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
|
/* vi: set sw=4 ts=4: */
/*
* leases.c -- tools to manage DHCP leases
* Russ Dill <Russ.Dill@asu.edu> July 2001
*/
#include "common.h"
#include "dhcpd.h"
/* Find the oldest expired lease, NULL if there are no expired leases */
static struct dhcpOfferedAddr *oldest_expired_lease(void)
{
struct dhcpOfferedAddr *oldest = NULL;
// TODO: use monotonic_sec()
unsigned long oldest_lease = time(0);
unsigned i;
for (i = 0; i < server_config.max_leases; i++)
if (oldest_lease > leases[i].expires) {
oldest_lease = leases[i].expires;
oldest = &(leases[i]);
}
return oldest;
}
/* 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].chaddr, chaddr, 16) == 0)
|| (yiaddr && leases[i].yiaddr == yiaddr)
) {
memset(&(leases[i]), 0, sizeof(leases[i]));
}
}
/* add a lease into the table, clearing out any old ones */
struct dhcpOfferedAddr *add_lease(const uint8_t *chaddr, uint32_t yiaddr, unsigned long lease)
{
struct dhcpOfferedAddr *oldest;
/* clean out any old ones */
clear_lease(chaddr, yiaddr);
oldest = oldest_expired_lease();
if (oldest) {
memcpy(oldest->chaddr, chaddr, 16);
oldest->yiaddr = yiaddr;
oldest->expires = time(0) + lease;
}
return oldest;
}
/* true if a lease has expired */
int lease_expired(struct dhcpOfferedAddr *lease)
{
return (lease->expires < (unsigned long) time(0));
}
/* Find the first lease that matches chaddr, NULL if no match */
struct dhcpOfferedAddr *find_lease_by_chaddr(const uint8_t *chaddr)
{
unsigned i;
for (i = 0; i < server_config.max_leases; i++)
if (!memcmp(leases[i].chaddr, chaddr, 16))
return &(leases[i]);
return NULL;
}
/* Find the first lease that matches yiaddr, NULL is no match */
struct dhcpOfferedAddr *find_lease_by_yiaddr(uint32_t yiaddr)
{
unsigned i;
for (i = 0; i < server_config.max_leases; i++)
if (leases[i].yiaddr == yiaddr)
return &(leases[i]);
return NULL;
}
/* check is an IP is taken, if it is, add it to the lease table */
static int nobody_responds_to_arp(uint32_t addr)
{
/* 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, server_config.server, server_config.arp, 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);
return 0;
}
/* find an assignable address, if check_expired is true, we check all the expired leases as well.
* Maybe this should try expired leases by age... */
uint32_t find_address(int check_expired)
{
uint32_t addr, ret;
struct dhcpOfferedAddr *lease = NULL;
addr = server_config.start_ip; /* addr is in host order here */
for (; addr <= server_config.end_ip; addr++) {
/* ie, 192.168.55.0 */
if (!(addr & 0xFF))
continue;
/* ie, 192.168.55.255 */
if ((addr & 0xFF) == 0xFF)
continue;
/* Only do if it isn't assigned as a static lease */
ret = htonl(addr);
if (!reservedIp(server_config.static_leases, ret)) {
/* lease is not taken */
lease = find_lease_by_yiaddr(ret);
/* no lease or it expired and we are checking for expired leases */
if ((!lease || (check_expired && lease_expired(lease)))
&& nobody_responds_to_arp(ret) /* it isn't used on the network */
) {
return ret;
}
}
}
return 0;
}
|
