catsit/daemon.c

/* Copyright (C) 2020  C. McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sysexits.h>
#include <unistd.h>

#include "daemon.h"

#ifndef RUNDIR
#define RUNDIR "/var/run"
#endif

#ifndef ETCDIR
#define ETCDIR "/usr/local/etc"
#endif

int restartInterval = 1000;
struct Set256 stopExits;

static void parseExits(char *list) {
	setClear(&stopExits);
	while (*list) {
		byte exit = strtoul(list, &list, 10);
		if (*list) {
			if (*list != ',') errx(EX_USAGE, "invalid exit status %s", list);
			list++;
		}
		setAdd(&stopExits, exit);
	}
}

int main(int argc, char *argv[]) {
	bool daemonize = true;

	const char *pidPath = NULL;
	const char *configPath = ETCDIR "/spawntab";
	const char *fifoPath = RUNDIR "/spawnd.pipe";

	const char *chdirPath = "/";
	const char *user = NULL;
	const char *group = NULL;

	setAdd(&stopExits, 127);
	setAdd(&stopExits, EX_USAGE);
	setAdd(&stopExits, EX_DATAERR);
	setAdd(&stopExits, EX_NOINPUT);
	setAdd(&stopExits, EX_OSFILE);
	setAdd(&stopExits, EX_CANTCREAT);
	setAdd(&stopExits, EX_CONFIG);

	for (int opt; 0 < (opt = getopt(argc, argv, "C:c:df:g:p:s:t:u:"));) {
		switch (opt) {
			break; case 'C': chdirPath = optarg;
			break; case 'c': fifoPath = optarg;
			break; case 'd': daemonize = false;
			break; case 'f': configPath = optarg;
			break; case 'g': group = optarg;
			break; case 'p': pidPath = optarg;
			break; case 's': parseExits(optarg);
			break; case 't': restartInterval = strtoul(optarg, NULL, 10);
			break; case 'u': user = optarg;
			break; default:  return EX_USAGE;
		}
	}

	int pidFile = -1;
	if (pidPath) {
		pidFile = open(
			pidPath, O_WRONLY | O_CREAT | O_EXLOCK | O_CLOEXEC, 0600
		);
		if (pidFile < 0) err(EX_CANTCREAT, "%s", pidPath);
	}

	// TODO: Read config file.
	
	int error = access(chdirPath, X_OK);
	if (error) err(EX_NOINPUT, "%s", chdirPath);

	// TODO: Do user, group lookup.

	// We can't lock a named pipe, so just warn if it already exists.
	error = mkfifo(fifoPath, 0600);
	if (error) {
		if (errno != EEXIST) err(EX_CANTCREAT, "%s", fifoPath);
		warn("%s", fifoPath);
	}

	int fifo = open(fifoPath, O_RDONLY | O_NONBLOCK | O_CLOEXEC);
	if (fifo < 0) err(EX_CANTCREAT, "%s", fifoPath);

	// TODO: Daemonize, write pid file.

	// TODO: Main loop.
	
	close(fifo);
	unlink(fifoPath);
	if (pidPath) {
		close(pidFile);
		unlink(pidPath);
	}
}