networking/udhcp/files.c - codeaurora/busybox - Gitiles

 /* vi: set sw=4 ts=4: */
 /*
  * files.c -- DHCP server file manipulation *
  * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
  *
  * Licensed under GPLv2, see file LICENSE in this tarball for details.
  */

 #include <netinet/ether.h>

 #include "common.h"
 #include "dhcpd.h"
 #include "options.h"


 /* on these functions, make sure your datatype matches */
 static int read_ip(const char *line, void *arg)
 {
 	len_and_sockaddr *lsa;

 	lsa = host_and_af2sockaddr(line, 0, AF_INET);
 	if (!lsa)
 		return 0;
 	*(uint32_t*)arg = lsa->u.sin.sin_addr.s_addr;
 	free(lsa);
 	return 1;
 }

 static int read_mac(const char *line, void *arg)
 {
 	return NULL == ether_aton_r(line, (struct ether_addr *)arg);
 }


 static int read_str(const char *line, void *arg)
 {
 	char **dest = arg;

 	free(*dest);
 	*dest = xstrdup(line);
 	return 1;
 }


 static int read_u32(const char *line, void *arg)
 {
 	*(uint32_t*)arg = bb_strtou32(line, NULL, 10);
 	return errno == 0;
 }


 static int read_yn(const char *line, void *arg)
 {
 	char *dest = arg;

 	if (!strcasecmp("yes", line)) {
 		*dest = 1;
 		return 1;
 	}
 	if (!strcasecmp("no", line)) {
 		*dest = 0;
 		return 1;
 	}
 	return 0;
 }


 /* find option 'code' in opt_list */
 struct option_set* FAST_FUNC find_option(struct option_set *opt_list, uint8_t code)
 {
 	while (opt_list && opt_list->data[OPT_CODE] < code)
 		opt_list = opt_list->next;

 	if (opt_list && opt_list->data[OPT_CODE] == code)
 		return opt_list;
 	return NULL;
 }


 /* add an option to the opt_list */
 static void attach_option(struct option_set **opt_list,
 		const struct dhcp_option *option, char *buffer, int length)
 {
 	struct option_set *existing, *new, **curr;

 	existing = find_option(*opt_list, option->code);
 	if (!existing) {
 		DEBUG("Attaching option %02x to list", option->code);

 #if ENABLE_FEATURE_UDHCP_RFC3397
 		if ((option->flags & TYPE_MASK) == OPTION_STR1035)
 			/* reuse buffer and length for RFC1035-formatted string */
 			buffer = (char *)dname_enc(NULL, 0, buffer, &length);
 #endif

 		/* make a new option */
 		new = xmalloc(sizeof(*new));
 		new->data = xmalloc(length + 2);
 		new->data[OPT_CODE] = option->code;
 		new->data[OPT_LEN] = length;
 		memcpy(new->data + 2, buffer, length);

 		curr = opt_list;
 		while (*curr && (*curr)->data[OPT_CODE] < option->code)
 			curr = &(*curr)->next;

 		new->next = *curr;
 		*curr = new;
 #if ENABLE_FEATURE_UDHCP_RFC3397
 		if ((option->flags & TYPE_MASK) == OPTION_STR1035 && buffer != NULL)
 			free(buffer);
 #endif
 		return;
 	}

 	/* add it to an existing option */
 	DEBUG("Attaching option %02x to existing member of list", option->code);
 	if (option->flags & OPTION_LIST) {
 #if ENABLE_FEATURE_UDHCP_RFC3397
 		if ((option->flags & TYPE_MASK) == OPTION_STR1035)
 			/* reuse buffer and length for RFC1035-formatted string */
 			buffer = (char *)dname_enc(existing->data + 2,
 					existing->data[OPT_LEN], buffer, &length);
 #endif
 		if (existing->data[OPT_LEN] + length <= 255) {
 			existing->data = xrealloc(existing->data,
 					existing->data[OPT_LEN] + length + 3);
 			if ((option->flags & TYPE_MASK) == OPTION_STRING) {
 				/* ' ' can bring us to 256 - bad */
 				if (existing->data[OPT_LEN] + length >= 255)
 					return;
 				/* add space separator between STRING options in a list */
 				existing->data[existing->data[OPT_LEN] + 2] = ' ';
 				existing->data[OPT_LEN]++;
 			}
 			memcpy(existing->data + existing->data[OPT_LEN] + 2, buffer, length);
 			existing->data[OPT_LEN] += length;
 		} /* else, ignore the data, we could put this in a second option in the future */
 #if ENABLE_FEATURE_UDHCP_RFC3397
 		if ((option->flags & TYPE_MASK) == OPTION_STR1035 && buffer != NULL)
 			free(buffer);
 #endif
 	} /* else, ignore the new data */
 }


 /* read a dhcp option and add it to opt_list */
 static int read_opt(const char *const_line, void *arg)
 {
 	struct option_set **opt_list = arg;
 	char *opt, *val, *endptr;
 	char *line;
 	const struct dhcp_option *option;
 	int retval, length, idx;
 	char buffer[8] ALIGNED(4);
 	uint16_t *result_u16 = (uint16_t *) buffer;
 	uint32_t *result_u32 = (uint32_t *) buffer;

 	/* Cheat, the only const line we'll actually get is "" */
 	line = (char *) const_line;
 	opt = strtok(line, " \t=");
 	if (!opt)
 		return 0;

 	idx = index_in_strings(dhcp_option_strings, opt); /* NB: was strcasecmp! */
 	if (idx < 0)
 		return 0;
 	option = &dhcp_options[idx];

 	retval = 0;
 	do {
 		val = strtok(NULL, ", \t");
 		if (!val) break;
 		length = dhcp_option_lengths[option->flags & TYPE_MASK];
 		retval = 0;
 		opt = buffer; /* new meaning for variable opt */
 		switch (option->flags & TYPE_MASK) {
 		case OPTION_IP:
 			retval = read_ip(val, buffer);
 			break;
 		case OPTION_IP_PAIR:
 			retval = read_ip(val, buffer);
 			val = strtok(NULL, ", \t/-");
 			if (!val)
 				retval = 0;
 			if (retval)
 				retval = read_ip(val, buffer + 4);
 			break;
 		case OPTION_STRING:
 #if ENABLE_FEATURE_UDHCP_RFC3397
 		case OPTION_STR1035:
 #endif
 			length = strlen(val);
 			if (length > 0) {
 				if (length > 254) length = 254;
 				opt = val;
 				retval = 1;
 			}
 			break;
 		case OPTION_BOOLEAN:
 			retval = read_yn(val, buffer);
 			break;
 		case OPTION_U8:
 			buffer[0] = strtoul(val, &endptr, 0);
 			retval = (endptr[0] == '\0');
 			break;
 		/* htonX are macros in older libc's, using temp var
 		 * in code below for safety */
 		/* TODO: use bb_strtoX? */
 		case OPTION_U16: {
 			unsigned long tmp = strtoul(val, &endptr, 0);
 			*result_u16 = htons(tmp);
 			retval = (endptr[0] == '\0' /*&& tmp < 0x10000*/);
 			break;
 		}
 		case OPTION_S16: {
 			long tmp = strtol(val, &endptr, 0);
 			*result_u16 = htons(tmp);
 			retval = (endptr[0] == '\0');
 			break;
 		}
 		case OPTION_U32: {
 			unsigned long tmp = strtoul(val, &endptr, 0);
 			*result_u32 = htonl(tmp);
 			retval = (endptr[0] == '\0');
 			break;
 		}
 		case OPTION_S32: {
 			long tmp = strtol(val, &endptr, 0);
 			*result_u32 = htonl(tmp);
 			retval = (endptr[0] == '\0');
 			break;
 		}
 		default:
 			break;
 		}
 		if (retval)
 			attach_option(opt_list, option, opt, length);
 	} while (retval && option->flags & OPTION_LIST);
 	return retval;
 }

 static int read_staticlease(const char *const_line, void *arg)
 {
 	char *line;
 	char *mac_string;
 	char *ip_string;
 	struct ether_addr mac_bytes;
 	uint32_t ip;

 	/* Read mac */
 	line = (char *) const_line;
 	mac_string = strtok_r(line, " \t", &line);
 	read_mac(mac_string, &mac_bytes);

 	/* Read ip */
 	ip_string = strtok_r(NULL, " \t", &line);
 	read_ip(ip_string, &ip);

 	addStaticLease(arg, (uint8_t*) &mac_bytes, ip);

 	if (ENABLE_UDHCP_DEBUG) printStaticLeases(arg);

 	return 1;
 }


 struct config_keyword {
 	const char *keyword;
 	int (*handler)(const char *line, void *var);
 	void *var;
 	const char *def;
 };

 static const struct config_keyword keywords[] = {
 	/* keyword       handler   variable address               default */
 	{"start",        read_ip,  &(server_config.start_ip),     "192.168.0.20"},
 	{"end",          read_ip,  &(server_config.end_ip),       "192.168.0.254"},
 	{"interface",    read_str, &(server_config.interface),    "eth0"},
 	/* Avoid "max_leases value not sane" warning by setting default
 	 * to default_end_ip - default_start_ip + 1: */
 	{"max_leases",   read_u32, &(server_config.max_leases),   "235"},
 //	{"remaining",    read_yn,  &(server_config.remaining),    "yes"},
 	{"auto_time",    read_u32, &(server_config.auto_time),    "7200"},
 	{"decline_time", read_u32, &(server_config.decline_time), "3600"},
 	{"conflict_time",read_u32, &(server_config.conflict_time),"3600"},
 	{"offer_time",   read_u32, &(server_config.offer_time),   "60"},
 	{"min_lease",    read_u32, &(server_config.min_lease),    "60"},
 	{"lease_file",   read_str, &(server_config.lease_file),   LEASES_FILE},
 	{"pidfile",      read_str, &(server_config.pidfile),      "/var/run/udhcpd.pid"},
 	{"siaddr",       read_ip,  &(server_config.siaddr),       "0.0.0.0"},
 	/* keywords with no defaults must be last! */
 	{"option",       read_opt, &(server_config.options),      ""},
 	{"opt",          read_opt, &(server_config.options),      ""},
 	{"notify_file",  read_str, &(server_config.notify_file),  ""},
 	{"sname",        read_str, &(server_config.sname),        ""},
 	{"boot_file",    read_str, &(server_config.boot_file),    ""},
 	{"static_lease", read_staticlease, &(server_config.static_leases), ""},
 };
 enum { KWS_WITH_DEFAULTS = ARRAY_SIZE(keywords) - 6 };

 void FAST_FUNC read_config(const char *file)
 {
 	parser_t *parser;
 	const struct config_keyword *k;
 	unsigned i;
 	char *token[2];

 	for (i = 0; i < KWS_WITH_DEFAULTS; i++)
 		keywords[i].handler(keywords[i].def, keywords[i].var);

 	parser = config_open(file);
 	while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) {
 		for (k = keywords, i = 0; i < ARRAY_SIZE(keywords); k++, i++) {
 			if (!strcasecmp(token[0], k->keyword)) {
 				if (!k->handler(token[1], k->var)) {
 					bb_error_msg("can't parse line %u in %s",
 							parser->lineno, file);
 					/* reset back to the default value */
 					k->handler(k->def, k->var);
 				}
 				break;
 			}
 		}
 	}
 	config_close(parser);

 	server_config.start_ip = ntohl(server_config.start_ip);
 	server_config.end_ip = ntohl(server_config.end_ip);
 }


 void FAST_FUNC write_leases(void)
 {
 	int fd;
 	unsigned i;
 	leasetime_t curr;

 	fd = open_or_warn(server_config.lease_file, O_WRONLY|O_CREAT|O_TRUNC);
 	if (fd < 0)
 		return;

 	curr = time(NULL);
 //TODO: write out current time? Readers need to adjust .expires field
 // to account for time between file was written and when it was read back.

 	for (i = 0; i < server_config.max_leases; i++) {
 		leasetime_t tmp_time;

 		if (leases[i].yiaddr == 0)
 			continue;

 		/* screw with the time in the struct, for easier writing */
 		tmp_time = leases[i].expires;

 		//if (server_config.remaining) {
 			leases[i].expires -= curr;
 			if ((signed_leasetime_t) leases[i].expires < 0)
 				leases[i].expires = 0;
 		//} /* else stick with the time we got */
 		leases[i].expires = htonl(leases[i].expires);

 		/* No error check. If the file gets truncated,
 		 * we lose some leases on restart. Oh well. */
 		full_write(fd, &leases[i], sizeof(leases[i]));

 		/* then restore it when done */
 		leases[i].expires = tmp_time;
 	}
 	close(fd);

 	if (server_config.notify_file) {
 // TODO: vfork-based child creation
 		char *cmd = xasprintf("%s %s", server_config.notify_file, server_config.lease_file);
 		system(cmd);
 		free(cmd);
 	}
 }


 void FAST_FUNC read_leases(const char *file)
 {
 	int fd;
 	unsigned i;
 //	leasetime_t curr;
 	struct dhcpOfferedAddr lease;

 	fd = open_or_warn(file, O_RDONLY);
 	if (fd < 0)
 		return;

 //	curr = time(NULL);
 	i = 0;
 	while (i < server_config.max_leases
 	 && full_read(fd, &lease, sizeof(lease)) == sizeof(lease)
 	) {
 		/* ADDME: what if it matches some static lease? */
 		uint32_t y = ntohl(lease.yiaddr);
 		if (y >= server_config.start_ip && y <= server_config.end_ip) {
 			leasetime_t expires = ntohl(lease.expires);
 //			if (!server_config.remaining)
 //				expires -= curr;
 			/* NB: add_lease takes "relative time", IOW,
 			 * lease duration, not lease deadline. */
 			if (!(add_lease(lease.chaddr, lease.yiaddr, expires))) {
 				bb_error_msg("too many leases while loading %s", file);
 				break;
 			}
 			i++;
 		}
 	}
 	DEBUG("Read %d leases", i);
 	close(fd);
 }
	/* vi: set sw=4 ts=4: */
	/*
	* files.c -- DHCP server file manipulation *
	* Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
	*
	* Licensed under GPLv2, see file LICENSE in this tarball for details.
	*/

	#include <netinet/ether.h>

	#include "common.h"
	#include "dhcpd.h"
	#include "options.h"


	/* on these functions, make sure your datatype matches */
	static int read_ip(const char line, void arg)
	{
	len_and_sockaddr *lsa;

	lsa = host_and_af2sockaddr(line, 0, AF_INET);
	if (!lsa)
	return 0;
	(uint32_t)arg = lsa->u.sin.sin_addr.s_addr;
	free(lsa);
	return 1;
	}

	static int read_mac(const char line, void arg)
	{
	return NULL == ether_aton_r(line, (struct ether_addr *)arg);
	}


	static int read_str(const char line, void arg)
	{
	char **dest = arg;

	free(*dest);
	*dest = xstrdup(line);
	return 1;
	}


	static int read_u32(const char line, void arg)
	{
	(uint32_t)arg = bb_strtou32(line, NULL, 10);
	return errno == 0;
	}


	static int read_yn(const char line, void arg)
	{
	char *dest = arg;

	if (!strcasecmp("yes", line)) {
	*dest = 1;
	return 1;
	}
	if (!strcasecmp("no", line)) {
	*dest = 0;
	return 1;
	}
	return 0;
	}


	/* find option 'code' in opt_list */
	struct option_set* FAST_FUNC find_option(struct option_set *opt_list, uint8_t code)
	{
	while (opt_list && opt_list->data[OPT_CODE] < code)
	opt_list = opt_list->next;

	if (opt_list && opt_list->data[OPT_CODE] == code)
	return opt_list;
	return NULL;
	}


	/* add an option to the opt_list */
	static void attach_option(struct option_set **opt_list,
	const struct dhcp_option option, char buffer, int length)
	{
	struct option_set existing, new, **curr;

	existing = find_option(*opt_list, option->code);
	if (!existing) {
	DEBUG("Attaching option %02x to list", option->code);

	#if ENABLE_FEATURE_UDHCP_RFC3397
	if ((option->flags & TYPE_MASK) == OPTION_STR1035)
	/* reuse buffer and length for RFC1035-formatted string */
	buffer = (char *)dname_enc(NULL, 0, buffer, &length);
	#endif

	/* make a new option */
	new = xmalloc(sizeof(*new));
	new->data = xmalloc(length + 2);
	new->data[OPT_CODE] = option->code;
	new->data[OPT_LEN] = length;
	memcpy(new->data + 2, buffer, length);

	curr = opt_list;
	while (curr && (curr)->data[OPT_CODE] < option->code)
	curr = &(*curr)->next;

	new->next = *curr;
	*curr = new;
	#if ENABLE_FEATURE_UDHCP_RFC3397
	if ((option->flags & TYPE_MASK) == OPTION_STR1035 && buffer != NULL)
	free(buffer);
	#endif
	return;
	}

	/* add it to an existing option */
	DEBUG("Attaching option %02x to existing member of list", option->code);
	if (option->flags & OPTION_LIST) {
	#if ENABLE_FEATURE_UDHCP_RFC3397
	if ((option->flags & TYPE_MASK) == OPTION_STR1035)
	/* reuse buffer and length for RFC1035-formatted string */
	buffer = (char *)dname_enc(existing->data + 2,
	existing->data[OPT_LEN], buffer, &length);
	#endif
	if (existing->data[OPT_LEN] + length <= 255) {
	existing->data = xrealloc(existing->data,
	existing->data[OPT_LEN] + length + 3);
	if ((option->flags & TYPE_MASK) == OPTION_STRING) {
	/* ' ' can bring us to 256 - bad */
	if (existing->data[OPT_LEN] + length >= 255)
	return;
	/* add space separator between STRING options in a list */
	existing->data[existing->data[OPT_LEN] + 2] = ' ';
	existing->data[OPT_LEN]++;
	}
	memcpy(existing->data + existing->data[OPT_LEN] + 2, buffer, length);
	existing->data[OPT_LEN] += length;
	} /* else, ignore the data, we could put this in a second option in the future */
	#if ENABLE_FEATURE_UDHCP_RFC3397
	if ((option->flags & TYPE_MASK) == OPTION_STR1035 && buffer != NULL)
	free(buffer);
	#endif
	} /* else, ignore the new data */
	}


	/* read a dhcp option and add it to opt_list */
	static int read_opt(const char const_line, void arg)
	{
	struct option_set **opt_list = arg;
	char opt, val, *endptr;
	char *line;
	const struct dhcp_option *option;
	int retval, length, idx;
	char buffer[8] ALIGNED(4);
	uint16_t result_u16 = (uint16_t ) buffer;
	uint32_t result_u32 = (uint32_t ) buffer;

	/* Cheat, the only const line we'll actually get is "" */
	line = (char *) const_line;
	opt = strtok(line, " \t=");
	if (!opt)
	return 0;

	idx = index_in_strings(dhcp_option_strings, opt); /* NB: was strcasecmp! */
	if (idx < 0)
	return 0;
	option = &dhcp_options[idx];

	retval = 0;
	do {
	val = strtok(NULL, ", \t");
	if (!val) break;
	length = dhcp_option_lengths[option->flags & TYPE_MASK];
	retval = 0;
	opt = buffer; /* new meaning for variable opt */
	switch (option->flags & TYPE_MASK) {
	case OPTION_IP:
	retval = read_ip(val, buffer);
	break;
	case OPTION_IP_PAIR:
	retval = read_ip(val, buffer);
	val = strtok(NULL, ", \t/-");
	if (!val)
	retval = 0;
	if (retval)
	retval = read_ip(val, buffer + 4);
	break;
	case OPTION_STRING:
	#if ENABLE_FEATURE_UDHCP_RFC3397
	case OPTION_STR1035:
	#endif
	length = strlen(val);
	if (length > 0) {
	if (length > 254) length = 254;
	opt = val;
	retval = 1;
	}
	break;
	case OPTION_BOOLEAN:
	retval = read_yn(val, buffer);
	break;
	case OPTION_U8:
	buffer[0] = strtoul(val, &endptr, 0);
	retval = (endptr[0] == '\0');
	break;
	/* htonX are macros in older libc's, using temp var
	* in code below for safety */
	/* TODO: use bb_strtoX? */
	case OPTION_U16: {
	unsigned long tmp = strtoul(val, &endptr, 0);
	*result_u16 = htons(tmp);
	retval = (endptr[0] == '\0' /&& tmp < 0x10000/);
	break;
	}
	case OPTION_S16: {
	long tmp = strtol(val, &endptr, 0);
	*result_u16 = htons(tmp);
	retval = (endptr[0] == '\0');
	break;
	}
	case OPTION_U32: {
	unsigned long tmp = strtoul(val, &endptr, 0);
	*result_u32 = htonl(tmp);
	retval = (endptr[0] == '\0');
	break;
	}
	case OPTION_S32: {
	long tmp = strtol(val, &endptr, 0);
	*result_u32 = htonl(tmp);
	retval = (endptr[0] == '\0');
	break;
	}
	default:
	break;
	}
	if (retval)
	attach_option(opt_list, option, opt, length);
	} while (retval && option->flags & OPTION_LIST);
	return retval;
	}

	static int read_staticlease(const char const_line, void arg)
	{
	char *line;
	char *mac_string;
	char *ip_string;
	struct ether_addr mac_bytes;
	uint32_t ip;

	/* Read mac */
	line = (char *) const_line;
	mac_string = strtok_r(line, " \t", &line);
	read_mac(mac_string, &mac_bytes);

	/* Read ip */
	ip_string = strtok_r(NULL, " \t", &line);
	read_ip(ip_string, &ip);

	addStaticLease(arg, (uint8_t*) &mac_bytes, ip);

	if (ENABLE_UDHCP_DEBUG) printStaticLeases(arg);

	return 1;
	}


	struct config_keyword {
	const char *keyword;
	int (handler)(const char line, void *var);
	void *var;
	const char *def;
	};

	static const struct config_keyword keywords[] = {
	/* keyword handler variable address default */
	{"start", read_ip, &(server_config.start_ip), "192.168.0.20"},
	{"end", read_ip, &(server_config.end_ip), "192.168.0.254"},
	{"interface", read_str, &(server_config.interface), "eth0"},
	/* Avoid "max_leases value not sane" warning by setting default
	* to default_end_ip - default_start_ip + 1: */
	{"max_leases", read_u32, &(server_config.max_leases), "235"},
	// {"remaining", read_yn, &(server_config.remaining), "yes"},
	{"auto_time", read_u32, &(server_config.auto_time), "7200"},
	{"decline_time", read_u32, &(server_config.decline_time), "3600"},
	{"conflict_time",read_u32, &(server_config.conflict_time),"3600"},
	{"offer_time", read_u32, &(server_config.offer_time), "60"},
	{"min_lease", read_u32, &(server_config.min_lease), "60"},
	{"lease_file", read_str, &(server_config.lease_file), LEASES_FILE},
	{"pidfile", read_str, &(server_config.pidfile), "/var/run/udhcpd.pid"},
	{"siaddr", read_ip, &(server_config.siaddr), "0.0.0.0"},
	/* keywords with no defaults must be last! */
	{"option", read_opt, &(server_config.options), ""},
	{"opt", read_opt, &(server_config.options), ""},
	{"notify_file", read_str, &(server_config.notify_file), ""},
	{"sname", read_str, &(server_config.sname), ""},
	{"boot_file", read_str, &(server_config.boot_file), ""},
	{"static_lease", read_staticlease, &(server_config.static_leases), ""},
	};
	enum { KWS_WITH_DEFAULTS = ARRAY_SIZE(keywords) - 6 };

	void FAST_FUNC read_config(const char *file)
	{
	parser_t *parser;
	const struct config_keyword *k;
	unsigned i;
	char *token[2];

	for (i = 0; i < KWS_WITH_DEFAULTS; i++)
	keywords[i].handler(keywords[i].def, keywords[i].var);

	parser = config_open(file);
	while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) {
	for (k = keywords, i = 0; i < ARRAY_SIZE(keywords); k++, i++) {
	if (!strcasecmp(token[0], k->keyword)) {
	if (!k->handler(token[1], k->var)) {
	bb_error_msg("can't parse line %u in %s",
	parser->lineno, file);
	/* reset back to the default value */
	k->handler(k->def, k->var);
	}
	break;
	}
	}
	}
	config_close(parser);

	server_config.start_ip = ntohl(server_config.start_ip);
	server_config.end_ip = ntohl(server_config.end_ip);
	}


	void FAST_FUNC write_leases(void)
	{
	int fd;
	unsigned i;
	leasetime_t curr;

	fd = open_or_warn(server_config.lease_file, O_WRONLY\|O_CREAT\|O_TRUNC);
	if (fd < 0)
	return;

	curr = time(NULL);
	//TODO: write out current time? Readers need to adjust .expires field
	// to account for time between file was written and when it was read back.

	for (i = 0; i < server_config.max_leases; i++) {
	leasetime_t tmp_time;

	if (leases[i].yiaddr == 0)
	continue;

	/* screw with the time in the struct, for easier writing */
	tmp_time = leases[i].expires;

	//if (server_config.remaining) {
	leases[i].expires -= curr;
	if ((signed_leasetime_t) leases[i].expires < 0)
	leases[i].expires = 0;
	//} /* else stick with the time we got */
	leases[i].expires = htonl(leases[i].expires);

	/* No error check. If the file gets truncated,
	* we lose some leases on restart. Oh well. */
	full_write(fd, &leases[i], sizeof(leases[i]));

	/* then restore it when done */
	leases[i].expires = tmp_time;
	}
	close(fd);

	if (server_config.notify_file) {
	// TODO: vfork-based child creation
	char *cmd = xasprintf("%s %s", server_config.notify_file, server_config.lease_file);
	system(cmd);
	free(cmd);
	}
	}


	void FAST_FUNC read_leases(const char *file)
	{
	int fd;
	unsigned i;
	// leasetime_t curr;
	struct dhcpOfferedAddr lease;

	fd = open_or_warn(file, O_RDONLY);
	if (fd < 0)
	return;

	// curr = time(NULL);
	i = 0;
	while (i < server_config.max_leases
	&& full_read(fd, &lease, sizeof(lease)) == sizeof(lease)
	) {
	/* ADDME: what if it matches some static lease? */
	uint32_t y = ntohl(lease.yiaddr);
	if (y >= server_config.start_ip && y <= server_config.end_ip) {
	leasetime_t expires = ntohl(lease.expires);
	// if (!server_config.remaining)
	// expires -= curr;
	/* NB: add_lease takes "relative time", IOW,
	* lease duration, not lease deadline. */
	if (!(add_lease(lease.chaddr, lease.yiaddr, expires))) {
	bb_error_msg("too many leases while loading %s", file);
	break;
	}
	i++;
	}
	}
	DEBUG("Read %d leases", i);
	close(fd);
	}