end of a pipe that is used to signal the fact that the child + process has finished initialising (see daemonize_daemon() and + daemonize_ready() for details) */ +static int daemonizefd = -1; + +void daemonize_closefds(void) +{ + int i; + /* close all file descriptors (except stdin/out/err) */ + i = sysconf(_SC_OPEN_MAX) - 1; + /* if the system does not have OPEN_MAX just close the first 32 and + hope we closed enough */ + if (i < 0) + i = 32; + for (; i > 3; i--) + close(i); +} + +void daemonize_redirect_stdio(void) +{ + /* close stdin, stdout and stderr */ + close(0); /* stdin */ + close(1); /* stdout */ + close(2); /* stderr */ + /* reconnect to /dev/null */ + open("/dev/null", O_RDWR); /* stdin, fd=0 */ + dup(0); /* stdout, fd=1 */ + dup(0); /* stderr, fd=2 */ +} + +/* try to fill the buffer until EOF or error */ +static int read_response(int fd, char *buffer, size_t bufsz) +{ + int rc; + size_t r = 0; + while (r < bufsz) + { + rc = read(fd, buffer + r, bufsz - r); + if (rc == 0) + break; + else if (rc > 0) + r += rc; + else if ((errno == EINTR) || (errno == EAGAIN)) + continue; /* ignore these errors and try again */ + else + return -1; + } + return r; +} + +/* ihe process calling daemonize_daemon() will end up here on success */ +static int wait_for_response(int fd) +{ + int i, l, rc; + char buffer[1024]; + /* read return code */ + i = read_response(fd, (void *)&rc, sizeof(int)); + if (i != sizeof(int)) + return -1; + /* read string length */ + i = read_response(fd, (void *)&l, sizeof(int)); + if ((i != sizeof(int)) || (l <= 0)) + _exit(rc); + /* read string */ + if ((size_t)l > (sizeof(buffer) - 1)) + l = sizeof(buffer) - 1; + i = read_response(fd, buffer, l); + buffer[sizeof(buffer) - 1] = '\0'; + if (i == l) + fprintf(stderr, "%s", buffer); + _exit(rc); +} + +int daemonize_daemon(void) +{ + int pipefds[2]; + int i; + /* set up a pipe for communication */ + if (pipe(pipefds) < 0) + return -1; + /* set O_NONBLOCK on the write end to ensure that a call to + daemonize_ready() will not lock the application */ + if ((i = fcntl(pipefds[1], F_GETFL, 0)) < 0) + { + close(pipefds[0]); + close(pipefds[1]); + return -1; + } + if (fcntl(pipefds[1], F_SETFL, i | O_NONBLOCK) < 0) + { + close(pipefds[0]); + close(pipefds[1]); + return -1; + } + /* fork() and exit() to detach from the parent process */ + switch (fork()) + { + case 0: + /* we are the child, close read end of pipe */ + close(pipefds[0]); + break; + case -1: + /* we are the parent, but have an error */ + close(pipefds[0]); + close(pipefds[1]); + return -1; + default: + /* we are the parent, close write end and wait for information */ + close(pipefds[1]); + return wait_for_response(pipefds[0]); + } + /* become process leader */ + if (setsid() < 0) + { + close(pipefds[1]); + _exit(EXIT_FAILURE); + } + /* fork again so we cannot allocate a pty */ + switch (fork()) + { + case 0: + /* we are the child */ + break; + case -1: + /* we are the parent, but have an error */ + close(pipefds[1]); + _exit(EXIT_FAILURE); + default: + /* we are the parent and we're done */ + close(pipefds[1]); + _exit(EXIT_SUCCESS); + } + daemonizefd = pipefds[1]; + return 0; +} + +void daemonize_ready(int status, const char *message) +{ + if (daemonizefd >= 0) + { + /* we ignore any errors writing */ + write(daemonizefd, &status, sizeof(int)); + if ((message == NULL) || (message[0] == '\0')) + { + status = 0; + write(daemonizefd, &status, sizeof(int)); + } + else + { + status = strlen(message); + write(daemonizefd, &status, sizeof(int)); + write(daemonizefd, message, status); + } + close(daemonizefd); + daemonizefd = -1; + } +} |