Add simple cron implementation

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>

4 files changed, 272 insertions, 0 deletions

diff --git a/crond/Makemodule.am b/crond/Makemodule.am
new file mode 100644
index 0000000..51960e9
--- /dev/null
+++ b/crond/Makemodule.am
@@ -0,0 +1,9 @@
+if GCROND
+gcrond_SOURCES = crond/main.c crond/gcrond.h crond/runjob.c
+gcrond_CPPFLAGS = $(AM_CPPFLAGS)
+gcrond_CFLAGS = $(AM_CFLAGS)
+gcrond_LDFLAGS = $(AM_LDFLAGS)
+gcrond_LDADD = libcron.a libinit.a libcfg.a
+
+sbin_PROGRAMS += gcrond
+endif
diff --git a/crond/gcrond.h b/crond/gcrond.h
new file mode 100644
index 0000000..4cc2417
--- /dev/null
+++ b/crond/gcrond.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef GCROND_H
+#define GCROND_H
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <errno.h>
+
+#include "crontab.h"
+#include "config.h"
+#include "util.h"
+
+int runjob(crontab_t *tab);
+
+#endif /* GCROND_H */
+
diff --git a/crond/main.c b/crond/main.c
new file mode 100644
index 0000000..d7cc33e
--- /dev/null
+++ b/crond/main.c
@@ -0,0 +1,139 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include "gcrond.h"
+
+static crontab_t *jobs;
+static sig_atomic_t run = 1;
+static sig_atomic_t rescan = 1;
+
+static void read_config(void)
+{
+	if (cronscan(GCRONDIR, &jobs)) {
+		fputs("Error reading configuration. Continuing anyway.\n",
+		      stderr);
+	}
+}
+
+static void cleanup_config(void)
+{
+	crontab_t *t;
+
+	while (jobs != NULL) {
+		t = jobs;
+		jobs = jobs->next;
+		delcron(t);
+	}
+}
+
+static int calc_timeout(void)
+{
+	time_t now = time(NULL), future;
+	struct tm tmstruct;
+	crontab_t mask, *t;
+	int minutes;
+
+	for (minutes = 0; minutes < 120; ++minutes) {
+		future = now + minutes * 60;
+
+		localtime_r(&future, &tmstruct);
+		cron_tm_to_mask(&mask, &tmstruct);
+
+		for (t = jobs; t != NULL; t = t->next) {
+			if (cron_should_run(t, &mask))
+				goto out;
+		}
+	}
+out:
+	return minutes ? minutes * 60 : 60;
+}
+
+static void runjobs(void)
+{
+	time_t now = time(NULL);
+	struct tm tmstruct;
+	crontab_t mask, *t;
+
+	localtime_r(&now, &tmstruct);
+	cron_tm_to_mask(&mask, &tmstruct);
+
+	for (t = jobs; t != NULL; t = t->next) {
+		if (cron_should_run(t, &mask))
+			runjob(t);
+	}
+}
+
+static void sighandler(int signo)
+{
+	switch (signo) {
+	case SIGINT:
+	case SIGTERM:
+		run = 0;
+		break;
+	case SIGHUP:
+		rescan = 1;
+		break;
+	}
+}
+
+int main(void)
+{
+	struct timespec stime;
+	struct sigaction act;
+	crontab_t *t;
+	int timeout;
+	pid_t pid;
+
+	memset(&act, 0, sizeof(act));
+	act.sa_handler = sighandler;
+	sigaction(SIGINT, &act, NULL);
+	sigaction(SIGTERM, &act, NULL);
+	sigaction(SIGHUP, &act, NULL);
+
+	while (run) {
+		if (rescan == 1) {
+			cleanup_config();
+			read_config();
+			timeout = 60;
+			rescan = 0;
+		} else {
+			runjobs();
+			timeout = calc_timeout();
+		}
+
+		stime.tv_sec = timeout;
+		stime.tv_nsec = 0;
+
+		while (nanosleep(&stime, &stime) != 0 && run && !rescan) {
+			if (errno != EINTR) {
+				perror("nanosleep");
+				break;
+			}
+		}
+
+		while ((pid = waitpid(-1, NULL, WNOHANG)) != -1) {
+			for (t = jobs; t != NULL; t = t->next) {
+				if (t->pid == pid) {
+					t->pid = -1;
+					break;
+				}
+			}
+		}
+	}
+
+	return EXIT_SUCCESS;
+}
diff --git a/crond/runjob.c b/crond/runjob.c
new file mode 100644
index 0000000..7650748
--- /dev/null
+++ b/crond/runjob.c
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#include "gcrond.h"
+
+int runjob(crontab_t *tab)
+{
+	struct sigaction act;
+	pid_t pid;
+	exec_t *e;
+	int ret;
+
+	if (tab->exec == NULL)
+		return 0;
+
+	pid = fork();
+	if (pid == -1) {
+		perror("fork");
+		return -1;
+	}
+
+	if (pid != 0) {
+		tab->pid = pid;
+		return 0;
+	}
+
+	/* XXX: inside the child process */
+	memset(&act, 0, sizeof(act));
+	act.sa_handler = SIG_DFL;
+	sigaction(SIGINT, &act, NULL);
+	sigaction(SIGTERM, &act, NULL);
+	sigaction(SIGHUP, &act, NULL);
+
+	if (setup_tty(tab->ctty, tab->tty_truncate))
+		exit(EXIT_FAILURE);
+
+	if (tab->gid != 0) {
+		if (setresgid(tab->gid, tab->gid, tab->gid)) {
+			perror("setgid");
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	if (tab->uid != 0) {
+		if (setresuid(tab->uid, tab->uid, tab->uid)) {
+			perror("setuid");
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	if (tab->exec->next == NULL)
+		argv_exec(tab->exec);
+
+	for (e = tab->exec; e != NULL; e = e->next) {
+		pid = fork();
+		if (pid == -1) {
+			perror("fork");
+			exit(EXIT_FAILURE);
+		}
+
+		if (pid == 0)
+			argv_exec(e);
+
+		while (waitpid(pid, &ret, 0) != pid)
+			;
+
+		ret = WIFEXITED(ret) ? WEXITSTATUS(ret) : EXIT_FAILURE;
+		if (ret != EXIT_SUCCESS)
+			break;
+	}
+
+	exit(ret);
+}