nut-debian/server/upsd.c

/* upsd.c - watches ups state files and answers queries

   Copyright (C)
	1999		Russell Kroll <rkroll@exploits.org>
	2008		Arjen de Korte <adkorte-guest@alioth.debian.org>
	2011 - 2012	Arnaud Quette <arnaud.quette.free.fr>
	2019 		Eaton (author: Arnaud Quette <ArnaudQuette@eaton.com>)

   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 2 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, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/

#include "config.h"	/* must be the first header */

#include "upsd.h"
#include "upstype.h"
#include "conf.h"

#include "netcmds.h"
#include "upsconf.h"

#include <sys/un.h>
#include <sys/socket.h>
#include <netdb.h>

#ifdef HAVE_SYS_SIGNAL_H
#include <sys/signal.h>
#endif
#ifdef HAVE_SIGNAL_H
#include <signal.h>
#endif

#include "user.h"
#include "nut_ctype.h"
#include "nut_stdint.h"
#include "stype.h"
#include "netssl.h"
#include "sstate.h"
#include "desc.h"
#include "neterr.h"

#ifdef HAVE_WRAP
#include <tcpd.h>
int	allow_severity = LOG_INFO;
int	deny_severity = LOG_WARNING;
#endif	/* HAVE_WRAP */

/* externally-visible settings and pointers */

upstype_t	*firstups = NULL;

/* default 15 seconds before data is marked stale */
int	maxage = 15;

/* default to 1h before cleaning up status tracking entries */
int	tracking_delay = 3600;

/*
 * Preloaded to ALLOW_NO_DEVICE from upsd.conf or environment variable
 * (with higher prio for envvar); defaults to disabled for legacy compat.
 */
int allow_no_device = 0;

/* preloaded to {OPEN_MAX} in main, can be overridden via upsd.conf */
nfds_t	maxconn = 0;

/* preloaded to STATEPATH in main, can be overridden via upsd.conf */
char	*statepath = NULL;

/* preloaded to DATADIR in main, can be overridden via upsd.conf */
char	*datapath = NULL;

/* everything else */
static const char	*progname;

nut_ctype_t	*firstclient = NULL;
/* static nut_ctype_t	*lastclient = NULL; */

/* default is to listen on all local interfaces */
static stype_t	*firstaddr = NULL;

static int 	opt_af = AF_UNSPEC;

typedef enum {
	DRIVER = 1,
	CLIENT,
	SERVER
} handler_type_t;

typedef struct {
	handler_type_t	type;
	void		*data;
} handler_t;


/* Commands and settings status tracking */

/* general enable/disable status info for commands and settings
 * (disabled by default)
 * Note that only client that requested it will have it enabled
 * (see nut_ctype.h) */
static int	tracking_enabled = 0;

/* Commands and settings status tracking structure */
typedef struct tracking_s {
	char	*id;
	int	status;
	time_t	request_time; /* for cleanup */
	/* doubly linked list */
	struct tracking_s	*prev;
	struct tracking_s	*next;
} tracking_t;

static tracking_t	*tracking_list = NULL;


	/* pollfd  */
static struct pollfd	*fds = NULL;
static handler_t	*handler = NULL;

	/* pid file */
static char	pidfn[SMALLBUF];

	/* set by signal handlers */
static int	reload_flag = 0, exit_flag = 0;

/* Minimalistic support for UUID v4 */
/* Ref: RFC 4122 https://tools.ietf.org/html/rfc4122#section-4.1.2 */
#define UUID4_BYTESIZE 16


static const char *inet_ntopW (struct sockaddr_storage *s)
{
	static char str[40];

	switch (s->ss_family)
	{
	case AF_INET:
		return inet_ntop (AF_INET, &(((struct sockaddr_in *)s)->sin_addr), str, 16);
	case AF_INET6:
		return inet_ntop (AF_INET6, &(((struct sockaddr_in6 *)s)->sin6_addr), str, 40);
	default:
		errno = EAFNOSUPPORT;
		return NULL;
	}
}

/* return a pointer to the named ups if possible */
upstype_t *get_ups_ptr(const char *name)
{
	upstype_t	*tmp;

	if (!name) {
		return NULL;
	}

	for (tmp = firstups; tmp; tmp = tmp->next) {
		if (!strcasecmp(tmp->name, name)) {
			return tmp;
		}
	}

	return NULL;
}

/* mark the data stale if this is new, otherwise cleanup any remaining junk */
static void ups_data_stale(upstype_t *ups)
{
	/* don't complain again if it's already known to be stale */
	if (ups->stale == 1) {
		return;
	}

	ups->stale = 1;

	upslogx(LOG_NOTICE, "Data for UPS [%s] is stale - check driver", ups->name);
}

/* mark the data ok if this is new, otherwise do nothing */
static void ups_data_ok(upstype_t *ups)
{
	if (ups->stale == 0) {
		return;
	}

	ups->stale = 0;

	upslogx(LOG_NOTICE, "UPS [%s] data is no longer stale", ups->name);
}

/* add another listening address */
void listen_add(const char *addr, const char *port)
{
	stype_t	*server;

	/* don't change listening addresses on reload */
	if (reload_flag) {
		return;
	}

	/* grab some memory and add the info */
	server = xcalloc(1, sizeof(*server));
	server->addr = xstrdup(addr);
	server->port = xstrdup(port);
	server->sock_fd = -1;
	server->next = firstaddr;

	firstaddr = server;

	upsdebugx(3, "listen_add: added %s:%s", server->addr, server->port);
}

/* create a listening socket for tcp connections */
static void setuptcp(stype_t *server)
{
	struct addrinfo		hints, *res, *ai;
	int	v = 0, one = 1;

	upsdebugx(3, "setuptcp: try to bind to %s port %s", server->addr, server->port);

	memset(&hints, 0, sizeof(hints));
	hints.ai_flags		= AI_PASSIVE;
	hints.ai_family		= opt_af;
	hints.ai_socktype	= SOCK_STREAM;
	hints.ai_protocol	= IPPROTO_TCP;

	if ((v = getaddrinfo(server->addr, server->port, &hints, &res)) != 0) {
		if (v == EAI_SYSTEM) {
			fatal_with_errno(EXIT_FAILURE, "getaddrinfo");
		}

		fatalx(EXIT_FAILURE, "getaddrinfo: %s", gai_strerror(v));
	}

	for (ai = res; ai; ai = ai->ai_next) {
		int sock_fd;

		if ((sock_fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol)) < 0) {
			upsdebug_with_errno(3, "setuptcp: socket");
			continue;
		}

		if (setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, (void *)&one, sizeof(one)) != 0) {
			fatal_with_errno(EXIT_FAILURE, "setuptcp: setsockopt");
		}

		if (bind(sock_fd, ai->ai_addr, ai->ai_addrlen) < 0) {
			upsdebug_with_errno(3, "setuptcp: bind");
			close(sock_fd);
			continue;
		}

		if ((v = fcntl(sock_fd, F_GETFL, 0)) == -1) {
			fatal_with_errno(EXIT_FAILURE, "setuptcp: fcntl(get)");
		}

		if (fcntl(sock_fd, F_SETFL, v | O_NDELAY) == -1) {
			fatal_with_errno(EXIT_FAILURE, "setuptcp: fcntl(set)");
		}

		if (listen(sock_fd, 16) < 0) {
			upsdebug_with_errno(3, "setuptcp: listen");
			close(sock_fd);
			continue;
		}

		server->sock_fd = sock_fd;
		break;
	}

	freeaddrinfo(res);

	/* leave up to the caller, server_load(), to fail silently if there is
	 * no other valid LISTEN interface */
	if (server->sock_fd < 0) {
		upslogx(LOG_ERR, "not listening on %s port %s", server->addr, server->port);
	} else {
		upslogx(LOG_INFO, "listening on %s port %s", server->addr, server->port);
	}

	return;
}

/* decrement the login counter for this ups */
static void declogins(const char *upsname)
{
	upstype_t	*ups;

	ups = get_ups_ptr(upsname);

	if (!ups) {
		upslogx(LOG_INFO, "Tried to decrement invalid ups name (%s)", upsname);
		return;
	}

	ups->numlogins--;

	if (ups->numlogins < 0) {
		upslogx(LOG_ERR, "Programming error: UPS [%s] has numlogins=%d", ups->name, ups->numlogins);
	}
}

/* disconnect a client connection and free all related memory */
static void client_disconnect(nut_ctype_t *client)
{
	if (!client) {
		return;
	}

	upsdebugx(2, "Disconnect from %s", client->addr);

	shutdown(client->sock_fd, 2);
	close(client->sock_fd);

	if (client->loginups) {
		declogins(client->loginups);
	}

	ssl_finish(client);

	pconf_finish(&client->ctx);

	if (client->prev) {
		client->prev->next = client->next;
	} else {
		/* deleting first entry */
		firstclient = client->next;
	}

	if (client->next) {
		client->next->prev = client->prev;
	} else {
		/* deleting last entry */
		/* lastclient = client->prev; */
	}

	free(client->addr);
	free(client->loginups);
	free(client->password);
	free(client->username);
	free(client);

	return;
}

/* send the buffer <sendbuf> of length <sendlen> to host <dest>
 * returns effectively a boolean: 0 = failed, 1 = sent ok
 */
int sendback(nut_ctype_t *client, const char *fmt, ...)
{
	ssize_t	res;
	size_t	len;
	char	ans[NUT_NET_ANSWER_MAX+1];
	va_list	ap;

	if (!client) {
		return 0;
	}

	va_start(ap, fmt);
	vsnprintf(ans, sizeof(ans), fmt, ap);
	va_end(ap);

	len = strlen(ans);

	/* System write() and our ssl_write() have a loophole that they write a
	 * size_t amount of bytes and upon success return that in ssize_t value
	 */
	assert(len < SSIZE_MAX);

#ifdef WITH_SSL
	if (client->ssl) {
		res = ssl_write(client, ans, len);
	} else
#endif /* WITH_SSL */
	{
		res = write(client->sock_fd, ans, len);
	}

	upsdebugx(2, "write: [destfd=%d] [len=%zu] [%s]", client->sock_fd, len, str_rtrim(ans, '\n'));

	if (res < 0 || len != (size_t)res) {
		upslog_with_errno(LOG_NOTICE, "write() failed for %s", client->addr);
		client->last_heard = 0;
		return 0;	/* failed */
	}

	return 1;	/* OK */
}

/* just a simple wrapper for now */
int send_err(nut_ctype_t *client, const char *errtype)
{
	if (!client) {
		return -1;
	}

	upsdebugx(4, "Sending error [%s] to client %s", errtype, client->addr);

	return sendback(client, "ERR %s\n", errtype);
}

/* disconnect anyone logged into this UPS */
void kick_login_clients(const char *upsname)
{
	nut_ctype_t	*client, *cnext;

	for (client = firstclient; client; client = cnext) {

		cnext = client->next;

		/* if it's not logged in, don't check it */
		if (!client->loginups) {
			continue;
		}

		if (!strcmp(client->loginups, upsname)) {
			upslogx(LOG_INFO, "Kicking client %s (was on UPS [%s])\n", client->addr, upsname);
			client_disconnect(client);
		}
	}
}

/* make sure a UPS is sane - connected, with fresh data */
int ups_available(const upstype_t *ups, nut_ctype_t *client)
{
	if (ups->sock_fd < 0) {
		send_err(client, NUT_ERR_DRIVER_NOT_CONNECTED);
		return 0;
	}

	if (ups->stale) {
		send_err(client, NUT_ERR_DATA_STALE);
		return 0;
	}

	/* must be OK */
	return 1;
}

/* check flags and access for an incoming command from the network */
static void check_command(int cmdnum, nut_ctype_t *client, size_t numarg,
	const char **arg)
{
	upsdebugx(6, "Entering %s: %s", __func__, numarg > 0 ? arg[0] : "<>");

	if (netcmds[cmdnum].flags & FLAG_USER) {
		/* command requires previous authentication */
#ifdef HAVE_WRAP
		struct request_info	req;
#endif	/* HAVE_WRAP */

		if (!client->username) {
			upsdebugx(1, "%s: client not logged in yet", __func__);
			send_err(client, NUT_ERR_USERNAME_REQUIRED);
			return;
		}

		if (!client->password) {
			upsdebugx(1, "%s: client not logged in yet", __func__);
			send_err(client, NUT_ERR_PASSWORD_REQUIRED);
			return;
		}

#ifdef HAVE_WRAP
		request_init(&req, RQ_DAEMON, progname, RQ_FILE, client->sock_fd, RQ_USER, client->username, 0);
		fromhost(&req);

		if (!hosts_access(&req)) {
			upsdebugx(1,
				"%s: while authenticating %s found that "
				"tcp-wrappers says access should be denied",
				__func__, client->username);
			send_err(client, NUT_ERR_ACCESS_DENIED);
			return;
		}
#endif	/* HAVE_WRAP */
	}

	upsdebugx(6, "%s: Calling command handler for %s", __func__, numarg > 0 ? arg[0] : "<>");

	/* looks good - call the command */
	netcmds[cmdnum].func(client, (numarg < 2) ? 0 : (numarg - 1), (numarg > 1) ? &arg[1] : NULL);
}

/* parse requests from the network */
static void parse_net(nut_ctype_t *client)
{
	int	i;

	/* shouldn't happen */
	if (client->ctx.numargs < 1) {
		send_err(client, NUT_ERR_UNKNOWN_COMMAND);
		return;
	}

	for (i = 0; netcmds[i].name; i++) {
		if (!strcasecmp(netcmds[i].name, client->ctx.arglist[0])) {
			check_command(i, client, client->ctx.numargs, (const char **) client->ctx.arglist);
			return;
		}
	}

	/* fallthrough = not matched by any entry in netcmds */

	send_err(client, NUT_ERR_UNKNOWN_COMMAND);
}

/* answer incoming tcp connections */
static void client_connect(stype_t *server)
{
	struct	sockaddr_storage csock;
#if defined(__hpux) && !defined(_XOPEN_SOURCE_EXTENDED)
	int	clen;
#else
	socklen_t	clen;
#endif
	int		fd;
	nut_ctype_t		*client;

	clen = sizeof(csock);
	fd = accept(server->sock_fd, (struct sockaddr *) &csock, &clen);

	if (fd < 0) {
		return;
	}

	client = xcalloc(1, sizeof(*client));

	client->sock_fd = fd;

	time(&client->last_heard);

	client->addr = xstrdup(inet_ntopW(&csock));

	client->tracking = 0;

	pconf_init(&client->ctx, NULL);

	if (firstclient) {
		firstclient->prev = client;
		client->next = firstclient;
	}

	firstclient = client;

/*
	if (lastclient) {
		client->prev = lastclient;
		lastclient->next = client;
	}

	lastclient = client;
 */
	upsdebugx(2, "Connect from %s", client->addr);
}

/* read tcp messages and handle them */
static void client_readline(nut_ctype_t *client)
{
	char	buf[SMALLBUF];
	int	i;
	ssize_t	ret;

#ifdef WITH_SSL
	if (client->ssl) {
		ret = ssl_read(client, buf, sizeof(buf));
	} else
#endif /* WITH_SSL */
	{
		ret = read(client->sock_fd, buf, sizeof(buf));
	}

	if (ret < 0) {
		upsdebug_with_errno(2, "Disconnect %s (read failure)", client->addr);
		client_disconnect(client);
		return;
	}

	if (ret == 0) {
		upsdebugx(2, "Disconnect %s (no data available)", client->addr);
		client_disconnect(client);
		return;
	}

	/* fragment handling code */
	for (i = 0; i < ret; i++) {

		/* add to the receive queue one by one */
		switch (pconf_char(&client->ctx, buf[i]))
		{
		case 1:
			time(&client->last_heard);	/* command received */
			parse_net(client);
			continue;

		case 0:
			continue;	/* haven't gotten a line yet */

		default:
			/* parse error */
			upslogx(LOG_NOTICE, "Parse error on sock: %s", client->ctx.errmsg);
			return;
		}
	}

	return;
}

void server_load(void)
{
	stype_t	*server;

	/* default behaviour if no LISTEN addres has been specified */
	if (!firstaddr) {
		if (opt_af != AF_INET) {
			listen_add("::1", string_const(PORT));
		}

		if (opt_af != AF_INET6) {
			listen_add("127.0.0.1", string_const(PORT));
		}
	}

	for (server = firstaddr; server; server = server->next) {
		setuptcp(server);
	}

	/* check if we have at least 1 valid LISTEN interface */
	if (firstaddr->sock_fd < 0) {
		fatalx(EXIT_FAILURE, "no listening interface available");
	}
}

void server_free(void)
{
	stype_t	*server, *snext;

	/* cleanup server fds */
	for (server = firstaddr; server; server = snext) {
		snext = server->next;

		if (server->sock_fd != -1) {
			close(server->sock_fd);
		}

		free(server->addr);
		free(server->port);
		free(server);
	}

	firstaddr = NULL;
}

static void client_free(void)
{
	nut_ctype_t		*client, *cnext;

	/* cleanup client fds */
	for (client = firstclient; client; client = cnext) {
		cnext = client->next;
		client_disconnect(client);
	}
}

static void driver_free(void)
{
	upstype_t	*ups, *unext;

	for (ups = firstups; ups; ups = unext) {
		upsdebugx(1, "%s: forgetting UPS [%s] (FD %d)",
			__func__, ups->name, ups->sock_fd);

		unext = ups->next;

		if (ups->sock_fd != -1) {
			close(ups->sock_fd);
		}

		sstate_infofree(ups);
		sstate_cmdfree(ups);

		pconf_finish(&ups->sock_ctx);

		free(ups->fn);
		free(ups->name);
		free(ups->desc);
		free(ups);
	}
}

static void upsd_cleanup(void)
{
	if (strlen(pidfn) > 0) {
		unlink(pidfn);
	}

	/* dump everything */

	user_flush();
	desc_free();

	server_free();
	client_free();
	driver_free();
	tracking_free();

	free(statepath);
	free(datapath);
	free(certfile);
	free(certname);
	free(certpasswd);

	free(fds);
	free(handler);
}

static void poll_reload(void)
{
	long	ret;

	ret = sysconf(_SC_OPEN_MAX);

	if ((intmax_t)ret < (intmax_t)maxconn) {
		fatalx(EXIT_FAILURE,
			"Your system limits the maximum number of connections to %ld\n"
			"but you requested %jd. The server won't start until this\n"
			"problem is resolved.\n", ret, (intmax_t)maxconn);
	}

	if (1 > maxconn) {
		fatalx(EXIT_FAILURE,
			"You requested %jd as maximum number of connections.\n"
			"The server won't start until this problem is resolved.\n", (intmax_t)maxconn);
	}

	/* How many items can we stuff into the array? */
	size_t maxalloc = SIZE_MAX / sizeof(void *);
	if ((uintmax_t)maxalloc < (uintmax_t)maxconn) {
		fatalx(EXIT_FAILURE,
			"You requested %jd as maximum number of connections, but we can only allocate %zu.\n"
			"The server won't start until this problem is resolved.\n", (intmax_t)maxconn, maxalloc);
	}

	/* The checks above effectively limit that maxconn is in size_t range */
	fds = xrealloc(fds, (size_t)maxconn * sizeof(*fds));
	handler = xrealloc(handler, (size_t)maxconn * sizeof(*handler));
}

/* instant command and setvar status tracking */

/* allocate a new status tracking entry */
int tracking_add(const char *id)
{
	tracking_t	*item;

	if ((!tracking_enabled) || (!id))
		return 0;

	item = xcalloc(1, sizeof(*item));

	item->id = xstrdup(id);
	item->status = STAT_PENDING;
	time(&item->request_time);

	if (tracking_list) {
		tracking_list->prev = item;
		item->next = tracking_list;
	}

	tracking_list = item;

	return 1;
}

/* set status of a specific tracking entry */
int tracking_set(const char *id, const char *value)
{
	tracking_t	*item, *next_item;

	/* sanity checks */
	if ((!tracking_list) || (!id) || (!value))
		return 0;

	for (item = tracking_list; item; item = next_item) {

		next_item = item->next;

		if (!strcasecmp(item->id, id)) {
			item->status = atoi(value);
			return 1;
		}
	}

	return 0; /* id not found! */
}

/* free a specific tracking entry */
int tracking_del(const char *id)
{
	tracking_t	*item, *next_item;

	/* sanity check */
	if ((!tracking_list) || (!id))
		return 0;

	upsdebugx(3, "%s: deleting id %s", __func__, id);

	for (item = tracking_list; item; item = next_item) {

		next_item = item->next;

		if (strcasecmp(item->id, id))
			continue;

		if (item->prev)
			item->prev->next = item->next;
		else
			/* deleting first entry */
			tracking_list = item->next;

		if (item->next)
			item->next->prev = item->prev;

		free(item->id);
		free(item);

		return 1;

	}

	return 0; /* id not found! */
}

/* free all status tracking entries */
void tracking_free(void)
{
	tracking_t	*item, *next_item;

	/* sanity check */
	if (!tracking_list)
		return;

	upsdebugx(3, "%s", __func__);

	for (item = tracking_list; item; item = next_item) {
		next_item = item->next;
		tracking_del(item->id);
	}
}

/* cleanup status tracking entries according to their age and tracking_delay */
void tracking_cleanup(void)
{
	tracking_t	*item, *next_item;
	time_t	now;

	/* sanity check */
	if (!tracking_list)
		return;

	time(&now);

	upsdebugx(3, "%s", __func__);

	for (item = tracking_list; item; item = next_item) {

		next_item = item->next;

		if (difftime(now, item->request_time) > tracking_delay) {
			tracking_del(item->id);
		}
	}
}

/* get status of a specific tracking entry */
char *tracking_get(const char *id)
{
	tracking_t	*item, *next_item;

	/* sanity checks */
	if ((!tracking_list) || (!id))
		return "ERR UNKNOWN";

	for (item = tracking_list; item; item = next_item) {

		next_item = item->next;

		if (strcasecmp(item->id, id))
			continue;

		switch (item->status)
		{
		case STAT_PENDING:
			return "PENDING";
		case STAT_HANDLED:
			return "SUCCESS";
		case STAT_UNKNOWN:
			return "ERR UNKNOWN";
		case STAT_INVALID:
			return "ERR INVALID-ARGUMENT";
		case STAT_FAILED:
			return "ERR FAILED";
		}
	}

	return "ERR UNKNOWN"; /* id not found! */
}

/* enable general status tracking (tracking_enabled) and return its value (1). */
int tracking_enable(void)
{
	tracking_enabled = 1;

	return tracking_enabled;
}

/* disable general status tracking only if no client use it anymore.
 * return the new value for tracking_enabled */
int tracking_disable(void)
{
	nut_ctype_t		*client, *cnext;

	for (client = firstclient; client; client = cnext) {
		cnext = client->next;
		if (client->tracking == 1)
			return 1;
	}
	return 0;
}

/* return current general status of tracking (tracking_enabled). */
int tracking_is_enabled(void)
{
	return tracking_enabled;
}

/* UUID v4 basic implementation
 * Note: 'dest' must be at least `UUID4_LEN` long */
int nut_uuid_v4(char *uuid_str)
{
	size_t		i;
	uint8_t nut_uuid[UUID4_BYTESIZE];

	if (!uuid_str)
		return 0;

	for (i = 0; i < UUID4_BYTESIZE; i++)
		nut_uuid[i] = (uint8_t)rand() + (uint8_t)rand();

	/* set variant and version */
	nut_uuid[6] = (nut_uuid[6] & 0x0F) | 0x40;
	nut_uuid[8] = (nut_uuid[8] & 0x3F) | 0x80;

	return snprintf(uuid_str, UUID4_LEN,
		"%02X%02X%02X%02X-%02X%02X-%02X%02X-%02X%02X-%02X%02X%02X%02X%02X%02X",
		nut_uuid[0], nut_uuid[1], nut_uuid[2], nut_uuid[3],
		nut_uuid[4], nut_uuid[5], nut_uuid[6], nut_uuid[7],
		nut_uuid[8], nut_uuid[9], nut_uuid[10], nut_uuid[11],
		nut_uuid[12], nut_uuid[13], nut_uuid[14], nut_uuid[15]);
}

/* service requests and check on new data */
static void mainloop(void)
{
	int	ret;
	nfds_t	i, nfds = 0;

	upstype_t	*ups;
	nut_ctype_t		*client, *cnext;
	stype_t		*server;
	time_t	now;

	time(&now);

	if (reload_flag) {
		conf_reload();
		poll_reload();
		reload_flag = 0;
	}

	/* cleanup instcmd/setvar status tracking entries if needed */
	tracking_cleanup();

	/* scan through driver sockets */
	for (ups = firstups; ups && (nfds < maxconn); ups = ups->next) {

		/* see if we need to (re)connect to the socket */
		if (ups->sock_fd < 0) {
			upsdebugx(1, "%s: UPS [%s] is not currently connected",
				__func__, ups->name);
			ups->sock_fd = sstate_connect(ups);
			upsdebugx(1, "%s: UPS [%s] is now connected as FD %d",
				__func__, ups->name, ups->sock_fd);
			continue;
		}

		/* throw some warnings if it's not feeding us data any more */
		if (sstate_dead(ups, maxage)) {
			ups_data_stale(ups);
		} else {
			ups_data_ok(ups);
		}

		fds[nfds].fd = ups->sock_fd;
		fds[nfds].events = POLLIN;

		handler[nfds].type = DRIVER;
		handler[nfds].data = ups;

		nfds++;
	}

	/* scan through client sockets */
	for (client = firstclient; client; client = cnext) {

		cnext = client->next;

		if (difftime(now, client->last_heard) > 60) {
			/* shed clients after 1 minute of inactivity */
			/* FIXME: create an upsd.conf parameter (CLIENT_INACTIVITY_DELAY) */
			client_disconnect(client);
			continue;
		}

		if (nfds >= maxconn) {
			/* ignore clients that we are unable to handle */
			continue;
		}

		fds[nfds].fd = client->sock_fd;
		fds[nfds].events = POLLIN;

		handler[nfds].type = CLIENT;
		handler[nfds].data = client;

		nfds++;
	}

	/* scan through server sockets */
	for (server = firstaddr; server && (nfds < maxconn); server = server->next) {

		if (server->sock_fd < 0) {
			continue;
		}

		fds[nfds].fd = server->sock_fd;
		fds[nfds].events = POLLIN;

		handler[nfds].type = SERVER;
		handler[nfds].data = server;

		nfds++;
	}

	upsdebugx(2, "%s: polling %jd filedescriptors", __func__, (intmax_t)nfds);

	ret = poll(fds, nfds, 2000);

	if (ret == 0) {
		upsdebugx(2, "%s: no data available", __func__);
		return;
	}

	if (ret < 0) {
		upslog_with_errno(LOG_ERR, "%s", __func__);
		return;
	}

	for (i = 0; i < nfds; i++) {

		if (fds[i].revents & (POLLHUP|POLLERR|POLLNVAL)) {

			switch(handler[i].type)
			{
			case DRIVER:
				sstate_disconnect((upstype_t *)handler[i].data);
				break;
			case CLIENT:
				client_disconnect((nut_ctype_t *)handler[i].data);
				break;
			case SERVER:
				upsdebugx(2, "%s: server disconnected", __func__);
				break;

#if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && ( (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_COVERED_SWITCH_DEFAULT) || (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE) )
# pragma GCC diagnostic push
#endif
#ifdef HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_COVERED_SWITCH_DEFAULT
# pragma GCC diagnostic ignored "-Wcovered-switch-default"
#endif
#ifdef HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE
# pragma GCC diagnostic ignored "-Wunreachable-code"
#endif
/* Older CLANG (e.g. clang-3.4) seems to not support the GCC pragmas above */
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wcovered-switch-default"
#pragma clang diagnostic ignored "-Wunreachable-code"
#endif
			/* All enum cases defined as of the time of coding
			 * have been covered above. Handle later definitions,
			 * memory corruptions and buggy inputs below...
			 */
			default:
				upsdebugx(2, "%s: <unknown> disconnected", __func__);
				break;
#ifdef __clang__
#pragma clang diagnostic pop
#endif
#if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && ( (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_COVERED_SWITCH_DEFAULT) || (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE) )
# pragma GCC diagnostic pop
#endif

			}

			continue;
		}

		if (fds[i].revents & POLLIN) {

			switch(handler[i].type)
			{
			case DRIVER:
				sstate_readline((upstype_t *)handler[i].data);
				break;
			case CLIENT:
				client_readline((nut_ctype_t *)handler[i].data);
				break;
			case SERVER:
				client_connect((stype_t *)handler[i].data);
				break;

#if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && ( (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_COVERED_SWITCH_DEFAULT) || (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE) )
# pragma GCC diagnostic push
#endif
#ifdef HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_COVERED_SWITCH_DEFAULT
# pragma GCC diagnostic ignored "-Wcovered-switch-default"
#endif
#ifdef HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE
# pragma GCC diagnostic ignored "-Wunreachable-code"
#endif
/* Older CLANG (e.g. clang-3.4) seems to not support the GCC pragmas above */
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wcovered-switch-default"
#pragma clang diagnostic ignored "-Wunreachable-code"
#endif
			/* All enum cases defined as of the time of coding
			 * have been covered above. Handle later definitions,
			 * memory corruptions and buggy inputs below...
			 */
			default:
				upsdebugx(2, "%s: <unknown> has data available", __func__);
				break;
#ifdef __clang__
#pragma clang diagnostic pop
#endif
#if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && ( (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_COVERED_SWITCH_DEFAULT) || (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_UNREACHABLE_CODE) )
# pragma GCC diagnostic pop
#endif
			}

			continue;
		}
	}
}

static void help(const char *arg_progname)
	__attribute__((noreturn));

static void help(const char *arg_progname)
{
	printf("Network server for UPS data.\n\n");
	printf("usage: %s [OPTIONS]\n", arg_progname);

	printf("\n");
	printf("  -c <command>	send <command> via signal to background process\n");
	printf("		commands:\n");
	printf("		 - reload: reread configuration files\n");
	printf("		 - stop: stop process and exit\n");
	printf("  -P <pid>	send the signal above to specified PID (bypassing PID file)\n");
	printf("  -D		raise debugging level (and stay foreground by default)\n");
	printf("  -F		stay foregrounded even if no debugging is enabled\n");
	printf("  -FF		stay foregrounded and still save the PID file\n");
	printf("  -B		stay backgrounded even if debugging is bumped\n");
	printf("  -h		display this help\n");
	printf("  -r <dir>	chroots to <dir>\n");
	printf("  -q		raise log level threshold\n");
	printf("  -u <user>	switch to <user> (if started as root)\n");
	printf("  -V		display the version of this software\n");
	printf("  -4		IPv4 only\n");
	printf("  -6		IPv6 only\n");

	exit(EXIT_SUCCESS);
}

static void set_reload_flag(int sig)
{
	NUT_UNUSED_VARIABLE(sig);
	reload_flag = 1;
}

static void set_exit_flag(int sig)
{
	exit_flag = sig;
}

static void setup_signals(void)
{
	struct sigaction	sa;

	sigemptyset(&sa.sa_mask);
	sigaddset(&sa.sa_mask, SIGHUP);
	sa.sa_flags = 0;

	/* basic signal setup to ignore SIGPIPE */
#if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_STRICT_PROTOTYPES)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wstrict-prototypes"
#endif
	sa.sa_handler = SIG_IGN;
#if (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_PUSH_POP) && (defined HAVE_PRAGMA_GCC_DIAGNOSTIC_IGNORED_STRICT_PROTOTYPES)
# pragma GCC diagnostic pop
#endif
	sigaction(SIGPIPE, &sa, NULL);

	/* handle shutdown signals */
	sa.sa_handler = set_exit_flag;
	sigaction(SIGINT, &sa, NULL);
	sigaction(SIGQUIT, &sa, NULL);
	sigaction(SIGTERM, &sa, NULL);

	/* handle reloading */
	sa.sa_handler = set_reload_flag;
	sigaction(SIGHUP, &sa, NULL);
}

void check_perms(const char *fn)
{
	int	ret;
	struct stat	st;

	ret = stat(fn, &st);

	if (ret != 0) {
		fatal_with_errno(EXIT_FAILURE, "stat %s", fn);
	}

	/* include the x bit here in case we check a directory */
	if (st.st_mode & (S_IROTH | S_IXOTH)) {
		upslogx(LOG_WARNING, "%s is world readable", fn);
	}
}

int main(int argc, char **argv)
{
	int	i, cmd = 0, cmdret = 0, foreground = -1;
	char	*chroot_path = NULL;
	const char	*user = RUN_AS_USER;
	struct passwd	*new_uid = NULL;
	pid_t	oldpid = -1;

	progname = xbasename(argv[0]);

	/* yes, xstrdup - the conf handlers call free on this later */
	statepath = xstrdup(dflt_statepath());
	datapath = xstrdup(DATADIR);

	/* set up some things for later */
	snprintf(pidfn, sizeof(pidfn), "%s/%s.pid", altpidpath(), progname);

	printf("Network UPS Tools %s %s\n", progname, UPS_VERSION);

	while ((i = getopt(argc, argv, "+h46p:qr:i:fu:Vc:P:DFB")) != -1) {
		switch (i) {
			case 'p':
			case 'i':
				fatalx(EXIT_FAILURE, "Specifying a listening addresses with '-i <address>' and '-p <port>'\n"
					"is deprecated. Use 'LISTEN <address> [<port>]' in 'upsd.conf' instead.\n"
					"See 'man 8 upsd.conf' for more information.");
#ifndef HAVE___ATTRIBUTE__NORETURN
					exit(EXIT_FAILURE);	/* Should not get here in practice, but compiler is afraid we can fall through */
#endif

			case 'q':
				nut_log_level++;
				break;

			case 'r':
				chroot_path = optarg;
				break;

			case 'u':
				user = optarg;
				break;

			case 'V':
				/* do nothing - we already printed the banner */
				exit(EXIT_SUCCESS);

			case 'c':
				if (!strncmp(optarg, "reload", strlen(optarg)))
					cmd = SIGCMD_RELOAD;
				if (!strncmp(optarg, "stop", strlen(optarg)))
					cmd = SIGCMD_STOP;

				/* bad command given */
				if (cmd == 0)
					help(progname);
				break;

			case 'P':
				if ((oldpid = parsepid(optarg)) < 0)
					help(progname);
				break;

			case 'D':
				nut_debug_level++;
				break;
			case 'F':
				if (foreground > 0) {
					/* specified twice to save PID file anyway */
					foreground = 2;
				} else {
					foreground = 1;
				}
				break;
			case 'B':
				foreground = 0;
				break;

			case '4':
				opt_af = AF_INET;
				break;

			case '6':
				opt_af = AF_INET6;
				break;

			case 'h':
			default:
				help(progname);
		}
	}

	if (foreground < 0) {
		if (nut_debug_level > 0) {
			foreground = 1;
		} else {
			foreground = 0;
		}
	}

	if (cmd) {
		if (oldpid < 0) {
			cmdret = sendsignalfn(pidfn, cmd);
		} else {
			cmdret = sendsignalpid(oldpid, cmd);
		}
		exit((cmdret == 0)?EXIT_SUCCESS:EXIT_FAILURE);
	}

	/* otherwise, we are being asked to start.
	 * so check if a previous instance is running by sending signal '0'
	 * (Ie 'kill <pid> 0') */
	if (oldpid < 0) {
		cmdret = sendsignalfn(pidfn, 0);
	} else {
		cmdret = sendsignalpid(oldpid, 0);
	}
	switch (cmdret) {
	case 0:
		printf("Fatal error: A previous upsd instance is already running!\n");
		printf("Either stop the previous instance first, or use the 'reload' command.\n");
		exit(EXIT_FAILURE);

	case -3:
	case -2:
		upslogx(LOG_WARNING, "Could not %s PID file '%s' "
			"to see if previous upsd instance is "
			"already running!\n",
			(cmdret == -3 ? "find" : "parse"),
			pidfn);
		break;

	case -1:
	default:
		/* Just failed to send signal, no competitor running */
		break;
	}

	argc -= optind;
	argv += optind;

	if (argc != 0) {
		help(progname);
	}

	atexit(upsd_cleanup);

	setup_signals();

	open_syslog(progname);

	/* send logging to the syslog pre-background for later use */
	syslogbit_set();

	/* do this here, since getpwnam() might not work in the chroot */
	new_uid = get_user_pwent(user);

	if (chroot_path) {
		chroot_start(chroot_path);
	}

	/* default to system limit (may be overridden in upsd.conf) */
	/* FIXME: Check for overflows (and int size of nfds_t vs. long) - see get_max_pid_t() for example */
	maxconn = (nfds_t)sysconf(_SC_OPEN_MAX);

	/* handle upsd.conf */
	load_upsdconf(0);	/* 0 = initial */

	/* CLI debug level can not be smaller than debug_min specified
	 * in upsd.conf. Note that non-zero debug_min does not impact
	 * foreground running mode.
	 */
	if (nut_debug_level_global > nut_debug_level)
		nut_debug_level = nut_debug_level_global;
	upsdebugx(1, "debug level is '%d'", nut_debug_level);

	{ /* scope */
	/* As documented above, the ALLOW_NO_DEVICE can be provided via
	 * envvars and then has higher priority than an upsd.conf setting
	 */
	const char *envvar = getenv("ALLOW_NO_DEVICE");
	if ( envvar != NULL) {
		if ( (!strncasecmp("TRUE", envvar, 4)) || (!strncasecmp("YES", envvar, 3)) || (!strncasecmp("ON", envvar, 2)) || (!strncasecmp("1", envvar, 1)) ) {
			/* Admins of this server expressed a desire to serve
			 * anything on the NUT protocol, even if nothing is
			 * configured yet - tell the clients so, properly.
			 */
			allow_no_device = 1;
		} else if ( (!strncasecmp("FALSE", envvar, 5)) || (!strncasecmp("NO", envvar, 2)) || (!strncasecmp("OFF", envvar, 3)) || (!strncasecmp("0", envvar, 1)) ) {
			/* Admins of this server expressed a desire to serve
			 * anything on the NUT protocol, even if nothing is
			 * configured yet - tell the clients so, properly.
			 */
			allow_no_device = 0;
		}
	}
	} /* scope */

	/* start server */
	server_load();

	become_user(new_uid);

	if (chdir(statepath)) {
		fatal_with_errno(EXIT_FAILURE, "Can't chdir to %s", statepath);
	}

	/* check statepath perms */
	check_perms(statepath);

	/* handle ups.conf */
	read_upsconf();
	upsconf_add(0);		/* 0 = initial */
	poll_reload();

	if (num_ups == 0) {
		if (allow_no_device) {
			upslogx(LOG_WARNING, "Normally at least one UPS must be defined in ups.conf, currently there are none (please configure the file and reload the service)");
		} else {
			fatalx(EXIT_FAILURE, "Fatal error: at least one UPS must be defined in ups.conf");
		}
	}

	/* try to bring in the var/cmd descriptions */
	desc_load();

	/* handle upsd.users */
	user_load();

	if (!foreground) {
		background();
		writepid(pidfn);
	} else {
		if (foreground == 2) {
			upslogx(LOG_WARNING, "Running as foreground process, but saving a PID file anyway");
			writepid(pidfn);
		} else {
			upslogx(LOG_WARNING, "Running as foreground process, not saving a PID file");
			memset(pidfn, 0, sizeof(pidfn));
		}
	}

	/* initialize SSL (keyfile must be readable by nut user) */
	ssl_init();

	while (!exit_flag) {
		mainloop();
	}

	ssl_cleanup();

	upslogx(LOG_INFO, "Signal %d: exiting", exit_flag);
	return EXIT_SUCCESS;
}