source: branches/3.2/mindi-busybox/networking/udhcp/leases.c @ 3232

Last change on this file since 3232 was 3232, checked in by bruno, 5 years ago
  • Update mindi-busybox to 1.21.1
File size: 5.0 KB
Line 
1/* vi: set sw=4 ts=4: */
2/*
3 * Russ Dill <Russ.Dill@asu.edu> July 2001
4 *
5 * Licensed under GPLv2, see file LICENSE in this source tree.
6 */
7#include "common.h"
8#include "dhcpd.h"
9
10/* Find the oldest expired lease, NULL if there are no expired leases */
11static struct dyn_lease *oldest_expired_lease(void)
12{
13    struct dyn_lease *oldest_lease = NULL;
14    leasetime_t oldest_time = time(NULL);
15    unsigned i;
16
17    /* 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        }
24    }
25    return oldest_lease;
26}
27
28/* Clear out all leases with matching nonzero chaddr OR yiaddr.
29 * If chaddr == NULL, this is a conflict lease.
30 */
31static void clear_leases(const uint8_t *chaddr, uint32_t yiaddr)
32{
33    unsigned i;
34
35    for (i = 0; i < server_config.max_leases; i++) {
36        if ((chaddr && memcmp(g_leases[i].lease_mac, chaddr, 6) == 0)
37         || (yiaddr && g_leases[i].lease_nip == yiaddr)
38        ) {
39            memset(&g_leases[i], 0, sizeof(g_leases[i]));
40        }
41    }
42}
43
44/* Add a lease into the table, clearing out any old ones.
45 * If chaddr == NULL, this is a conflict lease.
46 */
47struct 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{
52    struct dyn_lease *oldest;
53
54    /* clean out any old ones */
55    clear_leases(chaddr, yiaddr);
56
57    oldest = oldest_expired_lease();
58
59    if (oldest) {
60        memset(oldest, 0, sizeof(*oldest));
61        if (hostname) {
62            char *p;
63
64            hostname_len++; /* include NUL */
65            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        if (chaddr)
76            memcpy(oldest->lease_mac, chaddr, 6);
77        oldest->lease_nip = yiaddr;
78        oldest->expires = time(NULL) + leasetime;
79    }
80
81    return oldest;
82}
83
84/* True if a lease has expired */
85int FAST_FUNC is_expired_lease(struct dyn_lease *lease)
86{
87    return (lease->expires < (leasetime_t) time(NULL));
88}
89
90/* Find the first lease that matches MAC, NULL if no match */
91struct dyn_lease* FAST_FUNC find_lease_by_mac(const uint8_t *mac)
92{
93    unsigned i;
94
95    for (i = 0; i < server_config.max_leases; i++)
96        if (memcmp(g_leases[i].lease_mac, mac, 6) == 0)
97            return &g_leases[i];
98
99    return NULL;
100}
101
102/* Find the first lease that matches IP, NULL is no match */
103struct dyn_lease* FAST_FUNC find_lease_by_nip(uint32_t nip)
104{
105    unsigned i;
106
107    for (i = 0; i < server_config.max_leases; i++)
108        if (g_leases[i].lease_nip == nip)
109            return &g_leases[i];
110
111    return NULL;
112}
113
114/* Check if the IP is taken; if it is, add it to the lease table */
115static int nobody_responds_to_arp(uint32_t nip, const uint8_t *safe_mac)
116{
117    struct in_addr temp;
118    int r;
119
120    r = arpping(nip, safe_mac,
121            server_config.server_nip,
122            server_config.server_mac,
123            server_config.interface);
124    if (r)
125        return r;
126
127    temp.s_addr = nip;
128    bb_info_msg("%s belongs to someone, reserving it for %u seconds",
129        inet_ntoa(temp), (unsigned)server_config.conflict_time);
130    add_lease(NULL, nip, server_config.conflict_time, NULL, 0);
131    return 0;
132}
133
134/* Find a new usable (we think) address */
135uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac)
136{
137    uint32_t addr;
138    struct dyn_lease *oldest_lease = NULL;
139
140#if ENABLE_FEATURE_UDHCPD_BASE_IP_ON_MAC
141    uint32_t stop;
142    unsigned i, hash;
143
144    /* hash hwaddr: use the SDBM hashing algorithm.  Seems to give good
145     * dispersal even with similarly-valued "strings".
146     */
147    hash = 0;
148    for (i = 0; i < 6; i++)
149        hash += safe_mac[i] + (hash << 6) + (hash << 16) - hash;
150
151    /* pick a seed based on hwaddr then iterate until we find a free address. */
152    addr = server_config.start_ip
153        + (hash % (1 + server_config.end_ip - server_config.start_ip));
154    stop = addr;
155#else
156    addr = server_config.start_ip;
157#define stop (server_config.end_ip + 1)
158#endif
159    do {
160        uint32_t nip;
161        struct dyn_lease *lease;
162
163        /* ie, 192.168.55.0 */
164        if ((addr & 0xff) == 0)
165            goto next_addr;
166        /* ie, 192.168.55.255 */
167        if ((addr & 0xff) == 0xff)
168            goto next_addr;
169        nip = htonl(addr);
170        /* skip our own address */
171        if (nip == server_config.server_nip)
172            goto next_addr;
173        /* is this a static lease addr? */
174        if (is_nip_reserved(server_config.static_leases, nip))
175            goto next_addr;
176
177        lease = find_lease_by_nip(nip);
178        if (!lease) {
179//TODO: DHCP servers do not always sit on the same subnet as clients: should *ping*, not arp-ping!
180            if (nobody_responds_to_arp(nip, safe_mac))
181                return nip;
182        } else {
183            if (!oldest_lease || lease->expires < oldest_lease->expires)
184                oldest_lease = lease;
185        }
186
187 next_addr:
188        addr++;
189#if ENABLE_FEATURE_UDHCPD_BASE_IP_ON_MAC
190        if (addr > server_config.end_ip)
191            addr = server_config.start_ip;
192#endif
193    } while (addr != stop);
194
195    if (oldest_lease
196     && is_expired_lease(oldest_lease)
197     && nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac)
198    ) {
199        return oldest_lease->lease_nip;
200    }
201
202    return 0;
203}
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