1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
|
/* vi: set sw=4 ts=4: */
/*
* leases.c -- tools to manage DHCP leases
* 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 leases[i].expires >= current time
* and therefore can't ever match */
for (i = 0; i < server_config.max_leases; i++) {
if (leases[i].expires < oldest_time) {
oldest_time = leases[i].expires;
oldest_lease = &leases[i];
}
}
return oldest_lease;
}
/* Clear every lease out that chaddr OR yiaddr matches and is nonzero */
static void clear_lease(const uint8_t *chaddr, uint32_t yiaddr)
{
unsigned i, j;
for (j = 0; j < 16 && !chaddr[j]; j++)
continue;
for (i = 0; i < server_config.max_leases; i++) {
if ((j != 16 && memcmp(leases[i].lease_mac, chaddr, 6) == 0)
|| (yiaddr && leases[i].lease_nip == yiaddr)
) {
memset(&leases[i], 0, sizeof(leases[i]));
}
}
}
/* Add a lease into the table, clearing out any old ones */
struct dyn_lease* FAST_FUNC add_lease(
const uint8_t *chaddr, uint32_t yiaddr,
leasetime_t leasetime, uint8_t *hostname)
{
struct dyn_lease *oldest;
uint8_t hostname_length;
/* clean out any old ones */
clear_lease(chaddr, yiaddr);
oldest = oldest_expired_lease();
if (oldest) {
oldest->hostname[0] = '\0';
if (hostname) {
/* option size byte, + 1 for NUL */
hostname_length = hostname[-1] + 1;
if (hostname_length > sizeof(oldest->hostname))
hostname_length = sizeof(oldest->hostname);
hostname = (uint8_t*) safe_strncpy((char*)oldest->hostname, (char*)hostname, hostname_length);
/* sanitization (s/non-ASCII/^/g) */
while (*hostname) {
if (*hostname < ' ' || *hostname > 126)
*hostname = '^';
hostname++;
}
}
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 lease_expired(struct dyn_lease *lease)
{
return (lease->expires < (leasetime_t) time(NULL));
}
/* Find the first lease that matches chaddr, NULL if no match */
struct dyn_lease* FAST_FUNC find_lease_by_chaddr(const uint8_t *chaddr)
{
unsigned i;
for (i = 0; i < server_config.max_leases; i++)
if (memcmp(leases[i].lease_mac, chaddr, 6) == 0)
return &(leases[i]);
return NULL;
}
/* Find the first lease that matches yiaddr, NULL is no match */
struct dyn_lease* FAST_FUNC find_lease_by_yiaddr(uint32_t yiaddr)
{
unsigned i;
for (i = 0; i < server_config.max_leases; i++)
if (leases[i].lease_nip == yiaddr)
return &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 addr, const uint8_t *safe_mac)
{
/* 16 zero bytes */
static const uint8_t blank_chaddr[16] = { 0 };
/* = { 0 } helps gcc to put it in rodata, not bss */
struct in_addr temp;
int r;
r = arpping(addr, safe_mac,
server_config.server_nip,
server_config.server_mac,
server_config.interface);
if (r)
return r;
temp.s_addr = addr;
bb_info_msg("%s belongs to someone, reserving it for %u seconds",
inet_ntoa(temp), (unsigned)server_config.conflict_time);
add_lease(blank_chaddr, addr, server_config.conflict_time, NULL);
return 0;
}
/* Find a new usable (we think) address */
uint32_t FAST_FUNC find_free_or_expired_address(const uint8_t *chaddr)
{
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 net_addr;
struct dyn_lease *lease;
/* ie, 192.168.55.0 */
if ((addr & 0xff) == 0)
continue;
/* ie, 192.168.55.255 */
if ((addr & 0xff) == 0xff)
continue;
net_addr = htonl(addr);
/* is this a static lease addr? */
if (is_nip_reserved(server_config.static_leases, net_addr))
continue;
lease = find_lease_by_yiaddr(net_addr);
if (!lease) {
if (nobody_responds_to_arp(net_addr, chaddr))
return net_addr;
} else {
if (!oldest_lease || lease->expires < oldest_lease->expires)
oldest_lease = lease;
}
}
if (oldest_lease && lease_expired(oldest_lease)
&& nobody_responds_to_arp(oldest_lease->lease_nip, chaddr)
) {
return oldest_lease->lease_nip;
}
return 0;
}
|
