networking/udhcp/leases.c

/* vi: set sw=4 ts=4: */
/*
 * Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * Licensed under GPLv2, see file LICENSE in this tarball for details.
 */
#include "common.h"
#include "dhcpd.h"

/* Find the oldest expired lease, NULL if there are no expired leases */
static struct dyn_lease *oldest_expired_lease(void)
{
	struct dyn_lease *oldest_lease = NULL;
	leasetime_t oldest_time = time(NULL);
	unsigned i;

	/* Unexpired leases have g_leases[i].expires >= current time
	 * and therefore can't ever match */
	for (i = 0; i < server_config.max_leases; i++) {
		if (g_leases[i].expires < oldest_time) {
			oldest_time = g_leases[i].expires;
			oldest_lease = &g_leases[i];
		}
	}
	return oldest_lease;
}

/* Clear out all leases with matching nonzero chaddr OR yiaddr.
 * If chaddr == NULL, this is a conflict lease.
 */
static void clear_leases(const uint8_t *chaddr, uint32_t yiaddr)
{
	unsigned i;

	for (i = 0; i < server_config.max_leases; i++) {
		if ((chaddr && memcmp(g_leases[i].lease_mac, chaddr, 6) == 0)
		 || (yiaddr && g_leases[i].lease_nip == yiaddr)
		) {
			memset(&g_leases[i], 0, sizeof(g_leases[i]));
		}
	}
}

/* Add a lease into the table, clearing out any old ones.
 * If chaddr == NULL, this is a conflict lease.
 */
struct dyn_lease* FAST_FUNC add_lease(
		const uint8_t *chaddr, uint32_t yiaddr,
		leasetime_t leasetime,
		const char *hostname, int hostname_len)
{
	struct dyn_lease *oldest;

	/* clean out any old ones */
	clear_leases(chaddr, yiaddr);

	oldest = oldest_expired_lease();

	if (oldest) {
		memset(oldest, 0, sizeof(*oldest));
		if (hostname) {
			char *p;

			hostname_len++; /* include NUL */
			if (hostname_len > sizeof(oldest->hostname))
				hostname_len = sizeof(oldest->hostname);
			p = safe_strncpy(oldest->hostname, hostname, hostname_len);
			/* sanitization (s/non-ASCII/^/g) */
			while (*p) {
				if (*p < ' ' || *p > 126)
					*p = '^';
				p++;
			}
		}
		if (chaddr)
			memcpy(oldest->lease_mac, chaddr, 6);
		oldest->lease_nip = yiaddr;
		oldest->expires = time(NULL) + leasetime;
	}

	return oldest;
}

/* True if a lease has expired */
int FAST_FUNC is_expired_lease(struct dyn_lease *lease)
{
	return (lease->expires < (leasetime_t) time(NULL));
}

/* Find the first lease that matches MAC, NULL if no match */
struct dyn_lease* FAST_FUNC find_lease_by_mac(const uint8_t *mac)
{
	unsigned i;

	for (i = 0; i < server_config.max_leases; i++)
		if (memcmp(g_leases[i].lease_mac, mac, 6) == 0)
			return &g_leases[i];

	return NULL;
}

/* Find the first lease that matches IP, NULL is no match */
struct dyn_lease* FAST_FUNC find_lease_by_nip(uint32_t nip)
{
	unsigned i;

	for (i = 0; i < server_config.max_leases; i++)
		if (g_leases[i].lease_nip == nip)
			return &g_leases[i];

	return NULL;
}

/* Check if the IP is taken; if it is, add it to the lease table */
static int nobody_responds_to_arp(uint32_t nip, const uint8_t *safe_mac)
{
	struct in_addr temp;
	int r;

	r = arpping(nip, safe_mac,
			server_config.server_nip,
			server_config.server_mac,
			server_config.interface);
	if (r)
		return r;

	temp.s_addr = nip;
	bb_info_msg("%s belongs to someone, reserving it for %u seconds",
		inet_ntoa(temp), (unsigned)server_config.conflict_time);
	add_lease(NULL, nip, server_config.conflict_time, NULL, 0);
	return 0;
}

/* Find a new usable (we think) address */
uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac)
{
	uint32_t addr;
	struct dyn_lease *oldest_lease = NULL;

	addr = server_config.start_ip; /* addr is in host order here */
	for (; addr <= server_config.end_ip; addr++) {
		uint32_t nip;
		struct dyn_lease *lease;

		/* ie, 192.168.55.0 */
		if ((addr & 0xff) == 0)
			continue;
		/* ie, 192.168.55.255 */
		if ((addr & 0xff) == 0xff)
			continue;
		nip = htonl(addr);
		/* is this a static lease addr? */
		if (is_nip_reserved(server_config.static_leases, nip))
			continue;

		lease = find_lease_by_nip(nip);
		if (!lease) {
//TODO: DHCP servers do not always sit on the same subnet as clients: should *ping*, not arp-ping!
			if (nobody_responds_to_arp(nip, safe_mac))
				return nip;
		} else {
			if (!oldest_lease || lease->expires < oldest_lease->expires)
				oldest_lease = lease;
		}
	}

	if (oldest_lease
	 && is_expired_lease(oldest_lease)
	 && nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac)
	) {
		return oldest_lease->lease_nip;
	}

	return 0;
}
1	niro	532	/* vi: set sw=4 ts=4: */
2			/*
3			* Russ Dill <Russ.Dill@asu.edu> July 2001
4	niro	984	*
5			* Licensed under GPLv2, see file LICENSE in this tarball for details.
6	niro	532	*/
7			#include "common.h"
8			#include "dhcpd.h"
9
10	niro	816	/* Find the oldest expired lease, NULL if there are no expired leases */
11	niro	984	static struct dyn_lease *oldest_expired_lease(void)
12	niro	816	{
13	niro	984	struct dyn_lease *oldest_lease = NULL;
14			leasetime_t oldest_time = time(NULL);
15	niro	816	unsigned i;
16	niro	532
17	niro	984	/* Unexpired leases have g_leases[i].expires >= current time
18			* and therefore can't ever match */
19			for (i = 0; i < server_config.max_leases; i++) {
20			if (g_leases[i].expires < oldest_time) {
21			oldest_time = g_leases[i].expires;
22			oldest_lease = &g_leases[i];
23	niro	816	}
24	niro	984	}
25			return oldest_lease;
26	niro	816	}
27
28	niro	1123	/* Clear out all leases with matching nonzero chaddr OR yiaddr.
29			* If chaddr == NULL, this is a conflict lease.
30			*/
31			static void clear_leases(const uint8_t *chaddr, uint32_t yiaddr)
32	niro	532	{
33	niro	1123	unsigned i;
34	niro	532
35	niro	984	for (i = 0; i < server_config.max_leases; i++) {
36	niro	1123	if ((chaddr && memcmp(g_leases[i].lease_mac, chaddr, 6) == 0)
37	niro	984	\|\| (yiaddr && g_leases[i].lease_nip == yiaddr)
38	niro	816	) {
39	niro	984	memset(&g_leases[i], 0, sizeof(g_leases[i]));
40	niro	532	}
41	niro	984	}
42	niro	532	}
43
44	niro	1123	/* Add a lease into the table, clearing out any old ones.
45			* If chaddr == NULL, this is a conflict lease.
46			*/
47	niro	984	struct dyn_lease* FAST_FUNC add_lease(
48			const uint8_t *chaddr, uint32_t yiaddr,
49			leasetime_t leasetime,
50			const char *hostname, int hostname_len)
51	niro	532	{
52	niro	984	struct dyn_lease *oldest;
53	niro	532
54			/* clean out any old ones */
55	niro	1123	clear_leases(chaddr, yiaddr);
56	niro	532
57			oldest = oldest_expired_lease();
58
59			if (oldest) {
60	niro	1123	memset(oldest, 0, sizeof(*oldest));
61	niro	984	if (hostname) {
62			char *p;
63	niro	987
64			hostname_len++; /* include NUL */
65	niro	984	if (hostname_len > sizeof(oldest->hostname))
66			hostname_len = sizeof(oldest->hostname);
67			p = safe_strncpy(oldest->hostname, hostname, hostname_len);
68			/* sanitization (s/non-ASCII/^/g) */
69			while (*p) {
70			if (p < ' ' \|\| p > 126)
71			*p = '^';
72			p++;
73			}
74			}
75	niro	1123	if (chaddr)
76			memcpy(oldest->lease_mac, chaddr, 6);
77	niro	984	oldest->lease_nip = yiaddr;
78			oldest->expires = time(NULL) + leasetime;
79	niro	532	}
80
81			return oldest;
82			}
83
84	niro	984	/* True if a lease has expired */
85			int FAST_FUNC is_expired_lease(struct dyn_lease *lease)
86	niro	532	{
87	niro	984	return (lease->expires < (leasetime_t) time(NULL));
88	niro	532	}
89
90	niro	984	/* Find the first lease that matches MAC, NULL if no match */
91			struct dyn_lease* FAST_FUNC find_lease_by_mac(const uint8_t *mac)
92	niro	532	{
93	niro	816	unsigned i;
94	niro	532
95			for (i = 0; i < server_config.max_leases; i++)
96	niro	984	if (memcmp(g_leases[i].lease_mac, mac, 6) == 0)
97			return &g_leases[i];
98	niro	532
99			return NULL;
100			}
101
102	niro	984	/* Find the first lease that matches IP, NULL is no match */
103			struct dyn_lease* FAST_FUNC find_lease_by_nip(uint32_t nip)
104	niro	532	{
105	niro	816	unsigned i;
106	niro	532
107			for (i = 0; i < server_config.max_leases; i++)
108	niro	984	if (g_leases[i].lease_nip == nip)
109			return &g_leases[i];
110	niro	532
111			return NULL;
112			}
113
114	niro	984	/* Check if the IP is taken; if it is, add it to the lease table */
115			static int nobody_responds_to_arp(uint32_t nip, const uint8_t *safe_mac)
116	niro	532	{
117			struct in_addr temp;
118	niro	816	int r;
119	niro	532
120	niro	984	r = arpping(nip, safe_mac,
121			server_config.server_nip,
122			server_config.server_mac,
123			server_config.interface);
124	niro	816	if (r)
125			return r;
126
127	niro	984	temp.s_addr = nip;
128	niro	816	bb_info_msg("%s belongs to someone, reserving it for %u seconds",
129			inet_ntoa(temp), (unsigned)server_config.conflict_time);
130	niro	1123	add_lease(NULL, nip, server_config.conflict_time, NULL, 0);
131	niro	816	return 0;
132	niro	532	}
133
134	niro	984	/* Find a new usable (we think) address */
135			uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac)
136	niro	532	{
137	niro	984	uint32_t addr;
138			struct dyn_lease *oldest_lease = NULL;
139	niro	532
140	niro	816	addr = server_config.start_ip; /* addr is in host order here */
141			for (; addr <= server_config.end_ip; addr++) {
142	niro	984	uint32_t nip;
143			struct dyn_lease *lease;
144
145	niro	532	/* ie, 192.168.55.0 */
146	niro	984	if ((addr & 0xff) == 0)
147	niro	816	continue;
148	niro	532	/* ie, 192.168.55.255 */
149	niro	984	if ((addr & 0xff) == 0xff)
150	niro	816	continue;
151	niro	984	nip = htonl(addr);
152			/* is this a static lease addr? */
153			if (is_nip_reserved(server_config.static_leases, nip))
154			continue;
155
156			lease = find_lease_by_nip(nip);
157			if (!lease) {
158	niro	1123	//TODO: DHCP servers do not always sit on the same subnet as clients: should ping, not arp-ping!
159	niro	984	if (nobody_responds_to_arp(nip, safe_mac))
160			return nip;
161			} else {
162			if (!oldest_lease \|\| lease->expires < oldest_lease->expires)
163			oldest_lease = lease;
164	niro	532	}
165			}
166	niro	984
167	niro	1123	if (oldest_lease
168			&& is_expired_lease(oldest_lease)
169	niro	984	&& nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac)
170			) {
171			return oldest_lease->lease_nip;
172			}
173
174	niro	532	return 0;
175			}