| 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * leases.c -- tools to manage DHCP leases
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| 4 | * Russ Dill <Russ.Dill@asu.edu> July 2001
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| 5 | */
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| 6 |
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| 7 | #include "common.h"
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| 8 | #include "dhcpd.h"
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| 9 |
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| 10 |
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| 11 | /* Find the oldest expired lease, NULL if there are no expired leases */
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| 12 | static struct dhcpOfferedAddr *oldest_expired_lease(void)
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| 13 | {
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| 14 | struct dhcpOfferedAddr *oldest = NULL;
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| 15 | // TODO: use monotonic_sec()
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| 16 | unsigned long oldest_lease = time(0);
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| 17 | unsigned i;
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| 18 |
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| 19 | for (i = 0; i < server_config.max_leases; i++)
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| 20 | if (oldest_lease > leases[i].expires) {
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| 21 | oldest_lease = leases[i].expires;
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| 22 | oldest = &(leases[i]);
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| 23 | }
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| 24 | return oldest;
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| 25 | }
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| 26 |
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| 27 |
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| 28 | /* clear every lease out that chaddr OR yiaddr matches and is nonzero */
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| 29 | static void clear_lease(const uint8_t *chaddr, uint32_t yiaddr)
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| 30 | {
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| 31 | unsigned i, j;
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| 32 |
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| 33 | for (j = 0; j < 16 && !chaddr[j]; j++)
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| 34 | continue;
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| 35 |
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| 36 | for (i = 0; i < server_config.max_leases; i++)
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| 37 | if ((j != 16 && memcmp(leases[i].chaddr, chaddr, 16) == 0)
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| 38 | || (yiaddr && leases[i].yiaddr == yiaddr)
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| 39 | ) {
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| 40 | memset(&(leases[i]), 0, sizeof(leases[i]));
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| 41 | }
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| 42 | }
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| 43 |
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| 44 |
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| 45 | /* add a lease into the table, clearing out any old ones */
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| 46 | struct dhcpOfferedAddr *add_lease(const uint8_t *chaddr, uint32_t yiaddr, unsigned long lease)
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| 47 | {
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| 48 | struct dhcpOfferedAddr *oldest;
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| 49 |
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| 50 | /* clean out any old ones */
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| 51 | clear_lease(chaddr, yiaddr);
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| 52 |
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| 53 | oldest = oldest_expired_lease();
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| 54 |
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| 55 | if (oldest) {
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| 56 | memcpy(oldest->chaddr, chaddr, 16);
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| 57 | oldest->yiaddr = yiaddr;
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| 58 | oldest->expires = time(0) + lease;
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| 59 | }
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| 60 |
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| 61 | return oldest;
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| 62 | }
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| 63 |
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| 64 |
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| 65 | /* true if a lease has expired */
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| 66 | int lease_expired(struct dhcpOfferedAddr *lease)
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| 67 | {
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| 68 | return (lease->expires < (unsigned long) time(0));
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| 69 | }
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| 70 |
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| 71 |
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| 72 | /* Find the first lease that matches chaddr, NULL if no match */
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| 73 | struct dhcpOfferedAddr *find_lease_by_chaddr(const uint8_t *chaddr)
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| 74 | {
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| 75 | unsigned i;
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| 76 |
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| 77 | for (i = 0; i < server_config.max_leases; i++)
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| 78 | if (!memcmp(leases[i].chaddr, chaddr, 16))
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| 79 | return &(leases[i]);
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| 80 |
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| 81 | return NULL;
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| 82 | }
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| 83 |
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| 84 |
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| 85 | /* Find the first lease that matches yiaddr, NULL is no match */
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| 86 | struct dhcpOfferedAddr *find_lease_by_yiaddr(uint32_t yiaddr)
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| 87 | {
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| 88 | unsigned i;
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| 89 |
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| 90 | for (i = 0; i < server_config.max_leases; i++)
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| 91 | if (leases[i].yiaddr == yiaddr)
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| 92 | return &(leases[i]);
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| 93 |
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| 94 | return NULL;
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| 95 | }
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| 96 |
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| 97 |
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| 98 | /* check is an IP is taken, if it is, add it to the lease table */
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| 99 | static int nobody_responds_to_arp(uint32_t addr)
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| 100 | {
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| 101 | static const uint8_t blank_chaddr[16]; /* 16 zero bytes */
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| 102 |
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| 103 | struct in_addr temp;
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| 104 | int r;
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| 105 |
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| 106 | r = arpping(addr, server_config.server, server_config.arp, server_config.interface);
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| 107 | if (r)
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| 108 | return r;
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| 109 |
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| 110 | temp.s_addr = addr;
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| 111 | bb_info_msg("%s belongs to someone, reserving it for %u seconds",
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| 112 | inet_ntoa(temp), (unsigned)server_config.conflict_time);
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| 113 | add_lease(blank_chaddr, addr, server_config.conflict_time);
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| 114 | return 0;
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| 115 | }
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| 116 |
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| 117 |
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| 118 | /* find an assignable address, if check_expired is true, we check all the expired leases as well.
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| 119 | * Maybe this should try expired leases by age... */
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| 120 | uint32_t find_address(int check_expired)
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| 121 | {
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| 122 | uint32_t addr, ret;
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| 123 | struct dhcpOfferedAddr *lease = NULL;
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| 124 |
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| 125 | addr = server_config.start_ip; /* addr is in host order here */
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| 126 | for (; addr <= server_config.end_ip; addr++) {
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| 127 | /* ie, 192.168.55.0 */
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| 128 | if (!(addr & 0xFF))
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| 129 | continue;
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| 130 | /* ie, 192.168.55.255 */
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| 131 | if ((addr & 0xFF) == 0xFF)
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| 132 | continue;
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| 133 | /* Only do if it isn't assigned as a static lease */
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| 134 | ret = htonl(addr);
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| 135 | if (!reservedIp(server_config.static_leases, ret)) {
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| 136 | /* lease is not taken */
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| 137 | lease = find_lease_by_yiaddr(ret);
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| 138 | /* no lease or it expired and we are checking for expired leases */
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| 139 | if ((!lease || (check_expired && lease_expired(lease)))
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| 140 | && nobody_responds_to_arp(ret) /* it isn't used on the network */
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| 141 | ) {
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| 142 | return ret;
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| 143 | }
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| 144 | }
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| 145 | }
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| 146 | return 0;
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| 147 | }
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