path: root/dss.c

/* SPDX-License-Identifier: GPL-2.0 */

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <assert.h>
#include <errno.h>
#include <sys/types.h>
#include <signal.h>
#include <ctype.h>
#include <stdbool.h>
#include <sys/stat.h>
#include <unistd.h>
#include <inttypes.h>
#include <sys/time.h>
#include <time.h>
#include <sys/wait.h>
#include <fnmatch.h>
#include <limits.h>
#include <fcntl.h>
#include <lopsub.h>
#include <sys/mman.h>

#include "gcc-compat.h"
#include "log.h"
#include "str.h"
#include "err.h"
#include "file.h"
#include "exec.h"
#include "daemon.h"
#include "sig.h"
#include "df.h"
#include "tv.h"
#include "snap.h"
#include "ipc.h"
#include "dss.lsg.h"

#define CMD_PTR(_cname) lls_cmd(LSG_DSS_CMD_ ## _cname, dss_suite)
#define OPT_RESULT(_cname, _oname) (lls_opt_result(\
	LSG_DSS_ ## _cname ## _OPT_ ## _oname, (CMD_PTR(_cname) == CMD_PTR(DSS))? lpr : sublpr))
#define OPT_GIVEN(_cname, _oname) (lls_opt_given(OPT_RESULT(_cname, _oname)))
#define OPT_STRING_VAL(_cname, _oname) (lls_string_val(0, \
	OPT_RESULT(_cname, _oname)))
#define OPT_UINT32_VAL(_cname, _oname) (lls_uint32_val(0, \
		OPT_RESULT(_cname, _oname)))

struct dss_user_data {int (*handler)(void);};
#define EXPORT_CMD_HANDLER(_cmd) const struct dss_user_data \
	lsg_dss_com_ ## _cmd ## _user_data = { \
		.handler = com_ ## _cmd \
	};

/*
 * Command line and active options. We need to keep a copy of the parsed
 * command line options for the SIGHUP case where we merge the command line
 * options and the new config file options.
 */
static struct lls_parse_result *cmdline_lpr, *lpr;

/* Parsed subcommand options. */
static struct lls_parse_result *cmdline_sublpr, *sublpr;
/* The executing subcommand (NULL at startup). */
static const struct lls_command *subcmd;
/* Wether daemon_init() was called. */
static bool daemonized;
/* Non-NULL if we log to a file. */
static FILE *logfile;
/* Realpath of the config file. */
static char *config_file;
/* derived from config file path */
uint32_t ipc_key;
/* The read end of the signal pipe */
static int signal_pipe;
/* Process id of current pre-create-hook/rsync/post-create-hook process. */
static pid_t create_pid;
/* Whether the pre-create-hook/rsync/post-create-hook is currently stopped. */
static int create_process_stopped;
/* How many times in a row the rsync command failed. */
static int num_consecutive_rsync_errors;
/* Process id of current pre-remove/rm/post-remove process. */
static pid_t remove_pid;
/* When the next snapshot is due. */
static int64_t next_snapshot_time;
/* When to try to remove something. */
static struct timeval next_removal_check;
/* Creation time of the snapshot currently being created. */
static int64_t current_snapshot_creation_time;
/* Set by the pre-rm hook, cleared by handle_remove_exit(). */
struct snapshot *snapshot_currently_being_removed;
/* Needed by the post-create hook. */
static char *path_to_last_complete_snapshot;
static char *name_of_reference_snapshot;
/* See snap.h for details. */
enum hook_status snapshot_creation_status;
/* See snap.h for details. */
enum hook_status snapshot_removal_status;


DEFINE_DSS_ERRLIST;
static const char *hook_status_description[] = {HOOK_STATUS_ARRAY};

/* may be called with ds == NULL. */
static int disk_space_low(struct disk_space *ds)
{
	struct disk_space ds_struct;
	uint32_t val;

	if (!ds) {
		int ret = get_disk_space(".", &ds_struct);
		if (ret < 0)
			return ret;
		ds = &ds_struct;
	}
	val = OPT_UINT32_VAL(DSS, MIN_FREE_MB);
	if (val != 0)
		if (ds->free_mb < val)
			return 1;
	val = OPT_UINT32_VAL(DSS, MIN_FREE_PERCENT);
	if (val != 0)
		if (ds->percent_free < val)
			return 1;
	val = OPT_UINT32_VAL(DSS, MIN_FREE_PERCENT_INODES);
	if (val != 0)
		if (ds->percent_free_inodes < val)
			return 1;
	return 0;
}

static void dump_dss_config(const char *msg)
{
	const char dash[] = "-----------------------------";
	char *lopsub_dump;
	int ret;
	FILE *log = logfile? logfile : stderr;
	struct disk_space ds;
	int64_t now = get_current_time();

	if (OPT_UINT32_VAL(DSS, LOGLEVEL) > INFO)
		return;

	fprintf(log, "%s <%s config> %s\n", dash, msg, dash);
	fprintf(log, "\n*** disk space ***\n\n");
	ret = get_disk_space(".", &ds);
	if (ret >= 0) {
		DSS_INFO_LOG("disk space low: %s\n", disk_space_low(&ds)?
			"yes" : "no");
		log_disk_space(&ds);
	} else
		DSS_ERROR_LOG("can not get free disk space: %s\n",
			dss_strerror(-ret));

	/* we continue on errors from get_disk_space */

	fprintf(log, "\n*** non-default options ***\n\n");
	lopsub_dump = lls_dump_parse_result(lpr, CMD_PTR(DSS), true);
	fprintf(log, "%s", lopsub_dump);
	free(lopsub_dump);
	fprintf(log, "\n*** non-default options for \"run\" ***\n\n");
	lopsub_dump = lls_dump_parse_result(lpr, CMD_PTR(RUN), true);
	fprintf(log, "%s", lopsub_dump);
	free(lopsub_dump);
	fprintf(log, "\n*** internal state ***\n\n");
	fprintf(log,
		"pid: %d\n"
		"logfile: %s\n"
		"snapshot_currently_being_removed: %s\n"
		"path_to_last_complete_snapshot: %s\n"
		"reference_snapshot: %s\n"
		"snapshot_creation_status: %s\n"
		"snapshot_removal_status: %s\n"
		"num_consecutive_rsync_errors: %d\n"
		,
		(int) getpid(),
		logfile? OPT_STRING_VAL(RUN, LOGFILE) : "stderr",
		snapshot_currently_being_removed?
			snapshot_currently_being_removed->name : "(none)",
		path_to_last_complete_snapshot?
			path_to_last_complete_snapshot : "(none)",
		name_of_reference_snapshot?
			name_of_reference_snapshot : "(none)",
		hook_status_description[snapshot_creation_status],
		hook_status_description[snapshot_removal_status],
		num_consecutive_rsync_errors
	);
	if (create_pid != 0)
		fprintf(log,
			"create_pid: %" PRId32 "\n"
			"create process is %sstopped\n"
			,
			create_pid,
			create_process_stopped? "" : "not "
		);
	if (remove_pid != 0)
		fprintf(log, "remove_pid: %" PRId32 "\n", remove_pid);
	if (next_snapshot_time != 0)
		fprintf(log, "next snapshot due in %" PRId64 " seconds\n",
			next_snapshot_time - now);
	if (current_snapshot_creation_time != 0)
		fprintf(log, "current_snapshot_creation_time: %"
			PRId64 " (%" PRId64 " seconds ago)\n",
			current_snapshot_creation_time,
			now - current_snapshot_creation_time
		);
	if (next_removal_check.tv_sec != 0) {
		fprintf(log, "next removal check: %llu (%llu seconds ago)\n",
			(long long unsigned)next_removal_check.tv_sec,
			now - (long long unsigned)next_removal_check.tv_sec
		);

	}
	fprintf(log, "%s </%s config> %s\n", dash, msg, dash);
}

/* All DSS_XXX_LOG() macros use this function. */
__printf_2_3 void dss_log(int ll, const char* fmt,...)
{
	va_list argp;
	FILE *outfd;
	struct tm *tm;
	time_t t1;
	char str[255] = "";
	int lpr_ll = lpr? OPT_UINT32_VAL(DSS, LOGLEVEL) : WARNING;

	if (ll < lpr_ll)
		return;
	outfd = logfile? logfile : stderr;
	if (subcmd == CMD_PTR(RUN)) {
		time(&t1);
		tm = localtime(&t1);
		strftime(str, sizeof(str), "%b %d %H:%M:%S", tm);
		fprintf(outfd, "%s ", str);
		if (lpr_ll <= INFO)
			fprintf(outfd, "%i: ", ll);
	}
	va_start(argp, fmt);
	vfprintf(outfd, fmt, argp);
	va_end(argp);
}

/* Print a message either to stdout or to the log file. */
static __printf_1_2 void dss_msg(const char* fmt,...)
{
	FILE *outfd = logfile? logfile : stdout;
	va_list argp;
	va_start(argp, fmt);
	vfprintf(outfd, fmt, argp);
	va_end(argp);
}

static void set_config_file_name(void)
{

	if (OPT_GIVEN(DSS, CONFIG_FILE)) {
		const char *arg = OPT_STRING_VAL(DSS, CONFIG_FILE);
		config_file = realpath(arg, NULL);
		if (!config_file) {
			DSS_EMERG_LOG("could not resolve path %s: %s\n", arg,
				strerror(errno));
			exit(EXIT_FAILURE);
		}
	} else {
		char *home = get_homedir();
		char *arg = make_message("%s/.dssrc", home);
		free(home);
		config_file = realpath(arg, NULL);
		if (config_file)
			free(arg);
		else /* not fatal */
			config_file = arg;
	}
	DSS_DEBUG_LOG("config file: %s\n", config_file);
	ipc_key = super_fast_hash((uint8_t *)config_file,
		strlen(config_file), 0) >> 1;
}

static int send_signal(int sig, bool wait)
{
	pid_t pid;
	int ret = get_dss_pid(ipc_key, &pid);
	unsigned ms = 32;
	struct timespec ts;

	if (ret < 0)
		return ret;
	if (OPT_GIVEN(DSS, DRY_RUN)) {
		dss_msg("%d\n", (int)pid);
		return 0;
	}
	DSS_NOTICE_LOG("sending signal %d to pid %d\n", sig, (int)pid);
	ret = kill(pid, sig);
	if (ret < 0)
		return -ERRNO_TO_DSS_ERROR(errno);
	if (!wait)
		return 1;
	while (ms < 5000) {
		ts.tv_sec = ms / 1000;
		ts.tv_nsec = (ms % 1000) * 1000 * 1000;
		ret = nanosleep(&ts, NULL);
		if (ret < 0)
			return -ERRNO_TO_DSS_ERROR(errno);
		ret = kill(pid, 0);
		if (ret < 0) {
			if (errno != ESRCH)
				return -ERRNO_TO_DSS_ERROR(errno);
			return 1;
		}
		ms *= 2;
	}
	return -E_KILL_TIMEOUT;
}

struct signal_info {
	const char * const name;
	int num;
};

/*
 * The table below was taken 2016 from proc/sig.c of procps-3.2.8. Copyright
 * 1998-2003 by Albert Cahalan, GPLv2.
 */
static const struct signal_info signal_table[] = {
	{"ABRT",   SIGABRT},  /* IOT */
	{"ALRM",   SIGALRM},
	{"BUS",    SIGBUS},
	{"CHLD",   SIGCHLD},  /* CLD */
	{"CONT",   SIGCONT},
	{"FPE",    SIGFPE},
	{"HUP",    SIGHUP},
	{"ILL",    SIGILL},
	{"INT",    SIGINT},
	{"KILL",   SIGKILL},
	{"PIPE",   SIGPIPE},
#ifdef SIGPOLL
	{"POLL",   SIGPOLL},  /* IO */
#endif
	{"PROF",   SIGPROF},
#ifdef SIGPWR
	{"PWR",    SIGPWR},
#endif
	{"QUIT",   SIGQUIT},
	{"SEGV",   SIGSEGV},
#ifdef SIGSTKFLT
	{"STKFLT", SIGSTKFLT},
#endif
	{"STOP",   SIGSTOP},
	{"SYS",    SIGSYS},   /* UNUSED */
	{"TERM",   SIGTERM},
	{"TRAP",   SIGTRAP},
	{"TSTP",   SIGTSTP},
	{"TTIN",   SIGTTIN},
	{"TTOU",   SIGTTOU},
	{"URG",    SIGURG},
	{"USR1",   SIGUSR1},
	{"USR2",   SIGUSR2},
	{"VTALRM", SIGVTALRM},
	{"WINCH",  SIGWINCH},
	{"XCPU",   SIGXCPU},
	{"XFSZ",   SIGXFSZ}
};

#define SIGNAL_TABLE_SIZE (sizeof(signal_table) / sizeof(signal_table[0]))
#ifndef SIGRTMAX
#define SIGRTMAX 64
#endif

static int com_kill(void)
{
	bool w_given = OPT_GIVEN(KILL, WAIT);
	const char *arg = OPT_STRING_VAL(KILL, SIGNAL);
	int ret, i;

	if (*arg >= '0' && *arg <= '9') {
		int64_t val;
		ret = dss_atoi64(arg, &val);
		if (ret < 0)
			return ret;
		if (val < 0 || val > SIGRTMAX)
			return -ERRNO_TO_DSS_ERROR(EINVAL);
		return send_signal(val, w_given);
	}
	if (strncasecmp(arg, "sig", 3) == 0)
		arg += 3;
	if (strcasecmp(arg, "CLD") == 0)
		return send_signal(SIGCHLD, w_given);
	if (strcasecmp(arg, "IOT") == 0)
		return send_signal(SIGABRT, w_given);
	for (i = 0; i < SIGNAL_TABLE_SIZE; i++)
		if (strcasecmp(arg, signal_table[i].name) == 0)
			return send_signal(signal_table[i].num, w_given);
	DSS_ERROR_LOG("invalid sigspec: %s\n", arg);
	return -ERRNO_TO_DSS_ERROR(EINVAL);
}
EXPORT_CMD_HANDLER(kill);

static void dss_get_snapshot_list(struct snapshot_list *sl)
{
	get_snapshot_list(sl, OPT_UINT32_VAL(DSS, UNIT_INTERVAL),
		OPT_UINT32_VAL(DSS, NUM_INTERVALS));
}

static int64_t compute_next_snapshot_time(void)
{
	int64_t x = 0, now = get_current_time(), unit_interval
		= 24 * 3600 * OPT_UINT32_VAL(DSS, UNIT_INTERVAL), ret,
		last_completion_time;
	unsigned wanted = desired_number_of_snapshots(0,
		OPT_UINT32_VAL(DSS, NUM_INTERVALS)),
		num_complete = 0;
	int i;
	struct snapshot *s = NULL;
	struct snapshot_list sl;

	dss_get_snapshot_list(&sl);
	FOR_EACH_SNAPSHOT(s, i, &sl) {
		if (!(s->flags & SS_COMPLETE))
			continue;
		num_complete++;
		x += s->completion_time - s->creation_time;
		last_completion_time = s->completion_time;
	}
	assert(x >= 0);

	ret = now;
	if (num_complete == 0)
		goto out;
	x /= num_complete; /* avg time to create one snapshot */
	if (unit_interval < x * wanted) /* oops, no sleep at all */
		goto out;
	ret = last_completion_time + unit_interval / wanted - x;
out:
	free_snapshot_list(&sl);
	return ret;
}

static inline void invalidate_next_snapshot_time(void)
{
	next_snapshot_time = 0;
}

static inline int next_snapshot_time_is_valid(void)
{
	return next_snapshot_time != 0;
}

static int next_snapshot_is_due(void)
{
	int64_t now = get_current_time();

	if (!next_snapshot_time_is_valid())
		next_snapshot_time = compute_next_snapshot_time();
	if (next_snapshot_time <= now) {
		DSS_DEBUG_LOG("next snapshot: now\n");
		return 1;
	}
	DSS_DEBUG_LOG("next snapshot due in %" PRId64 " seconds\n",
		next_snapshot_time - now);
	return 0;
}

static void pre_create_hook(void)
{
	assert(snapshot_creation_status == HS_READY);
	/* make sure that the next snapshot time will be recomputed */
	invalidate_next_snapshot_time();
	DSS_DEBUG_LOG("executing %s\n", OPT_STRING_VAL(DSS, PRE_CREATE_HOOK));
	dss_exec_cmdline_pid(&create_pid, OPT_STRING_VAL(DSS, PRE_CREATE_HOOK));
	snapshot_creation_status = HS_PRE_RUNNING;
}

static void pre_remove_hook(struct snapshot *s, const char *why)
{
	char *cmd;

	if (!s)
		return;
	DSS_DEBUG_LOG("%s snapshot %s\n", why, s->name);
	assert(snapshot_removal_status == HS_READY);
	assert(remove_pid == 0);
	assert(!snapshot_currently_being_removed);

	snapshot_currently_being_removed = dss_malloc(sizeof(struct snapshot));
	*snapshot_currently_being_removed = *s;
	snapshot_currently_being_removed->name = dss_strdup(s->name);

	cmd = make_message("%s %s/%s", OPT_STRING_VAL(DSS, PRE_REMOVE_HOOK),
		OPT_STRING_VAL(DSS, DEST_DIR), s->name);
	DSS_DEBUG_LOG("executing %s\n", cmd);
	dss_exec_cmdline_pid(&remove_pid, cmd);
	free(cmd);
	snapshot_removal_status = HS_PRE_RUNNING;
}

static int exec_rm(void)
{
	struct snapshot *s = snapshot_currently_being_removed;
	char *new_name = being_deleted_name(s);
	char *argv[4];
	int ret;

	argv[0] = "rm";
	argv[1] = "-rf";
	argv[2] = new_name;
	argv[3] = NULL;

	assert(snapshot_removal_status == HS_PRE_SUCCESS);
	assert(remove_pid == 0);

	DSS_NOTICE_LOG("removing %s (interval = %i)\n", s->name, s->interval);
	ret = dss_rename(s->name, new_name);
	if (ret < 0)
		goto out;
	dss_exec(&remove_pid, argv[0], argv);
	snapshot_removal_status = HS_RUNNING;
out:
	free(new_name);
	return ret;
}

static int snapshot_is_being_created(struct snapshot *s)
{
	return s->creation_time == current_snapshot_creation_time;
}

static struct snapshot *find_orphaned_snapshot(struct snapshot_list *sl)
{
	struct snapshot *s;
	int i;

	DSS_DEBUG_LOG("looking for old incomplete snapshots\n");
	FOR_EACH_SNAPSHOT(s, i, sl) {
		if (snapshot_is_being_created(s))
			continue;
		/*
		 * We know that no rm is currently running, so if s is marked
		 * as being deleted, a previously started rm must have failed.
		 */
		if (s->flags & SS_BEING_DELETED)
			return s;

		if (s->flags & SS_COMPLETE) /* good snapshot */
			continue;
		/*
		 * This snapshot is incomplete and it is not the snapshot
		 * currently being created. However, we must not remove it if
		 * rsync is about to be restarted. As only the newest snapshot
		 * can be restarted, this snapshot is orphaned if it is not the
		 * newest snapshot or if we are not about to restart rsync.
		 */
		if (get_newest_snapshot(sl) != s)
			return s;
		if (snapshot_creation_status != HS_NEEDS_RESTART)
			return s;
	}
	/* no orphaned snapshots */
	return NULL;
}

static int is_reference_snapshot(struct snapshot *s)
{
	if (!name_of_reference_snapshot)
		return 0;
	return strcmp(s->name, name_of_reference_snapshot)? 0 : 1;
}

static struct snapshot *find_redundant_snapshot(struct snapshot_list *sl)
{
	int i, interval;
	struct snapshot *s;
	unsigned missing = 0;
	uint32_t N = OPT_UINT32_VAL(DSS, NUM_INTERVALS);

	DSS_DEBUG_LOG("looking for intervals containing too many snapshots\n");
	for (interval = N - 1; interval >= 0; interval--) {
		unsigned keep = desired_number_of_snapshots(interval, N);
		unsigned num = sl->interval_count[interval];
		struct snapshot *victim = NULL, *prev = NULL;
		int64_t score = LONG_MAX;

		if (keep >= num)
			missing += keep - num;
		if (keep + missing >= num)
			continue;
		/* redundant snapshot in this interval, pick snapshot with lowest score */
		FOR_EACH_SNAPSHOT(s, i, sl) {
			int64_t this_score;

			if (snapshot_is_being_created(s))
				continue;
			if (is_reference_snapshot(s))
				continue;
			if (s->interval > interval) {
				prev = s;
				continue;
			}
			if (s->interval < interval)
				break;
			if (!victim) {
				victim = s;
				prev = s;
				continue;
			}
			assert(prev);
			/* check if s is a better victim */
			this_score = s->creation_time - prev->creation_time;
			assert(this_score >= 0);
			if (this_score < score) {
				score = this_score;
				victim = s;
			}
			prev = s;
		}
		assert(victim);
		return victim;
	}
	return NULL;
}

static struct snapshot *find_outdated_snapshot(struct snapshot_list *sl)
{
	int i;
	struct snapshot *s;

	DSS_DEBUG_LOG("looking for snapshots belonging to intervals >= %d\n",
		OPT_UINT32_VAL(DSS, NUM_INTERVALS));
	FOR_EACH_SNAPSHOT(s, i, sl) {
		if (snapshot_is_being_created(s))
			continue;
		if (is_reference_snapshot(s))
			continue;
		if (s->interval < OPT_UINT32_VAL(DSS, NUM_INTERVALS))
			continue;
		return s;
	}
	return NULL;
}

static struct snapshot *find_oldest_removable_snapshot(struct snapshot_list *sl)
{
	int i, num_complete;
	struct snapshot *s, *ref = NULL;

	DSS_DEBUG_LOG("picking snapshot with earliest creation time\n");
	num_complete = num_complete_snapshots(sl);
	if (num_complete <= OPT_UINT32_VAL(DSS, MIN_COMPLETE))
		return NULL;
	FOR_EACH_SNAPSHOT(s, i, sl) {
		if (snapshot_is_being_created(s))
			continue;
		if (is_reference_snapshot(s)) { /* avoid this one */
			ref = s;
			continue;
		}
		return s;
	}
	assert(ref);
	DSS_WARNING_LOG("removing reference snapshot %s\n", ref->name);
	return ref;
}

/* returns NULL <==> *reason is set to NULL */
static struct snapshot *find_removable_snapshot(struct snapshot_list *sl,
		bool try_hard, char **reason)
{
	struct snapshot *victim;

	/*
	 * Don't remove anything if there is free space and we have fewer
	 * snapshots than configured, plus one. This way there is always one
	 * snapshot that can be recycled.
	 */
	if (!try_hard && sl->num_snapshots <=
			1 << OPT_UINT32_VAL(DSS, NUM_INTERVALS))
		goto nope;
	victim = find_orphaned_snapshot(sl);
	if (victim) {
		*reason = make_message("orphaned");
		return victim;
	}
	victim = find_outdated_snapshot(sl);
	if (victim) {
		*reason = make_message("outdated");
		return victim;
	}
	if (!OPT_GIVEN(DSS, KEEP_REDUNDANT)) {
		victim = find_redundant_snapshot(sl);
		if (victim) {
			*reason = make_message("redundant");
			return victim;
		}
	}
	if (!try_hard)
		goto nope;
	DSS_WARNING_LOG("nothing obvious to remove\n");
	victim = find_oldest_removable_snapshot(sl);
	if (victim) {
		*reason = make_message("oldest");
		return victim;
	}
nope:
	*reason = NULL;
	return NULL;
}

static int rename_incomplete_snapshot(int64_t start)
{
	char *old_name;
	int ret;
	int64_t now;

	/*
	 * We don't want the dss_rename() below to fail with EEXIST because the
	 * last complete snapshot was created (and completed) in the same
	 * second as this one.
	 */
	while ((now = get_current_time()) == start)
		sleep(1);
	free(path_to_last_complete_snapshot);
	ret = complete_name(start, now, &path_to_last_complete_snapshot);
	if (ret < 0)
		return ret;
	old_name = incomplete_name(start);
	ret = dss_rename(old_name, path_to_last_complete_snapshot);
	if (ret >= 0)
		DSS_NOTICE_LOG("%s -> %s\n", old_name,
			path_to_last_complete_snapshot);
	free(old_name);
	return ret;
}

static int try_to_free_disk_space(void)
{
	int ret;
	struct snapshot_list sl;
	struct snapshot *victim;
	struct timeval now;
	char *why;
	int low_disk_space;

	ret = disk_space_low(NULL);
	if (ret < 0)
		return ret;
	low_disk_space = ret;
	gettimeofday(&now, NULL);
	if (tv_diff(&next_removal_check, &now, NULL) > 0)
		return 0;
	if (!low_disk_space) {
		if (snapshot_creation_status != HS_READY)
			return 0;
		if (next_snapshot_is_due())
			return 0;
	}
	/* Idle or low disk space, look at existing snapshots. */
	dss_get_snapshot_list(&sl);
	victim = find_removable_snapshot(&sl, low_disk_space, &why);
	if (victim) {
		pre_remove_hook(victim, why);
		free(why);
	}
	free_snapshot_list(&sl);
	if (victim)
		return 1;
	if (!low_disk_space)
		return 0;
	DSS_CRIT_LOG("uhuhu: disk space low and nothing to remove\n");
	return -ERRNO_TO_DSS_ERROR(ENOSPC);
}

static void post_create_hook(void)
{
	char *cmd = make_message("%s %s/%s",
		OPT_STRING_VAL(DSS, POST_CREATE_HOOK),
		OPT_STRING_VAL(DSS, DEST_DIR), path_to_last_complete_snapshot);
	DSS_NOTICE_LOG("executing %s\n", cmd);
	dss_exec_cmdline_pid(&create_pid, cmd);
	free(cmd);
	snapshot_creation_status = HS_POST_RUNNING;
}

static void post_remove_hook(void)
{
	char *cmd;
	struct snapshot *s = snapshot_currently_being_removed;

	assert(s);

	cmd = make_message("%s %s/%s", OPT_STRING_VAL(DSS, POST_REMOVE_HOOK),
		OPT_STRING_VAL(DSS, DEST_DIR), s->name);
	DSS_NOTICE_LOG("executing %s\n", cmd);
	dss_exec_cmdline_pid(&remove_pid, cmd);
	free(cmd);
	snapshot_removal_status = HS_POST_RUNNING;
}

static void dss_kill(pid_t pid, int sig, const char *msg)
{
	const char *signame, *process_name;

	if (pid == 0)
		return;
	switch (sig) {
	case SIGTERM: signame = "TERM"; break;
	case SIGSTOP: signame = "STOP"; break;
	case SIGCONT: signame = "CONT"; break;
	default: signame = "????";
	}

	if (pid == create_pid)
		process_name = "create";
	else if (pid == remove_pid)
		process_name = "remove";
	else process_name = "??????";

	if (msg)
		DSS_INFO_LOG("%s\n", msg);
	DSS_DEBUG_LOG("sending signal %d (%s) to pid %d (%s process)\n",
		sig, signame, (int)pid, process_name);
	if (kill(pid, sig) >= 0)
		return;
	DSS_INFO_LOG("failed to send signal %d (%s) to pid %d (%s process)\n",
		sig, signame, (int)pid, process_name);
}

static void stop_create_process(void)
{
	if (create_process_stopped)
		return;
	dss_kill(create_pid, SIGSTOP, "suspending create process");
	create_process_stopped = 1;
}

static void restart_create_process(void)
{
	if (!create_process_stopped)
		return;
	dss_kill(create_pid, SIGCONT, "resuming create process");
	create_process_stopped = 0;
}

static void log_termination_msg(pid_t pid, int status)
{
	if (WIFEXITED(status))
		DSS_INFO_LOG("child %i exited. Exit status: %i\n", (int)pid,
			WEXITSTATUS(status));
	else if (WIFSIGNALED(status))
		DSS_NOTICE_LOG("child %i was killed by signal %i\n", (int)pid,
			WTERMSIG(status));
	else
		DSS_WARNING_LOG("child %i terminated abormally\n", (int)pid);
}

static int wait_for_process(pid_t pid, int *status)
{
	int ret;

	DSS_DEBUG_LOG("Waiting for process %d to terminate\n", (int)pid);
	for (;;) {
		fd_set rfds;

		FD_ZERO(&rfds);
		FD_SET(signal_pipe, &rfds);
		ret = dss_select(signal_pipe + 1, &rfds, NULL, NULL);
		if (ret < 0)
			break;
		ret = next_signal();
		if (!ret)
			continue;
		if (ret == SIGCHLD) {
			ret = waitpid(pid, status, 0);
			if (ret >= 0)
				break;
			if (errno != EINTR) { /* error */
				ret = -ERRNO_TO_DSS_ERROR(errno);
				break;
			}
		}
		/* SIGINT or SIGTERM */
		dss_kill(pid, SIGTERM, "killing child process");
	}
	if (ret < 0)
		DSS_ERROR_LOG("failed to wait for process %d\n", (int)pid);
	else
		log_termination_msg(pid, *status);
	return ret;
}

static void handle_pre_remove_exit(int status)
{
	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
		snapshot_removal_status = HS_READY;
		gettimeofday(&next_removal_check, NULL);
		next_removal_check.tv_sec += 60;
		return;
	}
	snapshot_removal_status = HS_PRE_SUCCESS;
}

static int handle_rm_exit(int status)
{
	if (!WIFEXITED(status)) {
		snapshot_removal_status = HS_READY;
		return -E_INVOLUNTARY_EXIT;
	}
	if (WEXITSTATUS(status)) {
		snapshot_removal_status = HS_READY;
		return -E_BAD_EXIT_CODE;
	}
	snapshot_removal_status = HS_SUCCESS;
	return 1;
}

static void handle_post_remove_exit(void)
{
	snapshot_removal_status = HS_READY;
}

static int handle_remove_exit(int status)
{
	int ret;
	struct snapshot *s = snapshot_currently_being_removed;

	assert(s);
	switch (snapshot_removal_status) {
	case HS_PRE_RUNNING:
		handle_pre_remove_exit(status);
		ret = 1;
		break;
	case HS_RUNNING:
		ret = handle_rm_exit(status);
		break;
	case HS_POST_RUNNING:
		handle_post_remove_exit();
		ret = 1;
		break;
	default:
		ret = -E_BUG;
	}
	if (snapshot_removal_status == HS_READY) {
		free(s->name);
		free(s);
		snapshot_currently_being_removed = NULL;
	}
	remove_pid = 0;
	return ret;
}

static int wait_for_remove_process(void)
{
	int status, ret;

	assert(remove_pid);
	assert(
		snapshot_removal_status == HS_PRE_RUNNING ||
		snapshot_removal_status == HS_RUNNING ||
		snapshot_removal_status == HS_POST_RUNNING
	);
	ret = wait_for_process(remove_pid, &status);
	if (ret < 0)
		return ret;
	return handle_remove_exit(status);
}

static int handle_rsync_exit(int status)
{
	int es, ret;

	if (!WIFEXITED(status)) {
		DSS_ERROR_LOG("rsync process %d died involuntary\n", (int)create_pid);
		ret = -E_INVOLUNTARY_EXIT;
		snapshot_creation_status = HS_READY;
		goto out;
	}
	es = WEXITSTATUS(status);
	/*
	 * Restart rsync on non-fatal errors:
	 * 24: Partial transfer due to vanished source files
	 */
	if (es != 0 && es != 24) {
		DSS_WARNING_LOG("rsync exit code %d, error count %d\n",
			es, ++num_consecutive_rsync_errors);
		if (!logfile) { /* called by com_run() */
			ret = -E_BAD_EXIT_CODE;
			goto out;
		}
		if (num_consecutive_rsync_errors >
				OPT_UINT32_VAL(RUN, MAX_RSYNC_ERRORS)) {
			ret = -E_TOO_MANY_RSYNC_ERRORS;
			snapshot_creation_status = HS_READY;
			goto out;
		}
		DSS_WARNING_LOG("restarting rsync process\n");
		snapshot_creation_status = HS_NEEDS_RESTART;
		next_snapshot_time = get_current_time() + 60;
		ret = 1;
		goto out;
	}
	num_consecutive_rsync_errors = 0;
	ret = rename_incomplete_snapshot(current_snapshot_creation_time);
	if (ret < 0)
		goto out;
	snapshot_creation_status = HS_SUCCESS;
	free(name_of_reference_snapshot);
	name_of_reference_snapshot = NULL;
out:
	create_process_stopped = 0;
	return ret;
}

static int handle_pre_create_hook_exit(int status)
{
	int es, ret;
	static int warn_count;

	if (!WIFEXITED(status)) {
		snapshot_creation_status = HS_READY;
		ret = -E_INVOLUNTARY_EXIT;
		goto out;
	}
	es = WEXITSTATUS(status);
	if (es) {
		if (!warn_count--) {
			DSS_NOTICE_LOG("pre_create_hook %s returned %d\n",
				OPT_STRING_VAL(DSS, PRE_CREATE_HOOK), es);
			DSS_NOTICE_LOG("deferring snapshot creation...\n");
			warn_count = 60; /* warn only once per hour */
		}
		next_snapshot_time = get_current_time() + 60;
		snapshot_creation_status = HS_READY;
		ret = 0;
		goto out;
	}
	warn_count = 0;
	snapshot_creation_status = HS_PRE_SUCCESS;
	ret = 1;
out:
	return ret;
}

static int handle_sigchld(void)
{
	pid_t pid;
	int status, ret = reap_child(&pid, &status);

	if (ret <= 0)
		return ret;

	if (pid == create_pid) {
		switch (snapshot_creation_status) {
		case HS_PRE_RUNNING:
			ret = handle_pre_create_hook_exit(status);
			break;
		case HS_RUNNING:
			ret = handle_rsync_exit(status);
			break;
		case HS_POST_RUNNING:
			snapshot_creation_status = HS_READY;
			ret = 1;
			break;
		default:
			DSS_EMERG_LOG("BUG: create can't die in status %d\n",
				snapshot_creation_status);
			return -E_BUG;
		}
		create_pid = 0;
		return ret;
	}
	if (pid == remove_pid) {
		ret = handle_remove_exit(status);
		if (ret < 0)
			return ret;
		return ret;
	}
	DSS_EMERG_LOG("BUG: unknown process %d died\n", (int)pid);
	return -E_BUG;
}

/* also checks if . is a mountpoint, if --mountpoint was given */
static int change_to_dest_dir(void)
{
	int ret;
	const char *dd = OPT_STRING_VAL(DSS, DEST_DIR);
	struct stat dot, dotdot;

	DSS_INFO_LOG("changing cwd to %s\n", dd);
	if (chdir(dd) < 0) {
		ret = -ERRNO_TO_DSS_ERROR(errno);
		DSS_ERROR_LOG("could not change cwd to %s\n", dd);
		return ret;
	}
	if (!OPT_GIVEN(DSS, MOUNTPOINT))
		return 0;
	if (stat(".", &dot) < 0) {
		ret = -ERRNO_TO_DSS_ERROR(errno);
		DSS_ERROR_LOG("could not stat .\n");
		return ret;
	}
	if (stat("..", &dotdot) < 0) {
		ret = -ERRNO_TO_DSS_ERROR(errno);
		DSS_ERROR_LOG("could not stat ..\n");
		return ret;
	}
	if (dot.st_dev == dotdot.st_dev && dot.st_ino != dotdot.st_ino) {
		DSS_ERROR_LOG("mountpoint check failed for %s\n", dd);
		return -E_MOUNTPOINT;
	}
	return 1;
}

static int check_config(void)
{
	uint32_t unit_interval = OPT_UINT32_VAL(DSS, UNIT_INTERVAL);
	uint32_t num_intervals = OPT_UINT32_VAL(DSS, NUM_INTERVALS);

	if (unit_interval == 0) {
		DSS_ERROR_LOG("bad unit interval: %i\n", unit_interval);
		return -E_INVALID_NUMBER;
	}
	DSS_DEBUG_LOG("unit interval: %i day(s)\n", unit_interval);

	if (num_intervals == 0 || num_intervals > 30) {
		DSS_ERROR_LOG("bad number of intervals: %i\n", num_intervals);
		return -E_INVALID_NUMBER;
	}
	if (subcmd == CMD_PTR(RUN) || subcmd == CMD_PTR(CREATE))
		if (!OPT_GIVEN(DSS, SOURCE_DIR)) {
			DSS_ERROR_LOG("--source-dir required\n");
			return -E_SYNTAX;
		}
	if (subcmd == CMD_PTR(RUN) || subcmd == CMD_PTR(CREATE)
			|| subcmd == CMD_PTR(LS) || subcmd == CMD_PTR(PRUNE)) {
		if (!OPT_GIVEN(DSS, DEST_DIR)) {
			DSS_ERROR_LOG("--dest-dir required\n");
			return -E_SYNTAX;
		}
	}
	DSS_DEBUG_LOG("number of intervals: %i\n", num_intervals);
	return 1;
}

static int lopsub_error(int lopsub_ret, char **errctx)
{
	const char *msg = lls_strerror(-lopsub_ret);
	if (*errctx)
		DSS_ERROR_LOG("%s: %s\n", *errctx, msg);
	else
		DSS_ERROR_LOG("%s\n", msg);
	free(*errctx);
	*errctx = NULL;
	return -E_LOPSUB;
}

static int parse_config_file(bool sighup, const struct lls_command *cmd)
{
	int ret, fd = -1;
	struct stat statbuf;
	void *map;
	size_t sz;
	int cf_argc;
	char **cf_argv, *errctx = NULL;
	struct lls_parse_result *cf_lpr, *merged_lpr, *clpr;
	const char *subcmd_name;

	ret = open(config_file, O_RDONLY);
	if (ret < 0) {
		if (errno != ENOENT || OPT_GIVEN(DSS, CONFIG_FILE)) {
			ret = -ERRNO_TO_DSS_ERROR(errno);
			DSS_ERROR_LOG("config file %s can not be opened\n",
				config_file);
			goto out;
		}
		/* no config file -- nothing to do */
		ret = 0;
		goto success;
	}
	fd = ret;
	ret = fstat(fd, &statbuf);
	if (ret < 0) {
		ret = -ERRNO_TO_DSS_ERROR(errno);
		DSS_ERROR_LOG("failed to stat config file %s\n", config_file);
		goto close_fd;
	}
	sz = statbuf.st_size;
	if (sz == 0) { /* config file is empty -- nothing to do */
		ret = 0;
		goto success;
	}
	map = mmap(NULL, sz, PROT_READ, MAP_PRIVATE, fd, 0);
	if (map == MAP_FAILED) {
		ret = -ERRNO_TO_DSS_ERROR(errno);
		DSS_ERROR_LOG("failed to mmap config file %s\n",
			config_file);
		goto close_fd;
	}
	if (cmd == CMD_PTR(DSS))
		subcmd_name = NULL;
	else
		subcmd_name = lls_command_name(cmd);
	ret = lls_convert_config(map, sz, subcmd_name, &cf_argv, &errctx);
	munmap(map, sz);
	if (ret < 0) {
		DSS_ERROR_LOG("failed to convert config file %s\n",
			config_file);
		ret = lopsub_error(ret, &errctx);
		goto close_fd;
	}
	cf_argc = ret;
	ret = lls_parse(cf_argc, cf_argv, cmd, &cf_lpr, &errctx);
	lls_free_argv(cf_argv);
	if (ret < 0) {
		ret = lopsub_error(ret, &errctx);
		goto close_fd;
	}
	clpr = cmd == CMD_PTR(DSS)? cmdline_lpr : cmdline_sublpr;
	if (sighup) /* config file overrides command line */
		ret = lls_merge(cf_lpr, clpr, cmd, &merged_lpr, &errctx);
	else /* command line options overrride config file options */
		ret = lls_merge(clpr, cf_lpr, cmd, &merged_lpr, &errctx);
	lls_free_parse_result(cf_lpr, cmd);
	if (ret < 0) {
		ret = lopsub_error(ret, &errctx);
		goto close_fd;
	}
	ret = 1;
success:
	assert(ret >= 0);
	DSS_DEBUG_LOG("loglevel: %d\n", OPT_UINT32_VAL(DSS, LOGLEVEL));
	if (cmd != CMD_PTR(DSS)) {
		if (ret > 0) {
			if (sublpr != cmdline_sublpr)
				lls_free_parse_result(sublpr, cmd);
			sublpr = merged_lpr;
		} else
			sublpr = cmdline_sublpr;
	} else {
		if (ret > 0) {
			if (lpr != cmdline_lpr)
				lls_free_parse_result(lpr, cmd);
			lpr = merged_lpr;
		} else
			lpr = cmdline_lpr;
	}
close_fd:
	if (fd >= 0)
		close(fd);
out:
	return ret;
}

static int handle_sighup(void)
{
	int ret;

	DSS_NOTICE_LOG("SIGHUP, re-reading config\n");
	dump_dss_config("old");
	ret = parse_config_file(true /* SIGHUP */, CMD_PTR(DSS));
	if (ret < 0)
		return ret;
	ret = parse_config_file(true /* SIGHUP */, CMD_PTR(RUN));
	if (ret < 0)
		return ret;
	ret = check_config();
	if (ret < 0)
		return ret;
	close_log(logfile);
	logfile = NULL;
	if (OPT_GIVEN(RUN, DAEMON) || daemonized) {
		logfile = open_log(OPT_STRING_VAL(RUN, LOGFILE));
		log_welcome(OPT_UINT32_VAL(DSS, LOGLEVEL));
		daemonized = true;
	}
	dump_dss_config("reloaded");
	invalidate_next_snapshot_time();
	return 1;
}

static void kill_children(void)
{
	restart_create_process();
	dss_kill(create_pid, SIGTERM, NULL);
	dss_kill(remove_pid, SIGTERM, NULL);
}

static int handle_signal(void)
{
	int sig, ret = next_signal();

	if (ret <= 0)
		goto out;
	sig = ret;
	switch (sig) {
	case SIGINT:
	case SIGTERM:
		return -E_SIGNAL;
	case SIGHUP:
		ret = handle_sighup();
		break;
	case SIGCHLD:
		ret = handle_sigchld();
		break;
	}
out:
	if (ret < 0)
		DSS_ERROR_LOG("%s\n", dss_strerror(-ret));
	return ret;
}

/*
 * We can not use rsync locally if the local user is different from the remote
 * user or if the src dir is not on the local host (or both).
 */
static int use_rsync_locally(char *logname)
{
	const char *h = OPT_STRING_VAL(DSS, REMOTE_HOST);

	if (strcmp(h, "localhost") && strcmp(h, "127.0.0.1"))
		return 0;
	if (OPT_GIVEN(DSS, REMOTE_USER) &&
			strcmp(OPT_STRING_VAL(DSS, REMOTE_USER), logname))
		return 0;
	return 1;
}

static int rename_resume_snap(int64_t creation_time)
{
	struct snapshot_list sl;
	struct snapshot *s = NULL;
	char *new_name = incomplete_name(creation_time);
	int ret;
	const char *why;

	sl.num_snapshots = 0;

	ret = 0;
	dss_get_snapshot_list(&sl);
	/*
	 * Snapshot recycling: We first look at the newest snapshot. If this
	 * snapshot happens to be incomplete, the last rsync process was
	 * aborted and we reuse this one. Otherwise we look at snapshots which
	 * could be removed (outdated and redundant snapshots) as candidates
	 * for recycling. If no outdated/redundant snapshot exists, we check if
	 * there is an orphaned snapshot, which likely is useless anyway.
	 *
	 * Only if no existing snapshot is suitable for recycling, we bite the
	 * bullet and create a new one.
	 */
	s = get_newest_snapshot(&sl);
	if (!s) /* no snapshots at all */
		goto out;
	/* re-use last snapshot if it is incomplete */
	why = "aborted";
	if ((s->flags & SS_COMPLETE) == 0)
		goto out;
	why = "outdated";
	s = find_outdated_snapshot(&sl);
	if (s)
		goto out;
	why = "redundant";
	s = find_redundant_snapshot(&sl);
	if (s)
		goto out;
	why = "orphaned";
	s = find_orphaned_snapshot(&sl);
out:
	if (s) {
		DSS_NOTICE_LOG("recycling %s snapshot %s\n", why, s->name);
		ret = dss_rename(s->name, new_name);
	}
	if (ret >= 0)
		DSS_NOTICE_LOG("creating %s\n", new_name);
	free(new_name);
	free_snapshot_list(&sl);
	return ret;
}

static void create_rsync_argv(char ***argv, int64_t *num)
{
	char *logname;
	int i = 0, j, N;
	struct snapshot_list sl;
	static bool seeded;

	dss_get_snapshot_list(&sl);
	assert(!name_of_reference_snapshot);
	name_of_reference_snapshot = name_of_newest_complete_snapshot(&sl);
	free_snapshot_list(&sl);

	/*
	 * We specify up to 6 arguments, one argument per given rsync option
	 * and one argument per given source dir. We also need space for the
	 * terminating NULL pointer.
	 */
	N = OPT_GIVEN(DSS, RSYNC_OPTION) + OPT_GIVEN(DSS, SOURCE_DIR);
	*argv = dss_malloc((7 + N) * sizeof(char *));
	(*argv)[i++] = dss_strdup("rsync");
	(*argv)[i++] = dss_strdup("-a");
	(*argv)[i++] = dss_strdup("--delete");
	if (!seeded) {
		srandom((unsigned)time(NULL)); /* no need to be fancy here */
		seeded = true;
	}
	if (1000 * (random() / (RAND_MAX + 1.0)) < OPT_UINT32_VAL(DSS, CHECKSUM)) {
		DSS_NOTICE_LOG("adding --checksum to rsync options\n");
		(*argv)[i++] = dss_strdup("--checksum");
	}
	for (j = 0; j < OPT_GIVEN(DSS, RSYNC_OPTION); j++)
		(*argv)[i++] = dss_strdup(lls_string_val(j,
			OPT_RESULT(DSS, RSYNC_OPTION)));
	if (name_of_reference_snapshot) {
		DSS_INFO_LOG("using %s as reference\n", name_of_reference_snapshot);
		(*argv)[i++] = make_message("--link-dest=../%s",
			name_of_reference_snapshot);
	} else
		DSS_INFO_LOG("no suitable reference snapshot found\n");
	logname = dss_logname();
	if (use_rsync_locally(logname)) {
		for (j = 0; j < OPT_GIVEN(DSS, SOURCE_DIR); j++)
			(*argv)[i++] = dss_strdup(lls_string_val(j,
				OPT_RESULT(DSS, SOURCE_DIR)));
	} else {
		/*
		 * dss-1.0 and earlier did not support multiple source
		 * directories.  These versions appended a slash to the end of
		 * the source directory to make sure that only the contents of
		 * the single source directory, but not the directory itself,
		 * are copied to the destination. For multiple source
		 * directories, however, this is not a good idea because the
		 * source directories may well contain identical file names,
		 * which would then be copied to the same location on the
		 * destination, overwriting each other. Moreover, we want the
		 * directory on the destination match the source. To preserve
		 * the old behaviour, we thus have to special-case N=1.
		 */
		for (j = 0; j < OPT_GIVEN(DSS, SOURCE_DIR); j++) {
			(*argv)[i++] = make_message("%s@%s:%s%s",
				OPT_GIVEN(DSS, REMOTE_USER)?
					OPT_STRING_VAL(DSS, REMOTE_USER) : logname,
				OPT_STRING_VAL(DSS, REMOTE_HOST),
				lls_string_val(j, OPT_RESULT(DSS, SOURCE_DIR)),
				OPT_GIVEN(DSS, SOURCE_DIR) == 1? "/" : ""
			);
		}
	}
	free(logname);
	*num = get_current_time();
	(*argv)[i++] = incomplete_name(*num);
	(*argv)[i++] = NULL;
	for (j = 0; j < i; j++)
		DSS_DEBUG_LOG("argv[%d] = %s\n", j, (*argv)[j]);
}

static void free_rsync_argv(char **argv)
{
	int i;

	if (!argv)
		return;
	for (i = 0; argv[i]; i++)
		free(argv[i]);
	free(argv);
}

static int create_snapshot(char **argv)
{
	int ret;

	assert(argv);
	ret = rename_resume_snap(current_snapshot_creation_time);
	if (ret < 0)
		return ret;
	dss_exec(&create_pid, argv[0], argv);
	snapshot_creation_status = HS_RUNNING;
	return ret;
}

static int select_loop(void)
{
	int ret;
	/* check every 60 seconds for free disk space */
	struct timeval tv;
	char **rsync_argv = NULL;

	for (;;) {
		fd_set rfds;
		struct timeval *tvp;

		if (remove_pid)
			tvp = NULL; /* sleep until rm hook/process dies */
		else { /* sleep one minute */
			tv.tv_sec = 60;
			tv.tv_usec = 0;
			tvp = &tv;
		}
		FD_ZERO(&rfds);
		FD_SET(signal_pipe, &rfds);
		ret = dss_select(signal_pipe + 1, &rfds, NULL, tvp);
		if (ret < 0)
			goto out;
		if (FD_ISSET(signal_pipe, &rfds)) {
			ret = handle_signal();
			if (ret < 0)
				goto out;
		}
		if (remove_pid)
			continue;
		if (snapshot_removal_status == HS_PRE_SUCCESS) {
			ret = exec_rm();
			if (ret < 0)
				goto out;
			continue;
		}
		if (snapshot_removal_status == HS_SUCCESS) {
			post_remove_hook();
			continue;
		}
		ret = try_to_free_disk_space();
		if (ret < 0)
			goto out;
		if (snapshot_removal_status != HS_READY) {
			stop_create_process();
			continue;
		}
		restart_create_process();
		switch (snapshot_creation_status) {
		case HS_READY:
			if (!next_snapshot_is_due())
				continue;
			pre_create_hook();
			continue;
		case HS_PRE_RUNNING:
		case HS_RUNNING:
		case HS_POST_RUNNING:
			continue;
		case HS_PRE_SUCCESS:
			if (!name_of_reference_snapshot) {
				free_rsync_argv(rsync_argv);
				create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
			}
			ret = create_snapshot(rsync_argv);
			if (ret < 0)
				goto out;
			continue;
		case HS_NEEDS_RESTART:
			if (!next_snapshot_is_due())
				continue;
			ret = create_snapshot(rsync_argv);
			if (ret < 0)
				goto out;
			continue;
		case HS_SUCCESS:
			post_create_hook();
			continue;
		}
	}
out:
	return ret;
}

static void exit_hook(int exit_code)
{
	pid_t pid;
	char **argv, *tmp = dss_strdup(OPT_STRING_VAL(DSS, EXIT_HOOK));
	unsigned n = split_args(tmp, &argv);

	n++;
	argv = dss_realloc(argv, (n + 1) * sizeof(char *));
	argv[n - 1] = dss_strdup(dss_strerror(-exit_code));
	argv[n] = NULL;
	dss_exec(&pid, argv[0], argv);
	free(argv[n - 1]);
	free(argv);
	free(tmp);
}

static void lock_dss_or_die(void)
{
	int ret = lock_dss(ipc_key);

	if (ret < 0) {
		DSS_EMERG_LOG("failed to lock: %s\n", dss_strerror(-ret));
		exit(EXIT_FAILURE);
	}
}

static int com_run(void)
{
	int ret, fd = -1;
	pid_t pid;

	if (OPT_GIVEN(DSS, DRY_RUN)) {
		DSS_ERROR_LOG("dry run not supported by this command\n");
		return -E_SYNTAX;
	}
	ret = get_dss_pid(ipc_key, &pid);
	if (ret >= 0) {
		DSS_ERROR_LOG("pid %d\n", (int)pid);
		return -E_ALREADY_RUNNING;
	}
	/*
	 * Order is important here: Since daemon_init() forks, it would drop
	 * the lock if it had been acquired already. Changing the cwd before
	 * grabbing the lock causes stat(2) to fail in case a relative config
	 * file path was given, which results in a different key ID for
	 * locking. Therefore we must first daemonize, then lock, then change
	 * the cwd.
	 */
	if (OPT_GIVEN(RUN, DAEMON)) {
		fd = daemon_init();
		daemonized = true;
		logfile = open_log(OPT_STRING_VAL(RUN, LOGFILE));
	}
	lock_dss_or_die();
	ret = change_to_dest_dir();
	if (ret < 0)
		return ret;
	dump_dss_config("startup");
	ret = install_sighandler(SIGHUP);
	if (ret < 0)
		return ret;
	if (fd >= 0) {
		ret = write(fd, "\0", 1);
		if (ret != 1) {
			DSS_ERROR_LOG("write to daemon pipe returned %d\n",
				ret);
			if (ret < 0)
				return -ERRNO_TO_DSS_ERROR(errno);
			return -E_BUG;
		}
	}
	ret = select_loop();
	if (ret >= 0) /* impossible */
		ret = -E_BUG;
	kill_children();
	exit_hook(ret);
	while (wait(NULL) >= 0 || errno != ECHILD)
		; /* still have children to wait for */
	return ret;
}
EXPORT_CMD_HANDLER(run);

static int com_prune(void)
{
	int ret;
	struct snapshot_list sl;
	struct snapshot *victim;
	struct disk_space ds;
	char *why;
	bool try_hard;

	lock_dss_or_die();
	ret = change_to_dest_dir();
	if (ret < 0)
		return ret;
	switch (OPT_UINT32_VAL(PRUNE, DISK_SPACE)) {
	case FDS_LOW: try_hard = true; break;
	case FDS_HIGH: try_hard = false; break;
	default:
		ret = get_disk_space(".", &ds);
		if (ret < 0)
			return ret;
		log_disk_space(&ds);
		try_hard = disk_space_low(&ds);
	}
	dss_get_snapshot_list(&sl);
	victim = find_removable_snapshot(&sl, try_hard, &why);
	if (!victim) {
		dss_msg("nothing to prune\n");
		ret = 0;
		goto free_sl;
	}
	if (OPT_GIVEN(DSS, DRY_RUN)) {
		dss_msg("picking %s snapshot %s (interval = %i)\n",
			why, victim->name, victim->interval);
		ret = 0;
		goto free_why;
	}
	pre_remove_hook(victim, why);
	if (snapshot_removal_status == HS_PRE_RUNNING) {
		ret = wait_for_remove_process();
		if (ret < 0)
			goto free_why;
		ret = -E_HOOK_FAILED;
		if (snapshot_removal_status != HS_PRE_SUCCESS)
			goto free_why;
	}
	ret = exec_rm();
	if (ret < 0)
		goto free_why;
	ret = wait_for_remove_process();
	if (ret < 0)
		goto free_why;
	assert(snapshot_removal_status == HS_SUCCESS);
	post_remove_hook();
	assert(snapshot_removal_status == HS_POST_RUNNING);
	ret = wait_for_remove_process();
free_why:
	free(why);
free_sl:
	free_snapshot_list(&sl);
	return ret;
}
EXPORT_CMD_HANDLER(prune);

static int com_create(void)
{
	int ret, status;
	char **rsync_argv;

	lock_dss_or_die();
	ret = change_to_dest_dir();
	if (ret < 0)
		return ret;
	if (OPT_GIVEN(DSS, DRY_RUN)) {
		int i;
		char *msg = NULL;
		create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
		for (i = 0; rsync_argv[i]; i++) {
			char *tmp = msg;
			msg = make_message("%s%s%s", tmp? tmp : "",
				tmp? " " : "", rsync_argv[i]);
			free(tmp);
		}
		free_rsync_argv(rsync_argv);
		dss_msg("%s\n", msg);
		free(msg);
		return 1;
	}
	pre_create_hook();
	if (create_pid) {
		ret = wait_for_process(create_pid, &status);
		if (ret < 0)
			return ret;
		ret = handle_pre_create_hook_exit(status);
		if (ret <= 0) /* error, or pre-create failed */
			return ret;
	}
	create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
	ret = create_snapshot(rsync_argv);
	if (ret < 0)
		goto out;
	ret = wait_for_process(create_pid, &status);
	if (ret < 0)
		goto out;
	ret = handle_rsync_exit(status);
	if (ret < 0)
		goto out;
	post_create_hook();
	if (create_pid)
		ret = wait_for_process(create_pid, &status);
out:
	free_rsync_argv(rsync_argv);
	return ret;
}
EXPORT_CMD_HANDLER(create);

static int com_ls(void)
{
	int i, ret;
	struct snapshot_list sl;
	struct snapshot *s;
	int64_t now = get_current_time();

	ret = change_to_dest_dir();
	if (ret < 0)
		return ret;
	dss_get_snapshot_list(&sl);
	FOR_EACH_SNAPSHOT(s, i, &sl) {
		int64_t d;
		if (s->flags & SS_COMPLETE)
			d = (s->completion_time - s->creation_time) / 60;
		else
			d = (now - s->creation_time) / 60;
		dss_msg("%u\t%s\t%3" PRId64 ":%02" PRId64 "\n", s->interval,
			s->name, d / 60, d % 60);
	}
	free_snapshot_list(&sl);
	return 1;
}
EXPORT_CMD_HANDLER(ls);

static int com_configtest(void)
{
	printf("Syntax Ok\n");
	return 0;
}
EXPORT_CMD_HANDLER(configtest);

static int setup_signal_handling(void)
{
	int ret;

	DSS_INFO_LOG("setting up signal handlers\n");
	signal_pipe = signal_init(); /* always successful */
	ret = install_sighandler(SIGINT);
	if (ret < 0)
		return ret;
	ret = install_sighandler(SIGTERM);
	if (ret < 0)
		return ret;
	return install_sighandler(SIGCHLD);
}

const char *dss_version(void);
static void handle_version_and_help(void)
{
	char *txt;

	if (OPT_GIVEN(DSS, VERSION)) {
		printf("%s\n", dss_version());
		exit(EXIT_SUCCESS);
	}
	if (OPT_GIVEN(DSS, DETAILED_HELP))
		txt = lls_long_help(CMD_PTR(DSS));
	else if (OPT_GIVEN(DSS, HELP))
		txt = lls_short_help(CMD_PTR(DSS));
	else
		return;
	printf("%s", txt);
	printf("\nRun dss help for help on subcommands.\n");
	free(txt);
	exit(EXIT_SUCCESS);
}

static void show_subcommand_summary(void)
{
	const struct lls_command *cmd;
	int i;

	printf("Available subcommands:\n");
	for (i = 1; (cmd = lls_cmd(i, dss_suite)); i++) {
		const char *name = lls_command_name(cmd);
		const char *purpose = lls_purpose(cmd);
		printf("%-11s%s\n", name, purpose);
	}
	printf("\nRun dss help <subcmd> for help on <subcmd>.\n");
}

static int com_help(void)
{
	int ret;
	char *errctx, *help;
	const char *arg;
	const struct lls_command *cmd;

	ret = lls_check_arg_count(sublpr, 0, 1, &errctx);
	if (ret < 0)
		return lopsub_error(ret, &errctx);
	if (lls_num_inputs(sublpr) == 0) {
		show_subcommand_summary();
		return 0;
	}
	arg = lls_input(0, sublpr);
	ret = lls_lookup_subcmd(arg, dss_suite, &errctx);
	if (ret < 0)
		return lopsub_error(ret, &errctx);
	cmd = lls_cmd(ret, dss_suite);
	if (OPT_GIVEN(HELP, LONG))
		help = lls_long_help(cmd);
	else
		help = lls_short_help(cmd);
	printf("%s", help);
	free(help);
	if (!OPT_GIVEN(HELP, LONG))
		printf("\nRun dss -- help -l %s for long help.\n", arg);
	return 0;
}
EXPORT_CMD_HANDLER(help);

int main(int argc, char **argv)
{
	int ret;
	char *errctx = NULL;
	unsigned num_inputs;
	const struct dss_user_data *ud;

	ret = lls_parse(argc, argv, CMD_PTR(DSS), &cmdline_lpr, &errctx);
	if (ret < 0) {
		ret = lopsub_error(ret, &errctx);
		goto out;
	}
	lpr = cmdline_lpr;
	set_config_file_name();
	ret = parse_config_file(false /* no SIGHUP */, CMD_PTR(DSS));
	if (ret < 0)
		goto out;
	handle_version_and_help();
	num_inputs = lls_num_inputs(lpr);
	if (num_inputs == 0) {
		show_subcommand_summary();
		ret = 0;
		goto out;
	}
	ret = lls_lookup_subcmd(argv[argc - num_inputs], dss_suite, &errctx);
	if (ret < 0) {
		ret = lopsub_error(ret, &errctx);
		goto out;
	}
	subcmd = lls_cmd(ret, dss_suite);
	ret = lls_parse(num_inputs, argv + argc - num_inputs, subcmd,
		&cmdline_sublpr, &errctx);
	if (ret < 0) {
		ret = lopsub_error(ret, &errctx);
		goto out;
	}
	sublpr = cmdline_sublpr;
	ret = parse_config_file(false /* no SIGHUP */, subcmd);
	if (ret < 0)
		goto out;
	ret = check_config();
	if (ret < 0)
		goto out;
	ret = setup_signal_handling();
	if (ret < 0)
		goto out;
	ud = lls_user_data(subcmd);
	ret = ud->handler();
	signal_shutdown();
out:
	if (ret < 0) {
		if (errctx)
			DSS_ERROR_LOG("%s\n", errctx);
		DSS_EMERG_LOG("%s\n", dss_strerror(-ret));
	}
	free(errctx);
	lls_free_parse_result(lpr, CMD_PTR(DSS));
	if (lpr != cmdline_lpr)
		lls_free_parse_result(cmdline_lpr, CMD_PTR(DSS));
	lls_free_parse_result(sublpr, subcmd);
	if (sublpr != cmdline_sublpr)
		lls_free_parse_result(cmdline_sublpr, subcmd);
	free(config_file);
	exit(ret >= 0? EXIT_SUCCESS : EXIT_FAILURE);
}